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Looking Before They Leap, World's Timekeepers Meeting In Geneva

  • Charles Recknagel

In the 40 years since leap seconds were created, a second has been added to a day just 34 times.

In the 40 years since leap seconds were created, a second has been added to a day just 34 times.

Few people realize that every now and then the world's timekeepers insert an extra second into our lives.

But today, the subject is in the news as they decide whether or not to continue the practice.

The debate takes place in Geneva, where a UN agency -- the International Telecommunication Union -- is considering a proposal to abolish the "leap second." If the agency's member states cannot agree among themselves, the matter is likely to be put to a vote before the meeting ends on February 17.

Does the average person have much at stake in the proceedings?

Probably not, if you consider that in the 40 years since leap seconds were created a second has been added to a day just 34 times. One would have to be incredibly time-conscious to feel the difference.

But for those whose jobs do require absolute precision in synchronizing their watches – such as those involved in telecommunications or computers – the seconds do mean something. And that makes the rather arcane debate in Geneva quite interesting.

Two Ways To Keep Time

The problem of leap seconds – to retain or abolish them – has its roots in the fact that there are two different ways to keep time.

One is by considering the Earth itself as a kind of clock and synchronizing our watches to its motion. The Earth's regular rotation around the sun, and the Earth's rotation on its own axis, provide ways to measure the passage of time with great accuracy.

But there is a problem with this system. The Earth's motion is not always exactly the same and those infinitesimal variations make keeping absolutely precise time impossible.

The second way to keep time is by using atomic clocks. By recording the incredibly regular vibrations of atoms, one can indeed calculate the passage of time absolutely accurately – or at least as accurately as anyone can imagine today.

It was to make sure that these two ways of telling time give the same results that timekeepers created the idea of the leap second. Every now and then, when astronomical time – the time based on tracking the Earth's motion – falls behind atomic time, timekeepers make it catch up again by adding on a second.

However, like any artificial solution, the leap second has drawbacks and, therefore, critics.

Potential For Problems

Several countries, including the United States and France, want to abolish the leap second because they say sporadically adjusting astronomical time – which is how most timekeepers keep time – is dangerous.

They say if the adjustments are ever missed or overlooked by people operating different parts of financial trading systems, air-traffic control systems, or cell-phone networks – systems which must run in perfect synchrony – there could be major problems.

But other countries, particularly Britain and China, with support from Russia, say the risk of human error is an acceptable condition for keeping the world's two ways of keeping time in agreement. They also say that for the 40 years during which leap seconds have been used, no foul-ups have occurred because of them.

What will the timekeepers decide as they meet in Geneva starting today?

It is too early to predict. The only thing they have agreed beforehand is that if leap seconds should be abolished, the change would not take place until 2018.

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