Cracking a 16-year proton mystery as ultra-precise hydrogen measurements confirm a smaller-than-expected core

The simplicity of a hydrogen atom makes it an ideal model for studying atomic structure and interactions. Yet, despite the fact that its simplest form consists of only one proton and one electron, physicists have had a hard time pinning down the exact charge radius of the proton. But a new study, published in the journal Physical Review Letters, outlines a method of measurement that helps to resolve some past discrepancies.