No more complaining that there’s not enough time to get it all done: On the last day of this year, you’ll have a whole extra second to finalize your New Year’s resolutions.
According to timekeepers at the International Earth Rotation and Reference Systems Service, the time determined by super-regular atomic clocks and the observed rotation of Earth have yet again become mismatched.
As long as all the world’s computer systems engineers have their ones and zeros in a row, there’ll be an additional breath of time at 6:59:59 p.m. ET on December 31, the U.S. Naval Observatory announced on July 6.
Atoms Versus Astronomy
Modern timepieces tick to the rhythm of Earth’s rotation based on the 24 hours it takes for the planet to complete one spin on its axis.
But on the level of seconds, the planet’s rate of spin fluctuates, mainly due to the gravitational effects of Earth’s moon. The push and pull of our orbital partner causes the planet’s massively heavy reserves of water to slosh around, which decelerates the spin between 1.5 and two milliseconds a day, on average.
Leap seconds are used to fill in the gap and make Earth’s observed speed align with our most accurate clocks—atomic devices that define a second by measuring the regular decay of radioactive elements such as cesium.
“If you don’t insert a leap second, eventually time based on those atomic clocks will be out of whack with solar time,” says science writer Dan Falk, whose 2008 book In Search of Time explores humanity’s relationship with time and our efforts to define and measure the temporal realm.
“It’s not a perfect solution. But Aristotle and Heraclitus were arguing about [time] 2,500 years ago, and we’re still arguing about it.”
For what it’s worth, the last time the atomic second and the astronomically defined second coincided was sometime in the 19th century, says Geoff Chester, a spokesman for the U.S. Naval Observatory.
Without leap seconds, the differences between official time as kept by atomic clocks and a day as defined by Earth’s rotation would slowly pile up. We’d face a two- to three-minute discrepancy between atomic time and astronomical time in 2100. By 2700, we’d get an extra half hour of sleep in the morning.
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SOURCE: National Geographic, Michelle Donahue
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