  We re-consider the idea that quantum fluctuations might reflect the existence
of an 'objective randomness', i.e. a basic property of the vacuum state which
is independent of any experimental accuracy of the observations or limited
knowledge of initial conditions. Besides being responsible for the observed
quantum behaviour, this might introduce a weak, residual form of `noise' which
is intrinsic to natural phenomena and could be important for the emergence of
complexity at higher physical levels. By adopting Stochastic Electro Dynamics
as a heuristic model, we are driven to a picture of the vacuum as a form of
highly turbulent ether, which is deep-rooted into the basic foundational
aspects of both quantum physics and relativity, and to search for experimental
tests of this scenario. An analysis of the most precise ether-drift
experiments, operating both at room temperature and in the cryogenic regime,
shows that, at present, there is some ambiguity in the interpretation of the
data. In fact the average amplitude of the signal has precisely the magnitude
expected, in a 'Lorentzian' form of relativity, from an underlying stochastic
ether and, as such, might not be a spurious instrumental effect. This puzzle,
however, should be solved in a next future with the use of new cryogenically
cooled optical resonators whose stability should improve by about two orders of
magnitude. In these new experimental conditions, the persistence of the present
amplitude would represent a clean evidence for the type of random vacuum we are
envisaging.
