To Antoniseb and others regarding blue shift.
The resulting shift of light is what the observer sees. There are two factors that dictate the resulting frequency. They are the separation of the particles and the velocity of the beam of particles. Consider two photons near the earth and inbound. The gravitation here will have more effect on the velocity of the two than upon the separation of the two. Therefore, relative to their condition nearby, the observer will see a blue shift. But if he could look at the pari at their nearby point, it would be red shifted as I discussed. The resulting blue shift is trivial relative to the long distant red shift.
Paull