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19
Relativity: The Special and General Theory
Now before the advent of the theory of relativity it had always tacitly been assumed in physics that
the statement of time had an absolute significance, i.e. that it is independent of the state of motion
of the body of reference. But we have just seen that this assumption is incompatible with the most
natural definition of simultaneity; if we discard this assumption, then the conflict between the law of
the propagation of light in vacuo and the principle of relativity (developed in
Section 7) disappears.
We were led to that conflict by the considerations of Section 6, which are now no longer tenable. In
that section we concluded that the man in the carriage, who traverses the distance w per
second relative to the carriage, traverses the same distance also with respect to the embankment
in each second of time. But, according to the foregoing considerations, the time required by a
particular occurrence with respect to the carriage must not be considered equal to the duration of
the same occurrence as judged from the embankment (as reference?body). Hence it cannot be
contended that the man in walking travels the distance w relative to the railway line in a time which
is equal to one second as judged from the embankment.
Moreover, the considerations of Section 6 are based on yet a second assumption, which, in the
light of a strict consideration, appears to be arbitrary, although it was always tacitly made even
before the introduction of the theory of relativity.
Next: On the Relativity of the Conception of Distance
Relativity: The Special and General Theory