  "Non-Locality is most naturally incorporated into a theory in which there is
a special frame of reference. One possible candidate for this special frame of
reference is the one in which the Cosmic Microwave Background (CMB) is
isotropic. However, other than the fact that a realistic interpretation of
quantum mechanics requires a preferred frame and the CMB provides us with one,
there is no readily apparent reason why the two should be linked" (L. Hardy).
Starting from this remark we first argue that, given the present view of the
vacuum, the basic tenets of Quantum Field Theory cannot guarantee that Einstein
Special Relativity, with no preferred frame, is the physically realized version
of relativity. Then, to try to understand the nature of the hypothetical
preferred $\Sigma-$frame, we consider the so called ether-drift experiments,
those precise optical measurements that try to detect in laboratory a small
angular dependence of the two-way velocity of light and then to correlate this
angular dependence with the direct CMB observations with satellites in space.
By considering all experiments performed so far, from Michelson-Morley to the
present experiments with optical resonators, and analyzing the small observed
residuals in a modern theoretical framework, the long sought $\Sigma-$ frame
tight to the CMB naturally emerges. Finally, if quantum non-locality reflects
some effect propagating at vastly superluminal speed $v_{QI} \to \infty $, its
ultimate origin could be hidden somewhere in the infinitely large speed $c_s
\to \infty$ of the vacuum density fluctuations.
