this post was submitted on 05 Oct 2023
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[–] [email protected] 8 points 1 year ago (4 children)

This would be possible if there was a material unaffected by gravity, right?

[–] [email protected] 9 points 1 year ago (2 children)

I think in that case, the earth would just depart the location of the train, leaving it drifting in space.

[–] [email protected] 2 points 1 year ago

I was assuming the rails are strong enough to keep the train on the Earth, but I guess infinite friction from the movement and rotation of the Earth probably isn't survivable by any railway material. Hypothetically, if you had a material unaffected by gravity (train), and a material that is absolutely invincible (the rails, and they are anchored to the center of the Earth), now does it work?

[–] [email protected] 7 points 1 year ago* (last edited 1 year ago)

No, the problem is not gravity, is that the train attached to earth has velocity dictated by the Earth movements, and keeps it because of inertia. In your theoretical experiment, the train would be launched on space at constant velocity.

[–] [email protected] 4 points 1 year ago

The problem isn't gravity, it's friction. The train would functionally be in orbit. The reason why things can't be in orbit at ground level is not because of gravity but because of friction (incl. air resistance).

If you eliminated friction (vacuum tube, frictionless surface, etc.) you could indeed have the train moving without any additional energy after getting it up to speed (and if you get it up to orbital speeds, the frictionless surface isn't even necessary). However, this isn't really practical (obviously).

If there is a nugget of a good idea in here, it's a train that never needs to accelerate or decelerate, just maintain a constant speed. Much of the energy of a train is lost in the stop-and-start.