I have been reading about Loop Quantum Gravity and about Spin Foam, and I am stuck on a (probably stupid) idea. It seems that one of the underpinnings of these concepts is that space-time is quantized in discrete units at the Planck scale. If space-time is quantized and the universe is expanding, our local units of space-time are the oldest and largest in existence. Light that came from stars very far away originated in younger domains with smaller units of space-time and their photons would be forced to traverse larger and larger units of space-time as they come to us. If the speed of light is truly invariant with respect to observer, this means that the photons coming from distant objects must cross larger and larger space-time unit distances in the same amount of time, and if they have to cross each unit in the same amount of time (with length L appropriate to observers in each locality) then the photons MUST arrive here redshifted or else violate conservation of energy. If they are to maintain a constant speed with growing L, they have to pay for this by becoming less energetic WRT wavelength. Is this idea off the wall? Have I missed a really basic "Pons Asinorum" type concept?