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Boardwalk around the earth...


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Lets say all of humanity gets together and builds a massive boardwalk that surrounds the earth about the equator. The boardwalk is 1 mile off of the ground. Then all of the supports for the walkway are taken down at the same time.

 

WOULD IT FLOAT??!?!?

 

Assume that gravity is somehow perfectly evenly distributed.

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no material known has the compressive strength to withstand the forces involved.

 

but even if you invent some unobtanium that can then it still won't work as it is an inherently unstable construction. even the minor perturbations from external gravity sources(moon, sun, jupiter, even people walking around) would destabilize it and contact with the ground would be made.

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If the gravity acting on it were perfectly evenly distributed, then it would probably. Why not?

 

assuming it were strong enough to take the stresses on the structure, then it would be incredibly unstable, since any slight deviation from perfect coincidence of the centers of gravity would pull the thing down somewhere. Such deviations are inevitable, for example the moon as mentioned in the post above.

 

It would not however be strong enough to take the stresses and strains, for the same reason that arches can only be built so big.

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I think that "perfectly evenly distributed" means that the Earth is a perfect sphere, has a constant density throughout, and there are no outside sources of gravity.

I would assume that if it was built from a sturdy material and gravity on it was perfectly balanced, it would float, but only until people started walking on it.

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making it spin fast will only decrease the compressive stresses it needs to withstand. it will not make it any more stable with regard to perturbations.

 

in the perfectly ideal universe where there is only a perfectly spherical uniformly dense earth and a perfectly circular perfectly uniform ring, then it'd work. but only until you introduce some non-uniformity. even quantum fluctuations would be enough to throw this thing off eventually. it may take thousands of years for the perturbation to grow large enough to be measurable but it'd happen.

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C'mon now, haven't you guys ever read Niven's "Ringworld"? All you need to do is build it out of scree, have some auto-fired rockets to keep it in place, and call on Louis Wu when things screw up.

 

You mean scrith. Building it out of scree doesn't make much sense. And technically they weren't rockets. They were giant ramjets, fueled by directed solar flares. So that's what we need.

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C'mon now, haven't you guys ever read Niven's "Ringworld"? All you need to do is build it out of scree, have some auto-fired rockets to keep it in place, and call on Louis Wu when things screw up.

Well, I am not sure I can help.

I'm afraid I did not build the Ringworld; I only went there for the rishathra.

 

 

A non orbital ring system is gravitationally stable to perturbations normal to the plane of the ring but is inherently gravitationally unstable to perturbations within the plane of the ring.

Placing the ring so close to the surface of the Earth makes the situation worse by allowing very little time for corrective action before the collision. At 1 mile high you are still in the atmosphere so a simple weather system such as a depression will start the inevitable fall to Earth.

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You mean scrith. Building it out of scree doesn't make much sense. And technically they weren't rockets. They were giant ramjets, fueled by directed solar flares. So that's what we need.

 

Thanks for the correction. :doh: It has been about 30 years since I read any of the series, shoulda checked.

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