We have bounds on the density near such boundaries and their distance from Earth above which they would become visible. [1] [1] https://en.wikipedia.org/wiki/B

We have bounds on the density near such boundaries and their distance from Earth above which they would become visible. [1] [1] https://en.wikipedia.org/wiki/Baryon_asymmetry#Regions_of_the_universe_where_antimatter_dominates https://en.wikipedia.org/wiki/Baryon_asymmetry#Regions_of_th...