What Is a Black Hole?

If you accept the general relativity view of it, black holes are kind of a hole in space. It makes a portion of space that's cut off from the rest of the universe. You can still see out from it, but nobody can see into it. The simplest black hole would be a perfect sphere and you can fall into it from any direction. But actually, if you look at a blackhole, you don't even really just see a black sphere. Daniel: "It looks like a bigger black circle than it actually is"