Loss of heat from magma of Earth

[Tan PK]

If the Earth's magma lost enough heat for it to solidify to a noticeable extent(permanent change, assuming irreversible), how would it affect its rotation about Earth's own axis and revolution around the Sun?

 

[russ_watters]

It wouldn't affect the Earth's rotation noticeably - only in tiny fractions of a percentage from the Earth doing less re-arranging of itself. It wouldn't affect the revolution at all.

 

[Antiphon]

It would however shut off the Earth's magetic field and then we'd have big problems with the solar wind. Some think this is why Mars is dead.

 

[Tan PK]

It wouldn't affect the Earth's rotation noticeably - only in tiny fractions of a percentage from the Earth doing less re-arranging of itself. It wouldn't affect the revolution at all.

If I were to assume that in a theoretical planet similar to Earth, and the significant solidification of magma was consistent through the whole body, what difference would it make?
Its something like a hollow steel ball with a more fluid interior versus another similar hollow steel ball with a less fluid interior. Would one spin faster/more unstably than the other? Would one travel faster than the other? (assuming both have same mass of fluid inside)

 

[russ_watters]

That one has a little liquid inside doesn't suggest anything about the rate of rotation compared to the other.

 

[Tan PK]

That one has a little liquid inside doesn't suggest anything about the rate of rotation compared to the other.

Is this about motion causing gels and liquids to act similarly?

 

[russ_watters]

I'm sorry, I'm not really sure what you are asking. But you seem to think there is a reason why having some liquid inside a planet would affect the rotation rate. Could you explain why you think that and maybe we can address that more directly.

Consider, though, that Jupiter, which is almost entirely gas and liquid and is much larger than Earth, rotates in 10 hours.

 

[Tan PK]

I'm sorry, I'm not really sure what you are asking. But you seem to think there is a reason why having some liquid inside a planet would affect the rotation rate. Could you explain why you think that and maybe we can address that more directly.

Consider, though, that Jupiter, which is almost entirely gas and liquid and is much larger than Earth, rotates in 10 hours.

Hmm. I may be wrong, but i think that a planet with maybe 5 arbitrary units of solid in its interior would rotate faster/revolve faster than a planet with 1 arbitrary units of liquid.

And would the solid adsorb more to the inner surface of the planet shell? Like if you spin a bucket with water in it, the bucket(planet shell) would move more independently in comparison to the liquid than one with cement in it.

 

[russ_watters]

Hmm. I may be wrong, but i think that a planet with maybe 5 arbitrary units of solid in its interior would rotate faster/revolve faster than a planet with 1 arbitrary units of liquid.

No, this is not necessarily the case.

And would the solid adsorb more to the inner surface of the planet shell? Like if you spin a bucket with water in it, the bucket(planet shell) would move more independently in comparison to the liquid than one with cement in it.

If you spin the bucket for just a little while, the entire mass of liquid in it will soon spin-up to the speed of the walls of the bucket due to viscous friction...and magma (and the Earth's mantle) is very viscous.

Also, consider that the Earth formed from a rotating cloud of debris, which is why it is rotating in the first place. So your spinning bucket analogy implies that the Earth had to be accelerated up to its current rotational speed, when the reality is that it was created with that speed.

 

[Tan PK]

Ahh. Thank you so much!