Earth completed its normal 24-hour rotation 1.59 milliseconds faster on June 29, setting a new record for the shortest day in modern history. (NASA)
Estimated duration: 4-5 minutes
Atlanta — If your day feels short, you’re right.
Scientists have recorded the shortest day on earth since the invention of atomic clocks.
The Earth’s rotation was measured to be 1.59 milliseconds shorter than a typical 24-hour day on June 29th. International Earth Rotation and Reference System Servicethe organization responsible for world timekeeping.
Rotation is the length of time it takes the Earth to rotate once around its axis, approximately 86,400 seconds.
The previous record was recorded on July 19, 2020, when it measured 1.47 milliseconds shorter than usual that day.
Atomic clocks are standardized units of measurement that have been used to tell time and measure the rotation of the Earth since the 1950s, said Dennis McCarthy, former head of time at the U.S. Naval Observatory.
Despite breaking the record for the shortest day in modern history on June 29, he said, the world continues to have a much shorter day.
A day on Earth lasted about 23.5 hours when dinosaurs were still roaming the planet 70 million years ago, according to a study published in 2020. Paleooceanography and Paleoclimatology.
Since 1820, scientists have recorded that the rotation of the Earth is slowing down. According to NASAIn the last few years, McCarthy said that speed has started to pick up.
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 displacement due to melting glaciers. There is, says McCarthy.
He said the Earth is slightly wider than it is high, making it a flattened spheroid. Polar glaciers are compressing the Arctic and Antarctic crust, McCarthy said.
As the poles melt due to the climate crisis, there will be less pressure on the top and bottom of the planet, which moves the crust upwards and makes the Earth more round, he said. helps speed up the planet’s rotation.
He said it’s the same phenomenon that figure skaters speed up and down.
As the skater moves his arms away from his body while spinning, more force is required to turn.
As the Earth rounds, he said, its mass moves closer to its center and spins faster.
Our everyday lives don’t even recognize those milliseconds.
– Dennis McCarthy, former U.S. Naval Observatory Timekeeper
Some have suggested a correlation with the Chandler wobble, McCarthy said. The axis on which our planet rotates does not coincide with the axis of symmetry, the invisible vertical line that divides the earth into two equal halves.
It wobbles slightly as the earth rotates, similar to how a soccer ball wobbles when thrown.
When a player throws a ball, it often doesn’t rotate around its axis of symmetry, so the ball wobbles slightly as it spins, he said.
“If you’re a really good passer in football, 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 likely doesn’t affect Earth’s rotation rate. A change in the shape of a planet changes the frequency of its wobble, not its rotation, he said.
Remove leap seconds
The Earth has been slowing its rotation since researchers began using atomic clocks to measure its rotation, McCarthy said.
“Our everyday lives don’t even recognize those milliseconds,” McCarthy said. “But when these things add up, it can change the rate at which we insert leap seconds.”
He said that when milliseconds increase over time, the scientific community adds leap seconds to clocks to slow down time on Earth. I was. According to Earth Sky.
The Earth is now spinning faster, so leap seconds need to be removed to keep time with the Earth’s increasing rotation speed, McCarthy said.
If the Earth continues this trend of rotation, the elimination of leap seconds will not be necessary for another three to four years, he said.