[Roccus]

I can't give you a quote or a link, but I always assumed this to be the case and caused the earth's magnetic field. For some reason I thought this was common knowledge. Oh well...

[anonymoussierra]

:}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}thank you

[Socratic]

I thought this was common knowledge.

So did I. Perhaps knowing that a solid crust riding on semi-liquid magma, over a solid core just naturally gives rise to the intuitive notion that they would be spinning at different rates. After all, when a spinning skater extends her arms, she slows down just like one would assume the crust would.