Earth's Shortest Day Could Be Fast Approaching And Most People Don't Even Realize It

There are multiple mysteries that scientists can't explain, with experts remaining particularly baffled when it comes to the cosmos. Scientists struggle to explain much about space, but that doesn't mean there aren't some home-grown conundrums that have baffled researchers. Take, for instance, the fact that our planet is spinning faster and nobody knows why.

One solar day is 86,400 seconds, or 24 hours. In this time, the planet completes one full rotation on its axis. This is just one of those well-established unchanging facts about our planet. Except that it does change. The Earth's rotation isn't a perfect thing. In fact, our home world is usually slowing down on its axis, which means the length of the day increases by an average of roughly 1.8 milliseconds per century. That's obviously imperceptible to us, but if you were to go back in time by 600 million years, a day would only be 21 hours long.

There are multiple reasons for the Earth's rotation not remaining constant. Everything from tidal effects of the moon and sun and the distribution of mass on our planet to seismic activity, weather, and the oceans can have an effect on the speed of the Earth's rotation. But since 2020, our world has actually been spinning faster. Not only have scientists failed to explain why that might be, it means we've already had several of the shortest days in history, and it looks like in 2025 we might once again break the record for Earth's shortest day.

Back in 2020, experts discovered that the Earth had started spinning faster than it had in the previous 50 years. That year saw the shortest 28 days on record and the days have continued to contract every year since. It looks as though that trend will continue, too, which means in 2025 we might well see the shortest day on record.

Though the Earth completes a full rotation in 86,400 seconds, there are tiny variations in this number which can be measured by atomic clocks. These timekeepers combine quartz crystal technology with atoms to tell time with extreme accuracy to the extent that after 10 million years, an atomic clock will be off by just one second. Using this technology, the International Earth Rotation and Reference Systems Service (IERS) can measure the length of days, and since 2020 has recorded shorter days. This began on July 19 of that year when the Earth completed a rotation 1.47 ms quicker than 86,400 seconds. In 2021, there was another recording of -1.47 ms and in 2022 a recording of -1.59 ms. In 2023, the shortest day was -1.31 ms shorter than the average, and in 2024 the Earth completed a rotation 1.66 ms slower than 86,400 seconds, marking the shortest day in recorded history. Now, it seems 2025 could break that record.

Due to the ongoing trend of the Earth's rotation speeding up, IERS has predicted the next shortest day will occur on either July 9, July 22, or August 5, 2025. On these dates, the moon will be furthest from the Earth's equator, which affects the speed of the planet's rotation. As such, the predictions identify August 5 as being the shortest day at roughly 1.51 ms shorter than average. But we might well see the Earth complete a rotation that would result in the day being shortened by more than 1.66 ms which would make 2025 the year with the shortest day in history.

Should we be worried about the Earth's rotation speeding up? Not necessarily. Back in 2022, Leonid Zotov, an Earth rotation expert from Moscow State University, co-authored a study published in the Journal of Geophysical Research: Solid Earth in which he and his colleagues looked into the cause of the increased rotational speed. Lamentably, they couldn't identify one single cause. Zotov told timeanddate.com "Most scientists believe it is something inside the Earth. Ocean and atmospheric models don't explain this huge acceleration." Still, it's thought our planet will slow down again eventually, but not before we have to subtract a second from our clocks to keep up with this new trend.

By 2029, timekeepers think they may need to take that second off our clocks for the first time in history. A study in the journal Nature predicted that if trends continue, our time will require a "negative discontinuity," which essentially means subtracting a second from the clock. That might not seem like much, but the study's authors warn that doing so will pose "an unprecedented problem" for computer network timing. Still, we probably have bigger problems to worry about than a negative temporal discontinuity, such as the ongoing impact of climate change which has prompted dire warnings from experts about the very near future of our planet.