Darren New <dne### [at] sanrrcom> wrote:
> If you take the Earth and condense it down to a black hole, then stop a
> particle in orbit 100 miles above where the surface used to be, the particle
> will accelerate towards the black hole, right? But to avoid crossing the
> event horizon, it must logically decelerate, as seen from the POV of someone
> in orbit (say).  You wouldn't stop at the original altitude of the surface,
> but you would stop before you get to the event horizon, so in this case,
> gravity must be causing you to decelerate.  Yes?

Depends on definition if speed, but as it is usually specified based on the
observer's timeframe: Yes. Gravitation near a black hole is so strong that -
from an observer's POV - through time delation and the warping of space it
causes "that poor old sod over there" to slow to a halt.

From that poor old sod's perspective, gravitation near a black hole is so strong
that it keeps speeding him up - his feet much stronger than his head (if he
plunges in feet first) - until he is ripped to isolated subatomic particles.

Paradoxically, while this happens, I think that he will at the same time see his
feet slow down to a standstill, just as an outside observer would. So maybe he's
not torn apart after all..!?!

(In a similarly paradoxical fashion, the particles at his head can still easily
influence those at his feet - but the influence of the feet particles on the
head particles will drastically diminish (remember them sending out less
photons?)

This actually shows that gravitation is a quite strange beast in the zoo of
forces: The influence of gravitation does *not* diminish while closing in on a
black hole.

So either gravitation cannot be a "normal" QM-style force (else the object would
send out fewer and fewer gravitons as its own timeframe slows down with respect
to an outside observer) - or the object's e=mc^2 increases towards infinity as
it comes close to the event horizon, but why should it? After all, we have seen
that from an outsider's point of view the object actually slows to a halt.

Hum... sounds to me like bad news for the people at the LHC - and speaks for the
"gravitation = spacetime geometry" view of GR.

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