Home > Agencies & Organisations, Astronomy, Earth, NASA (National Aeronautics & Space Administration), Solar System > NASA Explains Why Clocks Will Get An Extra Second On June 30

NASA Explains Why Clocks Will Get An Extra Second On June 30


If the day seems a little longer than usual on Saturday, June 30, 2012, that’s because it will be. An extra second, or “leap” second, will be added at midnight to account for the fact that it is taking Earth longer and longer to complete one full turn—a day—or, technically, a solar day.

From VLBI, scientists have learned that Earth is not the most reliable timekeeper. The planet’s rotation is slowing down overall because of tidal forces between Earth and the moon. Roughly every 100 years, the day gets about 1.4 milliseconds, or 1.4 thousandths of a second, longer. Granted, that’s about 100 or 200 times faster than the blink of an eye. But if you add up that small discrepancy every day for years and years, it can make a very big difference indeed.

Full Story: http://www.nasa.gov/topics/solarsystem/features/extra-second.html

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