Earth’s rotation is randomly speeding up, and nobody is quite sure why. These speedups, which have occurred several times over the last few years, haven’t had any effect on daily life, but they also haven’t gone unnoticed by science. Tuesday, Aug. 5 is the next date when Earth’s rotation is expected to speed up, shortening the day by between 1.25 and 1.51 milliseconds.
According to Time and Date, the current prediction is set by the International Earth Rotation and Reference Systems Service and the US Naval Observatory. The original prediction was 1.51 milliseconds, but it’s since been updated to 1.25 milliseconds. This is also the third time Earth’s rotation has sped up for a day this summer. The other two instances occurred on July 10 and July 22.
Should the first prediction be accurate, Aug. 5, 2025, will be the third shortest day on record behind June 30, 2022, when the Earth spun 1.59 milliseconds faster, and July 5, 2024, when it completed its rotation 1.66 milliseconds faster. If the prediction is off, then it may succeed those two as the shortest day Earth has seen in recorded history.
For reference, Earth generally takes approximately 86,400 seconds to make one full rotation. One millisecond is 0.001 seconds. So, this won’t be noticeable to humans and will not affect anything.
What’s causing Earth to spin faster?
There are numerous reasons why Earth could be spinning faster. The prevailing opinion is that it’s due to the moon’s current position over Earth. When the moon is further north or south than Earth’s equator, it can impact how fast the planet spins.
On Aug. 5, 2025, the moon will be quite a bit further south than the equator, which is likely causing the slightly faster spin. This is expected to have a short-term impact on Earth’s orbit.
Science can’t explain it
Scientists are puzzling over why Earth is speeding up at all. Approximately 245 million years ago, the dinosaurs roamed, and days were an hour and a half shorter than they are today. Earth’s rotation has been slowing ever since, mostly due to the moon’s impact on Earth’s oceans. Science has measured Earth’s rotation subtly slowing down since official records began in 1973.
However, a recent trend shows that Earth’s rotation is speeding up, and since these faster days are mostly explained by the moon’s orbit, science has yet to fully explain why. A research paper posted in Nature in 2023 suggests that Earth’s core may have started slowing down as recently as 2010, which would explain Earth’s faster rotation. However, confirmation doesn’t yet exist.