Orchid XP v8 wrote:
> So I suppose "how many points are there on the unit square" comes down 
> to "are the coordinates rational?"

Draw a dot at sqrt(2),sqrt(2).

> Oh. You mean something *outside* the mass itself causes it to become a 
> black hole?

Yes.

> But then, wouldn't that just mean that as soon as you remove the force, 
> it wouldn't be a black hole any more?

No.  Science!

(Altho there's arguments over whether quantum effects would eventually make 
a black hole too small to form on its own evaporate, but I didn't take that 
to be what you meant.)

>> Sure, the relative speed of light can even be superluminal.
> 
> No, it cannot.

It can travel faster than the speed of light in the medium in which it's 
traveling.

> This is exactly what relativity states. The speed of light, no matter 
> which way you measure it, is always constant. (Except as noted below.)

The speed of light in a vacuum is always constant. That doesn't mean it 
can't travel faster than the speed of light in the medium in which it is 
traveling.

> This part is correct. And I would expect light entering or leaving a 
> different medium to exhibit Doppler shift as a result (although it 
> doesn't seem to do this...)

That's not how light slows down. Light slows because it is being absorbed 
and re-emitted, not because the speed per se is different in different 
media.  The train always travels the same speed - but sometimes it stops at 
more stations.

> Wait - you actually use a sophisticated electronic accounting package 
> just for your home finance?

Yes. It's not all that sophisticated.

-- 
Darren New, San Diego CA, USA (PST)
  "How did he die?"   "He got shot in the hand."
     "That was fatal?"
          "He was holding a live grenade at the time."

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