Scientists have recorded the shortest day on Earth since the invention of atomic clocks.
The Earth’s rotation on June 29 was 1.59 milliseconds slower than the normal 24-hour clock, according to the International Earth Rotation Reference System Service, the organization responsible for world timekeeping.
Rotation is the time it takes for the Earth to rotate on its axis, approximately 84,600 seconds.
The previous record was recorded on July 19, 2020, when the day was measured 1.47 milliseconds shorter than normal.
Atomic clocks are standardized units of measurement that have been used since the 1950s to tell time and measure the rotation of the Earth, said Dennis McCarthy, former head of time at the U.S. Naval Observatory.
He said that June 29 broke the record for the shortest day in modern history, but the Earth was a much shorter day.
According to a 2020 study published in Paleoceanography and Paleoclimatology, when dinosaurs were still roaming the Earth 70 million years ago, a day on Earth lasted about 23.5 hours.
Scientists have documented the slowing of the Earth’s rotation since 1820, according to NASA. In recent years, it has started to accelerate, he said.
why speed up?
Researchers don’t have a definitive answer as to how or why the Earth is rotating slightly faster, but it could be due to isostatic adjustment of glaciers or land movement due to melting glaciers. says McCarthy.
The Earth is slightly wider than it is high, making it a flattened spheroid, he said. Glaciers at both poles are compressing the Arctic and Antarctic crust, McCarthy said.
He said that when the poles melt due to the climate crisis, the pressure on the top and bottom of the Earth will decrease, causing the crust to move upwards and the Earth to become round. The circular shape helps the planet spin faster, McCarthy said.
He said it’s the same phenomenon that figure skaters speed up and down.
When a skater pulls his arms away from his body during a turn, more force is required to turn. McCarthy says that bringing the arms closer to the body brings the weight closer to the center of gravity, which increases speed.
As Earth becomes rounder, its mass becomes closer to its center, which increases its rotational speed, he said.
Some have suggested a correlation with the Chandler wobble, McCarthy said. The axis our planet rotates on is not lined up with its axis of symmetry, an invisible vertical line that divides the Earth into two equal halves.
This creates a slight wobble as the Earth rotates, similar to how a football wobbles when it is thrown, he said.
When a player tosses a football, it wobbles slightly as it rotates since it often doesn’t spin around the axis of symmetry, he said.
“If you’re a really good football passer, align the axis of rotation with the football’s axis of symmetry and you won’t wobble,” McCarthy said.
But McCarthy says the Chandler wobble is due to the shape of the planet, so it’s unlikely to affect Earth’s rotation rate. It’s the frequency of the wobble, not the frequency of rotation, that changes as the planet changes shape, he said.
remove leap seconds
McCarthy said the Earth’s rotation has slowed since researchers began measuring it with atomic clocks.
“Our daily lives don’t even know that millisecond,” McCarthy said. “But when these things add up, it can change the rate at which we insert leap seconds.”
If milliseconds increase over time, he said the scientific community adds leap seconds to clocks to slow down time on Earth.Since 1972, according to EarthSky, leap seconds have been His 27 seconds are added.
According to McCarthy, the Earth is spinning faster, so we have to get rid of leap seconds to keep up with our time management as the Earth spins faster.
If the Earth continues this trend of rotation, the elimination of leap seconds probably won’t be necessary for another three to four years, he said.