On Jun/22/2018 Ã* 5:45 PM, JF Mezei Wrote :
On 2018-06-22 07:18, Jeff Findley wrote:

Because it's flexible, duh. Imagine that you took 10 meters of fishing
line with a weight at the bottom then cut it in the middle. Would it
stay straight as it fell? Try it!


This does not consider/test the issue that the top of the cable is
travelling at faster speed and as it is being pulled down, will
accelerate further. If the top of the cable wants to travel faster than
the bottom part of cable, a tension will exist which would not exist in
your fishing line example, and that tension should keep the cable straight.

That tension you talk about is caused by the centrifugal pseudo-force.
In the fishing line example Jeff gave there is the gravitational force
that should pull the line down.

In both cases, when the fishing line or the elevator cable snaps the
elasticity pulls back with more force than the gravity or centrifugal
force. With the caveat that we don't know what material would be used
for the hypothetical space elevator, so we don't know how elastic it
would be. But I think it is a safe assumption that if such an elevator
was to ever be built, the material would be sufficiently elastic for
tens of thousands of kilo-meters of it to give a very strong pull back.


Alain Fournier