An atomic clock has been used to take measurements outside a lab for the first time.
These super-accurate clocks require extreme cold and stability. The tick of an atomic clock is measured by the frequency of radiation emitted when electrons around an atom change energy states. The best ones measure time with an error of only 1 in 1 billion billion: after ticking for 32 billion years, they would be just 1 second off.
at the National Metrology Institute of Germany and his colleagues put a strontium atomic clock on the move with a specially designed trailer. It has rubber dampers to mitigate vibrations, and climate control to stabilise the temperature.
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The team used the clock to test a prediction of Einstein鈥檚 general relativity: that time moves more slowly when gravity is stronger. According to Einstein, clocks run slower at sea level than at the top of a mountain, where the tug of Earth鈥檚 gravity is less strong.
To confirm this, the team took measurements in the mountains of Modane, France, and in lower-lying Turin, Italy. Lisdat says they found that a year in the Alps is 84 nanoseconds longer than in Turin.
Nature Physics
Read more: Atomic clocks make best measurement yet of relativity of time
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