Mods, sorry this might seem very OT, but today I watched this really freaky and interesting documentary about the "Kozyrev Mirror," a time travel device that was theorized by the Russian astrophysicist Nikolai Kozyrev while in solitary confinement. Could this be Q's "Thing Mirror"?!? Link inside.
(media.greatawakening.win)
THINK MIRROR
The mathematical formula that proves that an object can reflect/refract waves in a manner that produces a "negative refractive index" was also created by a Russian mathematician in the early 1960's.
The theory being discussed is sound. The basic part of it simply boils down to the question of: How long can light be reflected into itself, and then later viewed in order to witness the past in the present?
A negative refractive index is interesting and real, but has no relationship to viewing the past. It does not (for example) pertain to making light propagate backward in time. It only pertains to the behavior of Snell's Law and other aspects of refraction.
I don't know what theory you are referring to. The idea of optical delay trains is an old one and the answer is that anything more than a microsecond would be a significant problem (without even considering signal loss upon each reflection). You would also be looking at an event from an effective optical distance of hundreds of meters. It would be easier to record the event on television and play it back. We've been doing that for about 80 years already. Even longer if you include motion picture photography. So, there's no problem about recording the present to be viewed in the future, but there is no way to view the past from the present without having such records available.