Chapter 38, Problem 4P

A muon formed high in the Earth’s atmosphere is measured by an observer on the Earth’s surface to travel at speed ν = 0.990c for a distance of 4.60 km before it decays into an electron, a neutrino, and an antineutrino $({\mu }^{-}\to c^{-}+v+\bar{v})$. (a) For what time interval does the muon live as measured in its reference frame? (b) How far does the Earth travel as measured in the frame of the muon?