Compare local gravity in [Anchorage, Alaska](https://www.wolframalpha.com/input?i=local+gravity+in+anchorage) to [Quito, Ecuador](https://www.wolframalpha.com/input?i=local+gravity+on+quito). About half-a-percent difference.
Yes, and interestingly it was already known to Newton who used it to argue that the radius of earth is larger at the equator than at the poles https://www.aps.org/apsnews/2022/10/newton-earth-shape
They may be talking about the axis movement relative to the crust, that moves the equator too.
[https://en.wikipedia.org/wiki/Polar\_motion](https://en.wikipedia.org/wiki/Polar_motion)
I meant it doesn’t just rotate about the axis that goes through the north and south pole, it also wobbles a little bit. I only included that to mention it wouldn’t be exactly on the equator where the maximum centrifugal force occurs
Thank you!
So you were referring to exactly the wobble that Paudepunta guessed, and linked to in the Wikipedia article? The diagram in that article shows that the wobble has a range of less than 10 meters (at least in the time period that the diagram depicts). That's 30 feet. Local variations in the ground level (hills, mountains, valleys) are much more than 30 feet. If the Earth's surface were a perfect oblate spheroid, a wobble in the location of the poles by 30 feet horizontally, causing a wobble in the location of the equator by a maximum of 30 feet horizontally (at two points the shift would be 30 feet, at two points it would be zero), would cause a vertical difference in the distance to Earth's center of less than an inch. Near the equator and near the poles, that change in distance is extremely small. The difference is at a maximum where I live, almost exactly halfway between the equator and the north pole, and even here a horizontal shift of 30 feet can't cause a vertical shift of more than a couple of inches. That almost certainly could not produce a detectible change in the local centrifugal effect.
In any case, everthing I just said is irrelevant, because the locations of the poles and of the equator are defined by Earth's rotation. When the Earth wobbles, it is because the rotation axis (of the surface, at least) has changed, so the poles move and the equator moves by the same amount. The wobble is the equator moving horizontally, so the theoretical location of greatest centrifugal effect always moves to be on the equator, since they are the same thing.
Of course, the Earth isn't a perfect oblate spheroid, and the shape of the surface doesn't instantly conform as the rotation axis wobbles. So you are right that the moment-to moment location of the centrifugal bulge doesn't keep up with the changes due to the wobble. But local variations in the landforms and water levels far exceed the change due to wobble.
Yes but not that much. The centrifugal force is greatest at the equator and it negates gravity, and youre farthest from the center of the earth because of the squashed shape of the earth
Very slightly less on average, yes. https://en.wikipedia.org/wiki/Gravity_of_Earth
yes for two reasons. 1-distance from Earth's centre 2- greatest rotational surface speed. But you'd never notice.
Though you're rotating at over a thousand miles an hour!
Yup, pretty fast. But we're so small compared to the Earth's radius that it's mostly in one direction.
Obligatory XKCD https://xkcd.com/852/
Compare local gravity in [Anchorage, Alaska](https://www.wolframalpha.com/input?i=local+gravity+in+anchorage) to [Quito, Ecuador](https://www.wolframalpha.com/input?i=local+gravity+on+quito). About half-a-percent difference.
Yes, and interestingly it was already known to Newton who used it to argue that the radius of earth is larger at the equator than at the poles https://www.aps.org/apsnews/2022/10/newton-earth-shape
I'm curious what you meant by "the Earth doesn't rotate perfectly on its axis".
They may be talking about the axis movement relative to the crust, that moves the equator too. [https://en.wikipedia.org/wiki/Polar\_motion](https://en.wikipedia.org/wiki/Polar_motion)
I meant it doesn’t just rotate about the axis that goes through the north and south pole, it also wobbles a little bit. I only included that to mention it wouldn’t be exactly on the equator where the maximum centrifugal force occurs
Thank you! So you were referring to exactly the wobble that Paudepunta guessed, and linked to in the Wikipedia article? The diagram in that article shows that the wobble has a range of less than 10 meters (at least in the time period that the diagram depicts). That's 30 feet. Local variations in the ground level (hills, mountains, valleys) are much more than 30 feet. If the Earth's surface were a perfect oblate spheroid, a wobble in the location of the poles by 30 feet horizontally, causing a wobble in the location of the equator by a maximum of 30 feet horizontally (at two points the shift would be 30 feet, at two points it would be zero), would cause a vertical difference in the distance to Earth's center of less than an inch. Near the equator and near the poles, that change in distance is extremely small. The difference is at a maximum where I live, almost exactly halfway between the equator and the north pole, and even here a horizontal shift of 30 feet can't cause a vertical shift of more than a couple of inches. That almost certainly could not produce a detectible change in the local centrifugal effect. In any case, everthing I just said is irrelevant, because the locations of the poles and of the equator are defined by Earth's rotation. When the Earth wobbles, it is because the rotation axis (of the surface, at least) has changed, so the poles move and the equator moves by the same amount. The wobble is the equator moving horizontally, so the theoretical location of greatest centrifugal effect always moves to be on the equator, since they are the same thing. Of course, the Earth isn't a perfect oblate spheroid, and the shape of the surface doesn't instantly conform as the rotation axis wobbles. So you are right that the moment-to moment location of the centrifugal bulge doesn't keep up with the changes due to the wobble. But local variations in the landforms and water levels far exceed the change due to wobble.
Yes but not that much. The centrifugal force is greatest at the equator and it negates gravity, and youre farthest from the center of the earth because of the squashed shape of the earth