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Checking the Positional Invariance of Planck's Consant Using GPS 41

Posted by Soulskill
from the more-accurate-than-a-divining-rod dept.
gzipped_tar writes "Whether the fundamental constants really stay the same is always a question worth asking. In particular, the constancy of Planck's Constant is something that cannot be simply ignored, owing to its universal importance in linking the quantum and classical pictures of our world. Using publicly available GPS data and terrestrial clocks, researchers form the California State University were able to verify that the value of h indeed stays the same across different positions in the vicinity of our Earth. Their result says the local position invariance of h is satisfied within a limit of 0.007. The paper is published in the journal Physical Review Letters (abstract), and a free-to-read preprint is available on arXiv. In short: by the well-known formula E = h * f, a hypothetical variation on h induces changes in f, the transition frequency that keeps the time in atomic clocks, both on earth and aboard the satellites. When taking account of other time variations, such as general relativistic time dilation, and assuming the invariance of E (atomic transition energy) on physical grounds, we can figure out an upper bound on the variation of h reflected in the measured variation in f."
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Checking the Positional Invariance of Planck's Consant Using GPS

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  • this reads like time cube

    • by EdIII (1114411)

      Nothing reads like time cube. Nothing. :)

      First off, your brain starts to bleed just from the background image. Then the evil cube gods start programming you with their evil 4 day belly button logic. Forced extraction of your educated stupidity and oneness, one god mentality is commenced.

      That whole website is a complete riot. It's like stream of consciousness writing from a mental patient they have not found the correct medication for.

      • by mmontour (2208)

        Nothing reads like time cube. Nothing. :)
        First off, your brain starts to bleed just from the background image

        The funniest thing for me is that when you finally scroll down to the bottom of that wall of crazy-text, there's a "next page" link.

        • by EdIII (1114411)

          Nothing reads like time cube. Nothing. :)
          First off, your brain starts to bleed just from the background image

          The funniest thing for me is that when you finally scroll down to the bottom of that wall of crazy-text, there's a "next page" link.

          Have you clicked it? :) That's where the real journey begins. If you think the first page was batshit crazy....

      • by Kreigaffe (765218)

        I don't know if it's LIKE that..
        I think it may BE that.

      • by khallow (566160)

        It's like stream of consciousness writing from a mental patient they have not found the correct medication for.

        Probably because the medication doesn't exist yet.

    • by tepples (727027) <[moc.liamg] [ta] [selppet]> on Friday March 16, 2012 @08:11PM (#39385105) Homepage Journal
      Time Cube starts to make a bit more sense when you realize that "four simultaneous 24-hour days" is just a long way of saying "four time zones". But GameCube [fateback.com] still makes more sense.
      • Time Cube starts to make a bit more sense when...

        Ok, take tepples away... there is no hope for him.

  • by Anonymous Coward

    Scientists get to have all the fun. Most people would have to worry about being fired for Plancking while on the job.

    *ba-dum tssh*

    • by Sulphur (1548251)

      Scientists get to have all the fun. Most people would have to worry about being fired for Plancking while on the job.

      *ba-dum tssh*

      Watch out for adulterated Planck.

  • by peter303 (12292) on Friday March 16, 2012 @06:42PM (#39384155)
    Errors in GPS results have been unwound to tell thinks about atmospheric ionization, general relativity, and now planck's constant.
  • Fix (Score:3, Informative)

    by wirelesslayers (2014486) on Friday March 16, 2012 @06:53PM (#39384305)
    Checking the Positional Invariance of Planck's Consant Using GPS
    to
    Checking the Positional Invariance of Planck's Constant Using GPS
  • Very large limits (Score:3, Interesting)

    by steamraven (2428480) on Friday March 16, 2012 @06:59PM (#39384375)
    Given that h is very small (1e-15, 1e-34 or 1e-27 depending on units), a limit of .007 seems rather large.
    • Re:Very large limits (Score:4, Informative)

      by Mac Scientist (153390) on Friday March 16, 2012 @07:37PM (#39384799)

      Given that h is very small (1e-15, 1e-34 or 1e-27 depending on units), a limit of .007 seems rather large.

