The universe's inferred expansion is based almost entirely on cosmological redshift. If it's found that it does not originate from space's stretching then the big bang would of course become unworkable. If it's found that other red/blue shift sources also emanate from galaxies then it'd be virtually impossible to know how much shift to attribute to each. So the big bang would again become untenable. If it turns out that the speed of light is not constant but varies everywhere then the entire concept of cosmological redshift collapses, taking along with it the big bang. If any one of these undermining conditions is true, we're forced to concede the fallacy of universal expansion, which returns us back to the very beginning. We're left wondering what it is exactly that causes a galaxy's redshift. Viable, practical, readily apparent alternates do exist. But they only become evident by recognizing the ever-decreasing density of a galaxy's gravity field.