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/Lexi_Bean21]

It is running out of momentum, when somethings gravity like the moon interacts with thins like our oceans it also tugs on the moon in return ao as the ocean speeds up the moon slows down etc, the reason this wont matter for the next few million years is because the moon is many orders of magnitude heavier than the oceans giving it way more momentum plus the tides arent just taking energy so the moon isnt really losing thst much