tag:blogger.com,1999:blog-53170123780923239232024-02-20T00:33:45.466-08:00bandung kota distrokota mode,pusat katalog distro bandung,yang semakin banyak diminati oleh pengunjung yang ada di kota maupun daerah yang ada di indonesiakatalog baju bandunghttp://www.blogger.com/profile/11320702173725403635noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5317012378092323923.post-92059699699892021162011-01-18T02:30:00.001-08:002011-01-18T02:30:51.636-08:00???<div style="border-bottom: solid #AAAAAA 1.0pt; border: none; mso-border-bottom-alt: solid #AAAAAA .5pt; mso-element: para-border-div; padding: 0cm 0cm 2.0pt 0cm;"> <div class="MsoNormal" style="border: none; margin-bottom: 7.2pt; mso-border-bottom-alt: solid #AAAAAA .5pt; mso-line-height-alt: 10.35pt; mso-outline-level: 2; mso-padding-alt: 0cm 0cm 2.0pt 0cm; padding: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 10.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">History</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 10.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:Black_hole_lensing_web.gif"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 6.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shapetype id="_x0000_t75"
coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe"
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alt="Schwarzschild black hole"
href="http://en.wikipedia.org/wiki/File:Black_hole_lensing_web.gif" style='width:180pt;
height:2in;visibility:visible;mso-wrap-style:square' o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image001.gif"
o:title="Schwarzschild black hole"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="Schwarzschild black hole" border="0" height="192" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif" v:shapes="Picture_x0020_1" width="240" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 6.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Simulation of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_lens" title="Gravitational lens"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational lensing</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">by a black hole which distorts the image of a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Galaxy" title="Galaxy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">galaxy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in the background (</span><a href="http://en.wikipedia.org/wiki/File:BlackHole_Lensing.gif" title="File:BlackHole Lensing.gif"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">click here for larger animation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">)<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The idea of a body so massive that even light could not escape was first put forward by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Geologist" title="Geologist"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">geologist</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/John_Michell" title="John Michell"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">John Michell</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in a letter written to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Henry_Cavendish" title="Henry Cavendish"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Henry Cavendish</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in 1783 to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Royal_Society" title="Royal Society"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Royal Society</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">:<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: .0001pt; margin-bottom: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of 500 to 1, a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light, and consequently supposing light to be attracted by the same force in proportion to its vis inertiae, with other bodies, all light emitted from such a body would be made to return towards it by its own proper gravity.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 12.0pt; margin-bottom: 5.0pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">—John Michell</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Michell1784-1"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[2]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1796, mathematician</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Pierre-Simon_Laplace" title="Pierre-Simon Laplace"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Pierre-Simon Laplace</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">promoted the same idea in the first and second editions of his book</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Exposition du système du Monde</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(it was removed from later editions).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-2"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[3]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-3"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[4]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Such "</span><a href="http://en.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics)" title="Dark star (Newtonian mechanics)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">dark stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">" were largely ignored in the nineteenth century, since it was not understood how a massless wave such as light could be influenced by gravity.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-4"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[5]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">General relativity</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1915,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Albert_Einstein" title="Albert Einstein"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Albert Einstein</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">developed his theory of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/General_relativity" title="General relativity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">general relativity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, having earlier shown that gravity does influence light's motion. A few months later,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Karl_Schwarzschild" title="Karl Schwarzschild"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Karl Schwarzschild</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gave</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Schwarzschild_metric" title="Schwarzschild metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">the solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">for the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_field" title="Gravitational field"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational field</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Point_mass" title="Point mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">point mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and a spherical mass.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Schwarzschild1916-5"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[6]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">A few months after Schwarzschild, Johannes Droste, a student of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Hendrik_Lorentz" title="Hendrik Lorentz"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Hendrik Lorentz</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, independently gave the same solution for the point mass and wrote more extensively about its properties.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-6"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[7]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This solution had a peculiar behaviour at what is now called the</span><a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" title="Schwarzschild radius"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Schwarzschild radius</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, where it became</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Mathematical_singularity" title="Mathematical singularity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">singular</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, meaning that some of the terms in the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Einstein_equations" title="Einstein equations"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Einstein equations</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">became infinite. The nature of this surface was not quite understood at the time. In 1924,</span><a href="http://en.wikipedia.org/wiki/Arthur_Eddington" title="Arthur Eddington"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Arthur Eddington</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed that the singularity disappeared after a change of coordinates (see</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Eddington%E2%80%93Finkelstein_coordinates" title="Eddington–Finkelstein coordinates"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Eddington–Finkelstein coordinates</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">), although it took until 1933 for</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Georges_Lema%C3%AEtre" title="Georges Lemaître"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Georges Lemaître</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to realize that this meant the singularity at the Schwarzschild radius was an unphysical</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Coordinate_singularity" title="Coordinate singularity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">coordinate singularity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-HooftHist-7"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[8]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1931,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Subrahmanyan_Chandrasekhar" title="Subrahmanyan Chandrasekhar"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Subrahmanyan Chandrasekhar</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">calculated, using general relativity, that a non-rotating body of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electron-degenerate_matter" title="Electron-degenerate matter"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">electron-degenerate matter</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">above a certain limiting mass (now called the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Chandrasekhar_limit" title="Chandrasekhar limit"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Chandrasekhar limit</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">at 1.44 solar masses) must have an infinite density. In other words, the object must have a radius of zero.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-venkataraman92-8"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[9]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">His arguments were opposed by many of his contemporaries like Eddington and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Lev_Landau" title="Lev Landau"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Lev Landau</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, who argued that some yet unknown mechanism would stop the collapse.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-9"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[10]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">They were partly correct: a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/White_dwarf" title="White dwarf"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">white dwarf</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">slightly more massive than the Chandrasekhar limit will collapse into a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Neutron_star" title="Neutron star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">neutron star</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-10"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[11]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">which is itself stable because of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Pauli_exclusion_principle" title="Pauli exclusion principle"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Pauli exclusion principle</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. But in 1939,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Robert_Oppenheimer" title="Robert Oppenheimer"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Robert Oppenheimer</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and others predicted that neutron stars above approximately three solar masses (the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit" title="Tolman–Oppenheimer–Volkoff limit"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Tolman–Oppenheimer–Volkoff limit</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">) would collapse into black holes for the reasons presented by Chandrasekhar, and concluded that no law of physics was likely to intervene and stop at least some stars from collapsing to black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-11"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[12]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Oppenheimer and his co-authors interpreted the singularity at the boundary of the Schwarzschild radius as indicating that this was the boundary of a bubble in which time stopped. This is a valid point of view for external observers, but not for infalling observers. Because of this property, the collapsed stars were called "frozen stars,"</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-12"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[13]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">because an outside observer would see the surface of the star frozen in time at the instant where its collapse takes it inside the Schwarzschild radius.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Golden age</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">See also:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Golden_age_of_general_relativity" title="Golden age of general relativity"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Golden age of general relativity</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1958,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/David_Finkelstein" title="David Finkelstein"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">David Finkelstein</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">identified the Schwarzschild surface</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">r</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">= 2<i>m</i></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Geometrized_units" title="Geometrized units"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">geometrized units</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, i.e. 2<i>Gm</i>/<i>c</i><sup>2</sup>, where</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">r</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is the radius of the surface and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">m</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is the mass of the black hole] as an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Event_horizon" title="Event horizon"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">event horizon</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, "a perfect unidirectional membrane: causal influences can cross it in only one direction".</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-13"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[14]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This did not strictly contradict Oppenheimer's results, but extended them to include the point of view of infalling observers.</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Eddington-Finkelstein_coordinates" title="Eddington-Finkelstein coordinates"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Finkelstein's solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">extended the Schwarzschild solution for the future of observers falling into the black hole. A</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kruskal-Szekeres_coordinates" title="Kruskal-Szekeres coordinates"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">complete extension</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">had already been found by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Martin_Kruskal" title="Martin Kruskal"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Martin Kruskal</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, who was urged to publish it.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-14"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[15]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">These results came at the beginning of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Golden_age_of_general_relativity" title="Golden age of general relativity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">golden age of general relativity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which was marked by general relativity and black holes becoming mainstream subjects of research. This process was helped by the discovery of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Pulsar" title="Pulsar"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">pulsars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in 1967,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-15"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[16]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-16"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[17]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">which were within a few years shown to be rapidly rotating</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Neutron_star" title="Neutron star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">neutron stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Until that time, neutron stars, like black holes, were regarded as just theoretical curiosities; but the discovery of pulsars showed their physical relevance and spurred a further interest in all types of compact objects that might be formed by gravitational collapse.