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. In 2020, the planet completed many of its revolutions
00:06 around its axis, milliseconds quicker than on average. That's a problem for coordinated
00:12 universal time, which uses ultra-accurate atomic clocks to meter out milliseconds, seconds,
00:19 and minutes. The Earth's spin varies naturally due to the effects of the atmosphere, oceans,
00:25 and core. But when atomic time and the length of the day determined by Earth's spin deviate
00:31 by more than about 0.4 seconds, international timekeepers have to adjust the clocks. Until
00:38 now, this has involved adding a leap second at the last minute of June or December, lengthening
00:44 the day by the blink of an eye. That's because the overall trend in the Earth's rotation
00:49 has been slowing. Until now. 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. If the trend continues, international timekeepers may eventually need
01:16 a negative leap second, subtracting a second from the end of the day rather than adding
01:21 one. The decision would be made by the International Earth Rotation and Reference Systems Service
01:28 in Paris, France.
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