Earth records its shortest day ever

As the Earth spins, its atmosphere and oceans are pulled by the Sun and Moon.

NASA/Unsplash

As the Earth spins, its atmosphere and oceans are pulled by the Sun and Moon.

Midnight arrived 1.59 milliseconds too soon on Wednesday, June 29, and nobody is sure why.

That day was the shortest since measurements began, with the Earth taking less time to complete a rotation than at any time since the 1960s.

In general there is a slight trend for days to get longer. As the Earth spins, its atmosphere and oceans are pulled by the Sun and Moon. Each tide represents energy coming out of its rotation, so sunrise to sunset slowly takes longer.

By looking at fossil evidence, such as growth rings set down by corals, scientists can see that although a year – the time taken to orbit the Sun – was the same in the time of the dinosaurs, they would have had more days in a year .

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Ever since the discovery of atomic clocks, which are vastly less variable than the Earth’s rotation, global timekeepers have had to take account of this slowing down, by adding occasional “leap seconds”.

The trend is not uniform. In recent years it has reversed, and the rotation has sped up slightly as data released by the International Earth Rotation and Reference System Service shows.It is not clear why but the rotation is also affected by shorter term trends such as geological processes and climate factors.

One possibility is that it reflects a change in how the planet wobbles. Just as in a gyroscope, the spinning Earth can wobble slightly.This appears to have decreased in the past five years – with the smoother spin possibly allowing a burst of speed, which has led to the record for the shortest day fall several times.

A second leap has not been added since 2016. Because of the potential effects on GPS navigation and the chance of problems arising in high-speed trading on the international markets, some countries are keen to do away with added leap seconds. If the trend for speedier spins continues, though, they might instead be dealing with the opposite problem – taking away a second.

– The Times, London

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