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In this period more general black hole solutions were found. In 1963,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Roy_Kerr" title="Roy Kerr"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Roy Kerr</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">found</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kerr_metric" title="Kerr metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">the exact solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">for a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Rotating_black_hole" title="Rotating black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">rotating black hole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Two years later</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Ezra_T._Newman" title="Ezra T. Newman"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Ezra T. Newman</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">found the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Axisymmetric" title="Axisymmetric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">axisymmetric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">solution for a black hole which is both rotating and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electric_charge" title="Electric charge"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">electrically charged</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-17"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[18]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Through the work of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Werner_Israel" title="Werner Israel"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Werner Israel</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-18"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[19]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Brandon_Carter" title="Brandon Carter"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Brandon Carter</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-19"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[20]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-20"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[21]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/w/index.php?title=D._C._Robinson&action=edit&redlink=1" title="D. C. Robinson (page does not exist)"><span style="color: #cc2200; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">D. C. Robinson</span></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-21"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[22]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/No-hair_theorem" title="No-hair theorem"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">no-hair theorem</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">emerged, stating that a stationary black hole solution is completely described by the three parameters of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kerr%E2%80%93Newman_metric" title="Kerr–Newman metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Kerr–Newman metric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">;</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Mass" title="Mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Angular_momentum" title="Angular momentum"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">angular momentum</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electric_charge" title="Electric charge"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">electric charge</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-HeuslerNoHair-22"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[23]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">For a long time, it was suspected that the strange features of the black hole solutions were pathological artefacts from the symmetry conditions imposed, and that the singularities would not appear in generic situations. This view was held in particular by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Vladimir_A._Belinsky" title="Vladimir A. Belinsky"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Belinsky</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Isaak_Markovich_Khalatnikov" title="Isaak Markovich Khalatnikov"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Khalatnikov</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Evgeny_Lifshitz" title="Evgeny Lifshitz"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Lifshitz</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, who tried to prove that no singularities appear in generic solutions. However, in the late sixties</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Roger_Penrose" title="Roger Penrose"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Roger Penrose</span></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-penrose1965-23"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[24]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stephen_Hawking" title="Stephen Hawking"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Stephen Hawking</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">used global techniques to prove that singularities are generic.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-24"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[25]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Work by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/James_M._Bardeen" title="James M. Bardeen"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">James Bardeen</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Jacob_Bekenstein" title="Jacob Bekenstein"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Jacob Bekenstein</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, Carter, and Hawking in the early 1970s led to the formulation of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Laws_of_black_hole_mechanics" title="Laws of black hole mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">laws of black hole mechanics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-25"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[26]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">These laws describe the behaviour of a black hole in close analogy to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Laws_of_thermodynamics" title="Laws of thermodynamics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">laws of thermodynamics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">by relating mass to energy, area to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Entropy" title="Entropy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">entropy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Surface_gravity" title="Surface gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">surface gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Temperature" title="Temperature"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">temperature</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The analogy was completed when Hawking, in 1974, showed that</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_field_theory" title="Quantum field theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum field theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">predicts that black holes should radiate like a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_body" title="Black body"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black body</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">with a temperature proportional to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Surface_gravity" title="Surface gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">surface gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of the black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Hawking1974-26"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[27]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The term "black hole" was first publicly used by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/John_Archibald_Wheeler" title="John Archibald Wheeler"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">John Wheeler</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">during a lecture in 1967. Although he is usually credited with coining the phrase, he always insisted that it was suggested to him by somebody else. The first recorded use of the term is in a 1964 letter by Anne Ewing to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/American_Association_for_the_Advancement_of_Science" title="American Association for the Advancement of Science"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">American Association for the Advancement of Science</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-27"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[28]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">After Wheeler's use of the term, it was quickly adopted in general use.<o:p></o:p></span></div><div style="border-bottom: solid #AAAAAA 1.0pt; border: none; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-element: para-border-div; padding: 0cm 0cm 2.0pt 0cm;"> <div class="MsoNormal" style="border: none; margin-bottom: 7.2pt; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-line-height-alt: 10.35pt; mso-outline-level: 2; mso-padding-alt: 0cm 0cm 2.0pt 0cm; padding: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Properties and structure</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/No-hair_theorem" title="No-hair theorem"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">no-hair theorem</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">states that, once it achieves a stable condition after formation, a black hole has only three independent physical properties:</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Mass" title="Mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electric_charge" title="Electric charge"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">charge</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Angular_momentum" title="Angular momentum"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">angular momentum</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-HeuslerNoHair-22"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[23]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Any two black holes that share the same values for these properties, or parameters, are indistinguishable according to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Classical_mechanics" title="Classical mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">classical</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(i.e. non-</span><a href="http://en.wikipedia.org/wiki/Quantum_mechanics" title="Quantum mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">) mechanics.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">These properties are special because they are visible from outside the black hole. For example, a charged black hole repels other like charges just like any other charged object. Similarly, the total mass inside a sphere containing a black hole can be found by using the gravitational analog of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gauss%27s_law" title="Gauss's law"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gauss's law</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/ADM_mass" title="ADM mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ADM mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, far away from the black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-28"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[29]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Likewise, the angular momentum can be measured from far away using</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Frame_dragging" title="Frame dragging"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">frame dragging</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitomagnetism" title="Gravitomagnetism"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitomagnetic field</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">When an object falls into a black hole, any</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Physical_information" title="Physical information"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">information</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">about the shape of the object or distribution of charge on it is evenly distributed along the horizon of the black hole, and is lost to outside observers. The behavior of the horizon in this situation is closely analogous to that of a conductive stretchy membrane with friction and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electrical_resistance" title="Electrical resistance"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">electrical resistance</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Dissipative_system" title="Dissipative system"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">dissipative system</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(see</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Membrane_paradigm" title="Membrane paradigm"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">membrane paradigm</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-29"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[30]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This is different from other</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Field_theories" title="Field theories"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">field theories</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">like electromagnetism, which does not have any friction or resistivity at the microscopic level, because they are</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/T-symmetry" title="T-symmetry"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">time-reversible</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Because the black hole eventually achieves a stable state with only three parameters, there is no way to avoid losing information about the initial conditions: the gravitational and electric fields of the black hole give very little information about what went in. The information that is lost includes every quantity that cannot be measured far away from the black hole horizon, including the total</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Baryon_number" title="Baryon number"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">baryon number</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Lepton_number" title="Lepton number"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">lepton number</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and all the other nearly conserved pseudo-charges of particle physics. This behavior is so puzzling that it has been called the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_hole_information_loss_paradox" title="Black hole information loss paradox"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black hole information loss paradox</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-30"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[31]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-31"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[32]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-32"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[33]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Physical properties</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The simplest black hole has mass but neither electric charge nor angular momentum. These black holes are often referred to as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Schwarzschild_metric" title="Schwarzschild metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Schwarzschild black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">after the physicist</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Karl_Schwarzschild" title="Karl Schwarzschild"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Karl Schwarzschild</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">who discovered this</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Solutions_of_the_Einstein_field_equations" title="Solutions of the Einstein field equations"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in 1915.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Schwarzschild1916-5"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[6]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">According to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Birkhoff%27s_theorem_(relativity)" title="Birkhoff's theorem (relativity)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Birkhoff's theorem</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, it is the only</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Vacuum_solution_(general_relativity)" title="Vacuum solution (general relativity)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">vacuum solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">that is</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Spherically_symmetric_spacetime" title="Spherically symmetric spacetime"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">spherically symmetric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-33"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[34]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This means that there is no observable difference between the gravitational field of such a black hole and that of any other spherical object of the same mass. The popular notion of a black hole "sucking in everything" in its surroundings is therefore only correct near the black hole horizon; far away, the external gravitational field is identical to that of any other body of the same mass.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-34"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[35]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Solutions describing more general black holes also exist.</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Charged_black_hole" title="Charged black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Charged black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">are described by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Reissner%E2%80%93Nordstr%C3%B6m_metric" title="Reissner–Nordström metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Reissner–Nordström metric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, while the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kerr_metric" title="Kerr metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Kerr metric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">describes a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Rotating_black_hole" title="Rotating black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">rotating black hole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The most general</span><a href="http://en.wikipedia.org/wiki/Stationary_spacetime" title="Stationary spacetime"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">stationary</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black hole solution known is the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kerr%E2%80%93Newman_metric" title="Kerr–Newman metric"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Kerr–Newman metric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which describes a black hole with both charge and angular momentum.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">While the mass of a black hole can take any positive value, the charge and angular momentum are constrained by the mass. In</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Planck_units" title="Planck units"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Planck units</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, the total electric charge <i>Q</i></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and the total angular momentum <i>J</i></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">are expected to satisfy<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 1.2pt; margin-left: 36.0pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes;"><!--[if gte vml 1]><v:shape id="Picture_x0020_2"
