Earth’s rotation speeding up again, Scientists predict shorter days this Summer

If you’ve ever wished for more hours in the day, now might not be the time. Scientists have found that Earth is spinning a little faster than usual this month, and that means the days are becoming slightly shorter. The difference is small, but it’s enough to catch the attention of astronomers.

After July 9 saw Earth shave off around 1.3 milliseconds from the usual 24-hour cycle, two more days, July 22 and August 5, are expected to do the same. Researchers predict that these days will each be between 1.3 and 1.5 milliseconds shorter than usual. It’s not something we’ll feel in daily life, but it does matter in global timekeeping.


Several factors can change the speed at which Earth spins. The most important one at the moment is the moon. While the moon usually slows down Earth’s rotation, on certain days, depending on its angle and distance from Earth’s equator, it can have the opposite effect.


On July 22 and August 5, the moon will be closer to the poles and farther from the equator, which can speed up the planet’s spin, much like a figure skater pulling their arms in to spin faster. The moon’s elliptical and tilted orbit adds to this strange effect.


While the moon is the major player here, it’s not the only thing that changes how Earth spins. Big earthquakes can shift mass under Earth’s surface, causing it to spin slightly faster or slower. The 2011 Japan earthquake shortened the day by 1.8 microseconds.

Even climate change and melting ice can shift mass on the planet. NASA says that between 2000 and 2018, melting polar ice added about 1.33 milliseconds per century to the day’s length. However, those changes tend to slow the Earth down, not speed it up. Seasonal shifts also play a role. In the northern summer, trees grow leaves, and this mass being lifted further from the Earth’s center can slow the spin slightly.


Although we won’t notice these shorter days in our routines, precision matters when it comes to global systems. GPS, satellites, internet networks, and military systems rely on exact timing. That’s why agencies like the International Earth Rotation and Reference Systems Service (IERS) keep track of Earth’s spin and occasionally adjust official time by adding or subtracting leap seconds.


As Earth keeps spinning a bit faster this month, scientists are watching closely. And even though we’re losing just milliseconds, it’s another reminder of how dynamic and ever-changing our planet is.