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A transition Down Under

Tim Radford and Bernard O'Riordan — © Guardian Newspapers Limited 2004

Australia abandons Greenwich Mean Time — and another link with Britain

LONDON/SYDNEY: Australia is about to sever yet another historical link with Britain. It will abandon Greenwich Mean Time (GMT) next week and adopt a new national standard based on the atomic clock. Rather than set their watches according to GMT, based on the movement of the sun over a brass mark at Greenwich on the Thames near London, Australians will adjust their chronometers according to the ultra-precise vibrations of a caesium 133 atom or, to give it a more formal name, Coordinated Universal Time (UTC).

"Really, GMT is just a little bit outmoded," said Richard Britain of Australia's National Measurement Institute. "Scientific atomic clocks are the way to go in terms of accurate timekeeping. But nobody is going to get their day shortened or their life lengthened."

New Zealand, Singapore, the U.S. and most of the European Union have already adopted UTC. When European space scientists land a probe on one of the moons of Saturn, when Australian surveyors rendezvous with relief aircraft in the Antarctic, when Egyptian jet pilots land at Heathrow, they all use UTC. British space scientists and Antarctic explorers use UTC, which is "maintained" by 40 time laboratories all over the world, using 260 atomic clocks. Some of these are at the National Physical Laboratory in Teddington, west London, and these keep British time accurate to about one second in three million years.

The most dramatic rupture, however, is with astronomy and with Australia's own history. For Australians now, the second has been decoupled from the year, a measure of time marked by one complete revolution of the earth around the sun.

The decision to use Greenwich as the basis for the planet's time grew out of the need to establish a reliable means to measure longitude.

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