The universe is all matter, no antimatter because in the second after the big bang, all matter/antimatter mutually annihilated leaving *slightly* more matter.
But imagine there's a part of the universe (now outside our lightcone) with *slightly* more antimatter, so antimatter won.
Science fiction story concept: Rogue rocky planet, no star, life evolves anyway because it's close to the matter/antimatter dominance interface & half the sky is pure light from mutually annihilating distant galaxies
@mcc a technological species with no phrase for "dead battery” because the entirety of known space is constantly awash in incredibly high energy radiation
@Catfish_Man
well, it's true there are a lot of very energetic particles out there, but the actual energy you get from something like an AGN in the gamma ray band is about the same as from the normal optical star light you get from a galaxy.
So yes, space is constantly awash in high energy radiation, but it is also just as awash with the much lower energy radiation we can see with our own eyes and yet the night is still dark.
@mcc
@tobychev it's not clear to me that we can model this hypothetical situation that doesn't exist anywhere in our light cone with stuff that does, but yes, this was not a terribly serious take