When they say the universe “may have” a complex geometry, is this speculation about what’s possible or based on some evidence that suggests this is the case instead of the simpler “it’s just 3d space plus time with all extending outwards in each direction that we are already aware of”?
Don’t get me wrong, I love me some speculation about what other realities would fit in with what we’ve observed, but actual evidence would be more cool, especially given that I don’t even know what such evidence would even look like, other than being able to see ourselves in some far off direction (though even then, I’d wonder how we could be sure it’s actually us and not some others that just look just like us and happen to do the same things at the same time).