Muon, also known as the mu meson, is a subatomic particle similar to the electron but with about 207 times more mass. Due to its short lifespan of only 2.2 microseconds, the muon is an unstable particle. It is formed during cosmic ray collisions in the atmosphere and is often used in particle physics experiments to study the properties of other subatomic particles. Some synonyms for mu meson include 2nd generation lepton, mu lepton, and muon neutrino. The discovery of the muon in 1936 by Carl Anderson and Seth Neddermeyer was a significant milestone in particle physics, and its properties continue to be studied today.