Space and Physics
PUBLISHED
The solar day is 24 hours long. That's the time it takes the Earth to complete one full rotation on its axis, and as far as humans can tell, this is very accurate.
However, we live in a world of high-precision machines that deal with the effects of physics that we don't feel. For the machines, a 24-hour day is definitely not exact. Left to their own devices, clocks will slowly go out of sync, which is not exactly ideal.
Since the 1970s, authorities have been mitigating this by adding a leap second every so often in order to keep atomic clocks and planetary rotation synchronized. This was a quirky little event when June 30 or December 31 might have had the peculiar time of 23:59:60.
But recently, there have been problems.
Negative seconds
Over the past few billions of years, the Earth’s spin has, by and large, been slowing down due to the interaction with the Moon. But this process is not smooth, and there are fluctuations in the spin due to the internal processes of the Earth. This means that since 2015, the Earth has actually been speeding up a bit.
This reversal in fortunes has an effect on the synchronization of clocks. While all the leap seconds needed until 2016 have been positive, which requires a relatively simple additional second every so often, the increase in spin meant there was a good chance of needing a negative leap second instead.
Just like how adding salt to a recipe is much easier than removing it, a negative leap second might have been a bad idea for all our technology.
The International Bureau of Weights and Measures, the group that assesses units of measurement, is meeting just outside Paris next month between October 13 and 15. The leap second was already on the chopping block, and it was expected that the organization was going to scrap it by 2035.
But now its demise might happen much sooner. Next month, in fact.
Gaining a leap hour
Removing the leap second won’t stop the Earth’s spin and our clocks going out of sync. So one proposal, as reported by Scientific American, is to instead add a leap hour.
This would mean that once there are 3,600 seconds accrued, we can then stick it all on in one go. Since the first addition of a leap second in 1972 there have only been 27, so if the leap hour is the way they want to go then we won’t have to worry about it for a few millennia.
Time is certainly something on the mind of the International Bureau of Weights and Measures at the moment, as thanks to the breakthrough in optical atomic clocks the precision at which we measure time is now beyond regular atomic clocks.
