Jim Gray,keeper of the American NBS-4 atomic clock. Gray is seen wearing a variety of clocks and watches. The NBS-4 is the long cylindrical object on the bench. It is a caesium clock,in which atoms of vapourised caesium-133 pass back and forth between magnets at each end. The caesium-133 atoms oscillate between two energy levels as they go. Counting these oscillations is the basis of the standard second (1 second = 9,192,631,770 oscillations). This accurate time keeping is passed to Paris,where signals from this and other atomic clocks are averaged to produce the world-wide Universal Time Coordinate (UTC) | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Tsiaras, Alexander |
Bildgröße: | 5135 px × 3425 px |
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