From: Reason (reason@exratio.com)
Date: Fri May 17 2002 - 01:33:25 MDT
-->Damien Broderick
>
> Wei Dai said
>
> >MBrains will want to be in stealth mode (envelop
> >your star in a shell and dump waste heat into a black hole) and hide from
> >each other.
>
> I was charmed by this black hole idea, which I haven't seen
> before in quite
> that form. It strikes me that one might prefer to have at least two holes
> on orthogonal orbits, and a perfect mirror on the outer shell that would
> reflect all and only incident stellar light and background radiation--but
> enough with the pesky details. My question:
>
> Is it terribly bad just to dump the degraded waste heat back on
> the central
> star? It might burn faster, but that's all the more useful energy, no? and
> you can always move, later on.
I used to simulate stellar interiors (photosphere down) for a couple of
years; we'd do a lot of strange stuff in the process of bootstrapping the
software towards simulating real stars. One thing I recall is that stars are
very sensitive to what you do with the outermost layers; the gradients in
temperature, density, pressure, radiation pressure and ion abundances in a
stable star change more in the outermost 1% of radius than in the preceeding
50%.
Without digging out the code, I'll take an educated guess at pumping heat
back into the upper levels of the star being a Bad Thing. You'd end up with
something that looked like it was trying to be a cross between a slow nova
and a transition from main sequence to giant; it certainly wouldn't be a
stable system; at the most basic level a star is something that produces
heat as a consequence of being above a certain energy-density threshhold.
I'm not sure on timescales for that, however.
(Anyone have a reference for that study from a decade or so back on how to
provoke a nova using a really big gamma ray laser? I wanted to compare the
output of that to the stellar output...)
> And is it in fact feasible to turn all your heat noise into, say, IR laser
> light and beam it that accurately at black holes?
Much better. Laser heat radiation is a good thing.
Reason
http://www.exratio.com/
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