Climate change is slowing Earth’s rotation
This simplifies things for the world’s timekeepers

THE PERFECT day should have 86,400 seconds: 24 hours for Earth to spin around its axis, 60 minutes in each hour, and 60 seconds in each minute. But the apparent precision of these simple calculations ignores the messy reality of planetary bodies. Tidal forces, combined with the roiling currents in Earth’s core and the redistribution of ice sheets at its surface, cause the planet’s rate of spin to vary ever so slightly from year to year.
This article appeared in the Science & technology section of the print edition under the headline “The years are getting longer...”
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