"The Enemy Within"

Star Trek's writers were captivated by the possibilities of the transporter early on, with this, the fifth broadcast episode of the new series. When the transporter splits Captain Kirk into two parts, the accident allows for exploration of two elements of the human psyche. The passive, "good" side of Kirk must subdue and reintegrate with the aggressive or "evil" side of himself.

Unlike most film and television at the time, this is not a pure melodrama of good versus evil, but an examination that in each of us, sometimes our less attractive qualities have value, and that in order to function we all need to have a little of both good and bad steering us.

Beyond the thematic ponderings, this episode also gave William Shatner a great opportunity to chow down on the scenery in both roles, giving a performance that's still fun to watch after multiple viewings. And with Sulu and his away team freezing down on the surface, the ticking clock of the situation keeps the philosophical musings from bogging down the pace of the story. Of course, there had to be some reason they couldn't send a shuttlecraft down to the planet to save them, right?

"Mirror, Mirror"

Good science fiction can encompass bits of everything, including the incredible sweep of history. In this Original Series classic, the transporter in this episode became a gateway to an entire other dimension, where the Federation is an Empire and Spock sports a goatee. This episode, while exciting and embracing all the ramifications of mirror doppelgangers of established characters, also gave viewers a window into an alternate history where the actions of a cruel empire are horrific on an unthinkable level.

The stakes of Star Trek have regularly been far higher than most television shows; while detectives are solving one murder on another network, Kirk and his "original" universe crewmates are working not only to get home but to try to save countless innocents on numerous planets from Kirk's power-mad counterpart on a galactic scale.

For many fans, episodes like this broadened the canvas of the show. Our universe is immense enough, but add parallel universes on top of that and the mind boggles. Despite the technological advances that will make our own lives easier, in the future humans may very well struggle to avert catastrophes and atrocities of unimaginable scope.

"Mirror, Mirror" would spawn several episodes of Deep Space Nine, not to mention some novels, creating an entire history of another universe to make fans wonder about Mirror Universe counterparts of every Star Trek character, and perhaps even themselves.

"Star Trek: The Motion Picture"

In the Original Series, Dr. McCoy would often lament the use of the transporter as an insane mode of travel, not trusting in the technology which would take someone apart, molecule by molecule, beam them over long distances and reassemble them, all in the space of a few seconds. He would make jokes about the dangers of the device, but it wasn't until the franchise's first feature film that we got a glimpse of the true horror he was talking about.

In one of Star Trek's most sobering and terrifying scenes, the ship's new Vulcan Science Officer, Sonak, as well as another crew member, are the victims of a tragic transporter malfunction. Mercifully, we are told, they don't live long. This is the stuff of nightmares, a brutal reminder that no matter how far we advance, and no matter how high the percentage of success, there will always be accidents, there will always be that less than one-percent that falls victim to random fate.

"Unnatural Selection"

For the most part, however, the transporter did serve its function correctly, and at times was an unconventional method of solving problems. In this episode, the transporter doesn't malfunction, but the "mishap" in question may very well be its use in resolving the episode's problem.

When Dr. Pulaski is afflicted with rapid aging, the transporter is what cures her. The "science" half of science fiction comes into play here; by looking at how the transporter "works" (taking a molecular profile of an individual and passing it through a transporter buffer) and applying that to a medical problem (using the transporter to restore Pulaski to her last-known "saved" version), it brings up all kinds of questions. If humans had transporter technology, could it be used for such medical purposes? Could beings afflicted with an incurable disease or hurt in an accident be reverted to their most recent pass through the transporter buffer?

Given the rest of Star Trek beyond this episode, the answers to those questions is presumably negative, as for the show's creators, it would result in a show resoundingly without conflict or drama (indeed, how dramatic would any crisis be if in the end, you could just throw everyone through the transporter and they'd be fine?). But this episode does beg the question that should humanity someday develop this kind of technology, the uses of it could very well go beyond the initial purpose of transportation.

