  In this Essay, we give a correct interpretation of a historical experiment by
Kundig on the transverse Doppler shift in a rotating system (Mossbauer rotor
experiment). This experiment has been recently first reanalyzed, and then
replied by an experimental research group. The results of reanalyzing the
experiment have shown that a correct re-processing of Kundig's experimental
data gives an interesting deviation of a relative redshift between emission and
absorption resonant lines from the standard prediction based on the
relativistic dilatation of time. Subsequent new experimental results by the
reply of Kundig experiment have shown a deviation from the standard prediction
even higher. By using the Equivalence Principle (EP), which states the
equivalence between the gravitational "force" and the pseudo-force experienced
by an observer in a non-inertial frame of reference (included a rotating frame
of reference), here the theoretical framework of the Mossbauer rotor experiment
is reanalyzed directly in the rotating frame of reference through a general
relativistic treatment. It will be shown that previous analyses missed an
important effect of clock synchronization. By adding this new effect, the
correct general relativistic prevision is in perfect agreement with the new
experimental results. Such an effect of clock synchronization has been missed
in various papers in the literature, with some subsequent claim of invalidity
of the relativity theory and/or some attempts to explain the experimental
results through "exotic" effects. The general relativistic interpretation in
this Essay shows, instead, that the new experimental results of the Mossbauer
rotor experiment are a new, strong and independent, proof of general
relativity.
