Re: Another dumb black hole question (charge and acceleration)
- From: Luke Campbell <lwcamp@xxxxxxxxx>
- Date: Sun, 30 Mar 2008 23:45:51 -0700 (PDT)
On Mar 30, 11:03 am, sigidu...@xxxxxxxxx wrote:
If we assume antigravity is possible, that implies we could get out of
an event horizon. Does this mean that, in certain extreme
circumstances, antigravity would be equivalent to time travel?
Sort of. The proof that nothing can escape from within a black hole's
event horizon depends on certain assumptions about how energy
behaves. In particular, if you can have regions where the energy
density is negative, the proof breaks down. Negative energy density
also gives "repulsive" gravity, along with faster than light travel
and (usually) time travel. Since the even horizon is essentially
where you can't escape without FTL travel, once you have this kind of
antigravity, you can bust out of a black hole.
And guess what, the region of space just outside of a black hole's
even horizon has a negative energy density. Curious, eh? (Actually,
this is what allows a black hole to decay away by emitting Hawking
radiation.)
Luke
.
- References:
- Another dumb black hole question (charge and acceleration)
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