Hang On A Leap Second
January 21st, 2012
07:52 AM ET

Hang On A Leap Second

A decision on whether to scrap the leap second has been postponed, for three years.

Let us bring you up to speed: Leap seconds were introduced in 1972. They are occasional, extra seconds added or subtracted from the world's atomic clocks to keep them synchronized with the Earth's rotational cycles. Tidal patterns, and the way our planet wobbles on its axis a little as it spins mean that some days end up a few milliseconds longer and shorter than others.

So, over long periods, the time based on hyper-accurate atomic clocks and the time based on the Earth's rotation drift apart. Over decades, that would amount to a minute; over centuries, that could add up to an hour; over millenia, you get the picture, dawn could end up as dusk. 

At least 24 leap seconds have been used in the past forty years, but now many countries, including the U.S. and some European nations, want to abandon the practice. They say leap seconds interfere with telecommunications, satellite navigation and the internet.

Only time will tell if the leap second survives. A decision may be made in in 2015.

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