Earth Is Spinning Too Quickly - Clocks Aren’t Keeping Up
Thanks to a speed-up of Earth's rotation, the length of the astronomical day and the length of the clock day aren't quite matching up. Eventually, international timekeepers may need to subtract a second.
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00:00 The Earth's spin is speeding up.
00:03 In 2020, the planet completed many of its revolutions around its axis, milliseconds
00:08 quicker than on average.
00:10 That's a problem for coordinated universal time, which uses ultra-accurate atomic clocks
00:16 to meter out milliseconds, seconds, and minutes.
00:20 The Earth's spin varies naturally due to the effects of the atmosphere, oceans, and
00:25 core.
00:26 When atomic time and the length of the day determined by Earth's spin deviate by more
00:31 than about 0.4 seconds, international timekeepers have to adjust the clocks.
00:38 Until now, this has involved adding a leap second at the last minute of June or December,
00:43 lengthening the day by the blink of an eye.
00:46 That's because the overall trend in the Earth's rotation has been slowing.
00:51 Until now.
00:52 In 2020, Earth experienced its 28 fastest days since 1960.
00:59 The quickest, July 19, saw the planet spin around 1.4602 milliseconds faster than its
01:07 average 86,400 seconds.
01:12 If the trend continues, international timekeepers may eventually need a negative leap second,
01:17 subtracting a second from the end of the day rather than adding one.
01:22 The decision would be made by the International Earth Rotation and Reference Systems Service
01:27 in Paris, France.
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