Article by: Andacs Robert Eugen, on 10 August 2022, at 11:34 am Los Angeles time

Scientists have recorded the shortest day on Earth since the invention of the atomic clock.

According to the International Earth Rotation and Reference Systems Service, a global timekeeping organization, our planet's rotation measured 1.59 milliseconds less than a normal 24-hour day on June 29.

A complete rotation is the length of time it takes the Earth to spin once on its axis, which is about 86,400 seconds. The previous record was documented on July 19, 2020, when the day measured 1.47 milliseconds shorter than normal.

An atomic clock is a standardized unit of measurement that has been used since the 1950s to measure Earth's rotation, said Dennis McCarthy, former director of the US Naval Observatory.

Despite June 29 breaking the record for the shortest day in modern history, there have been much shorter days on Earth, he said.

When dinosaurs still lived on Earth 70 million years ago, a single day on Earth lasted about 23 1/2 hours, according to a 2020 study published in Paleoceanography and Paleoclimatology.

Since the 1820s, scientists have documented the slowing of Earth's rotation, according to NASA. In recent years, that has started to accelerate, McCarthy said.

Researchers don't have a clear answer as to how or why the Earth is spinning a little faster, but it could be due to ground movement generated by melting glaciers, McCarthy said.

As the poles melt due to the climate crisis, there is less pressure on the top and bottom of the planet, which moves 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 that figure skaters use to increase and decrease their speed, he explained.

As the Earth gradually changes its shape and becomes rounder, the mass gets closer to its center, which increases its rotation speed, he said.

"Our day-to-day existence doesn't even recognize that millisecond," McCarthy said. "But if these things add up, then it could change the rate at which we introduce a leap second."

In cases where milliseconds accumulate in time, the scientific community has added a leap second to the clock to slow down our time to match Earth's, he said. 27 such seconds have been added since 1972, according to EarthSky.

Because the Earth is currently spinning faster, a leap second should be removed to align our timing with the Earth's increasing rotation speed, McCarthy said.

If the planet continues this rotation trend, the removal of a second probably won't have to happen for another three or four years, he said.