Fri, Nov 04, 2011 - Page 6 News List

Britain, old foe France in battle over fate of GMT


Leading scientists from around the world began a two-day meeting in Britain yesterday to consider a proposal that could eventually see Greenwich Mean Time (GMT) relegated to a footnote in history.

For more than 120 years GMT has been the international standard for timekeeping, but it is now under threat from a new definition of time itself based not on the rotation of the Earth, but on atomic clocks.

In January next year, the International Telecommunication Union will meet in Geneva to vote on whether to adopt the new measure, despite protests from Britain.

The two-day meeting of about 50 experts at a country house northwest of London, under the aegis of the prestigious Royal Society, will look at some of the issues involved.

Predictably the question has hurt Britain’s national pride — particularly when British believe their old rivals France are leading the push to change away from GMT to the new time standard.

GMT is based on the passage of the sun over the zero meridian line at the Greenwich Observatory in southeast London, and became the world standard for time at a conference in Washington in the US in 1884. France had lobbied for “Paris Mean Time” at the same conference.

In 1972 it was replaced in name by Universal Coordinated Time (UTC), but that essentially remained the same as GMT.

UTC is based on about 400 atomic clocks at laboratories around the world, but then corrected with “leap seconds” to align itself with the Earth’s rotational speed, which fluctates.

However, the tiny variations between Earth’s speed and atomic speed have become a problem for GPS, the global positioning systems and mobile phone networks on which the modern world relies.

“These networks need to be synchronized to the millisecond,” Arias said. “We are starting to have parallel definitions of time. Imagine a world where there were two or three definitions of a kilogram.”

British Science Minister David Willetts has opposed the plan, saying it has become more than just a scientific row.

“This is primarily a finely balanced scientific argument, but I do detect undercurrents of nationalism,” he said. “Britain’s position is that we should stick to real time as experienced by humans, which is based on the Earth’s rotation, not atomic clocks. Without leap seconds we will lose contact with the reality of Earth’s rotation. Eventually our midnight would happen at noon.”

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