# What causes the tides?

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8 hours ago, JamesF said:

It's also just occurred to me to wonder if there are "atmospheric tides" as well as sea tides

Yes, however tides in gasses tend to be dominated by heating effects so you don't notice the gravitational atmospheric tide so much. It's still a contributor though.

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It shouldn't be too hard to run the numbers. We'll keep things Newtonian for simplicity. So a = GM/r^2 G is Gravitational constant 6.67e-11 Radius of Earth, re, is 6,371km Mass of Sun is 2e30

The key part which is being missed is that it's the non-uniformity in the field which is important. If we imagine the Earth as a rigid sphere then: the water closest to the Moon "feels" a s

It's all vectors. The water is exerted a lot by the Earth and a little by the Moon. Doesn't matter if the gravitational force of the Moon and the Sun is much less than that of the Earth, the resulting

One point of interest I would like to add. When describing tides they are always described as flowing towards the land or away from it, but this is not really what is going on. What really happens is that a bulge is raised in the ocean by the tidal pull of the sun and moon, there are tons of places that explain the how and why of it.

So we have this bulge of water, but it does not move around the globe, the bulge stays in the same place under the sun and moon and the Earth rotates through it. Next time you watch the tide come in stop thinking of it as coming in, instead appreciate that it is staying still and the Earth is rotating  towards it. Naturally geographic features alter the local flow of the sea.

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On 21/10/2020 at 16:32, Waddensky said:

hate to reference Wikipedi

Multiple studies have shown wikipedia is a solid source on scientific and technical topics. I wouldn’t trust it on controversial hot topics like COVID because of the greater risk of page vandalism, but away from the flame wars it is excellent.

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16 hours ago, Ags said:

Multiple studies have shown wikipedia is a solid source on scientific and technical topics. I wouldn’t trust it on controversial hot topics like COVID because of the greater risk of page vandalism, but away from the flame wars it is excellent.

The difficulty is that Wikipedia is a tertiary source with a multitude of authors (including myself) without prior QC, and not all authors cite their sources correctly or sufficiently. The quality ranges from excellent to very poor and that makes it unsuitable as a source without assessing the solidity of the citing and the sources first.

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I thought it was due to Penguins all jumping in the sea at once - feeding at regular intervals - based on the science of a butterfly wing causing a hurricane etc.  I have an O level in Physics but can't claim to be an expert in tides.

Perhaps counting Penguins jumping into the sea will help you sleep now.

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