美文赏析

　　Since 1884，Greenwich Mean Time(GMT)has been the international standard for timekeeping，but it is now under threat from a new definition① of time itself based not on the rotation(旋转)of the Earth，but on atomic clocks.

　　In January the International Telecommunication

　　Union will meet in Geneva to vote on whether to adopt② the new measure，despite protests from Britain.No doubt，the question has hurt Britain's national pride—particularly when the British believe their old rival France is leading the push to change from GMT to the new time standard.

　　GMT is based on the passage of the sun over the zero meridian(经线)line at the Greenwich Observatory in southeast London，and became the world standard for time at a conference in Washington in 1884.France was striving③ for Paris Mean Time at the same conference.

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

　　UTC is based on about 400 atomic clocks around the world but then

　　corrected with“leap seconds”to correspond to④the Earth's rotational speed，which fluctuates(波动)．As a result，atomic time is slowly diverging(偏离)from GMT.

　　The tiny differences between Earth speed and atomic speed have become a problem for GPS，space

　　exploration and mobile phone networks on which the modern world relies.

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