Thank you everyone for your answer.I'll do more research.
My project is just a high school project and I didn't learn any of string in class. I just want to know how GR tell us that it's not have anything that can escape from black hole.
I do a little project about photon at the event horizon. I use GR to proved that anything in the event horizon can't escape from black hole, but a Prof. say that I must use string theory.But I did't accept with him.So, if someone know about it.Please Help me :cry: .
(I have to tell you that...