Earth’s rotation has sped up so much that timekeepers may need to subtract a second — a historic move with major implications for technology.
Earth is spinning faster than usual, prompting scientists to consider an unprecedented adjustment — adding a negative leap second to global timekeeping. On July 9 and July 22, days were shortened by 1.3 and 1.4 milliseconds, with Aug. 5 expected to lose 1.5 milliseconds, according to timeanddate.com.
This trend, observed since 2020, could disrupt GPS, banking, and communication systems that rely on Coordinated Universal Time (UTC), which is calculated using over 400 atomic clocks. Leap seconds — added to align UTC with Earth’s irregular rotation — have caused past disruptions.
“A negative leap second essentially involves removing a second from UTC,” said Judah Levine of NIST. But it’s never been done before.
“Even positive leap seconds still cause computing errors,” added Prof. Darryl Veitch.
Despite risks, experts say there’s a 30% chance we’ll need one in the next decade — unless Earth’s rotation slows down again due to climate effects like melting polar ice.