o:spid="_x0000_i1042" type="#_x0000_t75" alt="Q^2+\left ( \tfrac{J}{M} \right )^2\le M^2\, "
style='width:110.25pt;height:21.75pt;visibility:visible;mso-wrap-style:square'> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image002.gif"
o:title=", "/> </v:shape><![endif]--><!--[if !vml]--><img alt="Q^2+\left ( \tfrac{J}{M} \right )^2\le M^2\, " border="0" height="29" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image002.gif" v:shapes="Picture_x0020_2" width="147" /><!--[endif]--></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 24.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">for a black hole of mass</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Black holes saturating this inequality are called</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Extremal_black_hole" title="Extremal black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">extremal</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Solutions of Einstein's equations violating the inequality exist, but do not have a horizon. These solutions have</span><a href="http://en.wikipedia.org/wiki/Naked_singularity" title="Naked singularity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">naked singularities</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and are deemed</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">unphysical</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis" title="Cosmic censorship hypothesis"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">cosmic censorship hypothesis</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">rules out the formation of such singularities through the gravitational collapse of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Energy_conditions" title="Energy conditions"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">realistic matter</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-35"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[36]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This is supported by numerical simulations.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-36"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[37]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 24.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Due to the relatively large strength of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electromagnetism" title="Electromagnetism"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">electromagnetic force</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, black holes forming from the collapse of stars are expected to retain the nearly neutral charge of the star. Rotation, however, is expected to be a common feature of compact objects, and the black-hole candidate binary X-ray source</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/GRS_1915%2B105" title="GRS 1915+105"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">GRS 1915+105</span></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-37"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[38]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">appears to have an angular momentum near the maximum allowed value.<o:p></o:p></span></div><table border="1" cellpadding="0" cellspacing="0" class="MsoNormalTable" style="background: #F9F9F9; border-collapse: collapse; border: none; margin-left: 36.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-yfti-tbllook: 1184;"><tbody>
<tr style="mso-yfti-firstrow: yes; mso-yfti-irow: 0;"> <td style="background: #F2F2F2; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><b><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Class<o:p></o:p></span></b></div></td> <td style="background: #F2F2F2; border-left: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><b><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Mass<o:p></o:p></span></b></div></td> <td style="background: #F2F2F2; border-left: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><b><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Size<o:p></o:p></span></b></div></td> </tr>
<tr style="mso-yfti-irow: 1;"> <td style="border-top: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt;"><a href="http://en.wikipedia.org/wiki/Supermassive_black_hole" title="Supermassive black hole"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Supermassive black hole</span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~10<sup>5</sup>–10<sup>9</sup></span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Solar_mass" title="Solar mass"><i><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M</span></i><sub><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sun</span></sub></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~0.001–10</span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Astronomical_unit" title="Astronomical unit"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">AU</span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> </tr>
<tr style="mso-yfti-irow: 2;"> <td style="border-top: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt;"><a href="http://en.wikipedia.org/wiki/Intermediate-mass_black_hole" title="Intermediate-mass black hole"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Intermediate-mass black hole</span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~10<sup>3</sup></span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M</span></i><sub><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sun</span></sub><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~10<sup>3</sup></span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">km =</span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Earth_radius" title="Earth radius"><i><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">R</span></i><sub><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Earth</span></sub></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> </tr>
<tr style="mso-yfti-irow: 3;"> <td style="border-top: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt;"><a href="http://en.wikipedia.org/wiki/Stellar_black_hole" title="Stellar black hole"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Stellar black hole</span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~10</span><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M</span></i><sub><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sun</span></sub><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">~30 km<o:p></o:p></span></div></td> </tr>
<tr style="mso-yfti-irow: 4; mso-yfti-lastrow: yes;"> <td style="border-top: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt;"><a href="http://en.wikipedia.org/wiki/Micro_black_hole" title="Micro black hole"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Micro black hole</span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">up to ~<i>M</i></span><a href="http://en.wikipedia.org/wiki/Moon" title="Moon"><sub><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Moon</span></sub></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-bottom: solid #AAAAAA 1.0pt; border-left: none; border-right: solid #AAAAAA 1.0pt; border-top: none; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; text-align: center;"><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">up to ~0.1 mm<o:p></o:p></span></div></td> </tr>
</tbody></table><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 24.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Black holes are commonly classified according to their mass, independent of angular momentum</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">J</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">or electric charge</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Q</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The size of a black hole, as determined by the radius of the event horizon, or</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" title="Schwarzschild radius"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Schwarzschild radius</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, is roughly proportional to the mass</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">through<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 1.2pt; margin-left: 36.0pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes;"><!--[if gte vml 1]><v:shape id="Picture_x0020_3"
o:spid="_x0000_i1041" type="#_x0000_t75" alt="r_\mathrm{sh} =\frac{2GM}{c^2} \approx 2.95\, \frac{M}{M_\mathrm{Sun}}~\mathrm{km,}"
style='width:185.25pt;height:33pt;visibility:visible;mso-wrap-style:square'> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image003.gif"
o:title="mathrm{km,}"/> </v:shape><![endif]--><!--[if !vml]--><img alt="r_\mathrm{sh} =\frac{2GM}{c^2} \approx 2.95\, \frac{M}{M_\mathrm{Sun}}~\mathrm{km,}" border="0" height="44" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image003.gif" v:shapes="Picture_x0020_3" width="247" /><!--[endif]--></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">where</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">r</span></i><sub><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">sh</span></sub><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is the Schwarzschild radius and M<sub>Sun</sub></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Solar_mass" title="Solar mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">mass of the Sun</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. This relation is exact only for black holes with zero charge and angular momentum, for more general black holes it can differ up to a factor of 2. The table on the right lists the various classes of black hole that are distinguished.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Event horizon</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Event_horizon" title="Event horizon"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Event horizon</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><table border="1" cellpadding="0" cellspacing="0" class="MsoNormalTable" style="background-attachment: initial; background-clip: initial; background-color: #f9f9f9; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; border-bottom-style: none; border-collapse: collapse; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial; margin-left: 54pt; width: 400px;"><tbody>
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Far away from the black hole a particle can move in any direction. It is only restricted by the speed of light.<o:p></o:p></span></div></td> </tr>
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Closer to the black hole spacetime starts to deform. There are more paths going towards the black hole than paths moving away.<o:p></o:p></span></div></td> </tr>
<tr style="mso-yfti-irow: 2; mso-yfti-lastrow: yes;"> <td style="border-top: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-top-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 6.0pt; margin-left: 0cm; margin-right: 0cm; margin-top: 6.0pt;"><a href="http://en.wikipedia.org/wiki/File:BH-no-escape-3.svg"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_6"
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Inside of the event horizon all paths bring the particle closer to the center of the black hole. It is no longer possible for the particle to escape.<o:p></o:p></span></div></td> </tr>
</tbody></table><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The defining feature of a black hole is the appearance of an event horizon—a boundary in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Spacetime" title="Spacetime"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">spacetime</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">through which matter and light can only pass inward towards the mass of the black hole. Nothing, not even light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine if such an event occurred.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-38"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[39]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">As predicted by general relativity, the presence of a large mass deforms spacetime in such a way that the paths taken by particles bend towards the mass. At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-39"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[40]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-40"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[41]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Due to this effect, known as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_time_dilation" title="Gravitational time dilation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational time dilation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-41"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[42]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_redshift" title="Gravitational redshift"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational redshift</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-42"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[43]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-43"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[44]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">For a non rotating (static) black hole, the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" title="Schwarzschild radius"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Schwarzschild radius</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">delimits a spherical event horizon. The Schwarzschild radius of an object is proportional to the mass.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-44"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[45]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Rotating black holes have distorted, nonspherical event horizons. Since the event horizon is not a material surface but rather merely a mathematically defined demarcation boundary, nothing prevents matter or radiation from entering a black hole, only from exiting one. The description of black holes given by general relativity is known to be an approximation, and some scientists expect that</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_gravity" title="Quantum gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">effects will become significant near the vicinity of the event horizon.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-45"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[46]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This would allow observations of matter near a black hole's event horizon to be used to indirectly study</span><a href="http://en.wikipedia.org/wiki/General_relativity" title="General relativity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">general relativity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and proposed extensions to it.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Singularity</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Gravitational_singularity" title="Gravitational singularity"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational singularity</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">At the center of a black hole as described by general relativity lies a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_singularity" title="Gravitational singularity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational singularity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, a region where the spacetime curvature becomes infinite.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-46"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[47]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">For a non-rotating black hole this region takes the shape of a single point and for a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Rotating_black_hole" title="Rotating black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">rotating black hole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">it is smeared out to form a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Ring_singularity" title="Ring singularity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ring singularity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">lying in the plane of rotation.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-47"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[48]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In both cases the singular region has zero volume. It can also be shown that the singular region contains all the mass of the black hole solution.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-48"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[49]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The singular region can thus be thought of as having infinite</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Mass_density" title="Mass density"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">density</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">An observer falling into a Schwarzschild black hole (i.e. non-rotating and no charges) cannot avoid the singularity. Any attempt to do so will only shorten the time taken to get there.