to decay( to other particles)with an average lifetime of only 26.0ns In one particular experiment, pions were created in motion at a speed ofv=0.913c. In this case they were observed to travel in the laboratory an average distance of D=17.4m before decaying, from which we conclude that they decay in a time given by D/=637ns, much larger than the lifetime measured for pions at rest This effect. called time dilation", which cannot be explained by Newtonian physics. In Newtonian physics time is a universal coordinate having identical values for all observersto decay ( to other particles ) with an average lifetime of only . In one particular experiment, pions were created in motion at a speed of . In this case they were observed to travel in the laboratory an average distance of before decaying, from which we conclude that they decay in a time given by , much larger than the lifetime measured for pions at rest. This effect, called “time dilation”, which cannot be explained by Newtonian physics. In Newtonian physics time is a universal coordinate having identical values for all observers. 26.0ns v = 0.913c ns v D = 63.7 D =17.4m