This thread has certainly been fascinating reading so far, but I've never taken the science or continuity in STAR TREK too seriously. There is a scene in GALAXY QUEST where some fans are asking Nesmith (a parody of Shatner) about apparent continuity errors in the technology of the show. Nesmith has been having a bad day and brusquely tells the kids that there is no ship, it's all make-believe.
Never expect techno-babble to make much sense, such as a line in STAR TREK IV: THE VOYAGE HOME where a starship having lost all power will try deploying "solar sails" to generate enough power to maintain life support. Since we're talking about TOS, I'll point out a technical continuity error from "The Enemy Within." A handful of crewmen are trapped on a planet surface, and the transporter is out of order. Why weren't the men rescued with a shuttlecraft? Because it had not been "invented" yet by the show's creators. Again, I wouldn't lean too heavily on any particular circumstances or specific lines.
Robert Comsol wrote:
Without nuclear fusion there’d be no stars in the sky
It was pure speculation when Sir Arthur Eddington suggested that stars are balls of hydrogen continuously fusing under the pressure of gravity. An increasing abundance of observations conflict with this idea, but I don't want to detour the thread here. I can recommend other reading for anyone who is interested.
I always assumed—as little thought I gave to the matter—that "dilithium" crystals were used to focus the matter-antimatter reaction, or perhaps act as a lasing medium. Murray Leinster's MINERS IN THE SKY describes an ultra-dense crystal that is the key to spaceflight. The crystals can be found only in the deep cores of planets, which are normally inaccessible. Thus, the adventure takes place in the rings of a Saturn-like planet where the hopeful miners prospect the broken rubble. Of course the novel does not explain the crystals in detail—only that running an electrical current through them produces thrust of some sort. (A similar drive, with no crystals, appears in the Leinster novel THE WAILING ASTEROID.) Good stuff... so long as one does not take it too seriously.