The report, published July 27 by the Norwegian time zone tracking website timeanddate.com, said Earth completed one rotation on June 29 in 1.59 milliseconds less than 24 hours. According to the report, it was the shortest day on Earth since scientists began using atomic clocks to measure the planet’s rotation speed. Times are based on data provided by the International Earth Rotation and Reference System Service. The planet tends to take a few milliseconds or more to complete one rotation every century, the report adds. “Within this general pattern, however, the speed of Earth’s rotation fluctuates,” the authors wrote. “From one day to the next, the time it takes the Earth to complete one rotation goes up or down by a fraction of a millisecond.” The record comes as Earth appears to be spinning faster in recent years. The last record for the shortest day was set on July 19, 2020, with the Earth rotating 1.47 milliseconds in less than 24 hours. The site also reported that 2020 had the 28 shortest days on record since the 1960s. In 2021, the Earth rotated 1.46 milliseconds faster than 24 hours on July 9 for the shortest day of that year. The report from timeandday.com suspects the shorter days may be due to Earth’s inner or outer layers, oceans, tides or climate, but so far scientists aren’t sure. Other theories include the “Chandler oscillation,” a phenomenon used to describe small irregular movements at the Earth’s geographic poles, timeandday.com reported. The report notes that these faster rotations could lead to the introduction of a negative leap second, meaning clocks would skip a second.
