Prepare for a Faster-Spinning Earth: How Days Are Set to Get Shorter in the Coming Months!

Earth is spinning a bit faster these days, leading to some notably shorter days. On specific dates—July 9, July 22, and August 5—our 24-hour day will be up to 1.5 milliseconds shorter than usual. That’s because of the moon’s position affecting Earth’s rotation.

To understand this, remember that a day is based on how long it takes for Earth to fully rotate—about 86,400 seconds, or 24 hours. But things like the moon’s position, the sun’s pull, and even changes in Earth’s mass can impact this rotation.

Interestingly, Earth’s rotation has been slowing down over billions of years. Long ago, about 1 to 2 billion years ago, a day was only 19 hours long! This was due to the moon being much closer to Earth, which made its gravitational pull stronger, causing a faster spin.

In modern times, researchers have noticed fluctuations in how quickly Earth spins. In fact, scientists recorded the shortest day ever on July 5, 2020. That day was 1.66 milliseconds shorter than the traditional 24 hours.

During the upcoming short days in July and August, the moon will be farther from Earth’s equator. This changes how its gravitational pull affects our planet. Think of Earth like a spinning top; holding it at its center means it won’t spin as quickly compared to holding it from the top and bottom. With the moon closer to the poles, the Earth speeds up.

These changes are natural, but human activities are also playing a role. NASA research shows that shifts in ice and groundwater—partly due to climate change—are changing our days. Between 2000 and 2018, we’ve seen this lengthen days by about 1.33 milliseconds each century. One major event, like the 2011 Japan earthquake, even shortened our day by 1.8 microseconds!

Seasonal changes also impact Earth’s rotation. Richard Holme, a geophysicist at the University of Liverpool, explains that during summer in the northern hemisphere, trees grow leaves. This moves mass higher up, which affects how fast Earth spins. Just like when a figure skater pulls in their arms to spin faster, Earth’s speed changes based on mass distribution.

Despite these shifts, your clocks will still read 24 hours. The variation isn’t noticeable on a daily basis. We might only need to adjust time zones if the difference exceeds 0.9 seconds. So far, that hasn’t happened in a day. If it does, the International Earth Rotation and Reference Systems Service keeps track and will add a “leap second” to account for discrepancies.

As we learn more about how Earth spins, it’s clear that both natural rhythms and human activity shape our experience of time. Understanding this can deepen our appreciation for the dynamics of our planet.

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