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摘要

They might sound like they should be featuring in a futuristic sci-fi film and most people's faces go blank at the mention of them - but atomic clocks are actually at the heart of timekeeping standards. When it comes to measurement, you would be hard-pushed to find a better example of accurate timekeepers than these: currently the best accuracy of the atomic clock is realised to better than one second in 100 million years.Despite common misconceptions, we have relied on these clocks since the international introduction of the Caesium definition of the second in 1967. The first atomic clock, Caesium I, was designed by a man called Louis Essen and built at the National Physical Laboratory (NPL) in Teddington in 1955. Prior to this, the spinning Earth was the trusted timekeeper, despite the fact that it wobbles as it rotates.