How do we know the current universe is matter-dominated?
All we can measure from other galaxies are the electromagnetic radiation from high energy events, and we cna infer their mass from their gravitational interaction, right? But in these matters, antimatter is expected to behave no differently from matter (it emits the same photons, it interacts gravitationally the same way with itself and with matter, etc.)
So, how do we rule out that distant galaxies, or distant clusters, or distant filaments aren't actually composed of antimatter, and we can't detect any annihilations due to the low density of the intergalactic medium?