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Atomic clocks based on the oscillations of a cesium atom keep amazingly steady time and also define the precise length of a second.
The ability to accurately measure a second in time is at the heart of many essential technologies; the most recognizable may be the Global Positioning System (GPS).
Travellers have relied on accurate timekeeping for navigation since the development of the marine chronometer in the eighteenth century. Galileo, Europeâ€™s twenty-first century navigation system, also relies on clocks â€“ but they are millions of times more accurate than those earlier timepieces.
- Having no light.
- Of or relating to the region of a body of water that is not reached by sunlight and in which photosynthesis is unable to occur.