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New Atomic Clock Pushes Boundaries of Accuracy

Posted by timothy on from the pushes-them-the-right-way-even dept.

Neophytus writes "An interesting story on the BBC reports on how a new type of atomic clock is near completion that would only loose about a second in every 100 million years. Within ten years they hope to have a clock with billion year accuracy which would potentially bring advances in disease research by watching timing genes. More reports from this year's AAAS Annual meeting can be found on the BBC, and information about the event on the AAAS Annual Meeting website."

5 of 43 comments (clear)

  1. Sounds Good... by sepluv · · Score: 2, Informative
    Well...I guess the laser won't make any sound. Seriously though, why do they need things this accurate? I don't know but I'm sure there are some scientific experiments (atomic &c) which require extremely accurate timing. It is amazing that for instance radio telescopes need at least a picosecond accuracy (so that the computers can line up signals from different telescopes in an array) so they all have atomic clocks on site.

    It appears that these clocks are still in the early conceptual stages but they sound a helluva accurate (doubt they'll need more accuracy but u don't know).

    There are more prosaic applications as well, speeding up telecommunications and making them more secure from hackers.
    Why does that require 1 second in billions of years accuracy?

    Also, shouldnt these clocks use the measurement system detailed in the official CGPM SI defintion of the second to be used as scientific master clocks.


    Official Systeme International d'Unites definition:
    #The second is the duration of 9 192 631 770 periods of the radiation
    #corresponding to the transition between the two hyperfine levels of
    #the ground state of the caesium 133 atom.

    Can they be sure that what they are measuring does not change (especially if it involves light - although I think scientists have now decided to just assume c is constant now even if it is not and now base other measures (e.g.: the metre) on the value of c)?

    --
    Joe Llywelyn Griffith Blakesley
    [This post is in the public domain (copyright-free) unless otherwise stated]
    1. Re:Sounds Good... by Anonymous Coward · · Score: 2, Informative

      The applications cited are stupid. Measuring the relativistic effects of reasonable masses is a better application for a hyper-accurate clock.

      And, as you mentioned, VLBI, where you aim two radio-telescopes far away (like opposite sides of the planet) at the same object and combine the signals to get higher resolution, requires time sync to within a fraction of a cycle of the frequency being observed. This can always use more accurate clocks to make longer observations at higher frequencies.

      As for the definition, it is defined that way because that is the most accurate way to measure the second currently known. If somebody finds a better way (like the trapped mercury ion system discussed here), then the second will be redefined in terms of the new, more accurate reference. Just like how the metre was changed in 1983 from a multiple of the wavelength of a certain atom's radiation to 1/299,792,458 of a light-second. This new standard is equal, to the limits of measurement, to the old one, but the limits are those of the old standard; the new one can be measured more precisely.

      (See http://www.mel.nist.gov/div821/museum/length.htm for a description of how it's done... it involves building a highly stable laser, measuring its frequency against the second, using the constant 299,792,458 to compute the wavelength, and then counting wavelengths to get the distance. This gives you the meter to 7.2 parts in 10^12, compared to 2.5 parts in 10^11 for an iodine-stabilized HeNe laser or 4 parts in 10^9 for the old Krypton standard.)

      As for it not changing... nothing can ever be proved absolutely, but many people have measured it very carefully and have never observed any variation.

  2. Re:Disease research by baz00f · · Score: 3, Informative

    I am a biochemist/molecular biologist and I can't imagine what the author has in mind. I'm sure it was just a giddy deadline thing. He probably wrote something earlier on gene transcription timing or chronobiology and made an goofy link to this new "cutting edge research pushing back the foreskin of science..."

    Accuracy on the order of 1 second in 1 billion years is about 1 part in 3x10^16. I see no way that is important to have for measurements of any observable biological process.

  3. Additional info by bardencj · · Score: 3, Informative

    You can read a little more about the background of this new clock at NIST's archive of a paper in IEEE T. Instrum. Meas., for those of us who foolishly let our subscription lapse...

    It would appear the chief technological development that made this clock possible was the femtosecond laser. The paper also suggests that the average error could be reduced even further than the article suggests (down to attoseconds, perhaps) if higher-order Stark and Zeeman shifts are properly treated. As for practical uses, I personally can't think of any, except to finally answer the question "Does anybody really know what time it is?" But elimination of uncertainties is laudable anyway.

  4. Re:Disease research by baz00f · · Score: 2, Informative

    Yes, but we are talking accuracy here, not absolute values, so using a more accurate timebase to measure a femtosecond process still begs the question of why you would need that extreme "1 part in 10^16 of a femtosecond" accuracy. Measuring a nominally 1 fs reaction to 1 part in 100 (1% accuracy) is no doubt good enough.

    Protein folding is on the order of millseconds, but "something" is always occuring at all time scales. The Music of the Universe covers all frequencies.