CERN facility takes a solid tick forward towards a nuclear clock

Atomic clocks are the world's most precise timekeepers. Based on periodic transitions between two electronic states of an atom, they can track the passage of time with a precision as high as one part in a quintillion, meaning ...

A highly precise terahertz molecular clock

In recent years, many physicists worldwide have introduced atomic clocks, systems to measure the passing of time that are based on quantum states of atoms. These clocks can have numerous valuable applications, for instance ...

Dissecting the circadian clock in real time

As our bodies and minds continue to adjust to the recent time change, debates continue around society about whether to make daylight saving time a permanent fixture, eliminate it or stay with the current semi-annual clock ...

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A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece. In general usage today a "clock" refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one's person are often distinguished from clocks.

The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.

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