nitwit005 15 hours ago

Everything exposed to the sun will heat up until the energy it emits balances out the incoming energy.

Being a larger mass just means an object will take longer to heat up.

  • cma 8 hours ago

    Depending on how rich in internal radioactive sources of heat it isn't scale free with mass. Larger masses of the same makeup will reach different thermal equilibrium since the surface area grows at a slower rate than the internal heat production from decay which scales with mass.

    I don't know if it is significant, but tidal sources of heat might not scale the same either.

    • nitwit005 7 hours ago

      I think we can safely say the planet made of uranium is an edge case.

      The Earth's internal radioactivity is a miniscule energy source compared to the sun.

      • cma 7 hours ago

        Yes it's small, but:

        At least during emergence of life there was the faint young sun + higher proportions of radioactive elements, so could have made up 0.2% of outgoing thermal radiation or so on earth (ignoring outflow of residual heat from early collisions). I think 5-10 earth masses is the limit for terrestrial planets, and you can imagine having say 10x more radioactive elements and still hospitable to life, rather than being made of solid uranium. So maybe double digit percentage radiant heat outflow differences between very small and very large on those.

mr_toad 8 hours ago

Presumably a spherical ball of air would be able to transfer heat more quickly (from the hot to the cold side) than the same volume spread out as a very thin hollow layer.