e envelope (solid arrow). The interior constantly loses energy to the envelope and ultimately to outer space because of the flow of radiation from the core, through the envelope to the photosphere, and to space as the sun shines (Shipman 26).When a star exhausts its nuclear fuel and collapses under its own weight, it begins to shrink in size. If the core of the star is massive enough the collapsing star will shrink to a point where the gravity will become strong enough to trap even light (Shipman 24). Such strong gravity disturbs space and causes a black hole to have some certain properties like event horizon. Event horizon is a spherical surface that marks boundary of the black hole. As soon as matter passes through the horizon it cant get back out, it will move closer to black holes center approaching singularity (Bunn). In 1969, American relativist John Wheeler named these massive collapsed stars as black holes (Gribbin and White 74).The idea that a star can shrink and result in a great concentration of mass goes back to the 18th century. In the early 18th century, Isaac Newton researched and experimented with light. From his experiments he concluded the corpuscular theory of light, which states that light consists of tiny particles that move in straight lines at great speeds (Comptons Multimedia Encyclopedia). The French mathematician Pierre Simon de Laplace, in 1796, reasoned that light particles could not escape from a massive body (Shipman 65). The scientists disregarded Laplaces theory, until Albert Einstein in 1916 came up with the theory of relativity (Shipman 65). In theory of relativity Einstein stated that gravity is not a force but a curved field in the space-time continuum that is created by the presence of mass (Comptons Multimedia Encyclopedia). Not long after Einstein developed the theory of relativity, the German astronomer Karl Schwarzschild calculated how compressed an object with a given mass (in this case a star...
