From: Mike Lorrey (mlorrey@datamann.com)
Date: Fri May 17 2002 - 11:21:41 MDT
Damien Broderick wrote:
>
> At 05:49 AM 5/17/02 -0700, Robert wrote:
>
> >A normal Dyson Sphere doesn't work because, like a Niven
> >Ring, its not strong enough to support itself against
> >the gravitational pull of the star. But one can imagine
> >a sphere that could support itself against the gravitational
> >mass of a planet, moon, etc. (provided you have a way to
> >pin it in place as mentioned).
Actually, Niven rings don't work because of gravitational stability, not
material strength, while Dyson Spheres have a problem with supporting
themselves at the poles (though I would expect that gravitational
attraction at the poles would translate through the spherical structure
to tension at the equator), their spinning around the star should
provide enoughstability in two dimensions, I wasn't aware that the light
and solar wind pressure wouldn't stabilize a sphere against
gravitational instabilities (though, likely only at a certain diameter
for any given star).
In any event, one thing I haven't seen anybody propose with dyson
spheres around stars are EM field generators to give additional
stability. I know I've seen it proposed for spheres around black holes
(as Damien did in White Abacus.
The problem is, as in all engineering, the materials. Niven invented
'scrith' for his novels to get around this, and I know we've talked
about buckyfiber as a material in this app before.
>
> Shepherd black holes in circular orbit just inside and outside the shell,
> like those buggers in Saturn's rings? Or does that process only produce
> stability in dust?
Wasn't aware there were black holes in Saturn's rings. The accepted
wisdom is that rings are only stable in the long term, without active
measures, as dust or other mass quantities of discrete objects. Thus,
Criswell Spheres have been proposed along those lines, which Brin played
on in the second Uplift trilogy.
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