"A Matter of Perspective"

In another case of fortunate and unanticipated transporter side-effects, this episode sees Riker's life being saved by the transporter when a devious scientist's murder plot is thwarted. Dr. Apgar, who has developed a new energy source and seeks to sell it to the highest bidder, tries to kill Riker by shooting an energy beam into Riker's transporter beam. Apgar hopes that Riker's atoms will become dispersed, but the interaction of the energy and transporter beams only results in a feedback which causes an explosion, killing Apgar.

Once again, the transporter is a vehicle for moving the story along, as a side-effect of the device's intended use manages to save Riker's life and reminds us that technology designed for one purpose can often yield unexpected results and uses.

"Second Chances"

While "The Enemy Within" used the transporter to explore the internal aspect of the theme of duality (the two parts within a self), "Second Chances" uses science fiction to create a unique and rich situation exploring the differences between identical men who walked different paths.

The choices we all make in life help to shape who we are, and many of us have wondered how we'd have turned out if we'd made different choices years ago. In this episode, via a transporter mishap eight years earlier, an exact duplicate of William Thomas Riker (hence called Thomas Riker to avoid confusion) had been created, and then spent the time since trapped on Nervala IV.

While both men were exact duplicates when the accident happened, the eight years since then has shaped them both into different men (even more so, given Thomas Riker's actions with the Maquis in the subsequent DS9 episode "Defiant"). 

The simple premise spurred by a transporter accident creates a dramatic situation impossible to find in anything other than science fiction or fantasy. This episode not only shows us another side to Riker, but it also puts Troi into an interesting situation, as she gets a second chance to explore her failed (at the time) relationship with Riker anew via Thomas, who spent eight years alone pining for her.

And, as an unfortunate footnote, while many Star Trek characters find happy endings, Thomas Riker is a truly tragic character. Spending eight years alone on Nervala IV would be bad enough, but his actions in "Defiant" land him in a Cardassian labor camp while William Riker eventually married Troi.

"Tuvix"

In a sense, the premise of this episode harkens back to the horror classic "The Fly" (two beings go into machine, one fusion of the two comes out), but looks at it from a different perspective. When Neelix and Tuvok become fused into Tuvix, a new being created due to the strange properties of alien orchids combined with the transporter, one of Star Trek's classic themes gets a new twist.

When the Doctor devises a way to separate Tuvix back into his initial components, Captain Janeway is forced to choose between the rights and needs of the many versus the rights and needs of the one. Unlike many Star Trek episodes, this doesn't tie itself up nicely when it's done. Under the circumstances, there was no "right" choice for Janeway to make. All of Tuvix's pleas to continue living are no less compelling than arguments to bring back Tuvok and Neelix.

Again, the transporter is a conduit to an intractable dramatic situation that has no easy answers. Tuvix's existence is taken away from him, but allowing him to continue living would amount to taking away the existence of Neelix and Tuvok. The moral dilemma aside, this situation also gives the audience a taste of the complexity of leadership when there is no true, painless solution for Janeway to this problem.

"Strange New World"

In these early Enterprise days of transporter technology, humans are very wary of using this peculiar new device, and with good reason. In perhaps the first-ever (that we know of) transporter mishap, Enterprise NX-01 Crewman Novakovich achieves an unenviable distinction.

As a member of an away team exploring a pristine paradise of a planet, Novakovich ends up being beamed up during a storm only to have bits of twigs and rocks transport up with him, blending with him. Thankfully, Dr. Phlox is able to stabilize him and his injuries aren't life-threatening, but given that he was under the potent psychotropic effects of an indigenous compound in the air, it had to have been intensely horrifying to see sticks and stones merged with his own flesh.

The transporter, one of the key components that makes Star Trek unique, has provided some great escapes, deceptions, interventions and medical miracles over the years. The device even had its own recognized medical disorder, transporter psychosis. This rare medical diagnosis, first diagnosed in 2209, was virtually elminated by 2319.

As long as Star Trek is around, you can be sure a transporter will be close at hand. And while this technology has yet to threaten the existence of humankind or take over the galaxy with robotic drones, who knows what the future holds for this ingenious piece of equipment.