In Star Trek TOS, we see the Defiant disappear to unknown parts ('The Tholian Web'), and Star Trek: Enterprise revealed that the Defiant went back in time to the mirror universe ('In a Mirror Darkly', parts 1 & 2).

Because of this, one might wonder why (in-universe) the mirror universe didn't obtain (and maintain) technological superiority over the main timeline. (Granted, the out of universe answer is that TOS depicted the two universes as having essentially the same level of tech)

So does any work (whether STO, or a pocket books work) address why the mirror universe didn't simply leap frog the main universe's technology?

(Or to put it another way, why did the mirror universe's technology appear to stagnate for a century after obtaining access to the Defiant's advanced technology?)

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    I imagine in the everyone-for-themself dystopic mirror 'verse, there's a few elements that would limit how fthe advanced tech would be assimilated: a: whoever had the Defiant would want to just use it now, rather that tear the ship apart to learn how how it worked; b: it would be a tightly guarded secret, with few people having access to it; and c: because of points a and b, there's a low probability the tech would be learned and a great probability that the Defiant would be destroyed or forced to self-destruct by a zerg rush of low-tech ships from the multitude of other factions.
    – Joe L.
    Commented Jan 1, 2017 at 7:45
  • It's also possible that the captain and crew of the Defiant self-destructed to prevent anyone from the "evil" universe from benefiting from the advanced technology.
    – miltonaut
    Commented Jan 1, 2017 at 7:59
  • @JoeL. Or, rather than joining an existing faction in the mirror universe they went solo and some existing faction(s) who felt threatened by the big bad starship ganged up and totally destroyed it, leaving nothing to research except an expanding ball of gas. Or they fell into a space anomaly/discontinuity (they're everywhere in the Trek universe!). Or the Q continuum did something with them. Lots of possibilities. Commented Jan 1, 2017 at 15:07
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    No evidence, so a comment not an answer, but I just assumed that the Federation's science-based goals would far outpace the Mirror-verse's everyman for himself attitudes. It just so happens that the Federation "caught up." (This doesn't really explain Deep Space Nine's forays, though...)
    – Ghotir
    Commented Jan 1, 2017 at 16:45
  • The really baffling thing is why, despite completely different histories, there were still versions of the same people in three different time periods. If you want to explain any of it in-universe I think you have to assume that there is some kind of mechanism keeping the two universes tied together. (Perhaps just that there are an infinite number of possible timelines in both universes, and when you travel between the two universes you wind up in whatever mirror timeline is most analogous with your own.) Commented Jan 1, 2017 at 23:48

1 Answer 1


In the novels (specifically Age of the Empress and the short story "Nobunaga"), the Empire tried to reverse engineer the Defiant, but was unable to make much progress for a number of reasons: the ship was urgently needed to deal with rebels, information on it was tightly controlled for political and security reasons, there was sabotage (for instance, Mirror Trip was a key player in the reverse engineering project who went over to the rebels), and it was simply too advanced for them to replicate much of its technology even when they began to understand it.

They unquestionably gained some progress from their studies, but nothing groundbreaking. Essentially, by the time they fully understood what they'd reverse-engineered, they'd invented half of it anyway.

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