"Space is not composed of anything possessing mass. Not neutrinos, not photons. You're wrong. Period."
There currently is no proof that is the case.
When we speak of the distance between two objects, the distance is figurative. It is not a thing.
The nature of what is expanding is not yet clear.
Space has properties of energy. Then it has mass.
We simply do not have the ability to detect it yet.
I hear time and again that nothing is actually composed of energy
Son Goku and others chant that mantra. It is as figurative as treating
space as an expanding thing with no substance.
We used to thing air was "empty"
For space to exist and have no mass it cannot be physical. That does not follow. Nothing is "not physical" Everything is made of something.
If black holes can be infinitely dense then "space" can be infinitely
lacking density and still be physical.
There is no reason to believe the space between the nucleus of an atom and it's electrons is any different than that between galaxy clusters.
Mass retards the speed of time. Mass is then an island of "slowed experience".