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-49"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[50]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">When they reach the singularity, they are crushed to infinite density and their mass is added to the total of the black hole. Before that happens, they will have been torn apart by the growing</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Tidal_force" title="Tidal force"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">tidal forces</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in a process sometimes referred to as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Spaghettification" title="Spaghettification"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">spaghettification</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">or the noodle effect.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-50"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[51]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In the case of a charged (Reissner–Nordström) or rotating (Kerr) black hole it is possible to avoid the singularity. Extending these solutions as far as possible reveals the hypothetical possibility of exiting the black hole into a different spacetime with the black hole acting as a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Wormhole" title="Wormhole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">wormhole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-51"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[52]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The possibility of traveling to another universe is however only theoretical, since any perturbation will destroy this possibility.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-52"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[53]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">It also appears to be possible to follow</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Closed_timelike_curve" title="Closed timelike curve"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">closed timelike curves</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(going back to one's own past) around the Kerr singularity, which lead to problems with</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Causality_(physics)" title="Causality (physics)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">causality</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">like the</span><a href="http://en.wikipedia.org/wiki/Grandfather_paradox" title="Grandfather paradox"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">grandfather paradox</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-53"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[54]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">It is expected that none of these peculiar effects would survive in a proper quantum mechanical treatment of rotating and charged black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-54"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[55]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The appearance of singularities in general relativity is commonly perceived as signaling the breakdown of the theory.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-55"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[56]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This breakdown, however, is expected; it occurs in a situation where</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_mechanics" title="Quantum mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum mechanical</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">effects should describe these actions due to the extremely high density and therefore particle interactions. To date it has not been possible to combine quantum and gravitational effects into a single theory. It is generally expected that a theory of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_gravity" title="Quantum gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">will feature black holes without singularities.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-56"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[57]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-57"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[58]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Photon sphere</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Photon_sphere" title="Photon sphere"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Photon sphere</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The photon sphere is a spherical boundary of zero thickness such that</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Photon" title="Photon"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">photons</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">moving along</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Tangent" title="Tangent"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">tangents</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to the sphere will be trapped in a circular orbit. For non-rotating black holes, the photon sphere has a radius 1.5 times the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" title="Schwarzschild radius"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Schwarzschild radius</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The orbits are</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Instability" title="Instability"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">dynamically unstable</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, hence any small perturbation (such as a particle of infalling matter) will grow over time, either setting it on an outward trajectory escaping the black hole or on an inward spiral eventually crossing the event horizon.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">While light can still escape from inside the photon sphere, any light that crosses the photon sphere on an inbound trajectory will be captured by the black hole. Hence any light reaching an outside observer from inside the photon sphere must have been emitted by objects inside the photon sphere but still outside of the event horizon.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Other</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Compact_object" title="Compact object"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">compact objects</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, such as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Neutron_stars" title="Neutron stars"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">neutron stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, can also have photon spheres.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-58"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[59]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This follows from the fact that the gravitational field of an object does not depend on its actual size, hence any object that is smaller than 1.5 times the Schwarzschild radius corresponding to its mass will indeed have a photon sphere.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Ergosphere</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Ergosphere" title="Ergosphere"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Ergosphere</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:Ergosphere.svg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_7" o:spid="_x0000_i1037"
type="#_x0000_t75" alt="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Ergosphere.svg/220px-Ergosphere.svg.png"
href="http://en.wikipedia.org/wiki/File:Ergosphere.svg" style='width:165pt;
height:166.5pt;visibility:visible;mso-wrap-style:square' o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image010.png"
o:title="220px-Ergosphere.svg"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Ergosphere.svg/220px-Ergosphere.svg.png" border="0" height="222" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image011.gif" v:shapes="Picture_x0020_7" width="220" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><a href="http://en.wikipedia.org/wiki/File:Ergosphere.svg" title=""Enlarge" "><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_8"
o:spid="_x0000_i1036" type="#_x0000_t75" alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png"
href="http://en.wikipedia.org/wiki/File:Ergosphere.svg" title=""Enlarge""
style='width:11.25pt;height:8.25pt;visibility:visible;mso-wrap-style:square'
o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image012.gif"
o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_8" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The ergosphere is an oblate spheroid region outside of the event horizon, where objects cannot remain stationary.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Rotating black holes are surrounded by a region of spacetime in which it is impossible to stand still, called the ergosphere. This is the result of a process known as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Frame-dragging" title="Frame-dragging"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">frame-dragging</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">; general relativity predicts that any rotating mass will tend to slightly "drag" along the spacetime immediately surrounding it. Any object near the rotating mass will tend to start moving in the direction of rotation. For a rotating black hole this effect becomes so strong near the event horizon that an object would have to move faster than the speed of light in the opposite direction to just stand still.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-59"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[60]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The ergosphere of a black hole is bounded by the (outer) event horizon on the inside and an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Oblate_spheroid" title="Oblate spheroid"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">oblate spheroid</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which coincides with the event horizon at the poles and is noticeably wider around the equator. The outer boundary is sometimes called the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ergosurface</span></i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Objects and radiation can escape normally from the ergosphere. Through the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Penrose_process" title="Penrose process"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Penrose process</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, objects can emerge from the ergosphere with more energy than they entered. This energy is taken from the rotational energy of the black hole causing it to slow down.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-60"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[61]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div style="border-bottom: solid #AAAAAA 1.0pt; border: none; margin-left: 48.0pt; margin-right: 0cm; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-element: para-border-div; padding: 0cm 0cm 2.0pt 0cm;"> <div class="MsoNormal" style="border: none; margin-bottom: 7.2pt; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-line-height-alt: 10.35pt; mso-outline-level: 2; mso-padding-alt: 0cm 0cm 2.0pt 0cm; padding: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Formation and evolution</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Considering the exotic nature of black holes, it may be natural to question if such bizarre objects could exist in nature or to suggest that they are merely pathological solutions to Einstein's equations. Einstein himself wrongly thought that black holes would not form, because he held that the angular momentum of collapsing particles would stabilize their motion at some radius.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-61"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[62]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This led the general relativity community to dismiss all results to the contrary for many years. However, a minority of relativists continued to contend that black holes were physical objects,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-62"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[63]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and by the end of the 1960s, they had persuaded the majority of researchers in the field that there is no obstacle to forming an event horizon.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Once an event horizon forms,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Roger_Penrose" title="Roger Penrose"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Roger Penrose</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">proved that a singularity will form somewhere inside it.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-penrose1965-23"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[24]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Shortly afterwards,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stephen_Hawking" title="Stephen Hawking"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Stephen Hawking</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed that many cosmological solutions describing the</span><a href="http://en.wikipedia.org/wiki/Big_Bang" title="Big Bang"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Big Bang</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">have singularities without scalar fields or other exotic matter (see</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Penrose-Hawking_singularity_theorems" title="Penrose-Hawking singularity theorems"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Penrose-Hawking singularity theorems</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">). The</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Kerr_solution" title="Kerr solution"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Kerr solution</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/No-hair_theorem" title="No-hair theorem"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">no-hair theorem</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and the laws of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_hole_thermodynamics" title="Black hole thermodynamics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black hole thermodynamics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed that the physical properties of black holes were simple and comprehensible, making them respectable subjects for research.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-HawkingPenrose1970-63"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[64]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The primary formation process for black holes is expected to be the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_collapse" title="Gravitational collapse"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational collapse</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of heavy objects such as stars, but there are also more exotic processes that can lead to the production of black holes.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational collapse</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Gravitational_collapse" title="Gravitational collapse"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational collapse</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational collapse occurs when an object's internal</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Pressure" title="Pressure"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">pressure</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is insufficient to resist the object's own gravity. For stars this usually occurs either because a star has too little "fuel" left to maintain its temperature through</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stellar_nucleosynthesis" title="Stellar nucleosynthesis"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">stellar nucleosynthesis</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, or because a star which would have been stable receives extra matter in a way which does not raise its core temperature. In either case the star's temperature is no longer high enough to prevent it from collapsing under its own weight (the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Ideal_gas_law" title="Ideal gas law"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ideal gas law</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">explains the connection between pressure, temperature, and volume).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Carroll5.8-64"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[65]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The collapse may be stopped by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Degeneracy_pressure" title="Degeneracy pressure"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">degeneracy pressure</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of the star's constituents, condensing the matter in an exotic</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Degenerate_matter" title="Degenerate matter"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">denser state</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. The result is one of the various types of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Compact_star" title="Compact star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">compact star</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Which type of compact star is formed depends on the mass of the remnant — the matter left over after changes triggered by the collapse (such as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Supernova" title="Supernova"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">supernova</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">or pulsations leading to a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Planetary_nebula" title="Planetary nebula"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">planetary nebula</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">) have blown away the outer layers. Note that this can be substantially less than the original star — remnants exceeding 5 solar masses are produced by stars which were over 20 solar masses before the collapse.