(CNN) — If it seems to you that there is less time in the day, you are right.
Scientists recorded the shortest day on Earth since the invention of the atomic clock.
According to him International Service for Earth Rotation and Reference Systemsorganization in charge of the measurement of time throughout the world, on June 29 the rotation of our planet lasted 1.59 milliseconds less than a normal 24-hour day.
One rotation is the time it takes for the Earth to rotate once on its axis, which is about 84,600 seconds.
The previous record was documented on July 19, 2020, when the day measured 1.47 milliseconds less than normal.
The atomic clock is a standardized unit of measurement that has been used since the 1950s to tell time and measure the Earth’s rotation, said Dennis McCarthy, retired director of time at the US Naval Observatory.
Even though June 29 broke the record for the shortest day in modern history, there have been much shorter days on Earth, he said.
When dinosaurs still roamed the planet 70 million years ago, a single day on Earth lasted about 23 1/2 hours, according to a 2020 study published in the academic journal Paleoceanography and Paleoclimatology.
Since 1820, scientists have documented that the Earth’s rotation is slowing down, according to NASA. However, in recent years, it has started to accelerate, McCarthy said.
Why does the speed increase?
Researchers don’t have a definitive answer as to how or why Earth is spinning slightly faster, but it may be due to glacial isostatic adjustment, or movement of the earth due to glacial melt, McCarthy said.
Earth is slightly wider than it is tall, making it an oblate sphere, he said. Polar glaciers weigh down on Earth’s crust at the north and south poles, McCarthy said.
As the poles are melting due to the climate crisis, there is less pressure on the top and bottom of the planet, which pushes the crust up and makes the Earth rounder, he said. The circular shape helps the planet spin faster, McCarthy said.
It’s the same phenomenon figure skaters use to speed up and slow down, he said.
When skaters stretch their arms away from their body as they spin, they need more force to spin, he said.
When they bring their arms closer to the body, their speed increases because their body mass is closer to their center of gravity, McCarthy said.
As the Earth becomes rounder, its mass moves closer to its center, which increases its rotational speed, he said.
Remove a leap second (or extra second)
Ever since researchers began measuring Earth’s rotation rate using atomic clocks, Earth has been slowing down, McCarthy said.
“Our day to day life doesn’t even recognize that millisecond,” McCarthy said. “But if these things add up, then it could change the speed at which we insert a leap second.”
In cases where milliseconds add up over time, the scientific community has added an extra second to the clock to slow down our time to match Earth’s, he said. Since 1972 an additional 27 seconds have been added, according to EarthSky.
Since Earth is now spinning faster, a leap second would have to be subtracted for our clock to adjust to Earth’s increasing speed of rotation, McCarthy said.
If the planet continues this rotational trend, the suppression of a leap second probably won’t be necessary for another three or four years, he said.