I want to share an idea i just had, while i was thinking about river's ideas. I am not an expert so don't blast me if its naive. Just want the opinion of people with more knowledge in the field. Imagine you have a flask filled with a gas. You initially add some external energy (you heat it), and then you remove the energy source. All the molecules of the gas will have some initial kinetic energy. However, as time goes by and no external energy is added, then the entropy of the system will tend to increase, and the molecules will slowly approach an equillibrium state and the kinetic energy of the molecules will universally decrease over time. I think we all agree so far. Now i will make a metaphor. Lets say that this is the universe after the bing bang or after another massive event. Galaxies or cluster of galaxies are represented by the individual molecules. We ourselves reside in one of these molecules. Our galaxy, together with entire system of galaxies are losing energy over time, without realizing it from our perspective. Can this universal decrease in kinetic energy explain the red shift of light (doppler effect)? I mean, light that comes from a distant galaxy will radiate lower energy light waves over time, manifested as a shift towards the red, because of the lowering energy it contains?. But also all the distance between those two molecules will contain other molecules with decreasing energy. So the farther away, the more the shift in wave length of the light theoretically. can this be an alternative explanation for the doppler effect?