Earth's spin slowed down, we may need to add a 'negative leap second'

Officials are saying that we may have to add a "negative leap second" onto the official Universal Coordinated Time (UTC).

UTC is the international method for timekeeping and is based on the atomic clock that is the epitome of precision as it measures the time by the movement of electrons in atoms, hence its "atomic clock" name. Officials that operate the atomic clock look for differences between Earth's rotation speed in time, which averages out to be 86,400 seconds per day, versus what the atomic clock states.

When there is a discrepancy between the atomic clock and Earth's rotation speed, the atomic clock is adjusted, and its recorded down whether Earth's rotation speed has sped up or slowed down. For example, in 2016, a leap second was added at 23 hours, 59 minutes, and 59 seconds on Dec. 31. Officials have been adding leap seconds around every 18 months since 1972, but now reports are indicating that Earth's rotation speed has slowed down, which means that a second may have to be subtracted from the atomic clock, something that is known as a "negative leap second".

A negative leap second has never been added to the atomic clock before, and officials expect that one might be required around 10 years from now to re-sync Earth's rotation speed and atomic clock timings. However, Earth's rotation speed can vary as it relies on a number of factors such as movement of the core, oceans, and atmosphere. It's possible that the Earth could magically speed up in between that now and 10 years from now.

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