William Astley said: I found myself wondering about the pulsating equator recently. For those not in the know, Andre presented this excellent nutshell description in a previous thread. Check out this cool animation. I was thinking that it it boils down to a fluid mechanics problem. Can you find a realistic solution to the Navier-Stokes equations that would allow for a pulsating equator? The only force that is important in shaping the Earth (at a large scale) is gravity. If this is true then the only way you could get the equator to bulge (to my knowledge) would be to make it spin faster, and for it to pulsate it would have to slow down and speed up! Quite how that could happen is beyond me, I considered meteorites for a second, but after some consideration concluded that they would not be suitable. Unless there's some kind of transient anisotropy to gravity that we can't see in human timescales, I don't see any way the pulsating equator could physically work. Discuss.