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Core Turning Faster Than Earth

Thu., July 18, 1996

As the world turns, its core goes just a little faster.

Earth’s inner core, a solid iron crystal about the size of the moon, rotates about 1.1 degrees faster in a year than the rest of the planet, geologists from Lamont-Doherty Earth Observatory announced in today’s issue of the journal Nature.

That means that the core finishes a complete rotation not in 24 hours, but in 24 hours minus two-thirds of a second.

At that rate, Earth’s core “laps” the rest of the planet every 400 years, geologist Paul Richards said.

Richards and Lamont-Doherty geophysicist Xiaodong Song used an ingenious method to detect the core’s slightly faster spin. They studied old measurements that recorded how long it took sound waves from earthquakes on one side of the globe to pass through the core to seismographs located literally halfway around the world.

And the scientists are not surprised. Computer simulations have told them that the Earth’s inner core ought to rotate. So by confirming that it does, Song said he and Richards have helped further the understanding the planet’s magnetic field.


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