Earth’s days are getting longer and no one knows why

Everyone knows how long a day is: it’s 24 hours, or 86,400 seconds, right?

Wrong, according to new research which shows that not only has Earth had its shortest day on 29 June 2022, but that, in general, days have been mysteriously getting longer since 2020 - and no one is quite sure why.

The reversal of the trend is a ‘mystery’, according to scientists, as reported by ScienceAlert.

The year 2020 saw the 28 shortest days since 1960, beating the previous shortest day in 2005, according to TimeandDate.com.

But since that point days have been generally getting longer, even after compensating for known factors such as tides and seasonal effects.

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International timekeepers occasionally add a ‘leap second’ to years - to compensate for the fact that Earth’s rotation is changing.

The ‘leap seconds’ are added to keep Earth in time with ‘solar time’ – average length of a day, based on how long it takes Earth to rotate.

We don’t notice, of course – the atomic clocks which control the ones on your phone and your PC will adjust themselves, and everything will go on as normal.

Around the world, atomic clocks either ‘switch off’ for a second, or go to 23.59.60 before moving on to 00.00.00.

Since 2020, the long-term trajectory seems to have shifted towards lengthening, in a change which hasn’t been seen for decades.

Scientists are unsure what’s causing it, although some speculate it could be related to events such as back-to-back La Niña events or even an eruption in Tonga.

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Matt King, Director of the ARC Australian Centre for Excellence in Antarctic Science, University of Tasmania wrote in The Conversation, “Despite Earth reaching its shortest day on June 29 2022, the long-term trajectory seems to have shifted from shortening to lengthening since 2020.

"This change is unprecedented over the past 50 years.Scientists have speculated this recent, mysterious change in the planet's rotational speed is related to a phenomenon called the "Chandler wobble" – a small deviation in Earth's rotation axis with a period of about 430 days.

“Observations from radio telescopes also show that the wobble has diminished in recent years; the two may be linked.

“One final possibility, which we think is plausible, is that nothing specific has changed inside or around Earth.

"It could just be long-term tidal effects working in parallel with other periodic processes to produce a temporary change in Earth's rotation rate.”

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