The discovery that light speed in vacuum c is not constant over the entire vacuum energy range may raise significant questions about expanding universe concepts. A recent study reported evidence that light speed c begins to decrease at lower vacuum energy densities and that volumes at zero vacuum energy density, named absolute vacuum, were in fact completely opaque to electromagnetic (EM) wave transmission (Fig. 1 from [1]).
Fig. 1: Light Speed vs Media Density and Bit Operations Order
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These findings raise the possibility that
observed redshifts may not be due to an expanding universe, but rather to regions of lower vacuum density where light speed is decreased producing the exact same observed redshifts. This possiblity may raise serious questions about the veracity of the expanding universe theory in astrophysics. Indeed, the question of whether the universe is expanding, contracting or neither may be back on the table again.