this post was submitted on 11 Jan 2026
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Bathtub Thoughts

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This community is inspired by this post on !showerthoughts@lemmy.world:

We really need a community where you can just post about anything that you’re really passionate about, which you’re currently researching/thinking about, sothat others can learn something about it as well and maybe discuss about it.

This showerthoughts community is a bit like it because you can just post whatever comes to your mind, but i’d like it to be more in-depth and with higher quality. Something like showerthoughts, but bathtubthoughts, i.e. when you’re soaking in a hot bathtub and thinking about stuff for 20 minutes or sth, and then post that. You know what i mean?

Related communities:

!showerthoughts@lemmy.world

!todayilearned@lemmy.ml

!youshouldknow@lemmy.world

!infodump@lemmy.autism.place

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Technically, there's only two sources of energy in the universe: nuclear energy and the expansion of the cosmos.

Like, solar is fusion, ofc, the light coming from the sun. So is wind and water and bioenergy (indirectly). Geothermal is fission (heat comes from radioactive decay inside Earth).

But then there's another source of energy that nobody ever talks about: tidal power It works by converting the rise and fall of water with the tides into electrical energy. This energy ultimately comes from the moon orbiting around Earth, more precisely, its mechanical energy: The fact that the moon is distant from Earth is only because the universe expanded after the big bang. Had it not done this, the moon and earth would be located at the same location, and there would be no "orbiting" to extract energy out of :P


I wrote more about the subject of extracting (useful) energy out of cosmic expansion in this post here

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[–] FreeBeard@slrpnk.net 8 points 5 days ago (1 children)

Is geothermal every mainly fission? I thought it was mostly residual heat from earth's formation. In your picture it is also expansion. Here I disagree because your argument only holds for hydrogen and helium. Everything else comes from exploding stars so the mass distribution of the earth (and moon) is also nuclear's wrongdoing.

[–] CarbonIceDragon@pawb.social 6 points 5 days ago (1 children)

While not super relevant to earth, black holes are thought to slowly convert their mass into energy and radiate it off over a very long time (slower the bigger the thing is). Since what they are made of can't really be described as atoms anymore, this isn't really a nuclear process, and as far as I'm aware, this isn't driven by the universe's continued expansion either.

[–] gandalf_der_12te@discuss.tchncs.de 1 points 4 days ago* (last edited 4 days ago)

Hmm yeah you're right, it's not directly a nuclear process nor is it driven by cosmic expansion, but it's still somehow related to mechanical energy (i think), since basically black holes use their enormous gravitational force gradient to basically rip the vacuum apart and that way release energy. And gravitational energy is a kind of mechanical energy, i'd say.

[–] FoolsQuartz@lemmynsfw.com 3 points 4 days ago

Yes absolutely true. I've thought about this before. Thank you for explaining it so clearly