Subject: Re: universal expansion
My related, half baked theory is that virtual particles/antiparticles arising from zero point energy interact with light vanishingly rarely. But over universe size distances, the absorptioin/re-emissions add up, red shifting the light and distorting our perception of the age and size of the universe. This would work with regular old matter like burned out stars, too.

I don't know how that agrees with the the cluster and galaxy level observations, or dark energy.

https://en.wikipedia.org/wiki/..., who coined the term dark matter, also talked about "tired light" which is like this. There is also fun anecdote in his wikipedia entry: "He is remembered as both a genius and a curmudgeon.[15] One of his favorite insults was to refer to people whom he did not like as "spherical bastards", because, as he explained, they were bastards no matter which way one looked at them."

I am not a physicist, though, so I'm probably wrong and several grad students have researched and disproved my idea.