A pion is created in the higher reaches of Earth's atmosphere when an incoming high-energy cosmic ray particle collides with an atomic nucleus. A pion so formed descends toward Earth with a speed of, 0.99c. In a reference frame in which they are at rest, pion’s decay with an aver age life of 26 ns. As measured in a frame fixed with respect to Earth how far (on the average) wills such a pion move through the atmosphere before it decays?