system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] At what point did the timeline diverge to create the Mirror Universe and Terran Empire?
gpt
I don't believe there's any single point. The mirror universe is too consistent in its capacity to mirror the prime universe to be explained away as an alternate timeline. Somehow, despite drastically different events in the two universes, people keep ending up in roughly the same places with the same people.

We also have another clue that this is a truly different universe, not just a divergent timeline. The laws of physics are actually different. Light is somehow less bright. What's the significance of that? No idea. But it's not something that we'd see in an alternate timeline.

I think the mirror universe really is what it says in the name. Somehow it's connected to the prime universe and mirrors it. It's the other side of the coin, the other end of the dipole. It may be a natural phenomenon. It could just as likely be the creation of some omnipotent being like Q. Whatever it is, it's pretty much its own thing. The timeline didn't diverge because it's always been different.