Okay, let’s say we have something like Cloud City.
Cool? It has a certain gravitational potential energy, and just by keeping itself up it doesn’t change that potential energy. So it shouldn’t require any energy to keep it up, which is consistent, with say, having cloud city resting on a solid object.
But let’s say cloud city can only use jet engines to keep it up. If I point my jet engines down to keep the city up, aren’t I expending kinetic energy to keep it up?
Now I’d understand if it were in orbit or something, it wouldn’t use any kinetic energy, but if I have to use rocket jets, aren’t I expending kinetic energy to keep it up? I realize that it doesn’t violate conservation of energy since the KE from the rocket just becomes heat, but still, it doesn’t really make sense to me.
If it requires nothing, shouldn’t there be a way to keep it up without going into orbit and without using any energy?
