On 13/11/2012 4:04 AM, clipka wrote:
> Am 12.11.2012 19:50, schrieb Le_Forgeron:
>
>> But on the upper/bottom side(circle) of the torus, it seems that, if the
>> ground is just along the torus, the direction of a free water surface
>> would not be parallel to the ground. Wouldn't there be a kind of
>> desert/cliff making the transition on the small circle between both
>> region ? would it be some desert or waterfall ?
>
> Of course the gound itself, being subject to the same gravitational
> effcts, would settle in a non-perfect toroidal shape. (Similar to how
> the earth's shape is not spherical, due to the gravitational forces at
> the equator being partially offset by centrifugal forces.)
>

I did some quick calculations and knowing that the centripetal force is 
equal to minus the angular velocity squared times the radius times the 
mass (F = -W^2*r*m).
If the torus was revolving around its centre once in 24 hours. On the 
inner surface the force would be about 0.508g and on the outside surface 
0.529g. If the period was 12 hours the forces would be 2.03g and 2.116g 
respectively. Note the sleight of hand going from force to acceleration ;-)

This is not a stable configuration. If there was a star in the centre of 
the torus. Any slight movement of the torus to the centre would be 
magnified by the closer part being attracted to the star more than the 
part that is further away. Starting a wobble that would end up looking 
like a hula hoop.

Never the less a nice concept and image.

-- 
Regards
     Stephen

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