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Science Technology

New Most Precise Clock Based On Aluminum Ion 193

Posted by ScuttleMonkey
from the many-stitches-in-time dept.
eldavojohn writes "The National Institute for Standards and Technology has unveiled a new clock that will 'neither gain nor lose one second in about 3.7 billion years,' making it an atomic clock twice as precise as the previous pacesetter, which was based on mercury atoms. Experts call it a 'milestone for atomic clocks.' The press release describes the workings: 'The logic clock is based on a single aluminum ion (electrically charged atom) trapped by electric fields and vibrating at ultraviolet light frequencies, which are 100,000 times higher than microwave frequencies used in NIST-F1 and other similar time standards around the world.' This makes the aluminum ion clock a contender to replace the standard cesium fountain clock (within 1 second in about 100 million years) as NIST's standard. For those of you asking 'So what?' the article describes the important applications such a device holds: 'The extreme precision offered by optical clocks is already providing record measurements of possible changes in the fundamental "constants" of nature, a line of inquiry that has important implications for cosmology and tests of the laws of physics, such as Einstein's theories of special and general relativity. Next-generation clocks might lead to new types of gravity sensors for exploring underground natural resources and fundamental studies of the Earth. Other possible applications may include ultra-precise autonomous navigation, such as landing planes by GPS.'"
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New Most Precise Clock Based On Aluminum Ion

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  • by deglr6328 (150198) on Friday February 05, 2010 @02:04PM (#31037678)

    The long list of lame jokes that would inevitably accompany this article are obvious and unsurprising. But these "oooh now I can get to my next meeting within one yoctosecond of it starting" jokes may be more apt than you realize. There is a real issue of how to even use a clock this accurate at all. This new Al ion clock is supposedly accurate to one part in 10^17, yes? An article I read in SciAm ~8 years ago predicted this milestone would be reached within the decade, and it seems they were right. The problem is, you will introduce a relativistic time dilation to a clock with an accuracy on the order of 1 in 10^17 merely by walking down the street with it. Similarly, you will experience a comparable magnitude of time dilation by reducing the earth's gravity you experience by raising your elevation off the ground by only 10 centimeters. Aside from pure physics experiments like measuring a potential variation in the fine structure constant since the beginning of the universe and such, I don't know how practical application of a clock this accurate could be achieved. For instance, even if you manage to get a time standard of this level accuracy aboard a GPS satellite, you need to know the satellite's location in orbit, it's "ephemeris data", to an equal degree of accuracy in order to make use of such a time standard. Is that even possible? How do you transfer a time standard of such extreme precision between two clocks while preserving its integrity? If that can't be done, what is the practical use of an absolutely stationary clock that can never be moved? Even for the measurement of the fine structure constant at something like 1/10^18, you will have to take into consideration the movement of the continent due to plate tectonics and the movement of magma bubbles in the planet's mantle in order to have confidence in the accuracy of your answer.

  • by jmizrahi (1409493) on Friday February 05, 2010 @03:02PM (#31038530)
    You are absolutely correct, the time measured by such a clock is going to be dependent on general relativistic effects, most prominently by distance from the mean geoid. However, I fail to understand how you jump from that to concluding that it's useless. For example, you could use such a clock to make precision measurements of general relativity and test possible extensions. Moreover, a clock that sensitive should be able to "feel" changes in gravity caused by density fluctuations in the Earth. This could help find oil deposits, for example. The summary says as much. Generally speaking, you NEVER lose by increased precision. It is true that if your specific application is limited by low precision in some other component, you won't gain by increasing precision somewhere else. However, that's not the case here. I'll admit that I don't know enough about GPS and satellites to answer your specific question, but my impression is that they currently ARE limited by time standards.
  • by alexj33 (968322) on Friday February 05, 2010 @03:03PM (#31038542)

    will 'neither gain nor lose one second in about 3.7 billion years,'

    What clock are they going to check it against to verify its accuracy?

    And if there is such a clock, why isn't that clock being tested instead?

  • by IICV (652597) on Friday February 05, 2010 @03:29PM (#31038882)

    Allright then - you take twelve of these clocks, grouped into clusters of three, arranged in the shape of 3D right angle with each cluster as far away from the other as possible. You isolate them as well as you can, so that they are not disturbed by local vibration and other such things. Probably the best thing to do would be to launch them into space.

    Then you measure their time differences.

    If there's any differences, assuming you've isolated them well enough and are filtering out the expected noise, those differences must be due to external gravity waves.

    Tadaa, we've got a gravity wave antenna. Maybe someone's talking in that spectrum.

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