  The Michelson-Morley experiment was designed to detect the relative motion of
the Earth with respect to a preferred reference frame, the ether, by measuring
the fringe shifts in an optical interferometer. These shifts, that should have
been proportional to the square of the Earth's velocity, were found to be much
smaller than expected. As a consequence, that experiment was taken as an
evidence that there is no ether and, as such, played a crucial role for
deciding between Lorentzian Relativity and Einstein's Special Relativity.
However, according to some authors, the observed Earth's velocity was not
negligibly small. To provide an independent check, we have re-analyzed the
fringe shifts observed in each of the six different sessions of the
Michelson-Morley experiment. They are consistent with a non-zero observable
Earth's velocity $v_{\rm obs} = 8.4 \pm 0.5 km/s$. Assuming the existence of a
preferred reference frame and using Lorentz transformations, this $v_{\rm obs}$
corresponds to a real velocity, in the plane of the interferometer, $v_{\rm
earth} = 201 \pm 12 km/s$. This value, which is remarkably consistent with 1932
Miller's cosmic solution, suggests that the magnitude of the fringe shifts is
determined by the typical velocity of the solar system within our galaxy. This
conclusion is consistent with the results of all classical experiments
(Morley-Miller, Illingworth, Joos, Michelson-Pease-Pearson,...) and with the
existing data from present-day experiments.
