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Checking the Positional Invariance of Planck's Consant Using GPS

Posted by Soulskill on 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."

12 of 41 comments (clear)

  1. one scientist's "noise" is another's "signal" by peter303 · · Score: 3, Insightful

    Errors in GPS results have been unwound to tell thinks about atmospheric ionization, general relativity, and now planck's constant.

  2. Fix by wirelesslayers · · Score: 3, Informative

    Checking the Positional Invariance of Planck's Consant Using GPS
    to
    Checking the Positional Invariance of Planck's Constant Using GPS

    1. Re:Fix by fish+waffle · · Score: 3, Funny

      It seems pretty clear they meant Planck's Consonant. Some argued it was "P" but they've now verified that it's an "h".

  3. Very large limits by steamraven · · Score: 3, Interesting

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

    1. Re:Very large limits by Mac+Scientist · · Score: 4, Informative

      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.

    2. Re:Very large limits by Obfuscant · · Score: 2

      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.

    3. Re:Very large limits by FrootLoops · · Score: 3, Informative

      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.

  4. Re:Obviously... by marcosdumay · · Score: 3, Insightful

    As oposed to the well known engeneering saying that "variables won't, constants aren't"?

    Sometimes constants aren't constant in physics either. If we don't look for variances, we won't ever be sure that something is constant.

    --
    Rethinking email
  5. Re:some subject by EdIII · · Score: 2

    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.

  6. Four time zones by tepples · · Score: 4, Funny

    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 still makes more sense.

  7. Re:some subject by mmontour · · Score: 2

    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.

  8. Re:Good stuff to be sure. by TempestRose · · Score: 2

    And when I want to have points, I don't. When I don't want to have points, I do. I would love points for this. Someone mod this up, anon or not, funny as hell.