If you find yourself saying that there aren’t enough hours in the day, there’s a scientific reason behind that. Scientists believe that the Earth is spinning faster than it has in 50 years, which is causing each day to be slightly shorter than 24 hours. For decades, the Earth actually took slightly longer than 24 hours to complete a rotation, but since last year, it has been taking slightly less than 24 hours.
On July 19, 2020, the day was 1.4602 milliseconds shorter than the full 24 hours—the shortest day since scientists began keeping records in the 1960s. Similar to leap year, timekeepers at the Paris-based International Earth Rotation Service have added what’s known as so-called “leap seconds” to a total of 27 days since the 1970s, the most recent one occurring on New Year’s Eve in 2016. Those few extra seconds help satellites and communications equipment accurately align with solar time, which is determined by the positions of the stars, moon, and sun.
So, what exactly is causing this to happen? A 2015 study published in Science Advances suggests that it may be due to global warming. As glaciers melt, the redistribution of mass is making the Earth shift and spin faster on its axis. “It’s quite possible that a negative leap second will be needed if the Earth’s rotation rate increases further, but it’s too early to say if this is likely to happen,” says Peter Whibberley, senior research scientist with National Physical Laboratory’s time and frequency group.
On average, scientists say that the days are approximately 0.5 seconds shorter than 24 hours. While this difference is only noticed at the atomic level, experts say that it may have a significant impact. “It’s possible that the need for a negative leap second might push the decision towards ending leap seconds for good,” says Whibberley.