      Considering NIST in Washington, NRC in Ottawa, NPL in London, and METAS in Berne (all national metrology labs) have directly measured h to within 300 parts in a billion (1E9), this is an unusual report. Those results are within a relative limit of 0.0000003.

      Planck's constant cannot be measured with only a GPS or atomic clock, so this is at best some comparative result.

      • by Obfuscant (592200)

        Planck's constant cannot be measured with only a GPS or atomic clock, so this is at best some comparative result.

        Yeah, that's kinda the point of calling it positional independence. They're reporting how constant the constant is, not what its value is.

    • Don't tell him that, he's got a licence to kill!

    • by Shavano (2541114)

      I assume that's relative, but even so it's still very large considering the relative scale of the universe and the fact that we can easily measure frequency to 1 part in 10^10.

    • Re:Very large limits (Score:4, Informative)

      by FrootLoops (1817694) on Saturday March 17, 2012 @01:43AM (#39387101)

      The summary could have been clearer, but the 0.007 number isn't even remotely close to representing absolute error bounds. It's actually a scaled relative error--that is, the amount the ratio of Planck's constant at one position to the value at another position differs from 1, multiplied by a scale factor. That scale factor is somewhat complicated and depends on the speed of light as well as the gravitational field and velocity of measurement devices at each position. I don't know enough general relativity to explain the reasoning behind the particular scale factor chosen. Without that reasoning the quoted number is almost useless; perhaps someone else can provide it.

      From the abstract:

      The results indicate that h [Planck's constant] is invariant within a limit of |\beta_h| < 0.007, where \beta_h is a dimensionless parameter that represents the extent of LPI [local position invariance] violation.

      [For those unfamiliar with TeX markup, \beta is just the Greek letter beta, and _ indicates a subscript.]

      The paper defines \beta_h in equation (6):

      LPI violations for h can be written as
              h_x/h_o = 1 + \beta_h \Delta U / c^2
      where h_o is the locally measured value of h at reference point O, h_x is its locally measured value at x, and \beta_h is the parameter for Planck’s constant.

      \Delta U had been defined just after equation (1):

      The potential difference is \Delta U = U_x - U_o,
      where U_i = \Phi_i - v_i^2 / 2, \Phi_i is the gravitational potential energy per unit mass and v_i is the clock’s velocity.

  • by Anonymous Coward

    My big gripe with physics is a lot of its models assume...linearity of systems. I don't want to be the asshole who begins with "assume an invisible, silent, odorless dragon in the garage"...

    Because I know that's not science.

    But -- I'd like to see a little more exploration and less blind Faith in science. Which by definition is happening in the known universe. I'm not asking people to check the unknown universe, but let's measure on a bit more than... earth.

    Can we get this tested under more *interesting*

    • by stevelinton (4044)

      Can we get this tested under more *interesting* conditions than earth?

      Can we test plank's constant as we accelerate an object near light speed or subject it to overwhelming gravitational force? How about as we heat or cool it? How about as we take that quanta and accelerate or decelerate it?

      Many of these are possible, in a sense, although what you actually test is not Planck's constant but various combinations of it and other constants which eventually give pure dimensionless numbers. The best known of these is alpha which measures the strength of the electromagnetic force.

      Limits on values of alpha in extreme conditions (or over long periods of time) can be determined from astronomical observations -- different spectral lines would shift by different amounts if alpha, changed, for instance, so

  • That result is interesting but if the variation of h across Earth's orbit court be as high as 0.007, it could on principle be much greater across much.larger scales. Is it the same at the center of the galaxy? In other galactic clusters? Over billions of years? The conditions of measurement were very small compared to those scales.

    We can measure frequency with much more precision than anything else. I'm surprised their upper bound is so high.

  • It's spelled constant, not consant.

Never tell people how to do things. Tell them WHAT to do and they will surprise you with their ingenuity. -- Gen. George S. Patton, Jr.

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