The practice of adding ‘leap seconds’ to official clocks to keep them in sync with Earth’s rotation will be put on hold from 2035.
Key points
- The decision was made by representatives of governments worldwide at the General Conference on Weights and Measures (CGPM) outside Paris on 18 November.
- It means that from 2035, or possibly earlier, astronomical time (known as UT1), which is determined by Earth’s rotation, will be allowed to diverge by more than one second from Coordinated Universal Time (UTC), which is based on the steady tick of atomic clocks.
- Since 1972, whenever the two time systems have drifted apart by more than 0.9 seconds, a leap second has been added to UTC.
- Leap seconds aren’t predictable, because they depend on Earth’s natural rotation. They disrupt systems that are based on precise timekeeping.
- Although in the long term Earth’s rotation is slowing as a result of the pull of the Moon, a speed-up since 2020 has also made the issue more pressing, because, for the first time, a leap second might need to be removed, rather than added.
Earth is rotating faster
- In 2020, scientists recorded the 28 shortest days since 1960.
- On June 29, 2022, Earth completed its quickest-ever spin (by 1.59 milliseconds), followed quickly by a day that lasted 1.50 milliseconds less on July 26, 2022.
- The previous record for the shortest rotation was July 19, 2020, when the Earth’s rotation took 1.4602 milliseconds less than 24 hours.
Why Earth is spinning faster, still remains a mystery but some theories suggest that it could be because of the:
- melting of the glaciers means less weigh on the poles,
- Motions of our planet’s inner molten core,
- Seismic activity and
- ‘Chandler wobble,’ which is a small deviation in the Earth’s axis of rotation.
