I’ll toss out two possibilities. Take your pick of weirdness.

Perhaps the universe isn’t expanding and the cosmological redshift isn’t a redshift at all. This possibility was suggested by Eddington and Russell Rieerson worked out the math. In Rierson’s view called "inverse expansion", the universe remains the same immense size while its material contents grow smaller. The galaxies grow smaller, stars grow smaller, mountains grow smaller, we grow smaller, atoms grow smaller and all the way down. The universe appears to grow larger because we and everything else is growing smaller. What about the redshift? Since there is no expansion of the universe, there is no "stretching" of space to alter the condition of old light coming from distant sources so distant light reaches us in its original unshifted condition. Old light only appears redshifted because, as our atomic world grows smaller, wavelengths of light from modern sources grow proportionally shorter. So old light hasn’t redshifted… new light has blueshifted.

Heating and acceleration are characteristic of contraction (The collapse of the WTC is one example that comes to mind.) while cooling and slowing are characteristic of expansion. If our universe is expanding, we should observe the universe growing colder and its expansion slowing but this is the opposite of what we see. In theory, the universe is growing colder but observations indicate a universe that is growing warmer starting with a primal temperature of 2.73K and warming from there. Expansion theory explains perfectly well why hot looks cold and cold looks hot but I prefer explanations where what you see is what you get. Also, the observed accelerated expansion of the universe makes more sense with Rierson’s theory because acceleration is characteristic of contraction.


Another possible explanation for the cosmological redshift comes from general relativity. There is a phenomenon known as "frame dragging" where a large massive body in motion accelerates a smaller test particle. The most familiar example is the acceleration of the planet Mercury by the rotation of the sun. But the opposite should also hold true. A small, rapidly moving test particle should experience a negative acceleration "slowing" in the presence of a non-moving ponderous mass. This possibility was suggested by Sciama in the 1950’s but the theoretical effect has always been too small to test experimentally. We may now have some evidence for this effect with the unanticipated acceleration "slowing" of the Pioneer satellites as they leave the solar system. If this effect is real, then small test particles "photons" passing through the essentially static, total mass of the universe should be redshifted by this sort of cosmic "frame dragging".