Some days really are longer than others. And now scientists know by precisely how much.
Using a laser gyroscope, scientists have measured variations in Earth’s rotation rate smaller than a millionth of a percent. The technique could help scientists understand the complex flows of water and air that cause the tiniest of tweaks to the planet’s spin.
Earth’s rotation isn’t perfectly steady. The planet speeds up and slows down as it twirls, making a day slightly shorter or longer by several milliseconds. Many of those variations are well understood. For example, one such variation is caused by tidal forces, created by the gravitational pull of the moon and the sun, that deform the planet. Scientists know how to predict those effects on Earth’s rotation. But other variations, caused by the fluctuating flows of Earth’s atmosphere and waters, are more difficult to estimate.
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