Perhaps when light photons are travelling across huge distances some are coherent, or even entangled, allowing spooky transfer of energy from one to another. This would be analogous to inelastic collisions between particles in a rocket exhaust. Energy is lost via friction also. Spooky blue-shifting of a small number of photons in the particle stream might result in particle showers when those blue-shifted photons decay into particle-antiparticle pairs, and a loss in energy of the overall light stream and therefore a redshifted spectra. If this is ever observed we could then estimate the decay lifetime of photons, or coherent beams, or entangled photons. This would also call into question the Big Bang theory which is based on the cosmological redshift phenomenon.

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