time dilation

the pion is a particle that can be created in a high-energy particle
accelerator. it is a very unstable particle; pions created at rest are
observed to decay (to other particles) with an average lifetime of only 26.0
ns [26.0E(-9)]. in one particular experiment, pions were created in motion
at a speed of v = 0.913c (where c is the speed of light, 3.00E8 m/s). in
this case they were observed to travel in the laboratory an average distance
of D = 17.4 m before decaying, from which they decay in a time given by D/v
= 63.7 ns. this effect, called time dilation, suggest that something about
the relative motion between the pion and the laboratory has stretched the
measured time interval by a factor of about 2.5. this experiment reveals the
limitations of classical physics and serve as a test of einstein's special
theory of relativity


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