Tuesday, December 30, 2008

Tick tock ... tick: Extra second added to 2008

Those eager to put 2008 behind them will have to hold their good-byes for just a moment this New Year's Eve.

The world's official timekeepers have added a "leap second" to the last day of the year on Wednesday, to help match clocks to the Earth's slowing spin on its axis, which takes place at ever-changing rates affected by tides and other factors.

The U.S. Naval Observatory, keeper of the Pentagon's master clock, said it would add the extra second on Wednesday in coordination with the world's atomic clocks at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time, or UTC.

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Among the reasons for Earth's slowing whirl on its axis are the braking action of tides, snow or the lack of it at the polar ice caps, solar wind, space dust and magnetic storms, according to the U.S. Commerce Department's National Institute of Standards and Technology, another timekeeper.

By contrast, a leap day, February 29, occurs once every four years because a complete turn around the sun -- our year with all its seasons -- takes about 365 days and six hours.

In 1970, an international agreement established two time scales: one based on the Earth's rotation and another on highly accurate atomic clocks.

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