Warp wrote:
>   General relativity predicts one thing, quantum mechanics another. Why
> must GR be wrong and QM right? Why couldn't it be the other way around?

Did it say GR is wrong? That quote just says it conflicts.

(FWIW, I'm seeing more articles that imply GR is going to loose to QM than 
vice versa, but that might just be because it's easier to experiment on QM 
than on GR.)

>   I'm not sure that's exactly correct.

It's definitely a weird situation. I think the progress of time for someone 
falling in seems to be asymptotically zero, but I don't know that means 
anything for anyone outside or inside the doomed spacecraft.

>   While from the outside point of view the object never actually reaches
> the event horizon,

Why not?  It doesn't slow down - it just moves slower *inside* the space 
ship, yes?

> and consequently the frequency of the emitted light
> never reaches true zero, there's probably a limit to how low the frequency
> can be for it to be observed (as there are such limits in almost everything
> related to quantum particles).

I think that's quite the problem there. That's where GR and QM disagree: QM 
says there are lower limits on size, frequency, etc, while GR says space is 
smooth and continuous.

>   I don't really understand how the same object can both repel (with
> antigravity) and attract (with gravity) at the same time. Isn't that
> a bit contradictory? Which is it?

That does indeed sound strange. Perhaps if either one of us were deeply 
schooled in this... :-)

>   The article doesn't claim that time dilation near massive objects doesn't
> happen. It just says that time dilation near the event horizon of a black
> hole causes problems with respect to quantum mechanics.

I think it's saying the singularity causes the problem with QM, not the 
event horizon. Specifically, when the black hole evaporates due to Hawking 
radiation, you've lost the information (namely, the spin and charge and 
such) of the particles that fell in.

With a big enough black hole, you'll never know when you cross the event 
horizon. If your event horizon is galaxy-sized, the gravitational gradient 
is very mild.

> If these dark stars
> behave externally so much like black holes that they would be very hard to
> distinguish from them, how does it solve any such "problem"?

There wouldn't need to be a singularity in the middle of the black hole. 
If/when it evaporates, all the stuff that fell in can come back out the same 
way.

I think. I am not a cutting-edge theoretical physicist.

-- 
   Darren New, San Diego CA, USA (PST)
   Why is there a chainsaw in DOOM?
   There aren't any trees on Mars.

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