Re: opposite of relativistic time contraction

IsaacKuo wrote:
> On Mar 14, 4:54 pm, Ben Crowell
> <crowel...@[EMAIL PROTECTED]
> wrote:
> 
>> A somewhat related question is what is the simplest/cheapest/least
>> disruptive way for such a godlike species to apply large accelerations
>> to observers for a long time without ripping them apart with tidal
>> forces.
> 
> If you're going to use black holes, don't use a single black hole.
> You can minimize the tidal effects by creating a large 2d plane.
> This would involve a bunch of small black holes--one in the center,
> and the rest in circular orbits around the center.  The bulk of
> the star****p is in "front" of this plane, and accelerates the
> black hole array forward by gravity.

That makes sense. Ideally, you'd build the gravitational equivalent
of a flat capacitor plate, whose field is uniform. I think it helps,
but maybe not as much as you'd think. The single number that's
driving most of the difficulties here is the m=10^17 kg of the
black hole. That mass was set by the requirement that the tidal
forces not be too strong for the desired acceleration. With that
mass, you also get r=100 m for the distance that the passengers have
to be from the black hole. You can indeed reduce m by shaping the
field like this, but essentially r has to get smaller. 100 m is
already pretty darn close to be getting to a black hole. If you
reduce r to 10 m, then the total mass of your pancake-swarm of black
holes can be 100 times smaller than what we've been discussing.
The price you pay for that is that the payload's volume is now
pretty limited, and you have a pretty scary situation, where there
are black holes whizzing around outside the ****tholes almost
close enough to reach out and touch. (Careful where you toss the
garbage!) The reduction in mass is good, but I don't think it
qualitatively changes any of the considerations we've been discussing.

One thing that wasn't obvious to me was whether gravitational
radiation from the orbiting black holes would be significant.
I've tried to estimate it, and the result I get is that the
radiated power is about 10^-15 W, so that would be negligible.
The whole thing does probably have to be externally stabilized
by electric or magnetic forces, though. And that leads to the
issue of how you propel the whole thing and keep it
electromagnetically stable. It's not obvious to me whether
a solution exists, and whether such a solution avoids frying
the crew with electromagnetic radiation or gigantic DC fields.
The solution I'd been talking about involved putting magnetic
monopole charge on the black holes. If you then move them in
circular orbits, I guess you end up creating electric
fields.