‘Optical clock’ yields split-second success

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Physicists said Tuesday, July 9, that a so-called optical lattice clock, touted by some as the time-measuring device of the future, had passed a key accuracy test.


The performance boosts chances that the world's timekeepers will one day adopt it for defining the second, they said.

The atomic clock, introduced in 1955, measures time by using microwaves to probe atoms as they transit between two energy levels.

The high accuracy of these clocks lies behind the success of the Global Positioning System (GPS), which requires orbiting satellites to be synchronized so that their signals, received on Earth's surface, can be triangulated to give the receiver's location.

Impressive as these clocks are, they can — in theory — be outperformed by lasers.

Written By: AFP
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  1. When I was in grade 7 I puzzled, how would it be possible to create more accurate milling and measuring tools given you only had primitive ones. I never got a fully satisfactory answer, though I thought perhaps screws and taking integral numbers of turns might somehow let you at least divide a length accurately.

    When I heard about the lattice clock the same old question came up. How would you know the new one was more accurate that the caesium clock without an even more accurate clock to measure it against.

    Some musings.

    You might take 3 lattice clocks and see if they stay in sync better than 3 caesium clocks.
    You would have to make sure some synching mechanism is not at work. But even then it is possible the lattice clocks might be affected by say solar wind in systematic way that affected all three clocks, making them great for synching, but not for absolute measurement.

    On the net there are various accuracies of atomic clock. You are supposed to use one only as accurate as you need. You can’t really sync all that well with packets, so perhaps we won’t ever see these lattice clocks directly on the Internet..

    • In reply to #3 by Roedy:

      When I was in grade 7 I puzzled, how would it be possible to create more accurate milling and measuring tools given you only had primitive ones. I never got a fully satisfactory answer, though I thought perhaps screws and taking integral numbers of turns might somehow let you at least divide a lengt…

      Good question. I was thinking the same thing. I presume your “3 clocks” answer is right, except I’d try for more clocks.

      Take 10 clocks, and watch them drift apart. If there was a statistical model of the physics, then you could calculate if the distribution of the clocks times followed the model, and confirm the drift. You could compare with 10 “new method” clocks. Assuming the drift is Gaussian, you would see one distribution of clock times with a higher standard deviation, and the second with a lower distribution.

      Anyone know for sure? My quick googling got zilch.

  2. The most astonishing thing here to me is the incidental explanation which describes atoms of cesium that transit between two energy levels; billions of times per second.

    These are called ‘ticks of the atomic pendulum’.

    These ticks are ‘measured’, I presume meaning counted, more accurately in the lattice clock, using laser beams, than in the old cesium clock, that uses microwaves. Mainly because lasers operate at a frequency 40,000 times greater than microwaves.

    Another difference is the use of strontium atoms in the lattice instead of cesium. It doesn’t say why or whether that affects the accuracy.

    Is it not surprising that someone would consider accuracy of one second in 100 million years as not good enough?

    So now the new standard of accuracy may soon be one second in 300 million years. But for how long, when there is already an aluminium ion clock in Colorado, accurate to one second in 3.7 billion years?

    So by the time our sun goes supernova it will be about one and a half seconds out; spoiling all our forecasts!

    • So by the time our sun goes supernova it will be about one and a half seconds out; spoiling all our forecasts!>>

      So, in the voice of a creationist “SCIENCE IS WRONG”!!!!

      Fucking idiots.

      In reply to #5 by inquisador:

      The most astonishing thing here to me is the incidental explanation which describes atoms of cesium that transit between two energy levels; billions of times per second.

      These are called ‘ticks of the atomic pendulum’.

      These ticks are ‘measured’, I presume meaning counted, more accurately in the…

    • In reply to #6 by papa lazaru:

      Tricky business, this time thing.

      Especially since there isn’t one universal time!

      Out of my depths here! Is time itself stable enought to measure it with that degree of accuracy?

  3. So presumably they could use X-ray lasers (and higher frequencies?) to make more and more accurate measurements up to the limit imposed by the energy transition time. At that point perhaps they could move to other types of atom. I wonder what the technical constraints are. The nature article has more details, I’ll have a go at finding out there.

  4. In reply to #1 by aroundtown:

    The clock proved accurate to within one second every 300 million years, three times more precise than its cesium rival.

    Now that is one accurate clock. Will it be available in wristwatch form? :)

    Not noticeably, I think.

  5. ” The replacement for Greenwich Mean Time, Coordinated Universal Time (UTC) is the timing used for Internet, banking, and aviation standards, and other international timescales, maintained by the Paris-based Bureau International de Poids et Mesures (BIPM).

    Participating measurement institutes and observatories around the globe use collections of atomic clocks to estimate a current value for UTC. These clock data are fed through to the BIPM to be carefully weighted and averaged to derive a combined global value. The complexity of this effort is such that it takes around six weeks to arrive at a definitive final figure, ESA said. “

    http://www.gpsworld.com/esas-navigation-lab-helps-set-global-time/

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