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justahomeboy t1_j5lxhib wrote

Reply to comment by shiruken in Earth's inner core seems to be slowing its spin according to new research published in Nature Geoscience. The study authors suggest this might be part of an approximately 70-year cycle where the core speeds up and slows down relative to the rest of the planet. by shiruken

Do you mind explaining how the core and the rest of the planet can have different rotation speeds? I haven’t taken science courses since college so I’m ignorant to the subject matter.

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shiruken OP t1_j5m0uqb wrote

Don't really know the specifics, but it has to do with the structure of the Earth where the outer core is liquid while the inner core is solid. Anytime you start spinning layers with liquid, things get complicated.

The New York Time's coverage of this research offers this explanation:

>What’s going on? One idea is that two titanic forces are battling for control over the world’s heart. Earth’s magnetic field, generated by swirling iron currents in the liquid outer core, is pulling at the inner core, causing it to spin. That impulse is countered by the mantle, the mucilaginous layer above the outer core and below Earth’s crust, the immense gravitational field of which grasps the inner core and slows its spin.

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Bofgrey t1_j5nuek4 wrote

It is simple to understand if you grab an uncooked egg, spin it around on a table, bring it to a sudden stop by putting your hand on top, and then quickly lift your hand again. The rotating insides of the egg will bring it in motion again. (This is also a trick to check if an egg is cooked or not)

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KubaKuba t1_j5m0sp9 wrote

I wonder if orbit is a potential cause?

I could imagine rotational artifacts from a non perfectly circular orbital path causing a rotational speed difference between the core and the shell of the earth.

As a matter of fact I would be surprised if it wasn't that.

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