The Earth’s rotation is accelerating, causing days to shorten by milliseconds. This phenomenon has scientists reevaluating the need for leap seconds to keep clocks in sync.
In recent years, the planet’s rotation speed has increased, with some days now under 24 hours. On July 10, 2025, the Earth completed a turn 1.36 milliseconds earlier than expected. Further record-short days are forecasted on July 22 and August 5.
Timekeepers use atomic clocks to track time, but the Earth’s actual rotation is not perfectly stable due to various factors like the moon’s pull, seasonal changes, and the movement of its liquid core. To account for these variations, leap seconds have been added since 1972. However, with the Earth speeding up, scientists have not needed one in years.
In 2022, standards bodies voted to retire leap seconds by 2035. But if the trend continues, a negative leap second may be necessary – subtracting a second from UTC – to keep timekeepers aligned. Experts estimate around a 40% chance of this happening before 2035.
Several factors contribute to the Earth’s increasing rotation speed, including:
* Tidal forces: The moon slows down the equator while speeding up higher latitudes.
* Seasonal winds: Summer jet-stream shifts transfer angular momentum back to the solid Earth.
* Core dynamics: A sluggish liquid core lets the crust spin more rapidly.
Climate change also plays a role in slowing down the planet’s rotation. Melting ice sheets and rising seas cause mass redistribution, shifting the axis of the planet. This effect may eventually dominate our planet’s spin changes by century’s end, according to experts.
Source: https://www.futura-sciences.com/en/heres-why-days-are-actually-getting-shorter-and-scientists-are-puzzled_19085