Comment by sigmoid10
6 hours ago
This is yet another case where a layman-written wiki article about physics is highly confusing to other laypeople, because it only tells you half the story. Particularly because it seems to be based on a chapter of Feynman's popular science book. But the book actually goes on and points out how Feynman immediately dismissed Wheeler's hypothesis, because the universe contains a lot more electrons than positrons. You'd have to explain that imbalance first if you want to entertain this line of thought.
As a layperson myself - how can we tell that a distant celestial object is not made from antimatter? Afaik, it doesn't behave differently from matter, other than it annihilates on contact.
Also even if we could, that would only describe the practically and theoretically observable universe, which doesn't rule out other places looking very different (on its own)
Because distant celestial objects accelerate a lot of matter away from them as parts of different processes. For example if there were a sizeable chunk of space were antimatter than at the edge of this space there would be a constant glow of annihilation. We don't see that anywhere (well except things like quasars doing this at small scales.
So, yea, it would have to be outside the observable universe in which that means we can do no empirical science on it therefore it not being real to us.
What if most galaxies are actually dark matter, and we are the exception?
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Yea, it's really more about the fact that all electrons are exactly the same regardless of the level of precision we look at them. It would be like if we found another earth and that earth was the exact same earth. Not earth like, not very close to earth. The exact same earth down to the smallest fundamental level.