Re: Gravitational field visualization

On Wed, 28 Jan 2009 11:49:47 -0800, Erik Max Francis <max@xxxxxxxxxxx>
wrote:

Arthur T. wrote:
In Message-ID:<haGdnSSc0rvmhh3UnZ2dnUVZ_jULAAAA@xxxxxxxxxxxxx>,
Erik Max Francis <max@xxxxxxxxxxx> wrote:
Arthur T. wrote:

Has anyone done the math of the effective force on an
"inhabitant" of such a disk if it's rotating? How large could the
habitable area be made such that gravity combined with centrifugal
force yields something close to 90 degrees?
Centrifugal pseudoforce will push them outward, not inward. It will
exacerbate the effect, and it goes linearly across the disc.

Thanks for that correction. I was thinking that a push outward
is what's wanted to counteract the actual gravity pulling you
inwards. I didn't think about the fact that the centrifugal push is
being given to your feet, not your center of gravity. Thus, you're
probably right that it's in the wrong direction.

Right. It's the old centripetal/centrifugal gag again. The rotating
disk undergoes centripetal acceleration by definition. But to something
near/on/around the disc, it's not experience that centripetal
acceleration, and so wants to continue moving in a straight line. From
its point of view, it's (local region of) the disc that's accelerating.

Sorry, Eric, but your correction is in error;
Isaac is correct. You *want* the centrifugal force
to push you outward. Looking at your vector map,
each vector has a discward component and an
centerward component, and the centerward
component is, at least near the center, nearly
proportional to distance from the center. The
centrifugal force provides an edgeward component
which can nearly completely cancel the centerward
component, leaving only a discward component.
This can be done with a rigid disc.
--
Doesn't the fact that there are *exactly* 50 states seem a little suspicious?

George W. Harris For actual email address, replace each 'u' with an 'i'
.

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