Originally Posted By: redewenur
There is no known way in which the photons can lose energy

The operative term being 'no known way'.

Originally Posted By: redewenur
(Compton scattering is ruled out by the absence of blurring).

We have no way of knowing if the image of a distant galaxy is blurred or not due to the fact that we can obtain no image which does not contain the intervening particles.

Originally Posted By: redewenur
Each photon passing through the material is either absorbed or not absorbed.

My understanding is that ALL of the photons passing through the material are absorbed/emitted by the atoms they encounter which explains why a beam of light takes longer to travel through a medium than to cover the same distance via a vacuum.

Originally Posted By: redewenur
There's no half-measure whereby the photon simply loses energy. The energy does come from the photons - but only from those photons that are removed.

Your note refers to absorbers that are inserted between a radioactive source and a detector; it seems obvious to me that said absorbers will ABSORB some of those particles whereas the atoms in a glass block will, according to quantum theory, absorb the original photon then emit their own photon.

You refer to "..those photons that are removed." This obviously relates to the photons that are removed by the absorbers!

There are no purposefully inserted absorbers in a glass block. The atoms absorb then emit.

You further refer to charged particles "...going through matter that loses energy through many small energy transfers." This is what I believe takes place when a group of photons (a beam of light) travel through space encountering free particles along the way. One way to find out if the beam loses energy (redshifts) along the way would be to project one through a medium (e.g. horizontally through a lake).

It has been many years since I referred to the subject but I believe that when light travels radially down into the ocean it redshifts thus red colored objects - fish and coral - stand out more?