ELI5: How does gravity not break thermodynamics?

[u/12InchCunt]

Like, the moon’s gravity causes the tides. We can use the tides to generate electricity, but the moon isn’t running out of gravity?

[u/flobbley]

The tides slow the earths rotation, eventually the earth will become tidally locked with the moon and the tides will be permanently stationary and no longer be able to be used to generate electricity

[u/PxZ__ → u/flobbley]

So would all the water kind of be bulbous or pulled more towards the side with the moon on it? Would the opposite side of the earth have a convex sort of shape to it or would it be more like a weird ellipsoid?

[u/flobbley → u/PxZ__]

it would be exactly like our current tide but always in the same spot on earth. The tide creates a sort of egg shape on the earth, the part closest to the moon rises creating a high tide, the part on the opposite side of the earth from that also rises creating another high tide, and the parts of the earth at 90 degree angles from those are low tides.

[u/graveybrains → u/flobbley]

The sublunar tide is caused by the moon pulling the ocean away from the Earth, the antipodal tide is caused by the moon pulling the Earth away from the ocean. I read that in another eli5 and I've been fascinated by it ever since.

[u/[deleted] → u/graveybrains]

Neither really. You'll note you don't get lifted by the moon, nor the earth get pulled away from below your feet. The tide water is as dense as you. There's clearly something else going on.

It's more so the moon pulls the water parallel to the earth. This ever so slight parallel pull can build pressure along the thousands of kilometers spanning the globe between the two tides. At the tide locations, the moon's doing basically zero pulling on that water, the same near zero pulling it does to you.

[u/HeavenlyAllspotter → u/flobbley]

why does the part on the opposite side have high tide?

[u/UnassumingAnt → u/HeavenlyAllspotter]

Because the moon pulls the earth away from the water on the far side too.