130 The Poetry of Physics and The Physics of Poetry
The reason for this is that time for the moving meson, like a
moving clock, slows down and hence, the lifetime of the meson at rest,
t = 10-8 sec, takes longer to pass in the laboratory frame. In fact,
the measured lifetime of the meson, as a function of its velocity, is just
t = 10-8/ 1 −v^2 /c^2 sec, exactly the value one would predict on the basis
of the Theory of Relativity. The extra time that the meson lives in the
laboratory frame, as a result of its velocity, has a practical aspect. It gives
the elementary particle physicists enough time to study the meson before
it decays. If it was not for the time dilation of the meson’s lifetime, the
meson would decay after 10-8 sec and there would not always be enough
time to study it in the laboratory frame.
The slowing down of time in a moving frame of reference is not just a
theoretical idea but something, which occurs daily in the laboratory of
the elementary particle physicists. Although the time in the moving
frame appears to slow down for the stationary observer, an observer in
the moving frame does not experience time slowing down. As far as the
moving observers are concerned, their clocks run at the same rate. An
hour is an hour and the lifetime of a π meson is only 10-8 sec. This is to
be expected since, from their point of view, they are at rest and hence,
expect time to flow naturally. In fact, from the point of view of the
moving observers the stationary frame of reference is in motion with
respect to them, and therefore, they observe time slowing down in this
“so-called” stationary frame, which they interpret as moving. Both
observers in the two frames see the clocks in the other frame as slowing
down.
As paradoxical as this may seem, both the stationary and the moving
observer will observe each other’s clock slowing down. Each believes
that the time is dilated in the others’ frame. How is this possible? How
can time slow down for both? In addition to this mutual time dilation,
each observer will also observe the others’ meter stick to be shorter. Is
this possible? Which meter stick is really shorter? Which clock is really
telling the correct time? We cannot ask questions like this, because in
asking such a question, we are assuming the existence of the absolute
space and absolute time, which characterized Newtonian physics. Within
the framework of Einsteinian physics, we cannot discuss such things as
the real length of the stick or the real time of the clock. The observations
of the observers in the moving frame are as real and as valid to them as
the observations of the observers in the stationary frame are to them. We
simply must accept the notion that two observers moving with respect to