Facts and questions:
When we look at the starry night sky thru the telescope, we are actually looking into the past.
The past history of the universe is encapsulated inside the photon that we detected. The question is: Is this the original photon which have the original informations? Or is it just a faithful copy of the original photon preserving the original informations?
If this is the original photon then it did not aged. If this is a copy then many photon have died before it. Einstein would have said that this is the original photon and it never aged.
The farthest things, and therefore the oldest, our optical or radio telescopes can see are the quasars. The energy source of a quasar is billion times the energy of a single galaxy. Therefore the energy of the original photon must have been very large. The photon always move at 300,000 km/s, It must be the frequency or the wavelength that changed thru the ages of the journey. This explain the redshifts and the expansion of space.
Can a single photon from the big bang contain all the informations of the universe? Or at least two photons? How many photons will be needed to contain all informations of the universe?
If we were to be surrounded by photons into a perfectly closed volume, we will appear just like a photon with only size differences. Then we can move at the speed of light in vacuum and do some time traveling!