Our house There is a planet in Hurry. On June 29, 2022, Earth completed its shortest day since scientists began keeping records in the 1960s, pulling a full rotation 1.59 milliseconds faster than normal.
Land haste is a trend. In 2020, the planet recorded its 28 shortest days on record, and it continued to spin rapidly into 2021 and 2022. Before scientists could even verify that June 29 was that record-setting day, our world almost older than himself: it was blazed through on July 26, 2022, 1.50 milliseconds ahead of schedule.
We will likely see more shorter days as the Earth continues to accelerate, says Judah Levine, a professor at the University of Colorado-Boulder and a longtime expert at the National Institute of Standards and Technology (NIST). That Earth’s days are getting shorter is no cause for concern, he says, because the actual time difference is fractions of a second over the course of a year. But strangely, while scientists know that changes to the Earth’s inner and outer layers, oceans, tides and climate can affect how quickly it disappears, its they know what is driving the current rush.
Nobody is perfect – not even our planet. On average, the Earth rotates on its axis every 24 hours, or every 86,400 seconds. But for a variety of reasons, from the planet’s imperfect shape to its complex interior, each day is not exactly the same as the day before.
Plus, a 24-hour day is just the quality we’ve come to expect. Now. The Earth’s rotation is slowing down in the long term due to the pull of the Moon on our earth. Just a few hundred million years ago, for example, an Earth day was only 22 hours long. In the coming thousands of years, Earth’s day will last much longer.
So what’s driving the shorter days of late, which goes against the long-term trend? One hypothesis floating around so far involves the “Chandler wobble.” Discovered in the 1800s, the phenomenon explains how the less-than-perfect Earth wobbles slightly, like a spinning top, as it slows down. Leonid Zotov told timeanddate.com that the wobble had mysteriously disappeared between 2017 and 2020, which could help Earth finish the day a little faster.
Another idea is that climate change may be affecting the planet’s rotational speed. When glaciers melt into the ocean, the shape of the Earth changes slightly, becoming flatter at the poles and bulging at the equator. But Levine says this effect can’t explain why the planet would suddenly spin faster because melting glaciers should have the opposite effect: The planet’s moment of inertia would increase, slowing us down.
For Levine, the likely culprit is more precise.
“One of the possibilities is the exchange of momentum between the Earth and the atmosphere,” he says. “The sum of those two is a constant, which means, for example, that if the atmosphere slows down the Earth speeds up. Or conversely, if the atmosphere accelerates, the Earth slows.”
The same thing can happen deep inside our world: The deep core and the mantle – the large layer between the core and the surface – can move at slightly different speeds. According to him, there could be an exchange of angular momentum between the deep core of the Earth and the mantle.
“Both of those effects … can either pump speed into the Earth’s surface, or remove speed from the Earth’s surface,” Levine says. But the dynamics of the Earth’s atmosphere and interior are so complex that it is impossible, at least for now, to point to one of these factors as the definitive cause of the planet’s rapid speed.
Nature doesn’t always obey with the strictness of a clock or calendar, and the planetary timekeepers tend to make a few tweaks. There is a leap year, for example, because we need an extra day every four years to keep the 365-day calendar in line with the Earth’s revolution around the Sun. Because the day is getting much longer over time as the Earth’s rotational speed slows, timekeepers spend a leap second every now and then to keep human time in sync with the Solar System.
As the Earth accelerates, we are facing an unprecedented possibility: Adding a second negative leap. In other words, says Levine, if the planet continues to spin too fast, then by the end of the decade clock masters may have to erase an entire second. For example, the clocks might skip from 23:59:58 on December 31, 2029 to 00:00:00 on January 1, 2030.
“If you asked me about the negative thing [leap second] five years ago,” Levine says, “I would have said, ‘Never.’ But in the last year or so, the Earth has definitely been accelerating. And now, if that pace were to continue on – and it’s a big deal two then – we could have negative leadership second in about seven years, maybe eight years.”
This has never been done before. Some scientists wonder if doing so could introduce a troublesome barrier into computer systems. Given the way our world keeps surprising us, however, Levine is not yet convinced that time will come.
“You should remember, that requires extrapolation over six years – and we’ve already been burned by extrapolation. So, I wouldn’t be ready to bet the farm.”