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Carroll5.8-64"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[65]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">If the mass of the remnant exceeds about 3–4 solar masses (the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit" title="Tolman–Oppenheimer–Volkoff limit"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Tolman–Oppenheimer–Volkoff limit</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">)—either because the original star was very heavy or because the remnant collected additional mass through accretion of matter—even the degeneracy pressure of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Neutrons" title="Neutrons"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">neutrons</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is insufficient to stop the collapse. After this, no known mechanism (except possibly quark degeneracy pressure, see</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quark_star" title="Quark star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quark star</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">) is powerful enough to stop the collapse and the object will inevitably collapse to a black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Carroll5.8-64"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[65]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This gravitational collapse of heavy stars is assumed to be responsible for the formation of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stellar_mass_black_hole" title="Stellar mass black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">stellar mass black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Star_formation" title="Star formation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Star formation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in the young universe may have resulted in very heavy stars, which upon their collapse would have produced black holes of up to 10<sup>3</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">solar masses. These heavy black holes could be the seeds of the supermassive black holes found in the centers of most galaxies.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-ReesVolonteri-65"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[66]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">While most of the energy released during gravitational collapse is emitted very quickly, an outside observer does not actually see the end of this process. Even though the collapse takes a finite amount of time from the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Reference_frame" title="Reference frame"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">reference frame</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of infalling matter, a distant observer sees the infalling material slow and halt just above the event horizon, due to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_time_dilation" title="Gravitational time dilation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational time dilation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Light from the collapsing material takes longer and longer to reach the observer, with the light emitted just before the event horizon forms delayed an infinite amount of time. Thus the external observer never sees the formation of the event horizon; instead, the collapsing material seems to become dimmer and increasingly red-shifted, eventually fading away.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-66"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[67]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 4;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Primordial black holes in the Big Bang</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational collapse requires great densities. In the current epoch of the universe these high densities are only found in stars, but in the early universe shortly after the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Big_bang" title="Big bang"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">big bang</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">densities were much greater, possibly allowing for the creation of black holes. The high density alone is not enough to allow the formation of black holes since a uniform mass distribution will not allow the mass to bunch up. In order for</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Primordial_black_holes" title="Primordial black holes"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">primordial black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to form in such a dense medium, there must be initial density perturbations which can then grow under their own gravity. Different models for the early universe vary widely in their predictions of the size of these perturbations. Various models predict the creation of black holes, ranging from a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Planck_mass" title="Planck mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Planck mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to hundreds of thousands of solar masses.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-67"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[68]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Primordial black holes could thus account for the creation of any type of black hole.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">High-energy collisions</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:CMS_Higgs-event.jpg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_9"
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o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_10" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">A simulated event in the CMS detector, a collision in which a micro black hole may be created.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational collapse is not the only process that could create black holes. In principle, black holes could also be created in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/High-energy_physics" title="High-energy physics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">high-energy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">collisions that create sufficient density. However, to date, no such events have ever been detected either directly or indirectly as a deficiency of the mass balance in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Particle_accelerator" title="Particle accelerator"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">particle accelerator</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">experiments.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-68"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[69]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This suggests that there must be a lower limit for the mass of black holes. Theoretically, this boundary is expected to lie around the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Planck_mass" title="Planck mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Planck mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(<i>m</i><sub>P</sub></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">=</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">√</span><a href="http://en.wikipedia.org/wiki/Reduced_Planck_constant" title="Reduced Planck constant"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ħ</span></i></a><a href="http://en.wikipedia.org/wiki/Speed_of_light" title="Speed of light"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">c</span></i></a><span style="border: solid windowtext 1.5pt; color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; padding: 0cm;">/</span><a href="http://en.wikipedia.org/wiki/Gravitational_constant" title="Gravitational constant"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">G</span></i></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">≈</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">1.2×10</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">19<br />
</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Electronvolt#As_a_unit_of_mass" title="Electronvolt"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">GeV/<i>c</i><sup>2</sup></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">≈</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">2.2×10</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">−8<br />
</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> kg), where quantum effects are expected to make the theory of general relativity break down completely.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-69"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[70]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This would put the creation of black holes firmly out of reach of any high energy process occurring on or near the Earth. Certain developments in quantum gravity however suggest that the Planck mass could be much lower: some</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Braneworld" title="Braneworld"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">braneworld</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">scenarios for example put it much lower, maybe even as low as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">1 TeV/<i>c</i><sup>2</sup></span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-70"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[71]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This would make it possible for</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Micro_black_hole" title="Micro black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">micro black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to be created in the high energy collisions occurring when cosmic rays hit the Earth's atmosphere, or possibly in the new</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Large_Hadron_Collider" title="Large Hadron Collider"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Large Hadron Collider</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">at</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/CERN" title="CERN"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">CERN</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. These theories are however very speculative, and the creation of black holes in these processes is deemed unlikely by many specialists.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-LHCsafety-71"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[72]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Even if such micro black holes should be formed in these collisions, it is expected that they would</span><a href="http://en.wikipedia.org/wiki/Black_hole_evaporation" title="Black hole evaporation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">evaporate</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in about 10<sup>−25</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">seconds, posing no threat to Earth</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-72"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[73]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Growth</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Once a black hole has formed, it can continue to grow by absorbing additional matter. Any black hole will continually absorb gas and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Interstellar_dust" title="Interstellar dust"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">interstellar dust</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">from its direct surroundings and omnipresent</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Cosmic_background_radiation" title="Cosmic background radiation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">cosmic background radiation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. This is the primary process through which supermassive black holes seem to have grown.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-ReesVolonteri-65"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[66]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">A similar process has been suggested for the formation of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Intermediate-mass_black_hole" title="Intermediate-mass black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">intermediate-mass black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Globular_cluster" title="Globular cluster"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">globular clusters</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-73"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[74]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Another possibility is for a black hole to merge with other objects such as stars or even other black holes. This is thought to have been important especially for the early development of supermassive black holes, which are thought to have formed from the coagulation of many smaller objects.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-ReesVolonteri-65"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[66]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The process has also been proposed as the origin of some</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Intermediate-mass_black_hole" title="Intermediate-mass black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">intermediate-mass black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-74"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[75]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-75"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[76]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Evaporation</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Hawking_radiation" title="Hawking radiation"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Hawking radiation</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1974,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stephen_Hawking" title="Stephen Hawking"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Stephen Hawking</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed that black holes are not entirely black but emit small amounts of thermal radiation.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Hawking1974-26"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[27]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">He got this result by applying</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_field_theory" title="Quantum field theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum field theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in a static black hole background. The result of his calculations is that a black hole should emit particles in a perfect</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_body_spectrum" title="Black body spectrum"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black body spectrum</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. This effect has become known as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Hawking_radiation" title="Hawking radiation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Hawking radiation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Since Hawking's result, many others have verified the effect through various methods.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-76"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[77]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">If his theory of black hole radiation is correct, then black holes are expected to emit a thermal spectrum of radiation, and thereby lose mass, because according to the theory of relativity mass is just highly condensed energy (<i>E</i> =</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">mc</span></i><sup><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">2</span></sup><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Hawking1974-26"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[27]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Black holes will shrink and evaporate over time. The temperature of this spectrum (</span><a href="http://en.wikipedia.org/wiki/Hawking_temperature" title="Hawking temperature"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Hawking temperature</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">) is proportional to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Surface_gravity" title="Surface gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">surface gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of the black hole, which for a Schwarzschild black hole is inversely proportional to the mass. Large black holes, therefore, emit less radiation than small black holes.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">A stellar black hole of one solar mass has a Hawking temperature of about 100</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Nanokelvin" title="Nanokelvin"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">nanokelvins</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. This is far less than the 2.7 K temperature of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Cosmic_microwave_background" title="Cosmic microwave background"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">cosmic microwave background</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Stellar mass (and larger) black holes receive more mass from the cosmic microwave background than they emit through Hawking radiation and will thus grow instead of shrink. To have a Hawking temperature larger than 2.7 K (and be able to evaporate), a black hole needs to be lighter than the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Moon" title="Moon"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Moon</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(and therefore a diameter of less than a tenth of a millimeter).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-77"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[78]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">On the other hand, if a black hole is very small the radiation effects are expected to become very strong. Even a black hole that is heavy compared to a human would evaporate in an instant. A black hole the weight of a car (~10<sup>−24</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">m) would only take a nanosecond to evaporate, during which time it would briefly have a luminosity more than 200 times that of the sun. Lighter black holes are expected to evaporate even faster, for example a black hole of mass 1 TeV/<i>c</i><sup>2</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">would take less than 10<sup>−88</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">seconds to evaporate completely. Of course, for such a small black hole</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_gravity" title="Quantum gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum gravitation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">effects are expected to play an important role and could even – although current developments in quantum gravity do not indicate so</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-78"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[79]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> – hypothetically make such a small black hole stable.