Black Holes
Uploaded by Admin on Jan 22, 1999
Within our galaxy alone, there are millions upon millions of stars. Within our universe, there are millions upon millions of galaxies. Humans have known the existance of stars since they have had eyes. Although interpretations may have differed on what they were, they were always thought of as white glowing specks in the sky, but the mystery does not lie within what we can see, but what we can not see. There are billions of stars lighting the darkness of our universe, but the question lies in what happens when one of these enormous lamps burns out. Upon many speculations, one of the most facinating is the black hole theory. Not any star can become a Black Hole. For instance, the possibility of our sun becoming a black hole is highly unlikely, simply because it is too small. Only a very large star has the potential to become a black hole.
The definitions of black boles are somewhat sceptical. Generally, a black hole is an area of super-concentrated mass. So concentrated, that no object can escape its gravitational pull. In other words, once you get caught by it's graviational pull, you aren't getting out again. The velocity you need to break away from a graviational pull is called the "escape velocity". Roughly, earth's escape velocity is about 25,000 M.P.H. (11.2 kilometers/second). Earth's mass is nothing compared to the mass of a star that has the potential to become a black hole. A black hole has so much mass in such a small area, that its escape velocity is greater than the speed of light. So if were all living on earth, and earth was a black hole, we would need to go at the speed of light in order to get to the moon (and not to mention a lot of milk so our bones could support 800 million ton human beings).
Even though a black hole's gravitational pull is enormous, it does have its boundry. This boundry is called the "event horizon". This event horizon is the point where the black hole's gravitational pull begins. Once you cross the event horizon, there is no turning back. As stated before, the escape velocity of a black hole exceeds the speed of light, and since going faster than the speed of light is impossible, so is escaping a black hole's gravitational pull. This explains why all the black holes do not swallow everything...