Hi all,
I’m currently brainstorming a scifi story idea that involves the Earth completely losing the Sun as an energy source, as if it vanished. There’s obviously a lot of hypotheticals in this, but one of my questions revolves around geothermal energy.
Even though geothermal energy comes from the core of the Earth, does the sun play a role in maintaining it? Like, does the Sun’s gravity play a role in keeping the core spinning, and thus maintaining geothermal energy?
Thanks in advance!
Comments
The Sun doesn’t power geothermal energy. Earth’s internal heat comes from residual formation energy and radioactive decay. The Sun’s gravity doesn’t affect the core in any meaningful way. So even if the Sun vanished, Earth would stay geologically active for billions of years—just cold and dark on the surface.
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Earth’s internal heat flux is ‘powered’ by a combination of primordial heat (so Earth is slowly cooling) and radioactive decay. I can find no sources stating tidal heating is a significant contributor.
Without solar radiation Earth’s surface temperature would be dramatically lower and if nothing else changed this will result in a slight increase in Earth’s heat flux – greater temperature difference across a boundary means greater heat flow. But considering the Earth’s core is about 5700 K, dropping the surface from 290 K to say 40 K doesn’t change the temperature difference much. And freezing the oceans and atmosphere could offset this.
Long term the biggest effect might be from the loss of liquid water. Certain types of volcanism only occur because subducting plates carry water into the mantle, and it’s generally thought plate tectonics as we know it requires water to happen on an Earth-like planet. I don’t know of any studies about how that would change if the planet had an ice layer instead of liquid water.
that’s a really cool concept. while the sun’s gravity has some effect on earth, geothermal energy mainly comes from radioactive decay and residual heat from earth’s formation. so even if the sun vanished, earth’s core would still generate heat for a long time.