Theoretical Black Hole

Armed with Einstein’s theories, the German astronomer Karl Schwarzschild (1873-1916) developed the idea of the black hole as we know it today. He did not call it a black hole. This term was first used in the late 1960s by the American physicist John Wheeler. Before Wheeler, they were called “Frozen stars”.Reference for Technorati
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Dark Stars

Pierre Laplace (1749-1827), a French mathematician and astronomer, was one of the first people suggest that black holes could exist. As an expert on celestial Mechanics, he knew how the planets and moons move around the sun. In his book, Exposition of the System of the world, published in 1795, Laplace made an amazing prediction. Laplace realized that if a star were massive enough, its escape velocity would be greater than the speed of light. So he calculated how big a star would have to be, if it had the same overall density as Earth, to have an escape velocity equal to the speed of light. He calculated that the star would have to be 250 times the diameter of the Sun. Laplace predicted that a star of this size would have such an enormous gravitational pull that light particles would have such an enormous gravitational pull that light particles would never leave its surface. The star would be invisible.

Light and gravity

When Sir Isaac Newton devised his Law of universal Gravitation, he also suggested that light was subjected to the pull of gravity. On Earth, light always travels in a straight line, unless it hits an object. But light does bend as it passes close to bodies with very strong gravitational fields, such as very massive stars. This shows that the things we take for granted on Earth do not necessarily apply when super strong gravity is at work.

Black Hole

A black hole is a place in space where gravity is so super strong that nothing can escape it not even light. When scientists call a black hole a giant cosmic vacuum, they do not mean it sucks up anything that comes near it. However, anything passing close to a black hole will be affected by its strong gravitational pull. Astronomers think that events become very strange both near and inside black holes. The known world ceases to exist, time slows down, space is warped, and the accepted laws of physics no longer apply. No one should go into a mysterious black hole to investigate, because they would never return.
In most great mysteries, such as UFOs, science tries to explain the strange things that people claim to have seen. In the case of black holes, however things are the other way around. Scientists predicted the existence of black holes long before there was any real evidence that they existed. In fact, the very nature of black holes means they cannot be seen to be believed!