How the Atomic Clock Works

It is a common misconception that atomic clocks work from the same principles as the atomic bomb. This is not so, but it is an easily made mistake, because an atomic clock is a massive contraption that looks like it might be used as a weapon by some mad scientist. Atomic clocks are called such, because they have a terrifying accuracy that is achieved based on measurements of slight changes in the electrons that orbit the nucleus of an atom. The idea of this came about long before there was sufficient technology to make it possible, Lord Kelvin proposed the possibility back in 1879. The atomic clock became a reality in 1949 when one was built in the United States based upon magnetic resonance developed by Isidor Rabi. The first iteration was a failure in accuracy, it was less accurate than clocks already publicly available, but it proved that Lord Kelvin knew what he was talking about 130 years prior. Louis Essen was the first to build a successful atomic clock, he did it in 1955 in the UK. The most accurate way to measure time before this was ephemeris time, or the astronomical time scale, and this is what was used to set the first atomic clock. In the 1990s there were several improvements made on the atomic clock coinciding with the surge in technology during that era. Amazingly, in 2011 a chip-sized atomic clock entered the market that operates on battery power. The International Systems of Units (SI), the people who are in charge of defining measurements, used the atomic clock to define exactly how long a second is; to be precise it is exactly 9,192,631,770 cycles of radio transmissions discharged from caesium-133 as it changes energy states. This has become know as the caesium standard, and is not only important to the measurement of time, but also effects many other scales that use the second to define them, like voltage and amperage. Even though it is a relatively recent technology, atomic time measurement has wiped out every other timekeeping method in terms of accuracy and longevity of use. Our high tech world depends on the reliable precision of these clocks, they are used in television broadcasting and in satellite navigation. It is truly remarkable that so many large and important international mechanisms depend on the minute actions of one of the smallest objects in the known universe.

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