I had a strange thought experiment that I know is wrong, but I would like to know why.
Our universe is expanding, proof of this to simpletons like me is said to be the reason why the night sky is black (the light can never reach us since the furthest extents of the universe are expanding away from us faster then the speed of light). Building on this idea, the red shift of light coming from stars allows us to understand how far away the source is due to the lengthening of the sources electromagnetic waves.
My thought experiment starts with solar sails. Basically, they have the ability to convert light energy into a physical force which can then be used to propel a space craft.
From my understanding, the principle behind this is the electromagnetic force of the light hitting it interferes with the electromagnetic forces holding the material together (I'm thinking chemical bond stuff) thus creating the force.
Now what is to say the light coming from distant stars isn't also being constantly bombarded by electromagnetic forces of nearby matter causing it to lose energy as it travel across the vast reaches of space? Now, what form would this light be lost as? Would it simply be a filtering of photons? Or since the photon's are allowed to pass by, would their relative velocities be manipulated by the electromagnetic forces thus causing a spectrum shift comparable to that found in the red shift of distant stars? Further, if my logic isn't off, doesn't this mean there is a potential that the universe isn't expanding? Light is simply slowly losing energy as it crosses the vast expanses of space and it interacts with bits of matter here and there.