4 ms·
The force vector from a polar ice sheet doesn't get cancelled out by the rest of the earth though (because they aren't pointing in opposite directions). Plus, y
by _petronius 6y ago
The force vector from a polar ice sheet doesn't get cancelled out by the rest of the earth though (because they aren't pointing in opposite directions). Plus, you have to account for the force of the ice sheet, plus the water it attracts, plus the water that those combined attract, etc.
I'm no good with calculus so can't run that back-of-the-envelope for you, but it doesn't seem all that surprising to me.
- jfindley 6y agoEven if we ignore all that, and treat everything as a point mass, it's still believable, I think. The earths radius is very approximately 6.4km. So 1km out from the ice sheet, we have 1(1/6.4^2) (earth) vs 10^-5(1/1^2) (ice), which is very roughly 1/2500th of the effect of earths gravity. But the earths gravity is strong! The forces it exerts on the ocean are titanic - it doesn't seem outside the realms of belief that even this small percentage of the force could produce an observable effect, when the forces are so huge, and the differences are only measured in meters. I think part of the reason we find this difficult to grasp intuitively is we don't really have a good mental model of just how titanic many of these forces are - huge numbers are just not something we, as a species, are good at understanding.
- silvestrov 6y agoEarth’s radius is 6371 km, not ~6 km.
- ljcn 6y agoRadius of 6 km is comparable to the size of Halley's comet :-)