thulesgold t1_j5plwmb wrote
Reply to comment by MistWeaver80 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
It doesn't make sense. First of all, there is considerable friction between the core and mantle so having a spin rate difference between them for billions of years is improbable. Second of all, the theory the core spins faster then slows down also makes no sense. It would imply there is an elastic oscillation between the core and mantle as they trade off angular momentum, but this is something we can measure... If the core slowed, then the mantle would speed up making the day shorter. Since I haven't heard news reports of drastic time changes every 70 years Imma gonna call BS on all this recent news on core spin.
GeoGeoGeoGeo t1_j5suvl3 wrote
There is a suggested different spin rate between the inner solid core and liquid outer core. The difference, however, is exceptionally small, and they both rotate at the same speed to within 0.001%.
The difference in speed is believed to be a result of two competing forces: The gravitational tug of the surrounding mantle, and the torque induced by the electromagnetic field from the outer core.
So when they report that its stopped spinning they mean relative to the mantle, same as when they say its reversed, and sped up.
thulesgold t1_j5sw160 wrote
Sure but slowing down the angular momentum of such a large mass would have noticable effects. For example, since the core is spinning at different velocities relative to the outer core then oscillates back to the original velocity then that energy would need to be banked in a magnetic field or some other means so that the energy is regained. We would see strong changes in Earth's magnetic field. Either way, billions of years of this happening would reduce this oscillation to nothing and affect the rate of the spin of the earth as a whole (beyond slowing due to tidal forces).
It might be interesting to think about the moon forming collision and there was an oscillation billions of years ago but much worse than it is today.
LordZon t1_j5t1d60 wrote
What if it isn't a cycle? Then the findings make more sense. Ie the core really is stopping.
Viewing a single comment thread. View all comments