Did someone mess up physics? The size of proton, long thought to be understood, turns out to be wrong according to new research:
Speaking [...] at the April meeting of the American Physical Society, researchers said they need more data to understand why new measurements of proton size don't match old ones.
"The discrepancy is rather severe," said Randolf Pohl, a scientist at the Max Planck Institute of Quantum Optics. The question, Pohl and his colleagues said, is whether the explanation is a boring one — someone messed up the measurements — or something that will generate new physics theories. [...]
The proton is a positively charged particle in the nucleus of atoms, the building blocks of everything. Years of measurements pegged the proton at 0.8768 femtometers in radius (a femtometer is a millionth of a billionth of a meter).
But a new method used in 2009 found a different measurement: 0.84087 femtometers, a 4 percent difference in radius.
LiveScience has the report: Link
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Even more interesting is that the new method actually produces two different radii related to the proton from the same set of measurements: the average radius of the charge, and an average radius of magnetic effects. The latter is in agreement with older methods, while the former is the one with the 4% difference. So the same set of results both agree and disagree with results from different methods.