[ExI] Earth hoola hoop generator/transport ?

[Anders Sandberg]

On 2013-12-22 02:03, Alex Blainey wrote:
>
> I had a crazy idea while designing an integrated solar panel roof 
> system the other day. What if we make a maglev track around the 
> equator, build a big solid continuous train on it like a hoola hoop 
> around the world.
> Would it start to rotate with no driving force other than Earths 
> rotation? Effectivley it would actually be standing still and the 
> planet continuing to do what it does and rotating underneath it.

Is there a constant wind at the equator due to the Earth's rotation? No. 
The train will be at rest relative to the ground when it starts 
levitating and there is no force on it. And if it had any velocity, 
friction with the surroundings would slow it down (even in an evacuated 
tunnel there are always some losses, including ohmic electrical losses 
due to vortex currents).

>
> Then it got really wierd. What would happen to such a stationary (non 
> rotating from a helio centric point of view) object? I personally 
> believe that Earths orbit around the sun is partly a reaction to teh 
> gravitational pull from the sun.

Uh. How much physics do you know? Earth orbits *because* of gravity. And 
yes, something that lacked orbital velocity would just fall in. Move 30 
km/s back from Earth, and you will fall in. But if you do it on a track 
around Earth you only cancel the attraction from the Sun, not from the 
Earth. However, if you move fast enough you (8 km/s) get to surface 
orbital speed - you will be in orbit on ground level.



-- 
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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