Atomic clocks are precise timepieces, which are regulated in correspondence with a characteristic invariant frequency of an atomic/ molecular system. They can be electric or electronic timekeeping devices that are controlled by atomic or molecular oscillations.

A brief history of Atomic clocks

The year 1948 witnessed the creation of the first atomic clock, which utilized the vibrations of ammonia molecules. The error between a pair of such clocks- the difference in indicated time if both were started at the same instant and compared later on- was typically about one second in three thousand years. In 1955, the first cesium-beam clock (a device that uses the exact frequency of the microwave spectral line emitted by cesium atoms as a reference) was put in operation at the National Physical Laboratory at Teddington, England. It was anticipated that such a clock would gain/lose less than a second in three million years. The U.S. standard is the NIST-F1, in service since 1999 with an impeccable track record of neither gaining nor losing a second in 20 million years.

Features of Atomic clocks

As accurate timekeeping devices, regular clocks need to contain or be coupled with some apparatus that oscillates at a uniform rate to control the rate of movement of its hands, or the rate of change of its digits. Mechanical watches and clocks use oscillating balance wheels, pendulums and tuning forks but when the question is of measuring time in the most precise manner possible, it is atomic clocks that win hands down. Atomic clocks have the unique feature of using oscillation of atoms/molecules and thus afford greater accuracy and ordinary clocks have a lower frequency of oscillations so it is not possible to use them as a direct means of controlling a clock. An atomic clock is controlled by a highly stable crystal oscillator with an output that is automatically multiplied and compared with the frequency of the atomic system, which in turn, automatically corrects errors in the oscillator frequency. The time display is with a digital or similar stylish readout device.

Uses of Atomic clocks

Many a standards laboratory at the national level prefers timekeeping at the hands of atomic clocks, which averaged to produce a standard called international atomic time (IAT). The time signals from these standards laboratories are highly accurate and are relayed around the globe by short-wave-radio broadcast stations or by artificial satellites. These include signals being used for tracking space vehicles, electronic navigation systems and studying the activity of the earth's crust.

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