December 26, 2005
Monday

If 2005 is disappearing too fast for you, just hold on for a second, because this year you have an extra second to pause and reflect on the year before the ball drops and the calendar flips New Year's Eve.

Yep, it's a leap second moment, one of those rare occasions when clocks around the world take a stutter step in order to conform with the Earth's wobbly, gradually slowing spin.

But don't count on having many extra moments in the future, because there's a movement in the telecommunications field to do away with leap seconds as early as 2007.

In a 24/7 world, leap seconds that adjust the timekeeping of atomic clocks to the time based on the rising and setting of the sun are viewed by many technocrats as a nuisance, perhaps even a danger.

Atomic time, based on the radiation frequency of the cesium-133 atom, has been around since the 1950s. Timekeeping based on the Earth's rotation goes back thousands of years and is classically upheld by the Royal Observatory in Greenwich, England, where, by the way, the extra second is formally marked.

The trouble is, atomic clocks are so accurate, they can go for 3 million years without losing a second. Earth's rotation, it turns out, is somewhat less reliable. That's because the daily tidal influence of the moon's gravity acts as a brake on the spin.

When international agreement was reached on Co-coordinated Universal Time (UTC) in 1972, scientists figured that regular leap seconds would need to be added every 18 months to keep the two systems in sync.

Instead, the International Earth Rotation and Reference Systems Service based in Frankfort, Germany, has had to request only 22 leap seconds, coming on either June 30 or Dec. 31, since 1972, with the last extra second tacked on back in 1998. But over the long-haul, scientists expect that the slowing of the rotation will gradually increase over thousands of years, requiring even more frequent corrections to atomic time.

This is all too random for software programmers and others in electronics industries where a 61-second minute doesn't compute, literally. There have been glitches ranging from Global Positioning Satellite receivers displaying the time as 62 o'clock to broadcast services automatic DJs running errant tapes.

Citing those problems and the concern that things like air traffic control systems might be compromised by leap seconds, the U.S. government two years ago proposed to the International Telecommunications Union that leap seconds be abolished.

That plan was briefly discussed at meeting of the ITU in Switzerland last month, but delegates agreed to put off any decision until at least next year.

The notion has been officially opposed by a number of groups involved in astronomy and Earth observation, including the Royal Astronomical Society. They argue that disconnecting universal time from solar time is simply shifting a technological problem from one group to another.

Among other things, the change could cost observatories many thousands of dollars to regularly reprogram telescopes software to hit the right point in the sky on a given night.

Ultimately, without leap seconds, clocks would have no relevance to day and night, critics complain. "It could one day mean it says noon on our watches, but it's midnight outside," said Jonathan Betts, a curator of horology at the Greenwich Observatory.

On the other hand, with seven years and oodles of electronics manufacturing having passed since the last leap second, a lot of electronics engineers are holding their breath to see how the newer gear copes with a 61-second minute.

Dennis McCarthy, who has been working on the leap-second problem as Director of Time at the U.S. Naval Observatory in Washington for more than a decade and drafted the proposal presented to the ITU, argues that the drift between celestial and atomic time isn't that radical. "It's a two-minute problem over 100 years," he said.

The U.S. plan actually would keep the sun and clocks generally in sync by adding a "leap hour" every 500 or 600 years as the extra seconds pile up, a switch more acceptable to technology that copes with the spring forward, fall back adjustment for Daylight Saving Time each year.

For now, says Michael Hapgood, secretary of the RAS, "there are a lot of good people already involved in the debate. We need them to work together to improve current timekeeping for everyone's benefit, and not just for one group."

On the Net:

www.usno.navy.mil

www.ras.org.uk

tf.nist.gov/general/leaps.htm

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