Should We Abandon the Leap Second?
We have been adding “leap seconds” to time kept by our atomic clocks, but soon we may have to subtract one. Are the tiny adjustments worth the bother?
L ong ago we humans defined a day as the time it takes Earth to make one rotation about its axis, with one sunrise and one sunset. Our predecessors partitioned that day into 24 hours. But if Earth’s rotation slows down a little, it takes a bit longer than one day to complete it. That has been happening for many years. Because the atomic clocks we use to pace everything from Internet communications to GPS apps to automated stock trades never slow down, global timekeepers periodically have added a leap second to the clocks to keep them in sync with Earth. Since 1972 we have made this awkward addition 27 times.
For the first time, however, we may have to subtract a leap second because since around 1990 Earth’s rotation has been speeding up, counteracting the slowdown and shortening the day. There are two explanations for why, which I’ll explain ... in a second.
