I'm a layman and I'm curious to understand how mass affects the expansion of space and whether the expansion of space is uniform everywhere in the universe.
From looking at redshifts it seems we have determined that until 5 billion years ago the expansion was slowing down and since then it has been speeding up. Supposedly the average density of mass in the universe is affecting the expansion - is this just conjecture and the only theory we have or is there some solid evidence for thinking this?
Wikipedia says "the scale of space itself changes" but that the model is valid only on large scales (galaxy clusters and above) and that the expansion cannot be observed on a smaller scale. wikipediaIs it possible that space between say, planet Earth and the Sun is actually expanding but is currently unobservable. If not, how far from our local group of galaxies do we have to look before we encounter some space that is actually expanding.
I realise that we don't understand what dark energy is and I much prefer answers that say "we don't know" if we really don't know.
I asked a question here and was unconvinced by the answersphysics forum
