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[HCDX] The Story of Why WWV/H and all others are adding a second
Here is the reason that many time signal stations like CHU Canada and
WWV/WWVh are adding a sencond to this year.
New Year's Day will be a delayed this year - by one second, to be precise.
Scientists say they are adding the so-called leap second onto the end
of December 31 by tweaking their atomic clocks, the world's most
precise timekeepers, so they stay synchronised with the Earth's
That means Saturday night's countdown will be 5, 4, 3, 2, 1 - and 1.
Leap seconds are added because atomic clocks tend to run slightly
ahead of the Earth's rotation, largely because of the friction of
tides raised by the sun and moon.
It will be the first extra second added in seven years, Britain's
Royal Astronomical Society said.
Both civilian and military users have come to depend on the
ultra-precise time generated by atomic clocks.
The US Defence Department's master clock is required to be accurate to
less than a billionth of a second per day.
The decision to lengthen 2005 was made by the International Earth
Rotation and Reference Systems Service based at the Paris Observatory
The practice of adding seconds to selected years began in 1972.
But more seconds may have to be added more rapidly in years to come if
Earth, as predicted, slows down its rotation "on a nearly exponential
scale", according to Geoff Chester, a spokesperson for the US National
Institute of Standards and Technology - the observatory that keeps
official US time.
Dr Chester, who was quoted by the National Geographic magazine online,
said the slowdown is expected to come from the rising tidal friction.
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