Scientists have recorded the shortest day on Earth since the invention of the atomic clock.
Rotation is the time it takes the Earth to rotate once on its axis, which is approximately 84600 sec.
The previous record was documented on July 19, 2020, when the day’s measurement was 1.47 milliseconds shorter than usual.
The atomic clock is a standard unit of measurement that has been used since the 1950s to determine time and measure the Earth’s rotation, said Dennis McCarthy, retired time director at the US Naval Observatory.
He said that while June 29 broke the record for the shortest day in modern history, there were much shorter days on Earth.
Why increase speed?
McCarthy said researchers don’t have a definitive answer as to how or why the Earth is spinning a little faster, but it could be due to adaptation to glacial equilibrium or Earth’s motion due to melting glaciers.
He said that the Earth is a little wider than its height, making it an oblate spheroid. McCarthy said polar glaciers weigh heavily on the Earth’s crust at the North and South Poles.
He said that because the poles are melting due to the climate crisis, there is less pressure on the top and bottom of the planet, moving the crust up and making the Earth round. The circular shape helps the planet spin faster, McCarthy said.
It’s the same phenomenon that snowboarders use to increase and decrease their speed, he said.
He said that when skaters extend their arms away from their bodies as they spin, it takes more force to spin. McCarthy said that when they place their arms close to their bodies, their speed increases because their body mass is closer to the center of gravity.
He said that when the Earth rotates, its mass approaches its center, which increases the speed of its rotation.
McCarthy said that some have suggested a relationship with Bob Chandler. The axis around which our planet rotates does not align with the axis of symmetry, an invisible vertical line that divides the Earth into two equal halves.
This creates a slight wobble in the Earth’s rotation, similar to the way a soccer ball vibrates when thrown, he said.
He said that when a soccer player is thrown, it sways slightly as it spins, because it doesn’t usually rotate around the axis of symmetry.
“If you are a good runner in football, align the axis of rotation with the axis of symmetry in football, McCarthy said.
However, McCarthy said that Chandler’s oscillation probably does not affect the speed of Earth’s rotation because the oscillation is due to the shape of the planet. He said that if the shape of the planet changes, then the frequency of its vibration changes, not the frequency of its rotation.
Removing the leap second
McCarthy said that since researchers began measuring the speed of Earth’s rotation using atomic clocks, the Earth has been slowing down.
“Our daily existence doesn’t even acknowledge the millisecond,” McCarthy said. “But if these things come together, it can change the rate at which we enter a leap second.”
Because the Earth is now spinning faster, McCarthy said, a leap second must be taken to keep up with our timing as the Earth’s rotation speed increases.
If the planet continues in this rotational trend, he said, a second leap is unlikely for another three to four years.
