The Non-porn Black Holes

I told Fish I would post a link to this article. For a good description without getting too technical check out the Bad Astronomy blog post, here. Now I'm going to try to explain it in even simpler terms, and probably screw it up completely.

So, you probably know that a black hole is made when an extremely massive star collapses in on itself all the way down to a single point of extremely high gravity. The gravity of a black hole is so high that when you get a certain distance from it not even light can escape. This distance is called the event horizon.

OK, still with me? Now we get to the good stuff. Einstein theorized, and observations have begun to show, that as gravity increases, the flow of time slows down. This means an observer looking at the formation of a black hole from the outside would see a star begin to collapse, and then slow down in it's rate as the gravity increases. As the gravity of the black hole approaches infinity, then the flow of time approaches zero, so technically from the frame of reference outside the black hole it would take an infinite amount of time to form a perfect black hole (a point of infinite mass).

Now, we also know that black holes leak out mass, a process called Hawking Radiation, and eventually evaporate (in just a few billion years). The thing is, the Hawking Radiation isn't really affected by the time dilation of the enormous gravity. This means that the black hole will evaporate before ever forming an event horizon. It will approach it, however it would take an infinite amount of time to actually get there and it's lifetime is finite. So to sum up, in theory light cannot escape the gravitational pull of a black hole, but in practice black holes may never be able to reach that point since they have a limited lifetime. Neat stuff!