The Atomic Clock and International Time

Chip scale atomic clock photo by the National Institute of Standards and Technology.

There are many devices that have been used to measure time since the concept of time began. From the position of the sun to using the ingenious sun dial to nanosecond accurate clocks today, time telling has evolved over the ages. In the history of the clock, there have been sun dials, hour glasses, water clocks, pendulum clocks and mechanical clocks. However, the most accurate tool for measuring time in current day is the atomic clock.

What is an atomic clock?

It is a device that measures time using electronic transition frequency within an ultraviolet, microwave or optical region. The electromagnetic spectrum of atoms creates the frequency standard that is used in the timekeeping element of the atomic clock making it usable in international time distribution calculation by online calculators and even GPS systems. Atomic clocks are used at very low temperatures to measure atoms. They can maintain perfect accuracy for over millions of years.

According to the atomic clock, a second is the duration of 9,192,631,770 periods of radiation. This perfectly established standard of the transition between two levels of the Cesium 133 atom is what enables the atomic clock to track time so accurately.

Understanding the time measuring concept of the atomic clock

Timekeeping is based on counting intervals between things that occur repeatedly with negligible variation. That is why time measuring concepts such as the hour glass, water clock and pendulum swing were so applicable in their time. There was a repeated action that could be measured. The count between the intervals are corresponded to a unit of time such as seconds, minutes of hours. However, these methods of telling time develop discrepancies making the best natural and most accurate time keeping method, the exact vibration in energized atoms.

The frequencies of radiation from microwave, optical or ultraviolet sources causes sub atomic particles to jump back and forth between different energy states and the movement of time is based on this movement within the atom. Inside the atom clock, there is a detector that tracks the number of cesium atoms with a change in energy state, and feeds this information to the radio wave generator which works with other electronics in the atomic clock to count the frequency in the number of cesium atoms striking the detector.

Keeping time using the atomic clock

The National Institute of Standards and Technology (NIST) maintains the top atomic clocks. The cesium atomic clock only has an error of about 0.03 nanoseconds a day when measuring time. The clock can only loose one second of time in one million years. This super-accurate element of time keeping has been greatly applied to various aspects of modern life especially the Global Position System (GPS) to online time calculators. You can thank the atomic clock for being able to tell the exact time in cities in different time zones around the world.

Chip scale atomic clock photo by the National Institute of Standards and Technology.

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Paul Tomaszewski is a science & tech writer as well as a programmer and entrepreneur. He is the founder and editor-in-chief of CosmoBC. He has a degree in computer science from John Abbott College, a bachelor's degree in technology from the Memorial University of Newfoundland, and completed some business and economics classes at Concordia University in Montreal. While in college he was the vice-president of the Astronomy Club. In his spare time he is an amateur astronomer and enjoys reading or watching science-fiction. You can follow him on LinkedIn and Twitter.

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