On July 22, 2025, Earth will complete a full rotation in approximately 1.34 milliseconds less time than the standard 24 hours. This phenomenon marks one of the shortest days ever recorded, part of a puzzling trend in Earth’s rotational behavior observed over recent years. While the difference may seem negligible, it raises intriguing questions about the forces affecting our planet’s rotation.
Various factors contribute to the speed of Earth’s rotation, which is not a fixed value. In the distant past, a day on Earth was significantly shorter than the current 24 hours. According to a study published in 2023, days lasted about 19 hours for a considerable period of Earth’s early history. This alteration was primarily due to the interaction between solar atmospheric tides and lunar ocean tides. Over time, however, the primary influence on day length has shifted to tidal friction caused by the moon, which is gradually moving away from Earth. This process has led to a consistent lengthening of days.
Recent Trends in Earth’s Rotation
The trend of shorter days emerged notably from 2020 onwards. Prior to this period, the shortest day recorded was 1.05 milliseconds less than 24 hours, documented since the advent of atomic clocks in 1973. Subsequently, Earth has repeatedly broken its speed records, culminating in the shortest day ever measured on July 5, 2024, when Earth’s rotation was completed 1.66 milliseconds faster than usual.
Looking ahead, scientists have indicated that July 9, July 22, and August 5, 2025, could potentially be the shortest days of the year. However, new data suggests that July 10 has claimed the title for 2025, clocking in at 1.36 milliseconds less than 24 hours. This makes July 22 a close second, with an expected rotation completion of 1.34 milliseconds early. If predictions hold, August 5 will be approximately 1.25 milliseconds shorter than usual, confirming July 22 as the year’s second-shortest day.
Exploring the Causes
The underlying reasons for this acceleration in rotational speed remain unclear. Some researchers suggest that melting polar ice and rising sea levels may influence Earth’s spin, although this redistribution of mass might be moderating the acceleration rather than causing it. A more likely explanation involves the dynamics of Earth’s liquid core, which could be redistributing angular momentum, resulting in a slightly faster spin of the mantle and crust.
Leonid Zotov, a leading authority on Earth rotation at Moscow State University, stated, “The cause of this acceleration is not explained. Most scientists believe it is something inside the Earth. Ocean and atmospheric models don’t explain this huge acceleration.” Zotov predicts that Earth’s rotation may soon decelerate again, indicating that the recent speeding up could be a temporary anomaly within the long-term trend toward slower rotation and longer days.
As Earth approaches another milestone in its complex rotational history, the implications of these changes extend beyond mere curiosity. Understanding the mechanics behind Earth’s spin not only enhances our knowledge of planetary science but also invites further investigation into the interactions between our planet and its celestial neighbors.
