Shorter days ahead? Why Earth might spin faster on 3 days in July and August

Should we expect shorter days soon?

Earth is likely to spin slightly faster in July and August, which could lead to shorter days.

Notably, the Earth completes a little more than 365 full spins on its axis each year. That is the total number of days we have in a year.

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However, it was not always like this. Some studies show that in the past, Earth took between 490 and 372 days to complete one trip around the Sun.

So, which days in July and August might be the shortest? And what is the reason behind this change?

Let’s take a look:

Why and when Earth is predicted to spin faster

A scientist has warned that Earth’s rotation is speeding up unexpectedly, with the shortest day in history possibly just weeks away.

Graham Jones, an astrophysicist from the University of London, said the Earth’s spin may increase slightly on three specific days, July 9, July 22, and August 5, he told Daily Mail.

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The difference will be very small, measured only in milliseconds.

On these days, the length of a day might drop by 1.30, 1.38, or 1.51 milliseconds, one after the other.

Experts say that even a slight change can impact satellite systems, GPS accuracy, and how we keep track of time.

Leonid Zotov, a researcher at Moscow State University, said: “Nobody expected this, the cause of this acceleration is not explained.”

Since 2020, scientists have observed the Earth turning slightly quicker than usual, but they are still unsure why this is happening.

Earlier, the planet had been slowing down gradually, mainly due to the moon’s pull, which over time helped shape our current 24-hour days.

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Typically, the Earth takes 24 hours, or exactly 86,400 seconds, to complete one full spin, known as a solar day.

Judah Levine, a physicist at the National Institute of Standards and Technology, told Discover Magazine in 2021, “This lack of the need for leap seconds was not predicted.”

“The assumption was, in fact, that Earth would continue to slow down and leap seconds would continue to be needed. And so this effect, this result, is very surprising.”

If the Earth keeps rotating faster, timekeepers might need to make changes to official time, which could include removing a leap second for the first time ever in 2029.

Why is Earth spinning faster?

The Earth’s rotation is not perfectly steady. It can shift by a few milliseconds now and then.

This happens because natural forces, such as earthquakes and ocean movements, can change the planet’s spin slightly.

Other reasons include melting glaciers, changes in Earth’s molten core, and weather patterns like El Nino, which can either slow down or speed up rotation by small amounts.

Scientists use atomic clocks to track these tiny changes with high precision. The recent increase in spin has caught many of them off guard.

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According to reports, the fastest day so far was on July 5, 2024, when the Earth spun 1.66 milliseconds faster than the usual 24 hours.

Earthquakes are also known to affect the planet’s rotation. In March 2011, a magnitude 9.0 earthquake near Japan shifted the Earth’s axis and slightly shortened the length of a day.

Dr Richard Gross from Nasa’s Jet Propulsion Laboratory told Popular Mechanics in 2011, “Earthquakes can change the Earth’s rotation by rearranging the Earth’s mass. This is what a spinning ice skater does to make herself spin faster. She moves her arms closer to her body, she’s moving her mass closer to the axis about which she’s rotating.”

Understanding the causes of this spin change involves looking at what’s happening inside the Earth, from moving molten layers deep in the core to powerful ocean currents and winds high in the sky.

Earth’s interior is not solid all the way through. Its centre is made of hot, liquid metal that flows and shifts. This movement can change the planet’s balance, like a skater turning faster by pulling in their arms.

Currents in the ocean and jet streams, fast air flows high up in the atmosphere, also move mass around, leading to small changes in the speed of Earth’s rotation.

Scientists are looking at all of these, the moon’s pull, movement in the core, ocean flow, and wind, to understand what’s happening.