Scientists oppose idea to scrap 'leap second'

British scientists and historians have united against an American proposal to change the way time is tied to the daily rotation of the Earth on its axis.

They believe that a plan to abolish the "leap" second - an extra second added to the midnight pips at New Year - would effectively move the position of the Greenwich meridian eastwards.

The proposal from American time specialists is being debated today at a meeting of the International Telecommunications Union in Geneva and a decision is expected tomorrow.

It is believed that they want to scrap the leap second because of the technical problems it can cause when altering some atomic clocks.

However, Kristen Lippincott, deputy director of the National Maritime Museum in London, said that there are many disadvantages of abolishing the leap second.

"If you get rid of the leap second you are destroying the notion of what time is.

For the first time in history you will separate the time-keeping mechanism from the rotation of the Earth and the movement of the Sun and the stars," Dr Lippincott said.

"One practical effect is that the lines of longitude will slip gradually eastwards.

I'm sure they are proposing this for the best interests but there is no reason for it," she said.

The rotation of the Earth has been used as the basis for time keeping since the dawn of history but the planet does not always complete a full rotation in exactly 24 hours because it is spinning ever so slightly slower every year.

To counteract this effect, and to keep time in synchrony with the Earth's daily cycle of night and day, time keepers have sometimes added a "leap" second at the end of the pips, usually at New Year but sometimes in June, or exceptionally in March or September.

Leap seconds are not added every year and their appearance is judged necessary only after careful calculations about the speed at which the Earth's rotation has slowed down since the last leap second.

The International Earth Rotation and Reference Systems Service, an international body based at the Paris Observatory, has decided that an extra second will be added to the pips this New Year.

Before the age of atomic clocks, leap seconds were not needed because clocks could just be adjusted whenever it was thought necessary.

But because atomic clocks are so accurate, leap seconds are needed to keep them tuned to the not-so-accurate clock of the Earth's daily rotation.

Jonathan Betts, curator of horology at the Royal Observatory, said that if leap seconds are abolished it would eventually mean that time would bear little relevance to whether it is day or night.

"For me it would be a problem if the Sun were to rise at 4pm or at a different time like noon or midnight," Dr Betts said.

"I don't support the idea of the American delegation because I think all our human activities are linked to the rotation of the Earth first.

"And in fact it appears that 90 per cent of our users who need precise timescales are very satisfied by the present procedures," he said.

Scientists believe that without the use of leap seconds there is a danger of losing track of distant stars or spacecraft and satellite navigation on Earth could also be affected.

A spokeswoman for the National Physical Laboratory, Britain's official timekeeper, said that the proposal to scrap leap seconds will be fought.

"The UK is opposed to the proposal, and the other countries have raised concerns over specific details," she said.

- INDEPENDENT