system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What would be the properties of a universe which was mostly antimatter instead of mostly matter?
gpt
For the most part, they'd be identical. The difference between matter and antimatter is generally only important when the two come into contact with one another. This isn't *always* true (formally speaking: CP symmetry isn't absolute), but it usually is.