Don’t Panic About the Earth’s Shortest Day in Decades

Scientists at NASA and the California Institute of Technology have said there’s no reason to worry about the Earth spinning faster.

It’s taken as given that the Earth completes a full rotation in 24 hours. But that wasn’t the case on June 29 or July 26, when the International Earth Rotation and Reference Service Systems said that the Earth completed its rotation 1.59 and 1.5 ms earlier than usual, respectively. That made June 29 the shortest day we’ve recorded since we started keeping time with ultra-precise atomic clocks in 1970; July 26 was the second-shortest.

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Does that mean the sky is falling? Probably not. The Associated Press reports(Opens in a new window) that fluctuations in the Earth’s rotation speed aren’t typically cause for concern.

“It’s a completely normal thing,” NASA Goddard Space Flight Center scientist and program manager Stephen Merkowitz(Opens in a new window) told the AP. “There’s nothing magical or special about this. It’s not such an extreme data point that all the scientists are going to wake up and go, what’s going on?” California Institute of Technology emeritus professor of planetary science Andrew Ingersoll also said “the Earth’s rotation varies by milliseconds for many reasons,” and that “none of them are cause for concern.”

A millisecond doesn’t typically have a profound impact on someone’s life. It takes us about 13 ms(Opens in a new window) to process visual stimuli, according to MIT researchers, and it seems unlikely that anyone would have sat through all 2 hours and 56 minutes of “The Batman” if they were acutely aware of every passing millisecond. A fluctuation of 1.59 ms only matters in contexts that require very accurate time measurements; most people aren’t going to notice the Earth is spinning a little faster than usual.