Gravitational Radius

The French Mathematician Pierre Laplace used Newton’s laws to calculate the size of a body that would stop light from escaping. Karl Schwarzschild calculated at what distance from the center of a body the escape velocity would be the speed of light. He used Einstein’s relativity theory. Remember that the force of gravity between two objects gets greater as the objects get close together. At a certain distance from a body, the gravity becomes so great that the escape velocity becomes greater than the Speed of light.
Schwarzschild calculated the relationship between this distance from a body’s center and the mass of the body. This distance is known as the Schwarzschild radius. For bodies such as planets and stars, Schwarzschild’s radius is mush smaller than the body. For example for Earth it is less than one half of an inch, and it is about one and a half miles for the sun.
Schwarzschild’s theory was that a black hole was formed if the gravitational radius of a body was larger than its actual radius. This means a body would have to be squeezed into an extremely tiny space. For example, Earth would have to be squashed to the size of a pea for it to become a Black hole.

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
NHXCGTRF55NT

Changing the Rules

There are two important differences between Laplace’s idea of a dark star and the modern idea of a Black hole. The differences are due to two important discoveries of modern astrophysics. The first discovery is that nothing can travel faster than light. This means that if light cannot escape from a massive star, nothing can. This also means that a dark star is a hole, because nothing that is pulled in by the star’s gravity can never escape. The second difference is that Laplace used Newton’s law of gravity as the basis of his work. Modern astrophysics says that these laws do not work in and around Black holes.

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.

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!