The redshift of light (or any other electromagnetic radiation) arriving from very distant galaxies (some billion lightyears) is mainly due to the expansion of space.
While I do not question this I have problems to understand how light “knows” about the expansion. For me, space is merely a “concept” (like distance between objects) without any physical attributes. Therefore, I wonder how light can physically interact with a “concept” in a way which results in stretching of its wavelength. Unless space has some physical properties.
Which are the physical attributes of space that interact with light? Aether is dead! Vacuum fluctuations? Zero point energy?

Most probably, this has been discussed before here, but I can´t find it. So, if it has been discussed, a link would be appreciated as well.

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If everyone had even a basic grasp of scientific principles, this planet would be a better place (Phil Plait)

Die Lücke, die wir hinterlassen, ersetzt uns vollkommen [The gap we will leave behind will take our place entirely] (Carl Heinz Schroth)

1 + e^i*pi = 0