Re: OT: Dyson's Disaster

Lars Henrik Mathiesen wrote:
> > From: Anton Sherwood <bronto@...>
> >
> > Andreas Johansson wrote:
> > > Another problem: While the sphere won't be attracting anything inside
>it,
> > > any bodies within it will attract eachother, wherefore air will be
> > > dropping into the sun. Spinning the sphere won't help, since the air
>at
> > > the poles would still fall into the sun, creating a low pressure that
> > > sucks in more air und so weiter.
> >
> > The poles would then be effectively at high altitude.
> > Does the low pressure on mountaintops suck in air from below?
>
>Good point --- the mid latitudes will effectively be mountainsides
>climbing into airless space. As noted already: As you move away from
>the equator of sphere, the resultant force (sum of solar gravity and
>centrifugal force) will be at an angle to the surface; at some point
>it will be parallel to it, and everything will slide back towards the
>equator.
>
>So yes, if you fill the whole sphere with air, most of it will fall
>into the sun, but there'll be a broad equatorial belt that can retain
>an atmosphere. And the solar wind won't be blowing it away, it'll add
>to it instead.
Hm, to avoid falling into the star, the air must be going at least orbital
speed at that distance. Therefore the sphere must be spinning at orbital
speed too (otherwise friction'll slow down the gas). But orbital speed will
differ at different height in the air, producing friction anyway. If the
whole system spins at orbital speed for the innermost gas, the outer bits'll
rotate too quickly, pushing against the sphere, and lose energy, therefore
decrease in speed, thus causing friction again.

The atmo"sphere" would essentially be a gas belt oribiting the star, and
such are inherently unsable.

I think the only practical way to live on the inside of a Dyson sphere would
be to construct some sort of "tents" or "bubbles" to keep your air in.
Preferably, these should also block the nastier bits of the star's radiation
(x-rays, far UV, protons etc).

                                               Andreas

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