Hi everyone I had this very silly question pop up that unfortunately I cannot find an answer to myself. If an object - say, a hot-air balloon - flies at a low altitude above the Earth, it will of course remain above the same spot; you could I guess say that it rotates together with the Earth. However, if the balloon were to rise at a much higher altitude, I'd think that, at some point it will stop being "connected" to the mass of air rotating together with the planet, and it is conceivable that, watching from up there straight down, one would not see the same spot but whatever part of the Earth happens to be immediately underneath at that time, due to the rotation. This reasoning has got to be false, though, since no helicopter that wants to go from A to B could simply climb to a certain altitude and just 'wait' until they're above B - or could they? Is Earth's athmosphere the reason why air-borne objects are always (or at least up to a certain altitude) "engaged" to the planet's rotation? I've probably even phrased the problem in too simplistic terms, that maybe ignore the real phenomena at play, however any reply that might help clarify my question will be appreciated!