The standard model of particle physics, at the center of this news, explains the world of atoms and smaller things, and it was developed in the 1960s and 1970s. It has been universally accepted in the scientific world as being the most accurate subatomic theory devised so far. But that venerable model could well need to be changed because of this new measurement, which gives us reason to believe that the standard model is incomplete.What the standard model predicts — and what this new measurement assesses — are the magnetic properties of an ephemeral subatomic particle called a muon, which is very similar to the familiar electron, but with some differences. Muons are about 200 times heavier than electrons and they decay in a little over a millionth of a second. Otherwise, electrons and muons have a lot in common.