24. one point, from Lecture 24, short answers, tiny calculations

(a) .5 Real-life Gamma Effects. All the gamma factor effects have been observed many, many times at particle accelerators where electrons, protons, or other tiny particles are acclerated to high gamma factors. One such particle is a mu meson (muon), which is just like an electron (negatively charged, etc.), except heavier. The muon has a normal lifetime of two-millionths of a second in its own rest frame.

A muon travels through a lab two kilometers long. The experimenter in the lab finds that the muon has a mass 2000 times its rest mass. How long does the muon think the lab is? (.2) How many seconds does the physicist say the muon lives in the lab? (.2) How do you think the experimenter figured out the mass? (.1) Hint: it is "easy" to get the mass of a charged particle. Explain your answers and show your work.

(b) .5 What should it have been called? Einstein wanted to call it the Theory of Invariants instead of the Theory of Relativity. Name at least two invariant and three relative quantities in special relativity. (.1 apiece)

Revised October 26, 1997.