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Earth’s Rotation Speeding Up, Resulting in Shorter Days
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In a surprising turn, scientists have observed that the Earth’s rotation is increasing, causing days to become fractions of a millisecond shorter.While seemingly insignificant, this phenomenon has major implications for global timekeeping and could lead to the unprecedented subtraction of a leap second.
Shorter Days: A Millisecond Matter
The shortening of days isn’t measured in minutes or hours, but in milliseconds.High-precision atomic clocks have been tracking Earth’s Length of Day (LOD), revealing a steady decrease as 2020. This acceleration, though subtle, is prompting discussions about adjusting Coordinated Universal Time (UTC) [1].
Did You Know? The shortest day on record occurred on July 5, 2024, when Earth completed a rotation 1.66 milliseconds faster than the standard 24 hours.
Potential Leap Second Subtraction
Since 2020, the trend of shorter days has persisted. Experts suggest that if this continues, 2029 could mark the first time a leap second is subtracted, rather than added, to align atomic time with Earth’s rotation. Leap seconds are typically added to account for the Earth’s slightly irregular rotation [2].
Historical Shifts in Earth’s day Length
A typical day on Earth consists of 86,400 seconds, or 24 hours, based on its rotation. Though, this isn’t a constant value. Over millions of years, Earth’s rotation has gradually slowed due to gravitational interactions, internal core dynamics, and tidal forces from the Moon. For example, during the dinosaur era, a day lasted approximately 23 hours. Predictions suggest that Earth may eventually experience 25-hour days, but this change could take over 200 million years.
Pro Tip: Keep an eye on official announcements from the International Earth Rotation and Reference Systems Service (IERS) for any potential leap second adjustments.
Key Dates in 2025
Predictions for 2025 indicate similarly short days:
- july 9: LOD of -1.30 ms
- July 22: LOD of -1.38 ms
- August 5: LOD of -1.51 ms
These dates represent the shortest days of the year and reflect the ongoing acceleration trend.
The Mystery Behind the Acceleration
The cause of Earth’s faster rotation remains a scientific puzzle.Researchers are exploring various factors, including seismic shifts, changes in the planet’s fluid core, and fluctuations in earth’s angular momentum. While the Moon’s tidal friction is known to slow Earth’s spin, other internal dynamics might potentially be contributing to the current acceleration.
Despite the headlines, scientists emphasize that there is no cause for alarm. While Earth’s rotation rarely speeds up, such fluctuations have occurred in the past and usually stabilize over time. The long-term trend still indicates that Earth’s rotation is slowing down, not speeding up indefinitely.
Earth’s Rotation Speed: Key Metrics
| Metric | Value | Unit |
|---|---|---|
| Typical Day Length | 86,400 | Seconds |
| Shortest Day on record (July 5, 2024) | -1.66 | Milliseconds |
| Potential Leap Second Adjustment | 2029 |