The day of June 29, 2022 was 1.59 milliseconds shorter than the usual 24-hour day. This was reported by the International Earth Rotation and Reference System Service, which is responsible for global timekeeping.
The previous record was on July 19, 2020, when the day was 1.47 milliseconds shorter than normal. This is measured using an atomic clock, a standardized device for measuring time that uses as a standard the frequency of electronic transitions between energy levels in atoms. This frequency is so stable that atomic clocks can measure time more accurately than astronomical methods.
Dennis McCarthy, former director of the weather service of the US Naval Observatory, said that the Earth has started to accelerate in the last few years. Researchers donʼt have a definitive answer as to how or why the Earth is spinning slightly faster, but it may be due to the movement of the Earth due to melting glaciers. The Earth is slightly wider than it is tall, making it a flattened spheroid, where glaciers press against the Earthʼs crust at the North and South Poles. As the glaciers melt, the pressure on the top and bottom of the planet decreases, which lifts the crust up and makes the Earth rounder. The round shape helps the planet rotate faster. As the Earth gets rounder, its mass gets closer to its center, which increases the speed of its rotation.
This is the same phenomenon that skaters use to increase and decrease speed: when they pull their arms away from their body during a spin, they need more effort to spin. When they bring their arms closer to their bodies, their speed increases because their body mass is closer to their center of gravity.
Ever since researchers began measuring the speed of the Earthʼs rotation with the help of an atomic clock (from the middle of the 20th century), the speed of the Earthʼs rotation has slowed down. In such cases, the scientific community adds an extra second to the hour. According to EarthSky, 27 seconds have been added since 1972. Since the Earth now rotates faster, an extra second must be removed to keep up with the real-time countdown.
According to a 2020 study, when dinosaurs still roamed the planet 70 million years ago (that is, before the atomic clock), a day on Earth lasted about 23.5 hours. According to NASA, since 1820, scientists have recorded a slowdown in the Earthʼs rotation.