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A universal constant on the move

Is the proton losing weight, or has the fabric of the Universe changed?

How heavy is a proton compared to an electron? The answer seems to have changed over the past 12 billion years. Credit: © Punchstock


  1. ReinholdE., et al. Phys. Rev. Lett., 96. 151101 (2006).

  2. TzanavarisP., WebbJ. K., MurphyM. T., FlambaumV. V.& CurranS. J. Phys. Rev. Lett., 95. 041301 (2005).

  3. WebbJ. K., et al. Phys. Rev. Lett., 87. 091301 (2001).

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Peplow, M. A universal constant on the move. Nature (2006).

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