Proton appears to be smaller than previously thought
JUL 13, 2010
DOI: 10.1063/PT.5.024493
New York Times : An international team of researchers has measured the charge radius of the proton in experiments that are 10 times more accurate than earlier onesâmdash;and found that the proton, or hydrogen nucleus, measures 0.8418 femtometer instead of the 0.8768 femtometer previously thought. Although the difference may seem negligible, the proton is the primary building block of the visible universe. The 4% change in size yields a second, discrepant value of the Rydberg constant, and may lead to revising the theory of quantum electrodynamics. The scientists published their results in the 8 July issue of Nature .
© 2010 American Institute of Physics
