TITLE: Is it possible to escape from within event horizon?
QUESTION [5 upvotes]: I always think that it is not possible to escape from within event horizon. However, some one recently told me with deep conviction that it is possible with sustained energy output. I countered with calculations in Schwarzschild metric showing that any objects below event horizon in the simplistic black hole will hit the singularity within a finite proper time, and  was met with the response that Schwarzschild metric was a bad choice for coordinate system.
Now I understand that the singularity at $r=\frac{2GM}{c^2}$ in Schwarzschild metric is an artifact of the coordinate choice, and thus it seems that he could have a point. So my question is, can one prove that it is (or not) possible to escape from within the event horizon of a simple static black hole using a better metric?

REPLY [0 votes]: I'm thinking that they're looking at an extended Kerr diagram and stating that every past horizon is paired with a future horizon, where it is possible to escape back out to a "black hole exterior":
http://jila.colorado.edu/~ajsh/insidebh/penrose_kerr.gif
It should be stated, however, that this exterior is a different one than the one from which you entered, and the boundary conditions that led to the formation of the black hole, specifically, the fact that the hole formed out of collapsing matter and will eventually decay into hawking radiation, will kill the magic, and you won't even get this structure of escaping back out into something that has a conformal infinity again  (other than just escaping the black hole after it has evaporated).
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