Browse Definitions:

atomic clock (NIST-F1)

An atomic clock is the most accurate type of timepiece in the world, designed to measure time according to vibrations within atom s. NIST-F1, the United States' standard atomic clock, is said to be so accurate that it would neither gain nor lose a second in over 30 million years. Atomic clocks are used to coordinate systems that require extreme precision, such as Global Positioning System ( GPS ) navigation and the Internet. A group of atomic clocks located in a number of places throughout the world are used in conjunction to establish Coordinated Universal Time ( UTC ).

Like a regular clock, an atomic clock keeps time according to oscillation , which is a periodic variation or movement between two entities or between two states of a single entity, created by changes in energy. In a pendulum-driven clock, for example, the oscillation is the back and forth movement of the pendulum (the oscillator ). Such a clock keeps time according to the frequency of the pendulum's swing, which will be more or less accurate, depending on a number of variables. The precision of an atomic clock, on the other hand, depends upon the fact that an atom, caused to oscillate, will always vibrate at the same frequency.

In 1945, Isidor Rabi, a physics professor at Columbia University, proposed that atomic vibrations could be used to keep time, based on something he'd developed called atomic beam magnetic resonance . Four years later, the National Bureau of Standards (now the National Institute of Standards and Technology ) had developed an atomic clock that used the vibrations of ammonia molecules. NIST-F1, the United States' current standard, uses cesium atoms; it and a similar atomic clock standard in Paris are the most accurate timepieces ever made.

The first commercial cesium-based atomic clocks were manufactured by the National Company, a Massachusetts-based firm; Frequency Electronics, FTS, and Hewlett Packard ( HP ) are among the companies producing them today. Atomic clocks have never been widely used in consumer products because they are typically large and use too much power. Recently, however, NIST developed an atomic clockwork that overcomes these problems. About the size of a grain of rice and accurate to within one second in 126 years, the new mechanism could soon be manufactured on computer chips and used in consumer market handheld devices, such as radios, GPS systems, and cellular telephones.

This was last updated in March 2011

Continue Reading About atomic clock (NIST-F1)

Join the conversation


Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

Just reading the English translation of Einstein's article on "On the electrodynamics of moving bodies" and noticed a comment in Section 5 - "7 Not a pendulum-clock, which is physically a system to which the Earth belongs. This
case had to be excluded". My assumption has been that all clocks measure the same equivalent time. Can anyone explain why a pendulum clock is different? Newton actually took account of pendulum clock differences at different latitudes in The Principia.
hey,its nice content but little more bit in and find it


File Extensions and File Formats

Powered by:


  • risk map (risk heat map)

    A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces.

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...


  • federated identity management (FIM)

    Federated identity management (FIM) is an arrangement that can be made among multiple enterprises to let subscribers use the same...

  • cross-site scripting (XSS)

    Cross-site scripting (XSS) is a type of injection security attack in which an attacker injects data, such as a malicious script, ...

  • firewall

    In computing, a firewall is software or firmware that enforces a set of rules about what data packets will be allowed to enter or...



  • business continuity and disaster recovery (BCDR)

    Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

  • business continuity plan (BCP)

    A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...


  • volume manager

    A volume manager is software within an operating system (OS) that controls capacity allocation for storage arrays.

  • external storage device

    An external storage device, also referred to as auxiliary storage and secondary storage, is a device that contains all the ...

  • NetApp SolidFire

    NetApp SolidFire is a business division of NetApp Inc. that specializes in all-flash storage systems.


  • hybrid hard disk drive (HDD)

    A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.