Black holes are one of the more bizarre and intriguing predictions of .
Surprisingly, there is now a great deal of observational .
evidence that black holes do exist, both in binary star systems and at the center of most .
galaxies, including our own. Although we are gaining more knowledge of black holes, .
they still remain one of the strangest things anyone has ever heard of, and we may never .
know what exactly one of these things are and can do. It is impossible to manufacture .
black holes in a laboratory. The density of matter required is too great. In order to make a .
black hole the size of a baseball, you would have to pack all the matter in and on the .
Earth into a volume the size of a fist. Nature can make black holes, however. Matter .
naturally collapses unless there is some other force to hold it up. The objects in a room .
are kept from collapsing by electromagnetic forces. The gas in an active star is held up by .
thermal pressure. However, once a star uses up its thermonuclear fuel, it starts to .
collapse, and if there is enough mass to overcome other, microscopic forces, it collapses .
into a black hole. According to Einstein's theory, if we could pack enough matter into a .
small enough volume, the thing created inside will get so deep that the matter inside can .
never escape. A circle of no return forms. Any matter that passes the point of no return .
can no longer escape to the outside world. It necessarily keeps collapsing, moving .
towards the center. It gets deeper and deeper until finally a hole is literally torn in the .
fabric of spacetime: the density of matter at the center becomes essentially infinite. Thus, .
what is meant by "a hole in the fabric of spacetime" is: a tiny region of space where the .
known laws of physics break down. A black hole is a region of space so tightly packed .
with matter, that nothing, not even light can escape. Hidden at its center is a tear in the .