Mr. Laser Beam wrote:
It has been suggested that, had Picard and crew not appeared in the past of 2063 as shown in ST:FC, that the Mirror Universe resulted from it.
Meaning: the MU, and the resultant Terran Empire, is the 'natural' evolution of the timeline, and it was only Picard's interference from the future that created the 'good' regular universe. Not surprising, as in the 24th century of the MU there is no Empire, no Imperial Starfleet, and thus no mirror universe Ent-E, to travel back in the first place...
Problem is, there is divergence going back before 2063. According to Enterprise's two-parter, Earth literature is different between the two universes, the Prime's literature is "soft and weak" compared to the MU's. Except for Shakespeare, he's the same in both universes. There's a line stating the Terran Empire had already been around "for centuries."
Then there's my personal theory that Earth spins in the opposite direction in the MU (the sun rises in the west). I base this on the animated logo of the Terran Empire seen at the end of the Enterprise credits, which depicts Earth spinning in just a way. Hey, we've never seen which direction MU Earth spins on screen, who's to say it doesn't spin the opposite way?