If it's all antimatter it would behave in the same way as as if it is all matter. There could be antimatter galaxies, planets, etc. There could be universes that are dominated by what we call antimater. The only excitement would come if there were collisions between matter and antimatter.
Yes. My illustration clearly shows that. We are unfortunately surrounded by matter, thus the subsequent instantaneous destruction of antimatter created for the illustration is rendering my illustration unobservable to the naked eye. Squint. Look closer, you may catch a blur or flash!
What your "illustration" didn't point out is that an antimatter universe would look exactly like our universe.
Well, we could have called the matter we interact with "antimatter" if we had wanted to. The point is that it's really just a naming issue. The bad side comes when there is a mix of matter and antimatter. And, one of the big cosmology questions is how we ended up with such an overwhelming amount of one and little of the other.
If we called matter antimatter and antimatter the illustration I provided would appear the same to you. The two still can’t exist together long enough for you to observe with your eyes/optic nerve. Depends on how much antimatter is present. Small amounts (atom or subatomic particles no big deal). Yes sir. A real head scratcher.
