>>11443417What I'm referring to is after the atoms emit the light, spits it out, and the light doesn't hit anything, i.e. it's not abosorbed into a planet's surface or by another star. Where does the energy in the photon go when it's traveling in deep space? There isn't any matter to absorb it, but the light still undergoes redshift, so we know it's losing energy, but that energy doesn't go anywhere, it's just gone.
