Why Are Atomic Clocks Used?
An atomic clock is a type of clock that uses the atoms of various elements to help maintain constant timekeeping accuracy. While ammonia, hydrogen and rubidium have been used, cesium (caesium in Britain) is the most common element used because it was the first to work.
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History
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The first atomic clock was built in 1948 by the U.S. National Bureau of Standards using ammonia and copper pipe. Unfortunately, it was less accurate than mechanical clocks and thus was never used to keep time.
The first successful atomic clock came in 1955. Built by Louis Essen, the Caesium I was the first atomic clock that kept time more accurately than the average clock. Its ability to keep time was so accurate that it was more constant then the rotation of the Earth.
Only a year later, a cesium clock was available for purchase. The accuracy had become so advanced that it would lose one second every 6,000 years.
Function
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In an atomic clock, time is kept by a quartz crystal oscillator, which can change frequency over time and vary the clock's accuracy. To maintain accuracy, an atomic clock has a device that repeatedly checks the frequency of the oscillator.
The most accurate atomic clocks use a supply of cesium, with its 55 spinning electrons that are manipulated by an oven, magnets and radio waves to keep the quartz crystal oscillator at the right frequency. A decreasing number of changed electrons means that the oscillator needs to be adjusted, a task handled by an automated system until the number of changed atoms returns to the maximum.
In more recent atomic clocks, lasers are used instead of magnets to separate the cesium atoms and these only lose one second every 6 million years.
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Uses
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To the average person, the supreme accuracy of an atomic clock does not seem useful, but actually the clock proves indispensable in many ways. For example, those who use GPS devices are having their position pinpointed by several of 27 satellites, each of which carry three atomic clocks.
Communications companies use atomic clocks to get exact frequencies so multiple conversations can travel down the same wires. Without this sort of accuracy, communications would clutter due to so many people using the lines.
Comparison
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The average, non-atomic clock works by counting vibrations of something like a pendulum that maintains a consistent frequency. However, this mechanism can be affected by stimuli such as gravity, air pressure and even temperature, thus varying the speed of the clock. Atomic clocks, on the other hand, would only experience minor variations after hundreds of years, making them far more accurate than mechanical clocks.
Advances
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Newer, more accurate advances on the atomic clock are being researched and invented. The experimental cesium fountain involves the use of lasers to slow down millions of cesium atoms and then push them upwards to allow them to succumb to gravity, at which point they pass through radio waves and a laser measures the amount of energy change. Their accuracy has reached a loss of one second every 15 million years.
The trapped ion machine is a device that traps ions (atoms with electric charges) in place and exposes them to radiationto reduce problems with frequency. It is believed that once perfected, the machine should only lose a second every 10 billion years.
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