By means of the generalized, Galilei covariant Maxwell equations for inertial frames S(r,t,w) with substratum velocity w, Fitzgerald contraction = o 1- - co 2 2 1 2 bv wg of rods, Larmor dilation t = t o 1- - co 2 2 1 2 bv wg of clock periods, and velocity dependence of particle mass m = mo 1- - co 2 2 1 2 bv wg are shown to be Galilei-invariant vacuum substratum effects, where v - w = v?= inv is the respective object velocity relative to the substratum frame S (r?,t?,0). The Lorentz force transferred through the substratum is Galilei-invariant, F = e[E?+ w ? B + (v ? w) ? B ] = e(E? + v? ? B?) = inv. The kinetic energy K(v?) of high-velocity particles is given by the Galilei-invariant mass-energy relation K(v?) + Eo = mo(v?) co 2 , where Eo = mo co 2 (mass-energy equivalence). The Galilean measurement process in inertial frames S(r,t,w) is explained considering physical length contraction of measuring rods and rate retardation of measuring clocks, as well as synchronization of clocks in absolute time. Crucial experiments underlying Galilean electrodynamics are discussed briefly.
Contradicting Maxwell, Larmor, Heaviside, Hertz and others, Voigt (1887), Lorentz (1904) and Einstein (1905) introduced the hypothesis that Maxwell's equations and the electromagnetic (EM) wave equations hold in this form not only in the ether frame So (0) but in all other inertial frames (IF) S(w) with ether velocities w  0, too. This proposition is physically equivalent to the questionable assumptions: (i) an EM wave carrier or ether (vacuum substratum) does not exist, (j) the velocity of a light signal has the same value c in all IFs, and (k) electrodynamic phenomena are relative to the observer (nonexistence of a preferred or substratum frame So).
The substratum of the vacuum is the carrier of the elementary force interactions, such as electromagnetic (EM), gravitational, or nuclear. These basic fields occur as excitations whereas elementary particles are probably defects in the substratum. Experiments show that the substratum has physical properties e.g. a magnetic permeability  Vs/Am, dielectric permittivity  As/Vm, EM wave speed c =  m/s, and EM wave resistance .
The substratum has either very small or no gravitational mass density, and consists probably of positive and negative gravitational mass particles with positive inertial mass (confirmation of negative g-masses would invalidate equivalence principle). The substratum appears to be a superfluid since (subluminal) particles move in vacuum without experiencing retarding forces.
Galilei-covariant electrodynamics is generalized for moving dielectric media with motion induced polarization for dielectric permittivities e(w)>e. = 10-9/36 pi As/Vm. The interferometer experiments on light propagation in (i) flowing water by Fizeau and (ii) resting water by Hoek, relative to a terristrial laboratory frame S (which moves with a volocity v = -w ~ 3X10+5 m/s relative to the absolute cosmic frame S with isotropic light propagation) are explained quantitatively without resort to relativistic space-time concepts. The experiment of Hoek is shown to reveal a polarization effect in the induced electric ether field wXB, due to the terrestrial vacuum substratum velocity w. Thus, the Hoek experiment refutes the special theory of relativity.
By means of the generalized, Galilei convariant Maxwell equations, a theory of Cherenkov radiation is given for a dielectric at rest in a arbitrary inertial frame (w) with EM substratum flow w. The Frank-Tamm theory if shown to hold only in the substratum rest frame o(o) (isotropic light propagation) or approximately in inertial frames (w) with negligible substratum velocity, |w|/c0. Based on the new substratum Cherenkov effect theory, an experiment is proposed which permits measurement of the terrestrial substratum velocity w. Implementation of this experiment would provide empirical evidence (i) of the EM substratum of the physical vacuum (carrier of EM fields and waves) and (ii) of the non-relativity of the velocity of [charged] particles.
Based on the Galilean relativity principle and the experimental observation that the vacuum behaves like a carrier medium (EM substratum) for EM waves and fields, generalized Galilei behaves like a carrier medium (EM substratum) for EM waves and fields, generalized Galilei covariant Maxwell equations are derived. The generalized Maxwell equations for inertial frames (w) with substratum flow contain explicitly the substratum velocity w, and reduce to the usual Maxwell equations when wo. As illustrations, (i) the field invariants in transformations between inertial frames, and (ii) electric and magnetic induction in reference frames with substratum flow w, are discussed.