Sticklers for punctuality, prepare yourself for the upcoming leap second
Surely everyone has heard of the leap year, in which every fourth year is extended by a day to compensate for Earth’s slightly irregular orbit around the sun. But you probably haven’t heard of the leap second. Mark Brown of Wired UK has the scoop:
The International Earth Rotation and Reference Systems Service (IERS) in Paris — the grand arbiters of time on our big blue marble — has declared that a leap second will be introduced on 30 June, 2012. […]
We used to use the Earth’s dutiful rotation as a way of measuring time. It pirouettes on its axis once every 24 hours, which can then be divided into minutes and seconds. But the Earth’s rotation is annoyingly irregular, with some days ending up being a tiny bit longer or shorter than others.
There’s nothing science hates more than unpredictability, so in the 1950s atomic clocks were introduced to keep time.
By measuring the regular atomic vibration in the element cesium (which oscillates exactly 9,192,631,770 times a second), we ended up with a clock that can be used to score off seconds with remarkable accuracy. Multiple atomic clocks work in unison to precisely calculate world time.
But that leaves a problem. If we lived on atomic time it’d very slowly gravitate away from the Earth’s actual time. In a few years we’d be a second out of sync, in hundreds of years we’d be a minute out and after several hundred thousand years we could be eating lunch in the middle of the night.
So time-keepers introduced the leap second. As the atomic clock’s perfect accuracy (known as International Atomic Time, or TAI, from the French name Temps Atomique International) veers farther and farther away from the Earth’s clumsy rotation (called Solar Time), the IERS introduces a leap second to bring them back into perfect parity (known as Coordinated Universal Time, or UTC).
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