Black Holes

Black Holes

Since their theoretical existence was first proposed in 1783 by English geologist John Michell, black holes have remained one of astronomy’s greatest mysteries. In his paper to the Royal Society of England, Michell explained that a star approximately 500 times greater in diameter than our sun and of the same density would have an escape velocity (the speed at which an object must travel in order to break free from a body’s gravitational field) greater than the speed of light, thus effectively making the body invisible. Although Michell did not believe the existence of such a body was likely, he did consider the possibility that black holes could physically exist somewhere in the universe. Most scientist’s believed black holes could not be formed in nature until 1939, when Robert J. Oppenheimer explained how a star could become so massive that it might collapse under it’s own mass. It was now believed that black holes could, and more than likely were, formed in nature relatively frequently as neutron stars condensed into ultra-dense points of mass.

The formation of a black hole occurs through the process of gravitational collapse. Gravitational collapse is the sudden inward fall of a massive body under the influence of the force of it’s own gravity. As a result, it is impossible for anything, even light, to escape a black hole once it has passed the Event Horizon. Also known as “the point of no return” the Event Horizon is a sphere around the black hole that marks the limits of it’s gravitational pull. This is what allows scientists to see black holes. Once something is past the event horizon, it is sent into an infinite spiral (in the case of rotating black holes) in which the mass is brought to the point of singularity. Singularity is the theory that all mass entering a black hole is compressed into a single tiny point that becomes so dense, all known laws of physics and gravity do not apply. It can only be described by the use of Quantum physics and the controversial “string theory”.

No one has ever actually seen a black hole, doing so would be impossible as no electromagnetic waves are able to escape the pull of it’s gravity. However scientists can almost completely prove their existence by observing visible light, x-ray, and gamma radiation given off by nearby stars, and it’s curvature due to the black holes immense gravitational effect. Using this technique, dozens of black holes have been found, including one at the center of a galaxy