PTB
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.
Christian Lisdat at the National Metrology Institute of Germany …