9 hours ago
Get Ready For The Shortest Day Since Records Began As Earth Spins Faster
Earth could be about to record its fastest-ever rotation. Since 2020, Earth has been rotating faster than at any point since records began in 1973, with each successive year producing the shortest day. Last year, the shortest day was recorded on July 5, and Earth is expected to get close to this again on or close to July 9, July 22 and August 5, according to
"Rapidly spinning globe. Symbolic of time passing, travel and other metaphors of space and time."
Earth takes a nominal 24 hours to rotate once on its access, which is equal to 86,400 seconds.
Until 2020, Earth's rotation had been gradually slowing down, and the shortest ever day recorded was just 1.05 milliseconds under 86,400 seconds. However, on July 19, 2020, Earth rotated 1.47 milliseconds less than 86,400 seconds. Last year, on July 5, it was even shorter at 1.66 milliseconds.
Since 2020, Earth has seen 28 of its fastest days and predictions from International Earth Rotation and Reference Systems Service and U.S. Naval Observatory indicate that Earth will again rotate faster on July 9, July 22 or August 5.
The uncertainty comes from the exact position of the moon, which acts as a drag factor, particularly when it's close to the equator. In the long-term, the moon is gradually slowing down the Earth's rotation, its gravitational pull causing tides and making Earth's orbital path around the sun slightly elliptical.
Precise measurements of the length of a day come from atomic clocks and monitoring by the IERS.
Scientists do not know why Earth's rotation has been speeding up since 2020. various factors are likely at play, including the motion of Earth's core and mantle, a shifting of mass due to the melting of ice sheets and glaciers, and variations in ocean currents and air movement. All of these could influence the day length by milliseconds. It could also be down to the 'Chandler wobble' — the movement of Earth's geographical poles across its surface.
Historically, international timekeepers have added leap seconds to keep atomic time aligned with Earth's spin. However, since Earth is now rotating faster, not slower, so leap seconds are redundant. Instead, negative leap seconds— i.e., removing a second) — are being considered. IERS confirmed earlier this month that no leap second would be added in 2025. The last leap second was positive and used at the end of December 2016. Scientists are unsure what to do because the current speeding-up may be a blip in a longer trend of Earth's rotation slowing.
It may seem trivial, but the fact that Earth is spinning faster in 2025, shaving milliseconds off the day, is critical for maintaining time accuracy worldwide. Maintaining alignment between Earth time and atomic time is crucial for GPS and satellite navigation, financial systems reliant on precise timestamps and synchronizing networks across the world.
