The Earth is pretty good at keeping its pace. However, variations do happen. And on three separate days this summer — July 9, July 22, and August 5 — the Earth will spin notably faster than usual.
Of course, you’re not likely to feel dizzy or notice the shift at all, but scientists are well aware of the shift. They say that over a 24-hour period, the Earth’s rotation will take a few milliseconds less than it usually does — about 1.3 to 1.51 milliseconds less, to be exact. It’s faster than the blink of an eye or a heartbeat, but it’s significant, either way.
Why is Earth spinning faster now?
24 hours (86,400 seconds), or a full day, is the time it takes for the Earth to rotate fully on its axis. That exact rotation speed depends on a number of factors, including the Earth’s mass, as well as its distance from the moon. With the moon closer to the poles, the Earth’s spin speeds up. On the days the Earth’s rotation is set to speed up, the moon will be at its furthest distance from Earth’s equator, altering the impact of its gravitational pull on Earth’s axis.
Richard Holme, a geophysicist at the University of Liverpool, said, per Live Science, “‘There is more land in the northern hemisphere than the south. In northern summer, the trees get leaves, this means that mass is moved from the ground to above the ground — further away from the Earth’s spin axis.” Thus, it will spin faster.
Interestingly, while the Earth had been gradually speeding up on the regular, climate change has impacted the Earth’s rotation in a major way. It’s actually caused it to slow down.
A 2024 study published in Nature pointed to the melting of the polar ice caps as a significant factor in the Earth’s decelerated pace. At the time, Professor Duncan Agnew, from the Scripps Institution of Oceanography, and author of the study explained it by using the example of a skater spinning on ice. “If they hold their arms out, their spinning is slower, but if they bring them into their body, then they speed up. This demonstrates the conservation of angular momentum, a principle which applies to all spinning objects, including the Earth.”
He continued, “As polar ice melts, the water spreads out over the whole ocean, causing the same effect as the skater spreading their arms out — the Earth slows down. More rapid melting would slow the Earth more rapidly, opposing the speedup that has been seen in recent years.”
Experts began measuring the speed at which the Earth rotates in the 1950s. While variations in speed are not uncommon, the shortest day ever recorded happened just last year on July 5, 2024. On that day, the Earth completed its full rotation 1.66 milliseconds faster than usual. Experts believe July 9, 2025 may break the previously set record.
No comments