Re: Rzeczpospolita,was: Hi from Ukraine

> Date:         Tue, 4 Dec 2001 13:14:59 -0000
> From: Fabian <fabian@...>
>
> > On Tue, 4 Dec 2001, D Tse wrote:
> > > Anyone else's people live on a ringworld or (yikes!) a Dyson sphere?
>
> Anyone who wants realistic science will be in for a shock. I have been
> nformed by many people wiser than myself than the gravity of the inside of
> a ringworld or a Dyson sphere will be zero.
I thought this was well known in science fiction circles...

The sphere or ring itself will not exert any gravitational attraction
on matter inside them --- but the sun in the center of the system
still will. Since you usually want to have people on the inside to
take advantage of the sunlight, this will tend to make them fly off
the surface.

For a ringworld, this is easily fixed by spinning it. A Dyson sphere
can be spun as well, but that will not make anything stay put in the
polar regions --- including the atmosphere.

And there's the question of the dynamical stability of the whole
thing. The central sun won't be attracted to the ring or sphere, by
the same argument, but neither will there be any force tending to keep
it in the center. And once the sun moves off center I think the
nearest part of the structure must flex towards it, which will cause a
net force to make it move even more.

Lars Mathiesen (U of Copenhagen CS Dep) <thorinn@...> (Humour NOT marked)

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