2. Trouble with our ideas about length Suppose an observer in the above laboratory placed one marker at the location of the pion's formation and another at the location of its decay The distance between the markers is measured to be 17.4m. Now consider the observer who is traveling along with the pion at a speed of u=0.913c This observer, to whom the pion appear to be at rest, measures its lifetime to be 260ns, and the distance between the markers is (0913c)(260×103)=71m Thus two observers measure different value for the same length interval 3. Troubles with our ideas about light2. Trouble with our ideas about length Suppose an observer in the above laboratory placed one marker at the location of the pion’s formation and another at the location of its decay. The distance between the markers is measured to be 17.4m. Now consider the observer who is traveling along with the pion at a speed of u=0.913c. This observer, to whom the pion appear to be at rest, measures its lifetime to be 26.0ns, and the distance between the markers is Thus two observers measure different value for the same length interval. (0.913c)(26.0 10 ) 7.1m 9  = − 3. Troubles with our ideas about light