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-79"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[80]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div style="border-bottom: solid #AAAAAA 1.0pt; border: none; margin-left: 48.0pt; margin-right: 0cm; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-element: para-border-div; padding: 0cm 0cm 2.0pt 0cm;"> <div class="MsoNormal" style="border: none; margin-bottom: 7.2pt; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-line-height-alt: 10.35pt; mso-outline-level: 2; mso-padding-alt: 0cm 0cm 2.0pt 0cm; padding: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Observational evidence</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">By their very nature, black holes do not directly emit any signals other than the hypothetical Hawking radiation; since the Hawking radiation for an astrophysical black hole is predicted to be very weak, this makes it impossible to directly detect astrophysical black holes from the Earth. A possible exception to the Hawking radiation being weak is the last stage of the evaporation of light (primordial) black holes; searches for such flashes in the past has proven unsuccessful and provides stringent limits on the possibility of existence of light primordial black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-80"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[81]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">NASA's</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Fermi_Gamma-ray_Space_Telescope" title="Fermi Gamma-ray Space Telescope"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Fermi Gamma-ray Space Telescope</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">launched in 2008 will continue the search for these flashes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-81"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[82]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Astrophysicists searching for black holes thus have to rely on indirect observations. A black hole's existence can sometimes be inferred by observing its gravitational interactions with its surroundings.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Accretion of matter</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">See also:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Accretion_disc" title="Accretion disc"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Accretion disc</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:Black_hole_jet_diagram.jpg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_11"
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o:title="220px-Black_hole_jet_diagram"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Black_hole_jet_diagram.jpg/220px-Black_hole_jet_diagram.jpg" border="0" height="194" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image014.jpg" v:shapes="Picture_x0020_11" width="220" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><a href="http://en.wikipedia.org/wiki/File:Black_hole_jet_diagram.jpg" title=""Enlarge" "><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape
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o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_12" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Formation of extragalactic jets from a black hole's</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Accretion_disc" title="Accretion disc"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">accretion disk</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Due to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Conservation_of_angular_momentum" title="Conservation of angular momentum"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">conservation of angular momentum</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, gas falling into the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_well" title="Gravitational well"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational well</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">created by a massive object will typically form a disc-like structure around the object. Friction within the disc causes angular momentum to be transported outward allowing matter to fall further inward releasing potential energy and increasing the temperature of the gas.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-McClintockRemillard2006-82"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[83]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In the case of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Compact_object" title="Compact object"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">compact objects</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">such as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/White_dwarf" title="White dwarf"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">white dwarfs</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Neutron_star" title="Neutron star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">neutron stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and black holes, the gas in the inner regions becomes so hot that it will emit vast amounts of radiation (mainly X-rays), which may be detected by telescopes. This process of accretion is one of the most efficient energy producing process known; up to 40% of the rest mass of the accreted material can be emitted in radiation.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-McClintockRemillard2006-82"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[83]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(In nuclear fusion only about 0.7% of the rest mass will be emitted as energy.) In many cases, accretion discs are accompanied by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Relativistic_jets" title="Relativistic jets"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">relativistic jets</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">emitted along the poles, which carry away much of the energy. The mechanism for the creation of these jets is currently not well understood.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">As such many of the universe's more energetic phenomena have been attributed to the accretion of matter on black holes. In particular,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Active_galactic_nucleus" title="Active galactic nucleus"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">active galactic nuclei</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quasar" title="Quasar"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quasars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">are thought to be the accretion discs of supermassive black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Similarly, X-ray binaries are thought to be</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Binary_star" title="Binary star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">binary star</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">systems in which one of the two stars is a compact object accreting matter from its companion.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">It has also been suggested that some</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Ultraluminous_X-ray_source" title="Ultraluminous X-ray source"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ultraluminous X-ray sources</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">may be the accretion disks of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Intermediate-mass_black_hole" title="Intermediate-mass black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">intermediate-mass black holes</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-84"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[85]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">X-ray binaries</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">See also:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/X-ray_binary" title="X-ray binary"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">X-ray binary</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><a href="http://en.wikipedia.org/wiki/X-ray_binaries" title="X-ray binaries"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">X-ray binaries</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">are</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Binary_star" title="Binary star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">binary star</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">systems that are luminous in the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/X-ray" title="X-ray"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">X-ray</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">part of the spectrum. These X-ray emissions are generally thought to be caused by one of the component stars being a compact object accreting matter from the other (regular) star. The presence of an ordinary star in such a system provides a unique opportunity for studying the central object and determining if it might be a black hole.<o:p></o:p></span></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:Accretion_Disk_Binary_System.jpg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_13"
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o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_14" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Artist impression of a binary system with an accretion disk around a compact object being fed by material from the companion star.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">If such a system emits signals that can be directly traced back to the compact object, it cannot be a black hole. The absence of such a signal does, however, not exclude the possibility that the compact object is a neutron star. By studying the companion star it is often possible to obtain the orbital parameters of the system and obtain an estimate for the mass of the compact object. If this is much larger than the Tolman–Oppenheimer–Volkoff limit (that is, the maximum mass a neutron star can have before collapsing) then the object cannot be a neutron star and is generally expected to be a black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The first strong candidate for a black hole,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Cygnus_X-1" title="Cygnus X-1"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Cygnus X-1</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, was discovered in this way by</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Charles_Thomas_Bolton" title="Charles Thomas Bolton"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Charles Thomas Bolton</span></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-85"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[86]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/w/index.php?title=Louise_Webster&action=edit&redlink=1" title="Louise Webster (page does not exist)"><span style="color: #cc2200; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Webster</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/w/index.php?title=Paul_Murdin&action=edit&redlink=1" title="Paul Murdin (page does not exist)"><span style="color: #cc2200; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Murdin</span></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-86"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[87]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in 1972.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-87"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[88]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-88"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[89]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Some doubt, however, remained due to the uncertainties resultant from the companion star being much heavier than the candidate black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Currently, better candidates for black holes are found in a class of X-ray binaries called soft X-ray transients.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In this class of system the companion star is relatively low mass allowing for more accurate estimates in the black hole mass. Moreover, these systems are only active in X-ray for several months once every 10–50 years. During the period of low X-ray emission (called quiescence), the accretion disc is extremely faint allowing for detailed observation of the companion star during this period. One of the best such candidates is</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/V404_Cyg" title="V404 Cyg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">V404 Cyg</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 4;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Quiescence and advection-dominated accretion flow</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The faintness of the accretion disc during quiescence is thought to be caused by the flow entering a mode called an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Advection-dominated_accretion_flow" title="Advection-dominated accretion flow"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">advection-dominated accretion flow</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(ADAF). In this mode, almost all the energy generated by friction in the disc is swept along with the flow instead of radiated away. If this model is correct, then it forms strong qualitative evidence for the presence of an event horizon.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-89"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[90]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Because, if the object at the center of the disc had a solid surface, it would emit large amounts of radiation as the highly energetic gas hits the surface, an effect that is observed for neutron stars in a similar state.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-McClintockRemillard2006-82"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[83]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 4;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Quasi-periodic oscillations</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 11.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">See also:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Quasi-periodic_oscillations" title="Quasi-periodic oscillations"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Quasi-periodic oscillations</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The X-ray emission from accretion disks sometimes flickers at certain frequencies. These signals are called</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quasi-periodic_oscillations" title="Quasi-periodic oscillations"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quasi-periodic oscillations</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and are thought to be caused by material moving along the inner edge of the accretion disk (the innermost stable circular orbit). As such their frequency is linked to the mass of the compact object. They can thus be used as an alternative way to determine the mass of potential black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-90"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[91]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gamma ray bursts</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Intense but one-time</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gamma_ray_burst" title="Gamma ray burst"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gamma ray bursts</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(GRBs) may signal the birth of "new" black holes, because astrophysicists think that GRBs are caused either by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_collapse" title="Gravitational collapse"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational collapse</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of giant stars</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-91"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[92]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">or by collisions between neutron stars,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Harvard.edu-NeutronStars-92"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[93]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and both types of event involve sufficient mass and pressure to produce black holes. It appears that a collision between a neutron star and a black hole can also cause a GRB,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-93"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[94]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">so a GRB is not proof that a "new" black hole has been formed. All known GRBs come from outside our own galaxy, and most come from billions of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Light_year" title="Light year"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">light years</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">away</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-94"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[95]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">so the black holes associated with them are billions of years old.<o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Galactic nuclei</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">See also:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Active_galactic_nucleus" title="Active galactic nucleus"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Active galactic nucleus</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:M87_jet.jpg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_15" o:spid="_x0000_i1029"
type="#_x0000_t75" alt="http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/M87_jet.jpg/220px-M87_jet.jpg"
href="http://en.wikipedia.org/wiki/File:M87_jet.jpg" style='width:165pt;
height:172.5pt;visibility:visible;mso-wrap-style:square' o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image016.jpg"
o:title="220px-M87_jet"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/M87_jet.jpg/220px-M87_jet.jpg" border="0" height="230" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image016.jpg" v:shapes="Picture_x0020_15" width="220" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><a href="http://en.wikipedia.org/wiki/File:M87_jet.jpg" title=""Enlarge" "><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_16"
