Why is the Earth spinning faster all of a sudden?
by Kai Stubel
08/13/2022, 12:08 PM
The day is divided into 24 hours. But the Earth does not adhere to these specifications – sometimes it rotates a little slower or faster. What is remarkable is that it has been spinning faster and faster in recent years. But why is this?
The earth is spinning faster and faster. Thus, the length of the day decreases. June 29, 2022 was the shortest day since the 1960s. At that time, atomic clocks were used to accurately determine the length of the day. So June 29, 2022 was 1.59ms shorter than today’s average. This is 86,400 seconds, or 24 hours. Finally, on July 26, a new record was lost – the day was 1.5 milliseconds shorter.
And a trend is emerging: “Since 2016, the Earth has been accelerating,” Leonid Zotov of Lomonosov State University in Moscow told CBS. “It’s transforming this year faster than it was in 2021 and 2020.” In 2020, the average day length was less than 28 times. But why is the Earth’s rotation accelerating?
“The reason has not been clarified” to ntv.de, Ulrich Koehler, a planetary geologist at the Planetary Research Institute at the German Aerospace Center (DLR). “But it certainly has something to do with the fact that there are mass displacements in or on the land.” Because the Earth always rotates faster when the mass moves closer to its center. “You know it from a snowboarder doing a spin,” Kohler explains. “If he pulls her arms close to her body, she turns faster.” So one talks about the effect of rotation.
Climate change a possible cause
But what mass last came close to the center in Earth’s fall? According to Koehler, the answer to the mystery could lie in the outer fluid of Earth’s outer core. The currents could have shifted the proportions of the iron and nickel elements there. So nickel is slightly heavier than iron. If its ratio increases near the center of the Earth, this speeds up the rotation. However, this cannot be measured from the outside, it is only modeled, according to Köhler.
But many other influences can also affect the speed of rotation. The earthquake that triggered a devastating tsunami in the Indian Ocean in 2004 caused the rocks to sink and thus accelerate the Earth’s rotation. As a result, the length of the day decreased by 2.7 microseconds. “It may be that glaciers are melting at the Earth’s surface as a result of climate change as well,” Kohler says. However, he believes it is “too bold” to blame the accelerating rotation of the Earth solely on climate change.
Kohler suspects that the effects on the Earth’s rotation are so numerous that it’s hard to find the exact cause. “A change in the jet stream also affects the length of the day. Strong winds, which hit the Rocky Mountains or the Andes as obstacles, for example, can slow the Earth’s rotation a little.” volcanic eruptions The movement of mass from the center of the Earth outwards. “And that, in turn, has the opposite effect and slows the Earth’s rotation a little bit.”
In the long run, the rotation becomes slower
But the recent acceleration is likely to remain a temporary phenomenon. As it is seen in the long term, the speed of the Earth’s rotation is constantly decreasing. Over the course of Earth’s history so far, days have gotten longer and longer – averaging 1.78 milliseconds per century. In the time of the dinosaurs, a day lasted 23 hours and 30 minutes instead of 24 hours. 1.4 billion years ago that was less than 19 hours.
One reason is the moon. With its gravity it causes sea tides on Earth. These, in turn, slow the Earth’s rotation. This is one of the reasons why leap seconds were officially introduced in 1972. They would be added either at the end of July or the end of December and should give the Earth a chance to catch up again. This has already happened 27 times since the 1970s – but most recently in 2016. And there won’t be a second leap this year either. Due to the recent acceleration of the Earth, a second passive jump may soon be necessary – it will be the first.
by the way: The Earth’s long-term low angular momentum is transmitted to the Moon by the braking effect of the tides. This makes it faster and off the ground over time. Each year it averages about four centimeters.
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