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mathologies t1_j5o8iud wrote

Reply to comment by BoIshevik in What are the forces on Earth’s Inner Core that change its speed? by BayRunner

Core is molten for two reasons:

Initial formation of Earth generated a lot of thermal energy, because a lot of stuff smashed together

Continued decay of radioisotopes has contributed additional thermal energy-- without this, the core would have cooled by now

Thermal energy is lost from the core through heat transfer to the mantle, which brings it to the crust by way of convection; this is what ultimately causes plate movement, earthquakes, volcanism, subduction, etc. on Earth. Once the core is cool enough that mantle convection stops, tectonic forces will subside and uplift processes will cease. From that point, weathering and erosion will gradually erase all land above sea level, giving us an ocean planet. I think the Sun will be hot enough to boil our oceans well before that happens, though (solar brightening over geologic time).

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jabask t1_j5ogzt6 wrote

So if the oceans boil away, will the earth just become a smooth marble of rock with a bunch of fog over it?

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cklein0001 t1_j5ok4mp wrote

Think more "mars-scape, marscape?", as the core also gives us our magnetic field that protects our atmosphere from the solar winds. Once the core cools, the Earth's internal dynamo also slows, solar winds start buffeting our atmosphere out of Earth's gravitational field, and we start looking more like Mars.

Also scheduled to happen around the same geologic time as the Earth being swallowed / burned by the Sun.

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paul_wi11iams t1_j5pdu1z wrote

> swallowed

The version I heard was the expanding sun loses mass leaving Earth beyond its grasp.

> swallowed / burned

So its changed again, having become uncertain.

and even that is ignoring options for stellar engineering (assuming our descendants even care)

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cklein0001 t1_j5pep9v wrote

Yeah, several "what's gonna happen in unfathomable timescale" options to choose from.

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Rule_32 t1_j5ut7dr wrote

>sun loses mass leaving Earth beyond its grasp

This is incorrect. The Suns expansion does not equate to mass loss. Cosmologically its mass will have not decreased that much (which is what will determine where Earths orbit is) but it'll be fusing helium into carbon which is a hotter more energetic process and so the outer layers of the star will get pushed out and the star expands. Earths orbit won't change much however the Suns radius will expand to near or fully envelop Earth.

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