o:spid="_x0000_i1028" type="#_x0000_t75" alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png"
href="http://en.wikipedia.org/wiki/File:M87_jet.jpg" title=""Enlarge""
style='width:11.25pt;height:8.25pt;visibility:visible;mso-wrap-style:square'
o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image012.gif"
o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_16" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The jet originating from the center of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Messier_87" title="Messier 87"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M87</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">in this image comes from an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Active_galactic_nucleus" title="Active galactic nucleus"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">active galactic nucleus</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">that may contain a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Supermassive_black_hole" title="Supermassive black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">supermassive black hole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Credit:</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Hubble Space Telescope</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">/</span><a href="http://en.wikipedia.org/wiki/NASA" title="NASA"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">NASA</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">/</span><a href="http://en.wikipedia.org/wiki/ESA" title="ESA"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">ESA</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">It is now widely accepted that the center of every or at least nearly every galaxy contains a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Supermassive_black_hole" title="Supermassive black hole"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">supermassive black hole</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-King-95"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[96]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The close observational correlation between the mass of this hole and the velocity dispersion of the host galaxy's bulge, known as the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/M-sigma_relation" title="M-sigma relation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M-sigma relation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, strongly suggests a connection between the formation of the black hole and the galaxy itself.</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-msigma2000-96"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[97]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">For decades, astronomers have used the term "</span><a href="http://en.wikipedia.org/wiki/Active_galaxy" title="Active galaxy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">active galaxy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">" to describe galaxies with unusual characteristics, such as unusual</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Spectral_line" title="Spectral line"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">spectral line</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">emission and very strong radio emission.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-krolik1999-97"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[98]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-sparkegallagher2000-98"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[99]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">However, theoretical and observational studies have shown that the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Active_galactic_nucleus" title="Active galactic nucleus"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">active galactic nuclei</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">(AGN) in these galaxies may contain supermassive black holes.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-krolik1999-97"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[98]</span></sup></a><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-sparkegallagher2000-98"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[99]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The models of these AGN consist of a central black hole that may be millions or billions of times more massive than the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Sun" title="Sun"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sun</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">; a disk of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Interstellar_gas" title="Interstellar gas"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gas</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Interstellar_dust" title="Interstellar dust"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">dust</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">called an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Accretion_disc" title="Accretion disc"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">accretion disk</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">; and two</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Relativistic_jet" title="Relativistic jet"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">jets</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">that are perpendicular to the accretion disk.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-sparkegallagher2000-98"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[99]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Although supermassive black holes are expected to be found in most AGN, only some galaxies' nuclei have been more carefully studied in attempts to both identify and measure the actual masses of the central supermassive black hole candidates. Some of the most notable galaxies with supermassive black hole candidates include the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Andromeda_Galaxy" title="Andromeda Galaxy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Andromeda Galaxy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Messier_32" title="Messier 32"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">M32</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, M87,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/NGC_3115" title="NGC 3115"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">NGC 3115</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/w/index.php?title=NGC_3377&action=edit&redlink=1" title="NGC 3377 (page does not exist)"><span style="color: #cc2200; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">NGC 3377</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/NGC_4258" title="NGC 4258"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">NGC 4258</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, and the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Sombrero_Galaxy" title="Sombrero Galaxy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sombrero Galaxy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-kormendyrichstone1995-99"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[100]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Currently, the best evidence for a supermassive black hole comes from studying the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Proper_motion" title="Proper motion"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">proper motion</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of stars near the center of our own</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Milky_Way" title="Milky Way"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Milky Way</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Gillessen-100"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[101]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Since 1995 astronomers have tracked the motion of 90 stars in a region called</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Sagittarius_A*" title="Sagittarius A*"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sagittarius A*</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. By fitting their motion to</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Keplerian_orbit" title="Keplerian orbit"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Keplerian orbits</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">they were able to infer in 1998 that 2.6 million</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Solar_mass" title="Solar mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">solar masses</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">must be contained in a volume with a radius of 0.02</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Lightyear" title="Lightyear"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">lightyears</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Ghez1998-101"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[102]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Since then one of the stars—called</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/S2_(star)" title="S2 (star)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">S2</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">—has completed a full orbit. From the orbital data they were able to place better constraints on the mass and size of the object causing the orbital motion of stars in the Sagittarius A* region, finding that there is a spherical mass of 4.3 million solar masses contained within a radius of less than 0.002 lightyears.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Gillessen-100"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[101]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">While this is more than 3000 times the Schwarzschild radius corresponding to that mass, it is at least consistent with the central object being a supermassive black hole, and no "realistic cluster [of stars] is physically tenable."</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Ghez1998-101"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[102]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational lensing</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Further information:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Gravitational_lens" title="Gravitational lens"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Gravitational lens</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The deformation of spacetime around a massive object causes light rays to be deflected much like light passing through an optic</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Lens_(optics)" title="Lens (optics)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">lens</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. This phenomenon is known as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gravitational_lensing" title="Gravitational lensing"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">gravitational lensing</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Observations have been made of weak gravitational lensing, in which</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Photon" title="Photon"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">photons</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">are deflected by only a few</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Arcseconds" title="Arcseconds"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">arcseconds</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. However, it has never been directly observed for a black hole.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Valerio-102"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[103]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">One possibility for observing gravitational lensing by a black hole would be to observe stars in orbit around the black hole. There are several candidates for such an observation in orbit around</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Sagittarius_A*" title="Sagittarius A*"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Sagittarius A*</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-Valerio-102"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[103]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Alternatives</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The evidence for stellar black holes strongly relies on the existence of an upper limit for the mass of a neutron star. The size of this limit heavily depends on the assumptions made about the properties of dense matter. New exotic</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Phase_(matter)" title="Phase (matter)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">phases of matter</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">could push up this bound.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">A phase of free</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quark" title="Quark"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quarks</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">at high density might allow the existence of dense</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quark_star" title="Quark star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quark stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-103"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[104]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and some</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Supersymmetry" title="Supersymmetry"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">supersymmetric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">models predict the existence of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Q_star" title="Q star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Q stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-104"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[105]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Some extensions of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Standard_model" title="Standard model"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">standard model</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">posit the existence of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Preon" title="Preon"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">preons</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">as fundamental building blocks of quarks and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Lepton" title="Lepton"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">leptons</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">which could hypothetically form</span><a href="http://en.wikipedia.org/wiki/Preon_star" title="Preon star"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">preon stars</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-105"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[106]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">These hypothetical models could potentially explain a number of observations of stellar black hole candidates. However, it can be shown from general arguments in general relativity that any such object will have a maximum mass.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Since the average density of a black hole inside its Schwarzschild radius is inversely proportional to the square of its mass, supermassive black holes are much less dense than stellar black holes (the average density of a 10<sup>8</sup></span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">solar mass black hole is comparable to that of water).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Consequently, the physics of matter forming a supermassive black hole is much better understood and the possible alternative explanations for supermassive black hole observations are much more mundane. For example, a supermassive black hole could be modelled by a large cluster of very dark objects. However, typically such alternatives are not stable enough to explain the supermassive black hole candidates.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-CMS1999-83"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[84]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The evidence for stellar and supermassive black holes implies that in order for black holes not to form, general relativity must fail as a theory of gravity, perhaps due to the onset of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_mechanics" title="Quantum mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum mechanical</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">corrections. A much anticipated feature of a theory of quantum gravity is that it will not feature singularities or event horizons (and thus no black holes).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-106"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[107]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In recent years, much attention has been drawn by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Fuzzball_(string_theory)" title="Fuzzball (string theory)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">fuzzball</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">model in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/String_theory" title="String theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">string theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Based on calculations in specific situations in string theory, the proposal suggest that generically the individual states of a black hole solution do not have an event horizon or singularity (and can thus not really be considered to be a black hole), but that for a distant observer the statistical average of such states does appear just like an ordinary black hole in general relativity.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-107"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[108]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div style="border-bottom: solid #AAAAAA 1.0pt; border: none; margin-left: 48.0pt; margin-right: 0cm; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-element: para-border-div; padding: 0cm 0cm 2.0pt 0cm;"> <div class="MsoNormal" style="border: none; margin-bottom: 7.2pt; mso-border-bottom-alt: solid #AAAAAA .75pt; mso-line-height-alt: 10.35pt; mso-outline-level: 2; mso-padding-alt: 0cm 0cm 2.0pt 0cm; padding: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Open questions</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 14.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Entropy and thermodynamics</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Further information:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Black_hole_thermodynamics" title="Black hole thermodynamics"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Black hole thermodynamics</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><div align="center" class="MsoNormal" style="background: #F9F9F9; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/File:First_Gold_Beam-Beam_Collision_Events_at_RHIC_at_100_100_GeV_c_per_beam_recorded_by_STAR.jpg"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 9.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_17"
