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Isn't space mostly empty? Aren't galaxies like millions of light years apart, and don't they collide only incredibly rarely? If some galaxies were antimatter an
by johnfn 10y ago
Isn't space mostly empty? Aren't galaxies like millions of light years apart, and don't they collide only incredibly rarely? If some galaxies were antimatter and some matter, how would we know?
- danbruc 10y agoThe space between galaxies is not completely empty, there is still about one atom per cubic meter. Boundaries in outer space would stretch across billions of square light years, enough space to generate noticeable signals even at such low densities.
- hwillis 10y agoIt is the most energetic reaction possible. We can see the background radiation of the universe- hot objects give off heat, even when they are very, very cold. The universe glows like it's 3 degrees above absolute zero, and we can see it. Compared to that antimatter annihilation would look very bright indeed.
- danbruc 10y agoThe photons are much more energetic than the cosmic microwave background, the intensity could still be low enough to escape detection.
- lomnakkus 10y agoWatch this: https://www.ted.com/talks/david_deutsch_on_our_place_in_the_cosmos https://www.ted.com/talks/david_deutsch_on_our_place_in_the_...