Scientists Aren't Sure Why Earth Is Rotating Faster

June 29 was the shortest day in about 60 years. You couldn’t possibly have noticed, but scientists at the International Earth Rotation and Reference Systems Service certainly did. Per IFL Science, the Earth completed its daily rotation that day in exactly 1.59 milliseconds under than 24 hours. That’s the fastest recorded time since the 1960s, when scientists began measuring the planet’s rotational speed using atomic clocks. However, it is a continuation of a recent trend, as the Earth has repeatedly broken rotational speed records since 2020. According to the Independent, it almost happened again on July 26, when the day came up 1.50 milliseconds short.

Scientists aren’t certain, but it could be related to tides and oceans, processes in the Earth’s core, or possibly climate change. It may also be a result of the Chandler wobble, “a small deviation in the Earth’s axis of rotation … similar to the quiver one sees when a spinning top starts gaining momentum or slows down,” as the Independent explains it. The phenomenon is inconsistent with long-term trends that show Earth gradually slowing over the past 1.4 billion years, according to the Guardian, which notes that days were under 19 hours back then. On average, Earth has lost one 74,000th of a second every year since, thanks to the moon’s relentless gravitational tug.

In recent decades, keepers of the atomic clock have added 27 "leap seconds" to account for the gradual slowing in order to keep clocks consistent with the actual rate of the Earth’s orbit around the sun. If the speed trend continues, they may need to add an unprecedented "negative leap second” to make up the difference. The matter is cause for alarm among software giants like Google, Meta, Microsoft, and others who say leap seconds can play havoc on software and IT systems worldwide. In a blog on the subject last week, also per the Independent, Meta called the addition and subtraction of leap seconds "a risky practice that does more harm than good," despite what astronomers say. (More atomic clocks stories.)