Comment Antimatter galaxies (Score 1) 393
The article makes the point that there's a significant amount of matter in the interstellar space within our galaxy, which suggests that if other stars in our galaxy were made out of antimatter instead of matter, we would know about it because we'd detect annihilations. But can we say the same about intergalactic space? The article glosses over this question and skips to pointing out that we don't detect annihilations within other galaxies. What if those other galaxies are mostly antimatter, but there's essentially no matter to annihilate in intergalactic space? (Perhaps because it already annihilated in the early universe. Could that be the source of the CMB?)