Planet Earth has begun to spin at a slower rate, making the days longer, and scientists are struggling to understand why.
Overall, there are processes that can be pointed out that have lengthened Earth’s day by approximately 86,400 seconds.
Over millions of years, the planet’s rotation is slowed down by the friction caused by the moon. Every 100 years, about 2.3 milliseconds are added to the length of the day – billions of years ago, a day on Earth was only 19 hours long.
Now, however, Earth’s continuous deceleration is unprecedented and has been going on for the past 50 years, and overall Earth’s rotation has slowed by about 6 hours over the past 2,740 years, according to a study published in the Proceedings of the Royal Society A in 2016.
“The rotation rate is found to be deviating from uniformity, so that the change in the length of the mean solar day (lod) is increasing at an average rate of +1.8 ms per century. This is significantly less than the rate predicted based on tidal friction, which is +2.3 ms per century,” the researchers wrote.
Earth reached its shortest day on June 29, 2022, but the general trend is that days are getting longer—with no readily available explanation.
There are several theories: Weather systems melting the ice sheets may have a long-term effect as the planet shrinks inward at lower altitudes. However, they decrease at a constant rate, so they may not respond to such a sudden change.
It’s possible that fluctuations in the planet’s spin rate, known as the “Chandler wobble” — where a small, uneven movement of Earth’s geographic poles across the globe’s surface — are causing the impact.
Finally, processes in the Earth’s inner or outer layers, the oceans, tides, or even the climate can cause it. Large earthquakes can also change the length of the day, but the amount is usually negligible.
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