Einsteins akademischer Aufstieg
Bubble Chamber Photograph of π-μ-e Decay
The picture shows a decay chain of elementary particles. First a pion decays into a muon, the electron’s heavier partner. After a short distance the muon decays further to become an electron. From this we can conclude that the muon has a lifetime of a few millionths of a second. This shows what short range muons have when they move far below the speed of light.