The earth’s spinning is slowing down. Any clocks pegged to the earth’s rotation are therefore drifting out of alignment with our far more precise atomic clocks—only by a thousandth of a second every 50 years, but that’s still a problem for the computers that run the internet, cellphones, and financial systems.

In 1972, scientists began re-aligning atomic clocks with earth-rotation time by inserting a leap second every December 31, or as needed. It seemed like a good idea at the time—until computers started crashing at Google, Reddit, and major airlines. Google engineers proposed, instead, a leap smear: fractionally lengthening every second on December 31, so that that day contains the same total number of seconds. But really: If computer time drifts so infinitesimally from earth-rotation time, does anybody really care what time it is?

Guests: Theo Gray, scientist and author. Geoff Chester, public affairs officer for the for the Naval Observatory. Peter Hochschild, principal engineer, Google.

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