"The giant orb of iron and nickel that anchors Earth's center is spinning faster than the planet's surface, according to a new study that confirms scientists' expectations."
"Earth's core is made of a solid inner part and a fluid outer part, all of it mostly iron.
The solid inner core has an uneven consistency, with some parts denser than others, and this can either speed up or slow down shock waves from earthquakes as they pass through.
So the researchers speculated that if the Earth's inner core is rotating faster than the rest of the planet, then shock waves from waveform doublets would enter and exit through different parts of the core despite originating from roughly the same spot on the planet's surface.
By analyzing the minute changes in travel times and wave shapes for each doublet, the researchers concluded that the Earth's inner core is rotating faster than its surface by about 0.3-0.5 degrees per year.
That may not seem like much, but it's very fast compared to the movement of the Earth's crust, which generally slips around only a few centimeters per year compared to the mantle below, said Xiaodong Song, a geologist at the University of Illinois at Urbana-Champaign and an author on the study."
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It makes sense that the inner core should be rotating faster, since the tidal drag from the Sun an Moon would have the most leverage on the outer part.
Double-A