The Earth is spinning faster, threatening to take away one second: That could be a problem

Scientists report that on July 10, July 22, and August 5, 2025, the Earth will spin a little faster, making those days shorter by about 1.3 to 1.6 milliseconds, reports CNN.

Researchers from the International Earth Rotation and Reference Systems Service (IERS), supported by institutions such as the Scripps Institution of Oceanography, have identified the position of the moon as a key driver of this temporary change.

As they stated, July 10 was the shortest day of the year so far, lasting 1.36 milliseconds less than 24 hours. The length of a day is said to be the time it takes for a planet to rotate on its axis - an average of 24 hours or 86,400 seconds, but in reality, each rotation is slightly irregular due to various factors, such as the gravitational pull of the moon, seasonal changes in the atmosphere and the influence of the Earth's core.

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As a result, a full rotation typically takes a little less or a little more than 86,400 seconds—a difference of only a few milliseconds that has no apparent impact on everyday life. However, these deviations can, in the long run, affect computers, satellites and telecommunications, which is why even the smallest time deviations are tracked using atomic clocks, which were introduced in 1955.

Some experts believe that this could lead to a scenario similar to the Y2K problem, which threatened to bring modern civilization to a halt.

Atomic clocks count the oscillations of atoms in a vacuum chamber inside the clock to calculate 24 hours with the highest degree of precision, and the time obtained is called UTC or Coordinated Universal Time, which is based on about 450 atomic clocks and is the global standard for time measurement, as well as the time to which all our phones and computers are set.

Astronomers also track the Earth's rotation - using satellites that check the planet's position relative to fixed stars, they can detect small differences between the timing of atomic clocks and the time it actually takes for the Earth to complete a full rotation.

Last year, on July 5, 2024, Earth experienced the shortest day ever recorded since the advent of the atomic clock 65 years ago, at 1.66 milliseconds less than 24 hours. "Since 1972, we have had a trend of slightly faster days. But there are fluctuations.

It's actually like following the stock market. There are long-term trends and then there are peaks and troughs," said Duncan Agnew of the Scripps Institution of Oceanography and a research geophysicist at the University of California, San Diego.

After decades of relatively slow rotation, in 1972 the Earth's rotation had accumulated such a lag relative to atomic time that the International Earth Rotation and Reference Systems Service (IRS) mandated the addition of a "leap second" to UTC, similar to a leap year, which adds an extra day to February every four years to account for the difference between the Gregorian calendar and the time it takes Earth to complete one orbit around the Sun.

Since that year, a total of 27 leap seconds have been added to UTC, but the rate of addition has slowed due to the acceleration of the Earth—nine leap seconds were added during the 1970s, while no new leap seconds have been added since 2016. According to Agnew, the shortest changes in the Earth's rotation come from the Moon and the tides, which cause it to slow down when the satellite is above the equator, and faster when it is at higher or lower altitudes.

"This effect is amplified by the fact that the Earth naturally rotates faster during the summer - a result of the atmosphere itself slowing down due to seasonal changes, such as the jet stream moving north or south. The laws of physics dictate that the total angular momentum of the Earth and its atmosphere must remain constant, so the rotational speed lost by the atmosphere is taken over by the planet itself. Similarly, in the last 50 years, the Earth's core has also been slowing down, while the solid Earth around it has been speeding up," he said.

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He explains that scientists can use this to predict whether the coming day could be particularly short. Physicist and National Institute of Standards and Technology time-frequency division associate Judah Levin said these fluctuations have short-period correlations, meaning that if the Earth speeds up one day, it tends to speed up the next day as well.

"But that correlation disappears as you go to longer and longer intervals. And when you get to a year, the prediction becomes quite uncertain. In fact, the International Service for Earth Rotation and Reference Systems does not predict more than a year in advance," he said.

Since many fundamental technological systems rely on clocks and time to function, such as telecommunications, financial transactions, power grids and GPS satellites, the occurrence of a negative leap second is, according to Levin, somewhat similar to the Y2K problem - the moment at the turn of the last century when the world thought some kind of doomsday was coming because computers might not have been able to switch to the new date format, moving from '99' to '00'.

Climate change also contributes to the leap second problem, but in a surprising way because it serves to counteract the forces that speed up Earth's rotation. In a study published last year in the journal Nature, Agnew detailed how melting ice in Antarctica and Greenland is spreading across the oceans, slowing the Earth's rotation - similar to how a skater spins with their arms overhead, but spins more slowly if their arms are bent alongside their body.

"If that ice hadn't melted, if there hadn't been global warming, we'd already have a negative leap second or be very close to it," Agnew said.