That the conception of the "simultaneity" of events is devoid of
meaning can be deduced from equation (2) [see Note 4]. We owe the proof
to Einstein. "It is possible to select a suitable time-coordinate
in such a way that a time-measurement enters into physical laws
in exactly the same manner as regards its significance as a space
measurement (that is, they are fully equivalent symbolically), and
has likewise a definite coordinate direction.... It never occurred to
anyone that the use of a light-signal as a means of connection between
the moving-body and the observer, which is necessary in practice in
order to determine simultaneity, might affect the final result, i.e.,
of time measurements in different systems." (Freundlich). But that
is just what Einstein shows, because time-measurements are based on
"simultaneity of events," and this, as pointed out above, is devoid
of meaning.
Had the older masters the occasion to study enormous velocities, such
as the velocity of light, rather than relatively small ones--and even
the velocity of the earth around the sun is small as compared to the
velocity of light--discrepancies between theory and experiment would
have become apparent.