🌅 Earth’s Leap Second Was Just Voted Out

SOURCE

National Institute of Standards and Technology

WHAT TO KNOW

• Delegates from 69 countries at the International Bureau of Weights and Measures just voted to replace the leap second, doing away with the periodic correction experts have come to view as both tiresome and legitimately risky. The world’s timekeepers are now embracing the leap hour to keep computers and technical systems in sync with the Earth’s daily rotation, though it’s unlikely one will be needed for thousands of years.

WHY IT MATTERS

• A leap second functions much like a leap year. Every so often, when one full rotation of the Earth doesn’t equal exactly 24 hours, officials add an extra second to ensure modern timekeeping systems stay aligned with our planet’s daily rotation (27 leap seconds have been added since 1972). However, unlike predictable and stable leap years, leap seconds account for seemingly random irregularities in the Earth’s rotation, causing trouble for systems relied upon by everything from banks to critical infrastructure. The irregularities also created a 30% risk of a “negative leap second” being needed within the next decade, which would require systems to essentially delete a second from coordinated universal time (UTC). Experts say that’s a much harder update for computer systems to make than adding an additional second or spreading it out over a long period of time using gradual increments. The new leap hour aims to reduce that risk by allowing UTC to drift up to an hour from astronomical time before a correction is needed.

CONNECT THE DOTS

• Broadly speaking, the Earth’s rotation is slowing down (a day lasted about 23 hours when dinosaurs roamed the planet). However, since 2000, surface changes like melting polar ice caps and different processes inside the Earth’s fluid core have caused it to speed up, increasing the risk of a negative leap second. The risk is so drastic that major tech companies have become vocal proponents of ending the leap second in recent years, particularly after leap seconds caused high-profile outages at Reddit and LinkedIn in 2012 and Cloudflare in 2016.