HOW big is a proton? The most accurate measurement yet suggests it’s smaller than we thought. This could be due to an error, or it might just hint at totally new particle physics.
“The new experiment presents a puzzle with no obvious candidate for an explanation,” says Peter Mohr of the international , which calculates values for fundamental constants in physics, who was not involved in the new work.
The proton’s radius cannot be measured directly but can be inferred from the hydrogen atom, which consists of a proton and an electron. The electron can sit in a variety of…
