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Emily LakdawallaDecember 31, 2005

5...4...3...2...1...1...Happy New Year!

Read that title aloud. Yes, the last minute of 2005 is actually 61 seconds long. The U. S. Naval Observatory is adding a leap second to 2005 in order to match our clocks with the movement of the heavens, which actually means matching it to the gradually slowing rotation of Earth. (To learn more about that go to this page and scroll down to the part about the Earth-Moon System.) Actually, the leap second winds up at midnight only if you really observe UTC time. If I were anal enough to synch my computer's clock precisely to the U. S. Naval Observatory's Coordinated Universal Time, it would be the last minute of the 3 p.m. hour today that would contain that extra second.

Which is probably an example of the reasons that some people are angling to abolish these leap seconds altogether, and allow atomic time to begin to float with respect to celestial time. There are so many everyday devices and systems that depend upon timing events down to the second or even to the millisecond that it becomes a tremendous headache to keep all these electronics up-to-date with the insertion of leap seconds, which cannot be predicted years in advance like changes in daylight saving time can. Most people think it would be easier to abolish the leap second, or at least let them occur less frequently, say every couple of decades. But the Royal Astronomical Society has envisioned one terrifying consequence of such a change:

The proposal is subject to the law of unintended consequences. Quite apart from professional scientists, such as astronomers, who might be adversely affected by such a change, over hundreds of years the civil time would no longer coincide, even approximately, with the "Sun time" traditionally shown on a sundial. Even over a few decades, when the error might grow up to a half a minute or so, one can imagine the arguments that lawyers and insurance companies might have about whether an event had occurred just before or just after midnight; and in today's modern electronic era differences of seconds between different people's interpretation of the correct time might sometimes lead to dispute!

Rather than combating the lawyers and insurance adjusters, it might be less work to try to speed up the rotation of the Earth...well, maybe not. Actually I'd love to see that court case play out.

Read more: fun, Earth

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Emily Lakdawalla

Senior Editor and Planetary Evangelist for The Planetary Society
Read more articles by Emily Lakdawalla

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