back to article Atomic time boffins build better second-watcher

US researchers recently named the atomic clock at the UK's National Physical Laboratory (NPL) in London the most accurate atomic timepiece on the planet. Experts from the University of Pennsylvania found that NPL-CSF2 loses just one nanosecond every two months. It's a badge of honour for NPL, the birthplace of the first …

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  1. Anonymous Coward
    Anonymous Coward

    >"or more precisely A1+"

    Ironically less precise owing to typo!

  2. A Non e-mouse Silver badge

    This may seem a silly question, but: How do you prove that your clock is more accurate than someone elses ?

    1. Alan Firminger

      Surely

      How do you prove that a clock is more accurate than everybody else's ?

  3. Anonymous Coward
    Anonymous Coward

    So, how do they do that?

    How can you tell if the most accurate clock in the world is losing time?

    By definition wouldn't you be measuring it with an ever-so slightly less accurate one?

    "A man with one watch knows the time, a man with two is never sure"

  4. Fractured Cell
    Alert

    Probably built in someones shed.

    Is it just me, or is the CSF2 held together with that old stalwart of British engineering -- string?

    1. asdf
      Joke

      as opposed

      The stalward of merkin engineering is duct tape.

  5. Anonymous Coward
    Anonymous Coward

    Goon Show

    Eccles: I know the time - I asked a man once and he wrote it down for me on a piece of paper

    1. Astarte

      Stable Time

      Eccles was right. I too have a piece of paper from the same show in 1957 and it still says 8 o'clock! Hasn't lost or gained at all.

  6. DragonLord
    WTF?

    Circular reference

    Erm, is it me, or does the theory behind atomic time have a circular reference in it. Namely that to measure a second they have to excite atoms until they do something so many times a second?

    1. Anonymous Coward
      Anonymous Coward

      re. Circular reference

      No circular reference; all clocks work by having something happen "many times a second", the "something" (like a pendulum swing for example) will have a known frequency and the clock mechanism just counts how many cycles have occurred.

      The tricky bit is working out the frequency of the thing you're using to "measure time" (most "real world" clocks are calibrated against a known accurate time source).

      1. DragonLord

        I'm fairly sure that Hz is defined as cycles per second, and as these atomic clocks are "more accurate" than any other clock, they don't have a "known accurate time source" to measure against, thus the comment about them having a circular reference. IMO this will become increasingly true if they ditch UTC, as they won't even have the 24/60/60 breakdown of the solar day.

        Wouldn't it be better for them to define a second as x number of y event that occurs when z quantity of material has been heated up to temperature t?

        1. Fred Bauer

          The second is already precisely defined

          as 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.

          So, you just have to count cycles, until you get enough to make up a second.

          The issue is how to count and average the radiation. It's the error in generating and detecting the radiation that's key.

        2. Stratman

          Since 1967 the Second has been defined as 9,192,631,770 wobbles of a Caesium 133 atom.

          Which is handy if you happen to have a clock uses wobbling Caesium atoms as its reference.

          1. DragonLord

            However in the article/attached documentation, didn't they refer to the act of exciting said caesium 133 atoms using microwaves until they get the requisite number of wobbles/second? This would infer that if you put more or less energy in they will wobble at a different frequency...

            1. Liam Johnson

              It is more like a filter, you pump in radiation at around the right frequency and tune it until the cesium atoms wobble the most.

  7. JimmyPage Silver badge
    Boffin

    Measuring time

    don't they use pulsars ?

    1. Anonymous Coward
      Anonymous Coward

      Oh look

      another witless downvote.

      Seems a perfectly valid comment to me. And the OP did use a "?" implying he was seeking knowledge rather than imparting it.

  8. Mark Berry

    It's a pity the NPL can not be relied upon for time. I remember not too long ago their NTP server failed, and the first they knew about it was when I phoned them up.

  9. Yet Another Anonymous coward Silver badge

    How do you know?

    You compare your time with the average of a bunch of other clocks around the world.

    Some individual clocks drift faster or slower - if yours stays at the average you are the winner.

    You have to love the NPL attitude, leap seconds will become unworkable in only 1700years and if a massive comet hit the earth everyone would have to adjust their watches.

  10. ian 22

    One leap second per month?

    In 1700 years, the Earth's rotation will be slowing at such a rate as the lengthen the the year by 12 seconds? If that rate is maintained the year will be more than one hour longer in 2000 years.

    Outrageous! The Vogons will hear of this!

    1. Anonymous Coward
      Anonymous Coward

      Not fast enough.

      I'd be happier with 1 rotation every 32 hours. That way I could get more work done, have a longer leisure time and get more sleep.

    2. Keith Williams
      FAIL

      and not only that

      but because the atomic time is disconnected from the UTC, approximately 528000 years after that, a new Pope Gregory will have to re-adjust our dates by 11 days again.

  11. Charlie van Becelaere
    Unhappy

    Somehow ...

    I thought an atomic time boffin would be much more imposing.

    1. Liam Johnson

      The is just his 3 dimensional projection for god sake!

  12. bubba-bear

    From Sundials to Atomic Clocks: Understanding Time and Frequency

    NIST (the US National Institute of Standards and Technology) has a pdf booklet named "From Sundials to Atomic Clocks: Understanding Time and Frequency" available at http://www.boulder.nist.gov/timefreq/general/pdf/1796.pdf

    NIST has a good description of NIST-F1 which is a cesium fountain atomic clock at http://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm

  13. All names Taken

    Does he get his jeans from Tesco?

  14. Anonymous Coward
    Anonymous Coward

    But what difference will it make ?

    Nice article, but it's a pity that despite there being so many accurate time sources out there, nobody bothers to use them.

    My VoIP desk phone, which presumably gets its time from an NTP server somewhere, is always showing a different time to my laptop connected to the same network...

  15. Magani
    Joke

    I'm gobsmacked...

    ...at the amount of technology required to calculate beer-o-clock.

    (icon for the humour-free among us)

  16. Martin Huizing
    Joke

    Man at a bar...

    Man at a bar asks another man what the time is.

    He replies; "Time to buy a watch."

  17. Llib
    FAIL

    WHERE is Fort Collins??

    Well, their time might be accurate, but the height of a foot (at El Reg!) is way off.

    "NPL is at an elevation of 79 feet above sea level and suffers more from the effects of gravity on its results than Fort Collins, which is more than 3,315 ft, above sea level in the Rocky Mountains in Boulder Colorado, where the effect of gravity is less."

    Wow. Fort Collins is in Boulder?? at 3315 feet?? REALLY?!?

    (Is somebody, used to sea level, getting dizzy from the altitude?)

    Denver, Colorado is famous as "The Mile-High City" (statue mile, of course, so 5280 ft.).

    Boulder Colorado is just a bit higher - 5430 ft above sea level (at City Hall). It has the Univ of Colorado - and the NIST Time and Frequency Division. Don't know the elevation at their clocks, but it should be close.

    ( http://www.nist.gov/pml/div688/staff.cfm )

    Fort Collins, Colorado, is NOT in Boulder, Colorado. It's not even in the same county. It's about 32 miles further north than Boulder, and is the home of Colorado State Univ. -- as well as NIST "time" radio stations WWV & WWVB, and an Internet time server. It's also lower -- 5003 ft at City Hall.

    ( the 10 MHz antenna is at: 40° 40' 47.8" N 105° 02' 25.1" W - to within 10 feet or so )

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