Hi Dave,
If contraction existed, we would see the galaxies as they were when they emitted their light, thus larger than they are now, and the particles they are made up would also look larger and thus carry a longer wavelength, so it seems to explain the redshift, and the farther the galaxies would be, the more the redshift would be important, which could explain its acceleration if contraction itself would be an acceleration, and contraction could be an acceleration if it was linked to the acceleration of gravitation.
Unexpectedly, contraction also seems to explain dark matter, and for the same reason, which is that the stars would see the core of their galaxy as it was when it emitted its light, thus larger and also more attractive than it is now since larger also means closer, so they would have to orbit at a faster speed than what we expect them to. We do indeed expect the dimensions of different parts of the galaxies to be the same as those we see from Earth, but if the galaxies are contracting, what we see is not what the stars see. While the stars would see the core at a time when it was much larger because its light took time to reach them, we would see the stars and the core at the same time since their light took the same time to reach us. Indeed, to measure the speed of stars using the Doppler effect, we only observe those whose line of sight relative to the core is perpendicular to our own line of sight, those that are directly moving towards or away from us, and that are therefore practically at the same distance from us as their core.
I looked for a way to test this possibility, and finally, it's hard to find a better way than those two anomalies. The contraction of gravitational systems would produce real movements - the earth for instance would really be contracting in the direction of the sun while orbiting it - and this
is exactly what we see when we look at pictures of spiral galaxies, we see a movement spiraling towards the core similar to that of water spiraling down the drain. This motion would tend to cancel out the redshift - and the aberration - caused by the contraction, which would cause gravitation, but there would still have to be a residual effect otherwise there would be no gravitation, and it is this residual effect that we would measure when we observe galaxies; it is this residual effect that would bind us gravitationally to them.
