If it seems to you that the days are getting shorter as you get older, you might not be imagining it.
On June 29, 2022, the Earth made one full rotation, which took 1.59 milliseconds less than the average day length of 86,400 seconds, or 24 hours. While the 1.59 milliseconds cut may not seem like much, it’s part of a larger and weirder trend.
Indeed, on July 26, 2022, another new record was set almost set when Earth ends its day 1.50 milliseconds shorter than usual, as reported by The Guardian and the time tracking website Time and date. Time and Date notes that 2020 had the highest number of short days since scientists began using atomic clocks to make daily measurements in the 1960s. Scientists first started noticing the trend in 2016.
While the length of an average day may vary slightly in the short term, in the long term the length of the day has been increasing since the Earth-Moon system formed. This is because over time the force of gravity has moved energy from the Earth – via the tides – to the Moon, moving it slightly further away from us. Meanwhile, because the two bodies are in tidal lock—meaning the Moon’s rotation and spin rates are equivalent, so we only see one side of it—physics dictates that Earth’s day must lengthen if the two bodies are to to remain in tidal lock as the moon moves away. Billions of years ago, the Moon was much closer and the length of an Earth day was much shorter.
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While scientists know that Earth’s days are getting shorter on a short-term scale, the ultimate reason for this remains unclear – along with the effect it may have on the way we as humans keep track of time.
“The speed of the Earth’s rotation is a complicated matter. It has to do with the exchange of angular momentum between the Earth and the atmosphere and the effects of the ocean and the effect of the moon,” Judah Levine, a physicist in the Time and Frequency Division of the National Institute of Standards and Technology, said Discover Magazine. “You can’t predict what’s going to happen very far into the future.”
But Fred Watson, the astronomer of Australia, said ABC News in Australia that if nothing is done to stop it, “you will gradually take the seasons out of the calendar.”
“When you start looking at the really small things, you realize that the Earth is not just a solid ball that spins,” Watson said. “There’s liquid inside, there’s liquid outside, and there’s atmosphere, and all those things splash around a little bit.”
Matt King from the University of Tasmania described the trend to ABC News Australia as “certainly strange”.
“Clearly something has changed, and in a way that we haven’t seen since the beginning of precision radio astronomy in the 1970s,” King said.
Could it be related to extreme weather conditions? As reported by The GuardianNASA has reported that the Earth’s rotation can slow down stronger winds in El Niño years and can slow the planet’s rotation. Similarly, the melting of the ice caps moves the Earth’s matter and thus can change the rotation rate.
Although this minor siphoning of time has little impact on our daily lives, some scientists have called for the introduction of a negative “leap second” that would subtract one second from the day to keep the world on track towards atomic time if the trend continues . Since 1972, leap seconds have been added every few years. The last one was added in 2016.
“It’s entirely possible that a negative leap second would be needed if the Earth’s spin rate increased further, but it’s too early to say whether that’s likely to happen,” said physicist Peter Wibberley of the UK’s National Physics Laboratory. Telegraph. “There are also international discussions about the future of leap seconds and it is also possible that the need for a negative leap second will push the decision to end leap seconds forever.”