Leap Second

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Leap Second

Wondering what scientific debates are going on as a result of the new year? Take a look at this article on leap seconds. Things that you will learn:

In 1958 an atomic second was defined as the time it takes for an atom of cesium 133 to tick through 9,192,631,770 cycles

The trouble is that the heavens behave more capriciously than cesium. Also, the length of Earth's day is increasing by about two milliseconds per century because of the tides, whereas today's atomic clocks, unaffected by cosmic events, tick away with an accuracy within one second for every 20 million years.

Because of this discrepancy, atomic time has been pulling ahead of astronomical time for the past 47 years. To fix this, the International Telecommunication Union in 1972 stipulated that "Coordinated Universal Time," an atomic time used as the world standard, could not diverge from astronomical time by more than 0.9 seconds.

The adjustment tool was the leap second, to be added or subtracted at the discretion of the International Earth Rotation and Reference Systems Service, either at the end of June or the end of the year. Beginning in 1972, there have been 21 leap seconds, the last one in 1998.

"Astronomers wanted a time scale that represented the Earth's movement, and the clock community wanted a smooth scale," said physicist Judah Levine of the National Institute of Standards and Technology and the University of Colorado, who favors eliminating leap seconds. "The compromise has become increasingly difficult to maintain."

In November, a working group of the International Telecommunication Union meeting in Geneva decided to postpone discussions of the U.S. proposal, which would have abandoned leap seconds in 2007 and let Coordinated Universal Time and astronomical time diverge for several hundred years before inserting a "leap hour." The group said more time was needed to form a consensus, and suggested that this year's leap second offered a welcome opportunity to determine whether change is necessary.


I wonder if having computer and other systems get their time automatically from satellites wouldn’t solve this problem. In other words ensure that a satellite has the exact time and allow all devices to sync up with it. This way you can add leap seconds as needed and all the world’s devices (in the future anyway) would be updated. The same signal would be available online allowing devices with internet but not satellite access to also stay up to date.



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