What is Atomic clock: Definition and 30 Discussions

An atomic clock is a clock whose timekeeping mechanism is based on the interaction of electromagnetic radiation with the excited states of certain atoms. Specifically, either a hyperfine transition in the microwave region, or an electron transition in the optical or ultraviolet region, of the emission spectrum of an atom is used as a frequency standard for the timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.
The principle of operation of an atomic clock is based on atomic physics: it measures the electromagnetic signal that electrons in atoms emit when they change energy levels. Early atomic clocks were based on masers at room temperature. Since 2004, more accurate atomic clocks first cool the atoms to near absolute zero temperature by slowing them with lasers and probing them in atomic fountains in a microwave-filled cavity. An example of this is the NIST-F1 atomic clock, one of the national primary time and frequency standards of the United States.
The accuracy of an atomic clock depends on two factors:

the temperature of the sample atoms—colder atoms move much more slowly, allowing longer probe times
the frequency and intrinsic linewidth of the electronic or hyperfine transition. Higher frequencies and narrow lines increase the precision.National standards agencies in many countries maintain a network of atomic clocks which are intercompared and kept synchronized to an accuracy of 10−9 seconds per day (approximately 1 part in 1014). These clocks collectively define a continuous and stable time scale, the International Atomic Time (TAI). For civil time, another time scale is disseminated, Coordinated Universal Time (UTC). UTC is derived from TAI but has added leap seconds from UT1, to account for variations in the rotation of the Earth with respect to the solar time.

View More On Wikipedia.org
  1. D

    I Is There an Atomic Clock Experiment on the Moon Testing Relativity?

    I learned recently that there are plans to create a dedicated global satellite navigation system (GNSS) for the Moon, so we will have atomic clocks on and around the Moon, but we have at least one there now, in order to compare it with a clock on Earth? You know about such an experiment and its...
  2. MatthewKM

    I Atomic Clock Speed graph between two stationary masses

    A question about general relativity and clocks. Clocks run slower in lower gravity. Or said a different way, the oscillation frequency of a subatomic particle approaches maximum as gravitational effect approaches minimum.The further away from the centre of mass of a planetary body, the faster a...
  3. dom_quixote

    I Atomic Clock Exp on Ballistic Flight: Proving Clocks are Accelerometers

    In the past, scientists have experimented with atomic clocks aboard airplanes in order to prove the Special Theory of Relativity. In our humble opinion, ALL watches are accelerometers. Effect observed in a chaotic pendulum in free fall: Too bad they didn't do the same experiment with an...
  4. Bruce Harvey

    A Can Quantum Mechanics Calculate the Frequency of an Atomic Clock?

    I have searched in vain for a detailed calculation of the frequency 9192631770 Hz from basic physical constants using Quantum Mechanics. Can anyone help with this please
  5. Danny Boy

    A Concepts in a quantum synchronization setup

    In a https://jila.colorado.edu/thompson/sites/default/files/pdf/PhysRevLett.113.154101_0.pdf on quantum synchronization, they introduce the setup given in the attached 'Fig1.png'. I would like confirm a few concepts regarding this setup. The setup is described in the following way: The general...
  6. iVenky

    I Why are atomic clocks so accurate?

    For any clock, the way I define accuracy of the clock is based on the Q factor (the ability to reject noise) and the inherent noise in the system. In that case, can you explain me why atomic clocks are so accurate? Do they have high Q factor? (if so, how)? or low noise to begin with?
  7. P

    What was the rotational velocity of Earth on Dec 31, 1899

    I ask because time is defined with reference to this day (the SI second is based on a caesium clock is calibrated with reference to the 1952 ephemeris time standard, which was based on a second being 1/86 400th of Jan 0, 1900 (with Jan 0 being Dec 31 of 1899). So... how do I calculate the...
  8. P

    I SI definition of second: what day/year is the reference year

    The SI definition of a second was originally based on 1/86 400 of a day - but the Earth's rotation is a) unsteady and b) changing so it was changed to a defined number of cycles of an atomic clock. Was there a specific day for which the atomic clock was calibrated? Put another way, why were 9...
  9. G

    I GPS and Cs atomic clock question

    Ok, so pardon my ignorance if this can found easily online but I have these few questions. I was actually reading quite a complicated article about GPS and relativity but it had too much maths in it for my abilty. Ok, first of all, apart from the complicated details regarding the workings of...
  10. D

    I Time Difference on a quantum level

    As we know from special theory of relativity, time flows slower for a moving observer. But also, thanks to gravity, time ticks slower and faster depending on whether the gravitational force is stronger or weaker. This f.ex. means that time will flow slower for a person living on the 10th floor...
  11. Auto-Didact

    A Weinberg: detecting changes to QM using atomic clocks

    Steven Weinberg has lately been critical of QM. He now also has a technical paper out called 'Lindblad Decoherence in Atomic Clocks', available on arxiv. Here is the abstract: It's a short paper (6 pgs of text), arguing for objective collapse (a la GRW/Diosi-Penrose/etc) instead of...
  12. Grayman

    B Problem with the atomic clock and time dilation

    The atomic clock is used as evidence of time dilation and to provide more evidence that light speed is invariant. The problem I have with this is that the clock uses frequency and light. It has a feedback loop that is supposed to correct for inaccuracies but the entire loop will obviously be...
  13. Marco Masi

    A Hyperfine structure transition of Cs-133: calculation?

