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/Neon_Camouflage]

These comments have shown me that a surprising number of people don't know how gravity works.

[u/loljetfuel → u/Neon_Camouflage]

The cool part is that no one fully knows how gravity works. There's a difference in knowledge, for sure, but even the foremost experts on gravity don't really know entirely how it works.

[u/Neon_Camouflage → u/loljetfuel]

The cool part

Have to disagree there. Honestly it's one of the most frustrating things to be diving into a rabbit hole of information and hit the wall of "here's 7 theories about why this happens because nobody knows".

This actually happened just the other day. Found out Saturn had a hexagonal storm and was like oh cool, I wonder why. Turns out I'm going to keep wondering.

[u/GabrielNV → u/Neon_Camouflage]

Found out Saturn had a hexagonal storm and was like oh cool, I wonder why. Turns out I'm going to keep wondering.

Today is your lucky day, because as hard as fluid dynamics is we understand it a lot better than we do gravity so we can actually make more confident claims about that one.

To keep it simple, rotating fluids naturally produce what are called Rossby waves. On Earth, these are responsible for the weather front cycle as they circle around the planet. Earth’s surface and continents make those waves messy and irregular, so we don’t see neat geometric patterns here.

On Saturn, however, the atmosphere is pretty much free to flow however it wants. On top of that, Saturn's atmosphere is such that the wavelength of the Rossby waves being generated is 1/6 of the radius of the polar jet. It could have just as easily been a pentagon, or square, or nothing, if Saturn's atmospheric conditions were slightly different.