(..) And, indeed, how the universe works. Narrator: Their power comes From one of the primary forces in nature -- gravity. Dr. Kaku: I teach astronomy. And we teach our students That the fundamental principle of gravity is, "gravity sucks." (..)

(..) A black hole is pretty much the end point of everything. It's the end point of a star. It's the end point of matter. It's the end point of energy. It's the end point of gravity. I mean, that's really it. That's the top of the scale. Narrator: Although they have the power to destroy (..)