    I'm looking for the theoretical calculation of the hyperfine structure transition frequency of Ca-133 which is used in atomic clocks to define the second according to SI-Units. Google, Google... there is a lot about the hyperfine Hamiltonian of hydrogen, but couldn't find none about that of...
  14. Tom MS

    I Resonant Frequency of an Atom in an Atomic Clock

    Beam standard atomic clocks work by changing the magnetic state of a cesium atom by applying a microwave frequency that matches the resonant frequency of a cesium atom. What is this resonant frequency of the atom in terms of actual events that occur on the atomic level...
  15. J

    Atomic clock: energy between two levels

    Homework Statement With the atomic clock a second is defined as the time it takes for EM radiation to oscillate 9192631770 times, which equals the energy gap between two energy levels of a caesium-133 atom. Note: it's a translation and the term used with the oscillation is "oscillation periods"...
  16. G

    An atomic clock and a normal clock

    Two clocks in a spaceship floating though space at 99% the speed of light. One is a atomic clock and uses light and mirrors to measure time, the other clock uses cogs and gears like a conventional clock. From the perspective from inside the ship both clocks tick and tock at the usual rate...
  17. J

    The atomic clock on a jetliner experiment

    Something I don't understand about that experiment, or about relativity in general. Why the clock on the jet flying around the world is the slower one. I mean isn't the stationary clock moving the same speed away from the jetliner clock relative to the jetliner clock?
  18. N

    Instability of an atomic clock

    Hi When I read "popular" papers on atomic clocks, many journalists write that the clock loses 1 second in XX million/billion years. But when I look at some professional papers, people talk about a fractional instability of e.g. 10-14t-1/2, the authors never use the former way of characterizing...
  19. A

    Atomic clock used in spaceships

    Hi, Not sure how stupid my question might be. Could anyone please clarify me, why the atomic clock in a spaceship is taken as a reference while explaining a special theory of relativity?. I always wonder how 2 people one outside the spaceship and the other inside it feels about a time in...
  20. H

    Atomic Clock Time Dilation Experiment

    Homework Statement Two atomic clocks are synchronized. One is placed on a satellite which orbits around the Earth at high speeds for a whole year. The other is placed in a lab and remains at rest with respect to the earth. You may assume both clocks can measure time accurately to many...
  21. I

    Does anyone have information on how exactly a atomic clock works?

    Does anyone have information on how exactly a atomic clock works? I have had advanced quantum mechanics courses so I am sure I wil understand it. My problem is that I can't find any descriptive materials (with drawings), the wikipedia page is very vague about the different things. So can...
  22. R

    Does gps receiver need synchronization with atomic clock

    with synchronization what the gps receiver does is compute time difference between his current time (synchronized with atomic clock onborad each satellite) and the time tag of a satellite when the signal was sent. This difference gives the travel time of an signal from the satellite and hence...
  23. R

    Atomic Clocks & Moore's Law: Is There a Connection?

    Attached are two diagrams. One describing Moore's law, the other describing the development of atomic clocks since the 50's. Is there a connection between these diagrams, not in the strict graph-math equivalence sense, but in the sense, that conclusions regarding atomic clocks' future accuracy...
  24. R

    Atomic Clock Accuracy: Moore's Law & Beyond

    Attached are two diagrams. One describing Moore's law, the other describing the development of atomic clocks since the 50's. Is there a connection between these diagrams, not in the strict graph-math equivalence sense, but in the sense that conclusions regarding atomic clocks future accuracy...
  25. D

    What is the relationship between latitude and the accuracy of an atomic clock?

    Atomic clock should record different time depending on their geo location: different latitude -> different rotation speed. Question: The most precise time on Earth - where is it valid? On what Latitude?
  26. P

    Exploring Cesium Atomic Clock Functionality

    Can anyone recommend me some papers explaing how cesium atomic clock works?
  27. R

    Atomic Clock Reveals Slowing of Time Predicted by Einstein

    An article in Wired concerning a new atomic clock has as part of its lead sentence "The new timekeeper could one day ... detect the slowing of time predicted by Einstein’s theory of general relativity." See http://www.wired.com/wiredscience/2010/02/quantum-logic-atomic-clock/#ixzz0f1IPhJLR...
  28. W

    Ramsey fringes and the atomic clock

    Hi, I'm currently researching into the formation and history of atomic clocks. Quartz and crystal clocks can determine resonance frequency measurements to an order of 10^8, but using Ramsey fringes this can become more accurate. Could someone help me explain why Ramsey fringes are a far...
  29. M

    Atomic clock - optical pumping

    I am doing some research on atomic clocks. From what I have read, I understand that in Rb atomic clocks you: -optically pump a cell of Rb, so that the electrons are all in a single hyperfine state -subject the cell to microwaves of appropriate frequency, so that the electrons will be...
  30. B

    Did the Apollo Missions Use an Atomic Clock for Time Dilation Experiments?

    Did they take an atomic clock on one of the Apollo missions for time dilation experiment if not why not ?