Question #1; Here are a few points on this topic. The proposal is many years old. I want to comment on the 4th point A thought experiment: Suppose 2 photons of identical energy and momentum (wavelength & momentum?) leave a distant source and utimately get individually detected by our instrument. Suppose, in expected aggreement with our usual empirical observations and formal theory, one photon makes it here "the usual expected way". The 2nd photon, because of natural causes, changes momentum and/or energy, in a way permanently different from its original state and then arrives at our detector. Just suppose it could, in spite of present theory. For the different combinations of photon #2's delta 'energy/momentum' states, predict the differences in the detector's measurement compared to photon #1? energy decreased / momentum same energy decreased / momentum increased energy increased / momentum same energy increased / momentum increased [/list=1] Question #2: Would we know if the photons we measure in day-to-day observations are unchanged during their journey from intersteller source to detector?