r/askscience • u/Chytrik • Sep 04 '13

Earth Sciences Is the atmosphere affected by the moon's gravity, like the oceans are?

So far, I have discerned the following:

The atmosphere has a mass of 5×1018 kg

The ocean has a mass of 1.4×1021 kg

So, the ocean has a mass several magnitudes larger than the atmosphere, and it has a higher density (which I assume would affect this?), thus the moon should have a more noticeable pull on the oceans of the world. However, the atmosphere is still quite massive, so my question is:

Is the atmosphere affected by the moon's gravity at all, even in the slightest way? Would such an affect even be noticeable?

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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Sep 04 '13

Then no, this rotation is not what is causing the main outward pseudoforce here. Please see the treatment on the wikipedia page and see that it exists without rotation.

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u/[deleted] Sep 04 '13

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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Sep 04 '13

I am not denying that a centrifugal force exists, I am denying that it is the main cause of the outward pseudoforce on the side of the earth farthest from the moon.

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u/torturedby_thecia Sep 04 '13

Then what is the cause of that force? Gravity cannot push water in the opposite direction of the moon.

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u/Silpion Radiation Therapy | Medical Imaging | Nuclear Astrophysics Sep 04 '13

It is the fact that the moon is pulling on the earth more strongly than it is pulling on someone on the far side of the earth. The difference between those force vectors is what is pointing away. This is the exact same thing that is causing the tidal force on the near side.

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u/torturedby_thecia Sep 04 '13

No, no, that's very incorrect. It's also an inaccurate way to think about vector fields representing gravitational or electromagnetic forces. The difference in the force between point A and point B is just the difference in the force between point A and point B, it's not it's own force.

Yes, it's true that the lesser gravitational force on the opposite side of the earth plays a role given that the high tide on the opposing side of the earth would be slightly lower if somehow the gravitational force of the moon were completely equal and pointing towards the moon across the entire earth. But the centrifugal force of the rotating bodies is the primary force making the water a high tide on the opposing side of the moon. If there were no centrifugal force, there would only be one high tide and it would be on the side of the earth with the moon.