If summer feels like its flying by – you may be right.
Earth has seen a stretch of historically shorter days this month as the planet’s rotation mysteriously accelerates.
The shortest, July 9 and 10, each registered 1.3 milliseconds less than the standard 24-hour day, which measures exactly 86,400 seconds long. The head-scratching phenomenon repeated on July 22 – and experts expect it once more on August 5.
While scientists have been puzzled by the increase in speed, some have chalked it up to normal variations in Earth’s rotation, governed by the moon’s gravitational pull, effects of the atmosphere and our planet’s core.
One astronomer, however, has another theory.
Speaking to the Daily Mail, Professor David Jewitt, an astronomer at UCLA, explained that the cosmic trend may come down to a principle called the conservation of angular momentum, a physics rule that governs how rotating bodies behave when mass shifts.
In short, he says, as Earth’s mass distribution changes – whether from melting glaciers, shifting tectonic plates, or even atmospheric dynamics – it can cause the planet to spin slightly faster.
Though the slight changes are just fractions of a millisecond, the accumulation of them could be enough to disrupt computers and satellites, and even challenge timekeeping systems around the world.
Earth is set to experience another short day on August 5, 2025 (Stock Image)
Scientists say Earth’s increasing rotation speed could have disastrous consequences, intensifying hurricanes, raising sea levels and triggering catastrophic flooding.
As the planet spins faster, centrifugal force pushes water away from the poles toward the equator.
Even a one-mile-per-hour increase in rotational speed could raise sea levels by several inches near the equator, enough to cause severe flooding in coastal cities already near sea level.
In a more extreme scenario, where Earth spins 100 miles per hour faster, equatorial regions could begin to drown under rushing polar waters.
For survivors of the flooding, daily life would become increasingly hostile. A faster spin would shorten the solar day to just 22 hours, throwing off circadian rhythms, like resetting your internal clock two hours earlier every day with no time to adjust.
Studies have shown that changes like daylight saving lead to increased rates of heart attacks, strokes, and driving accidents – this would be even more severe.
NASA astronomer Dr Sten Odenwald explains that weather patterns would also grow more extreme with a faster spin, fueling more powerful storms.
‘Hurricanes will spin faster and carry more energy,’ Dr Odenwald says, due to the intensified Coriolis effect, the force that causes storms to rotate.
Deviations – even as small as these – are tracked using atomic clocks, which precisely measure time by counting the oscillation of atoms in its vacuum chamber. The result is the global timekeeping standard, Coordinated Universal Time or UTC.
Astronomers also use a variety of tools, such as satellites, to identify discrepancies between atomic clocks and Earth’s rotation.
‘It’s like watching the stock market, really,’ Duncan Agnew, a research geophysicist at the University of California, San Diego, told CNN. ‘There are long-term trends, and then there are peaks and falls.’
Recent years have seen a number of short days. July 19, 2020, clocked in at 1.47 milliseconds shorter than usual, while June 30, 2022, lost 1.59 milliseconds. Last year, on July 5, 2024, Earth experienced the shortest day on record since the creation of the atomic clock in 1949, which was 1.66 milliseconds shorter than the typical day.
Jewitt told the Daily Mail that Earth rotates in a closed system – outer space – making its rotation relatively consistent.
But changes can be influenced by the moon’s gravitational pull, ocean currents and jet streams, or even within the planet’s core.
Earth’s interior, namely its molten core, can impact the planet’s spin, and Agnew previously told CBS News that its unpredictable behavior has triggered an acceleration for nearly half a century.
It was, however, offset by ice melting at Earth’s poles, which slowed the planet’s rotation by shifting the mass from the poles to the center.
Last year, multiple NASA-funded studies suggested that melting glaciers, which redistributed water, caused the Earth’s axis to change – thus impacting rotation.
The phenomenon has been likened to how a figure skater spins: they slow when their arms are extended outwards, but accelerate when their limbs are over their head.
‘If everybody sat down at the same time, that would be like a skater pulling in their arms, and that would make the Earth rotate a little bit faster,’ Jewitt explained.
Other surface-level phenomena, like tree growth, can also affect Earth’s rotation, he added. As trees’ leaves fall, that places Earth’s mass closer to the axis of rotation, thus making it, in theory, spin faster.
Professor David Jewitt has said that the change in the speed of Earth’s rotation likely stems from changes inside the planet’s core
There have already been three days in 2025 that were shorter than the standard 24-hour solar day (Stock Image)
But contrary to the latest phenomenon, the Earth’s rotation speed has actually slowed in the grand cosmic scheme – and its a trend researchers say will continue.
Millions of years ago, during the Proterozoic eon, a single day on Earth is believed to have been approximately 19 hours long – just five hours shy of our modern-day standard.
As the planet’s rotation has gradually decelerated by mere fractions of a second, timekeepers introduced ‘leap seconds’ in 1972.
Since then, 27 leap seconds have been tacked on to the UTC, but the rate at which they’ve been added has slowed over the years due to Earth’s acceleration. There hasn’t been a leap second added since 2016.
But if our planet’s spin continues to increase, experts warn one second might need to be removed from the UTC, referred to as a ‘negative leap second.’ In that instance, it would mean we’ve lost enough cumulative milliseconds that the clocks would need to be adjusted in order to keep up with Earth’s rotation.
There has never been a ‘negative leap second,’ Agnew said, ‘but the probability of having one between now and 2035 is about 40 percent.’
