But what is a mirror?
A mirror is a reflective surface, now typically of glass coated with a metal amalgam, that reflects a clear image. It also means something regarded as accurately representing something else: the stage is supposed to be the mirror of life. In Computing, it is a site on a network that stores some or all of the contents from another site.As a verb, mirror means to show a reflection something such the clear water mirrored the sky.
It also means to correspond to, such as gradations of educational attainment that mirror differences in social background.
The origin of the word "mirror" is Middle English: from Old French mirour, based on Latin mirare ‘look at.’ Early senses also included ‘a crystal used in magic’ and ‘a person deserving imitation.’
And the early sense may be the basis for the plots of LOST. Ben told Locke that the island was "a magic box," and if wished hard enough, he would get his wish granted. In Locke's case, his wish was to confront his devious father, Cooper, for one last time. In that situation, Cooper said that he was driving along then he was run off the road in an accident - - - and suddenly wound up as a prisoner on the island. Cooper clearly believed he had died and gone to hell.
Sideways Jack once looked into a mirror and saw unfamiliar scars, scars from his childhood or injuries from the island plane crash. That could have meant that Jack was looking at his future self, or that Jack was looking through a portal to another universe.
The main characters in the sideways world would frequently confronted themselves in mirrors or reflective surfaces. According to Jack Bender, executor producer and director of LOST, these scenes showed the characters figuratively and literally "confronting their images and the reflections of themselves." The visual metaphor expressed the flash sideways' theme of introspection, and also represented how the flash sideways showed "what you wish for or what you're scared of."
That may be a too simple, too vague explanation of this device.
And it does not explain why the series added a second dimension of the sideways world into the main story line.
The various fan theories on mirrors from lostpedia are:
Deja Vu
- The mirror moments correspond to characters' brief *remembrance*
of their lives on the island, before some major shift causes the
alternate timeline to take over their lives and cause fairly complete
amnesia. The reflective gaze is especially apt to triggers these
memories, though it need not be the only way a character experiences
deja vu.
- This seems to be supported by Jack's behavior. He notices an inexplicable bruise on his neck at LAX airport and later suffers similar confusion over his appendectomy (albeit via direct body inspection, not mirror use).
Parallel "Bleed Through"
- The moments when alt-timeline characters observe themselves in mirrors represent the effect of a bleed-through with the simultaneously occurring main time line.
Mirror as Window into Different Timeline
- Gazing through a mirror, either on the Island Lighthouse or within the alt-timeline, provides a means of seeing into the other timeline. Jacob uses the mirror to gaze into many different possible outcomes, past, future, and within the flash-sideways. Characters in the flash-sideways gazing or reacting emotionally to a mirror are subliminal accessing a different chronology/reality.
Many scientists believe that there are multiple parallel universes that exist simultaneous in the same space. Think of it like your car radio - - - each separate station is a different universe but in the same space of your vehicle. Just like when a storm or electric power lines cause radio interference, two stations may blur today on the sound speakers. This overlap may be what was happening at certain points in the LOST story lines. Mainland Jack was seeing images of Island Jack; Sideways Jack was seeing images of Island Jack. But each Jack was a different "person" in a different "universe." That would explain the major differences in Jack's personal life: in the Mainland, he had been married without a child to Sarah; but in the Sideways world he had been married to Juliet and he had a son. "Jack" never reconciled the differences in his personal life between the Mainland and the Sideways realities. Maybe, he did not need to. Perhaps his "death" in the portal island world collapsed his various separate lives into one universe - - - the sideways one.
That would explain why Juliet suddenly fell for a complete stranger, Sawyer, with only a glancing touch. Their island universe experience suddenly rushed into their sideways world and overwhelmed their sideways past experiences.
Three different universes. Three different Jacks, Juliets, Sawyers, etc. Their lives seem to collapse into one time line like the matter at the event horizon of a black hole.
