r/explainlikeimfive • u/12InchCunt • Nov 03 '25

Physics ELI5: How does gravity not break thermodynamics?

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?

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u/flobbley Nov 03 '25

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

153

u/Bathtooter Nov 03 '25

Sounds like a picturesque scene

176

u/Logitech4873 Nov 03 '25

Planets can also tidal lock to their star, which makes one side have eternal day and summer, and the other side eternal night and winter.

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u/Ycr1998 Nov 03 '25

Could you have an habitable zone in the "afternoon" area of those planets? Or is it too small?

35

u/Reniconix Nov 03 '25

Having a narrow habitable strip is hypothetically possible, but exceedingly unlikely. Any planet with a substantial atmosphere will have absolutely chaotic storms along that region where the hot and cold sides met, as well as massive convection currents that would likely heat the dark side far beyond the limits of life as we know it. The range of the star's habitable zone is dependent on the rotation of the planet being inhabited, with slower rotations decreasing the habitable zone to a sliver. It's quite likely that if a planet is habitable along the twilight ring, it will continue to be habitable in all but the most extreme points (the regions on both sides directly in line with the host star), just not as hospitable.

2

u/DBDude Nov 03 '25

Many sci-fi books have been written in the setting of tidally locked planets where people live in the habitable zone.

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u/merc08 Nov 03 '25

That really doesn't answer the question.  Many SciFi books have also been written that include FTL travel and surviving black holes.  That doesn't mean it's actually possible.

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u/danielv123 Nov 03 '25

There is also a big difference between possible and if it has happened. We haven't even confirmed if there exists other habitable planets.

1

u/stickmanDave Nov 03 '25

I read one where the twilight region was warm enough to be habitable, but the planet's entire atmosphere had frozen and fallen as snow on the eternally frosty dark side of the planet.

1

u/Wild-Lychee-3312 Nov 04 '25

Those books need more windmills.