Originally Posted by GDK:
“In Mirror, Mirror, the DS9 and Enterprise episodes that went to "the" mirror universe and TNG's Parallels it's not clear what (if anything) "caused" those universes. They may have been due to a time travel incident altering the course of events, they may have always been there as part of the multiverse or "created" from any of the many branch points where decisions were made differently in each "version" of the universe.
One fan theory has suggested that the mirror universe is the universe created from the "Edith Keeler" timeline created in the original series episode City on the Edge of Forever.”
“In Mirror, Mirror, the DS9 and Enterprise episodes that went to "the" mirror universe and TNG's Parallels it's not clear what (if anything) "caused" those universes. They may have been due to a time travel incident altering the course of events, they may have always been there as part of the multiverse or "created" from any of the many branch points where decisions were made differently in each "version" of the universe.
One fan theory has suggested that the mirror universe is the universe created from the "Edith Keeler" timeline created in the original series episode City on the Edge of Forever.”
I seem to remember an episode where the meeting between Cochrane and the Vulcans ended violently and this led to the creation of the Mirror Universe.
The prime universe that meeting was peaceful (and as shown in First Contact)




They will stream it in whatever quality they get it in. Probably not 4K.