Earth just had its shortest day ever — and an irregular wobble at the poles may be to blame
ZME Science by Tibi Puiu August 2, 2022
https://www.zmescience.com/science/news-science/earth-just-had-its-shortest-day-ever-and-an-irregular-wobble-at-the-poles-may-be-to-blame/Days were actually supposed to get longer, not shorter. What gives? If you thought time flies way too fast these days, you’re not technically wrong. On June 29, Earth experienced the shortest day ever since record-keeping with high-precision atomic clocks began, clocking in a full revolution around its axis 1.59 milliseconds short of 24 hours.
The days on Earth are supposed to get increasingly longer as time passes due to exchanges in angular momentums between Earth and the Moon. When life on the planet first emerged, about 3.5 billion years ago, a day lasted 12 hours. At the emergence of photosynthesis 2.5 billion years ago, the day lasted 18 hours. And 1.7 billion years ago when the first eukaryotic cells emerged, a day lasted 21 hours long.
While Earth’s rotation speed is on a decreasing trend, the past few decades have been an anomaly with the planet’s spin going against the grain and actually turning faster.
In 2020, scientists registered 28 of the shortest days in the past 50 years, with the shortest of those, on 19 July, shaving 1.47 milliseconds off the 86,400 seconds that make up 24 hours. The new 29 June record is just a few milliseconds shorter, but it still counts.
It’s not entirely clear why days are getting shorter rather than longer as they have across geological history, but there are many factors that can have an influence. Strong winds during El Nino can slightly slow down the planet’s rotation due to drag from the atmosphere, while earthquakes can have the opposite effect shortening days.
But what may explain the current temporary day shortening are wobbles in Earth’s axis due to the fact that Earth is not exactly a perfect sphere. Earth has a bulge at the equator and its poles are slightly squashed. Any spinning sphere-like object that is not entirely spherical will wobble in some way.
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