I was recently reading some of the nice answers to the (related) question: If space itself is expanding, how could we ever tell?
From many of the answers their appears to be a symmetry between:
- A universe in which all matter-things (plus light) remain the same size, while the space between them expands. (The one we appear to live in)
- A universe where the space remains the same size and all objects in the universe shrink. Along with an appropriate change in physical length-scale constants. (One equally compatible with our observations?)
Said another way: At one point in time your ruler fit between those two galaxies $10^{50}$ times, now it fits between them $10^{51}$ times. This is usually explained as the space growing, I believe it could equally well be described by the ruler shrinking.
Is this symmetry obeyed? Are their any cosmological models presented in terms of matter shrinking?