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> The forces still apply, they're just not shifting daily. No, the forces are completely different. If we have an object on the surface of the earth that has e

> The forces still apply, they're just not shifting daily. No, the forces are completely different. If we have an object on the surface of the earth that has enough mass to roughly produce the same nearby gravitational acceleration as that felt by the moon (which is minuscule and undetectable by most instruments), that object would not produce changes in ocean levels as we see with the moon. Again, the oceans are not rising/falling due to the moon's gravity pulling on them. It only happens because the moon is far enough away that its tiny gravitational acceleration on the earth is (1) felt everywhere on earth, and (2) felt everywhere on earth in slightly different amounts. For a smaller, closer object (even with similar nearby gravitational acceleration), the tidal forces will not be the same because that gravitational acceleration will fall off to near zero in a very short distance.

coliveira 6y ago
You are mixing tidal forces with local attraction forces due to ice. Even though the forces due to ice are not felt everywhere in the planet, they do have an effect that can be calculated, and it is stronger in the body of water closer to the poles. The result of this force causes water attraction in the polar regions. So the effect that is felt in other parts of the planet is not due to the gravity force, but due to the displacement of water happening in polar regions - after all the water needs to go somewhere.
- deleted 6y ago
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- curiousgeorgio 6y ago
  I was originally responding to the claim that "it's still 524 times higher than the effect of the moon's gravity which creates the tides" - that's why I mentioned tidal forces. If the ice creates that much direct, local gravitational attraction[1], then my point is we shouldn't be comparing it to the moon at all (because the forces involved are not the same as those involved with the moon and tides). [1] Even the claim about the ice sheet (and its melting) contributing significantly (via gravity) to global sea level change seems dubious since, as noted elsewhere in this discussion, the Earth Gravitational Model appears to be affected much more by factors other than ice sheet thickness or surface features.

coliveira 6y ago

You are mixing tidal forces with local attraction forces due to ice. Even though the forces due to ice are not felt everywhere in the planet, they do have an effect that can be calculated, and it is stronger in the body of water closer to the poles. The result of this force causes water attraction in the polar regions. So the effect that is felt in other parts of the planet is not due to the gravity force, but due to the displacement of water happening in polar regions - after all the water needs to go somewhere.

deleted 6y ago
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curiousgeorgio 6y ago
I was originally responding to the claim that "it's still 524 times higher than the effect of the moon's gravity which creates the tides" - that's why I mentioned tidal forces. If the ice creates that much direct, local gravitational attraction[1], then my point is we shouldn't be comparing it to the moon at all (because the forces involved are not the same as those involved with the moon and tides). [1] Even the claim about the ice sheet (and its melting) contributing significantly (via gravity) to global sea level change seems dubious since, as noted elsewhere in this discussion, the Earth Gravitational Model appears to be affected much more by factors other than ice sheet thickness or surface features.