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o:title="magnify-clip"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" border="0" height="11" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif" v:shapes="Picture_x0020_18" width="15" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="background: #F9F9F9; line-height: 16.8pt; margin-bottom: 9.6pt; margin-left: 64.8pt; margin-right: 0cm; margin-top: 0cm;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">If ultra-high-energy collisions of particles in a</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Particle_accelerator" title="Particle accelerator"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">particle accelerator</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">can create microscopic black holes, it is expected that all types of particles will be emitted by black hole evaporation, providing key evidence for any</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Grand_unified_theory" title="Grand unified theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">grand unified theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">. Above are the high energy particles produced in a gold ion collision on the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Relativistic_Heavy_Ion_Collider" title="Relativistic Heavy Ion Collider"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">RHIC</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 8.5pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.<o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">In 1971,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Stephen_Hawking" title="Stephen Hawking"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Stephen Hawking</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed under general conditions</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-108"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[Note 1]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">that the total area of the event horizons of any collection of classical black holes can never decrease, even if they collide and merge.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-109"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[109]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">This result, now known as the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Second_law_of_black_hole_mechanics" title="Second law of black hole mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">second law of black hole mechanics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, is remarkably similar to the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Second_law_of_thermodynamics" title="Second law of thermodynamics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">second law of thermodynamics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which states that the total</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Entropy" title="Entropy"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">entropy</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">of a system can never decrease. As with classical objects at</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Absolute_zero" title="Absolute zero"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">absolute zero</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">temperature, it was assumed that black holes had zero entropy. If this were the case, the second law of thermodynamics would be violated by entropy-laden matter entering the black hole, resulting in a decrease of the total entropy of the universe. Therefore,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Jacob_Bekenstein" title="Jacob Bekenstein"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Jacob Bekenstein</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">proposed that a black hole should have an entropy, and that it should be proportional to its horizon area.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-wald99-110"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[110]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">The link with the laws of thermodynamics was further strengthened by Hawking's discovery that</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_field_theory" title="Quantum field theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum field theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">predicts that a black hole radiates</span><a href="http://en.wikipedia.org/wiki/Blackbody_radiation" title="Blackbody radiation"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">blackbody radiation</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">at a constant temperature. This seemingly causes a violation of the second law of black hole mechanics, since the radiation will carry away energy from the black hole causing it to shrink. The radiation, however also carries away entropy, and it can be proven under general assumptions that the sum of the entropy of the matter surrounding the black hole and one quarter of the area of the horizon as measured in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Planck_units" title="Planck units"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Planck units</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">is in fact always increasing. This allows the formulation of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/First_law_of_black_hole_mechanics" title="First law of black hole mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">first law of black hole mechanics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">as an analogue of the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/First_law_of_thermodynamics" title="First law of thermodynamics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">first law of thermodynamics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, with the mass acting as energy, the surface gravity as temperature and the area as entropy.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-wald99-110"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[110]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">One puzzling feature is that the entropy of a black hole scales with its area rather than with its volume, since entropy is normally an</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Extensive_quantity" title="Extensive quantity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">extensive quantity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">that scales linearly with the volume of the system. This odd property led</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Gerard_%27t_Hooft" title="Gerard 't Hooft"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">'t Hooft</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Leonard_Susskind" title="Leonard Susskind"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Susskind</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">to propose the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Holographic_principle" title="Holographic principle"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">holographic principle</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which suggests that anything that happens in volume of spacetime can be described by data on the boundary of that volume.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-111"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[111]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Although general relativity can be used to perform a semi-classical calculation of black hole entropy, this situation is theoretically unsatisfying. In</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Statistical_mechanics" title="Statistical mechanics"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">statistical mechanics</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, entropy is understood as counting the number of microscopic configurations of a system which have the same macroscopic qualities (such as</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Mass" title="Mass"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">mass</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Charge_(physics)" title="Charge (physics)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">charge</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Pressure" title="Pressure"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">pressure</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, etc.). Without a satisfactory theory of</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Quantum_gravity" title="Quantum gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">quantum gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, one cannot perform such a computation for black holes. Some progress has been made in various approaches to quantum gravity. In 1995,</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Andrew_Strominger" title="Andrew Strominger"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Strominger</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">and</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/w/index.php?title=Cumrum_Vafa&action=edit&redlink=1" title="Cumrum Vafa (page does not exist)"><span style="color: #cc2200; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Vafa</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">showed that counting the microstates of a specific</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Supersymmetry" title="Supersymmetry"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">supersymmetric</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black hole in</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/String_theory" title="String theory"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">string theory</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">reproduced the Bekenstein–Hawking entropy.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-112"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[112]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Since then, similar results have been reported for different black holes both in string theory and in other approaches to quantum gravity like</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Loop_quantum_gravity" title="Loop quantum gravity"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">loop quantum gravity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">.</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-113"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[113]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal" style="margin-bottom: 3.6pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm; mso-line-height-alt: 10.35pt; mso-outline-level: 3;"><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Black hole unitarity</span></b><b><span style="color: black; font-family: "Arial","sans-serif"; font-size: 13.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div><div class="MsoNormal" style="line-height: 10.35pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 0cm;"><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Main article:</span></i><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Black_hole_information_paradox" title="Black hole information paradox"><i><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Black hole information paradox</span></i></a><i><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></i></div><table border="1" cellpadding="0" cellspacing="0" class="MsoNormalTable" style="background-attachment: initial; background-clip: initial; background-color: #f9f9f9; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; border-bottom-style: none; border-collapse: collapse; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial; margin-left: 60pt; width: 346px;"><tbody>
<tr style="mso-yfti-firstrow: yes; mso-yfti-irow: 0;"> <td colspan="2" style="border: none; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: 12.0pt; text-align: center;"><a href="http://en.wikipedia.org/wiki/Unsolved_problems_in_physics" title="Unsolved problems in physics"><b><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Unsolved problems in physics</span></b></a><b><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></b></div></td> </tr>
<tr style="mso-yfti-irow: 1; mso-yfti-lastrow: yes;"> <td style="border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 12.0pt;"><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Is</span></i><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><a href="http://en.wikipedia.org/wiki/Physical_information" title="Physical information"><i><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">physical information</span></i></a><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span></i><i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">lost in black holes?</span></i><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> <td style="border-left: none; border: solid #AAAAAA 1.0pt; mso-border-alt: solid #AAAAAA .75pt; mso-border-left-alt: solid #AAAAAA .75pt; padding: 2.4pt 2.4pt 2.4pt 2.4pt;"> <div class="MsoNormal" style="line-height: normal; margin-bottom: 12.0pt;"><a href="http://en.wikipedia.org/wiki/File:Question_mark2.svg"><span style="color: #0645ad; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN; mso-no-proof: yes; text-decoration: none; text-underline: none;"><!--[if gte vml 1]><v:shape id="Picture_x0020_19"
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height:39pt;visibility:visible;mso-wrap-style:square' o:button="t"> <v:fill o:detectmouseclick="t"/> <v:imagedata src="file:///C:\Users\TOSHIBA\AppData\Local\Temp\msohtmlclip1\01\clip_image018.png"
o:title="Question mark2"/> </v:shape><![endif]--><!--[if !vml]--><span style="mso-ignore: vglayout;"><img alt="Question mark2.svg" border="0" height="52" src="file:///C:/Users/TOSHIBA/AppData/Local/Temp/msohtmlclip1/01/clip_image019.gif" v:shapes="Picture_x0020_19" width="40" /></span><!--[endif]--></span></a><span style="color: black; font-family: "Times New Roman","serif"; font-size: 10.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div></td> </tr>
</tbody></table><div class="MsoNormal" style="line-height: 18.0pt; margin-bottom: 6.0pt; margin-left: 48.0pt; margin-right: 0cm; margin-top: 4.8pt;"><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">An open question in fundamental physics is the so-called information loss paradox, or</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Black_hole_information_paradox" title="Black hole information paradox"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">black hole unitarity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">paradox. Classically, the laws of physics are the same run forward or in reverse (</span><a href="http://en.wikipedia.org/wiki/T-symmetry" title="T-symmetry"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">T-symmetry</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">).</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Liouville%27s_theorem_(Hamiltonian)" title="Liouville's theorem (Hamiltonian)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">Liouville's theorem</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">dictates conservation of phase space volume, which can be thought of as "conservation of information", so there is some problem even in classical physics. In quantum mechanics, this corresponds to a vital property called</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Unitarity_(physics)" title="Unitarity (physics)"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">unitarity</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">, which has to do with the conservation of probability (it can also be thought of as a conservation of quantum phase space volume as expressed by the</span><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"> </span><a href="http://en.wikipedia.org/wiki/Density_matrix" title="Density matrix"><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">density matrix</span></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">).</span><a href="http://en.wikipedia.org/wiki/Black_hole#cite_note-PlayDice000-114"><sup><span style="color: #0645ad; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-bidi-font-size: 11.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;">[114]</span></sup></a><span style="color: black; font-family: "Arial","sans-serif"; font-size: 7.0pt; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: IN;"><o:p></o:p></span></div><div class="MsoNormal"><br />
</div>katalog baju bandunghttp://www.blogger.com/profile/11320702173725403635noreply@blogger.com0tag:blogger.com,1999:blog-5317012378092323923.post-13698764064999300852011-01-18T02:12:00.000-08:002011-01-18T02:12:33.533-08:00maraknya katalog distro bandungSiapa yang ga kenal sama distro bandung seperti black id,cosmic,diery dan lainnya yang sudah menguasai distro di seluruh indonesia..produk yang selalu up to date,selalu di minati oleh kawula muda yang ada di seluruh indonesia...tapi sayang mereka tidak menyediakan katalog fisik,karena apa? di tiap kota besar yang ada di indonesia pasti sudah sedia outletnya..hebat bukan? kemajuan yang sangat luar biasa...eiit tapi tunggu dulu ada juga distro yang sebagian besar pemasaranya melalui katalog..seperti g-shop dan catenzo.<br />
Melihat kesuksesan g-shop dan catenzo yang sudah semakin terkenal pula di kalangan remaja dari sabang sampai merauke..kini bermunculan produk2 katalog distro terbaru seperti ricbers dan cbr six,yang memang semuanya belum saya tampilkan di sini..tp g lama lagi pasti saya tampilkan semua produk katalog distro nya disini..so..tunggu aja y tanggal mainnya...g lama lagi katalog baru nya bakal muncul..<br />
yups..salam kenal.katalog baju bandunghttp://www.blogger.com/profile/11320702173725403635noreply@blogger.com0