Re: OT: Dyson's Disaster

I wrote:
>Anton Sherwood wrote:
>> > Lars Henrik Mathiesen wrote:
>> >> 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.
>>
>>Andreas Johansson wrote:
>> > Actually, displacing the sun from the centre won't change anything
>> > (except the depth of your tan!) for the same reason that it won't be
>> > any force from the sphere on the sun. . . .
>>
>>But there is a force from the sun on each part of the sphere.  The
>>forces are globally balanced, but the local mass doesn't know that. ;)
>>
>>If the sphere is infinitely rigid, of course, that's not a problem.
>
>I may be wrong, but I think the sphere'll act as an arch, and therefore
>won't need to be extremely strong to survive that effect.
>
>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. Tip: Get a spacesuit and don't make a polar picnic.
Also, filling the sphere with air at one atmosphere of pressure requires
about a thousand solar masses of gaseous nitrogen and oxygen. A such mass
won't be particularly stable - maybe we'll see a really weird supernova,
maybe the thing'd just collapse into a singularity.

                                                          Andreas

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