Problem 1-24: The proper mean lifetime of π mesons (pions) is 2.6 x 108 s. Suppose a beam of such particles has speed 0.9c. (a) What would their mean life be as measured in the laboratory? (b) How far would they travel (on average) before they decay? (c) What would your answer be to part b if you neglected time dilation? (d) What is the interval in spacetime between creation of a typical pion and its decay?