Molecule may will replace Greenwich mean time

For more than 120 years, Greenwich Mean Time (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 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 north-west of London, under the aegis of£¨ÔÚ¡­¡­Ö§³ÖÏ£© the prestigious Royal Society, on Thursday and Friday will look at some of the issues involved.

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

"We understand that in Britain they have a sense of loss for GMT," said Elisa Felicitas Arias, director of the time department at the France-based International Bureau of Weights and Measures (BIPM), which pushed for the change.

GMT is based on the passage of the Sun over the zero meridian line£¨×ÓÎçÏߣ© at the Greenwich Observatory in southeast London, and became the world standard for time at a conference in Washington 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 fluctuates.