A team of scientists set out to find the size of protons, and in doing so have upset the current body of literature on quantum electrodynamics. According to the report published in the journal Science, the scientists used a laser to determine that the radius of a proton is smaller than 0.84087 femtometers, a size so small it is hardly comprehensible without something to put it into perspective.
One nanometer is the equivalent of one million femtometers, to put its size into perspective. Until now, it was believed that a proton has a radius of 0.8768 femtometers, but according to the study, the actual size is approximately 4-percent smaller. The size difference is said to be explainable by one of three ideas.
Either: A), the scientists are wrong, which is both the easiest and more unlikely reason; B), the current understanding of a proton's structure could be limiting a complete - and thus correct - calculation; or C), the actual quantum electrodynamics theories themselves are incorrect, another possibility considered unlikely.
The explanations comes from Swiss Federal Institute of Technology physicist Aldo Antognini, who is one of the authors of the published report. Although the finding is significant, this isn't the first time a proton has measured in at a size other than the accepted radius. The differences are likely due to the different methods used to calculate the size. The latest measurement is the result of a method involving measuring protons with orbiting muons instead of electrons.