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09th Aug 2022

The Earth is slowing down – and scientists don’t know why

Jack Peat

If you feel like you’ve had a long day, it’s probably because you have! 

The Earth has started to spin at a slower rate, baffling scientists observing the planet’s rotations.

Precise astronomical observations, combined with atomic clocks, have revealed that the length of a day is suddenly getting longer owing to a slowing down of the planet’s rotation.

Over millions of years, a slight deceleration has been observed, with around 2.3 milliseconds added to the day every 100 years.

Billions of years ago, a day on Earth only lasted 19 hours. Now it’s 24, and it could be about to get longer!

According to reports in the Independent, there has been unprecedented slowness over the past 50 years.

A study published in the Proceedings of the Royal Society A found that “the rate of rotation departs from uniformity, such that the change in the length of the mean solar day (lod) increases at an average rate of +1.8 ms per century.

“This is significantly less than the rate predicted on the basis of tidal friction, which is +2.3 ms per century.”

The Earth reached its shortest day on 29 June 2022, but the general trend is that the days are lengthening – with no explanation readily available.

There are a few theories: weather systems melting the ice sheets could have an effect over the long-term, as at lower altitudes the planet is shrinking inwards. However, these have been decreasing at a consistent rate, so may not fit such a sudden change.

It is possible that fluctuations in the planet’s rotational speed known as the “Chandler wobble” – where small, irregular movement of Earth’s geographical poles across the surface of the globe – could be causing an impact.

Processes in Earth’s inner or outer layers, oceans, tides, or even climate, may also be causing it, such as major earthquakes that can change the length of a day, albeit by a miniscule amount.

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