That's actually not possible due to something called the GZK cutoff. Which is a weird phenomena that causes apparently empty space to turn somewhat cloudy for s

That's actually not possible due to something called the GZK cutoff. Which is a weird phenomena that causes apparently empty space to turn somewhat cloudy for sufficiently high energy photons. Here is how it works. If an electron and a positron meet, they turn into two very high energy photons. Because physics is time reversible, if two high energy photons meet, they have a chance to turn into an electron-positron pair. If an extremely high energy photon meets a low energy one, there is a moving reference frame in which they have the same energy, and are both high energy. Therefore they have a chance to turn into an electron-positron pair whose center of mass is in that reference frame. The result is that if a photon is above something like 10^15 eV in energy, it can annihilate itself against any photon in the cosmic microwave background radiation (CMBR). There are lots of photons in the CMBR. Those collisions are sufficiently likely that such photons essentially cannot travel intergalactic distances. If you go back to the early universe, the CMBR was much denser than it is today. Making the distance that such photons could reasonably travel even shorter then than it is today. That said, no good storyteller should let inconvenient physical fact keep them from writing a good story.