Black Holes

Black holes have been studied extensively, but even today little is fully understood about them because they cannot be directly observed. Sometime in the 18th century, John Michell and Pierre-Simon Laplace became the first to consider the possibility of objects whose field of gravity would be too strong for even light to escape. In 1916, Karl Schwarzchild was responsible for the first modern theory of general relativity containing a black hole. Theoretical work concerning black holes began during the 1960s.

A black hole is created when a star many times larger than our own sun reaches supernova. Afterward, the star is overcome by the force of its gravity pulling inward and essentially "eats" itself. The final stage of a star's life, known as supernova, causes an explosion that scatters the star's matter into space. This results in a "cold" remnant where fusion ceases to occur.

Nothing, not even light, can escape the awesome gravitational pull of a black hole at a critical distance. This critical distance is referred to as the event horizon, and it is the space around the core, called the singularity, of a black hole. A rotating black hole has several event horizons, namely the ergosphere, outer event horizon, and inner event horizon. It is impossible for matter to escape the event horizon because that requires moving faster than the speed of light, which cannot be done.

Stephen Hawking showed in 1974 that black holes aren't really black. They emit tiny amounts of thermal radiation. The effect in which these particles are emitted is known as Hawking radiation.

Upon entering a black hole, any object would be crushed at an atomic level or lower and bombarded with radiation, and will be fully destroyed upon reaching the Singularity. A black hole shrinks to zero volume, becoming infinitely dense. Black holes suck matter and energy in, but to no greater degree than our own sun's gravitational pull. There are tiny black holes and extremely large black holes, even in the Milky Way.

Over time, black holes grow smaller due to x-ray emission, and eventually disappear. This disappearance is referred to as "evaporation".

Sources:

"Black Holes, Black Hole Information, Facts, News, Photos -- National Geographic", National Geographic
Daniel Rebecchi, "Black Hole Facts", Black Holes Webquest
"Black Hole", Wikipedia