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New value for alpha, the fine structure constant

  1. Aug 1, 2006 #1


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    alpha reciprocal new value is 137.035 999 710(96)
    (uncertainty 0.70 ppb)

    "The new value, based on the most precise measurements ever of the magnetic moment of the electron, has an uncertainty of 0.7 parts per billion. The new value is ten times better than the next most accurate way to measure alpha."
    "Until now, the best measurement of g had an uncertainty of 4 parts per trillion. Now, Gerald Gabrielse and colleagues at Harvard University have increased this precision by a factor of almost six to 0.76 parts per trillion (Phys. Rev. Lett. 97 030801). By inserting this new value of g into new and improved QED equations, the Harvard physicists, with colleagues from Cornell University and RIKEN in Japan have determined a new value for alpha that is ten times more accurate than the next most accurate value (Phys. Rev. Lett. 97 030802).

    Gabrielse and colleagues measured g by studying the motion of a single electron held inside a trap made of charged electrodes and magnetic coils. The combined electric and magnetic forces keep the electron moving in a circular "cyclotron" orbit. On top of this planar motion, the electron also wobbles vertically up and down in the direction of the magnetic field. This set-up allowed the researchers to cleverly tweak the electron's motion and measure its energy levels with great precision. The value of g was determined by observing transitions between the lowest spin and cyclotron energy levels of the electron.

    Gabrielse thinks a better value of alpha could help in plans to redefine the kilogram that do not rely on using an actual weight kept in a vault in Paris."



    these are not on arxiv, as far as I know.
    they are on his personal website----and also in published hardcopy.
    so if you want to download do it now, he may not always have them posted at his website

    the new value of the electron magnetic moment is

    g/2 = 1.001 159 652 180 85(76)
    (uncertainty 0.76 ppt-------parts per trillion!)
    Last edited: Aug 1, 2006
  2. jcsd
  3. Aug 1, 2006 #2


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    Just as a note that I highlighted this paper a few days ago in Recent Noteworthy Papers thread in the General Physics forum.

  4. Aug 1, 2006 #3

    Hans de Vries

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    Alejandro and me had a look at this earlier in May at Lubos Motl's blog here:


    with a number of post on Physics Forums here:


    There was some confusion since Lubo had some typo's in both numbers...

    Regards, Hans
  5. Aug 1, 2006 #4


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    kudos to all who caught this early.
    Hans, can you tell me if your FORMULAS for dimensionless constants have any bearing on the new values? (I agree that would be asking a lot, but wanted to inquire anyway.)

    ZapperZ thanks for calling attention to the RECENT NOTEWORTHY PAPER thread in General Physics,
    I am glad to learn you are keeping such a thread current, I will start checking it out
    Last edited: Aug 2, 2006
  6. Aug 2, 2006 #5

    What the hell is that supposed to mean ? I flashed it first :rolleyes: ?

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