Science Friction_ Where the Known Meets the Unknown - Michael Shermer [131]
How do we conduct a historical thought experiment? Mach explains: “When experimenting in thought it is permissible to modify unimportant circumstances in order to bring out new features in a given case.” He also warns: “But it is not to be antecedently assumed that the universe is without influence on the phenomenon in question.” Mach’s admonition is well taken, and “The City on the Edge of Forever” presents a healthy balance between specific circumstances (contingencies) and universal effects (necessities), and how their interaction shapes altered histories. The story line offers a simple but powerful message about the actions of individuals and the contingencies of life, while recognizing that these occur within the context of influencing larger forces.
In “The City on the Edge of Forever” the theme of the present and future contingently linked to the past—where every individual and event has some relative effect (usually small, occasionally large)—is played out in this science fiction thought experiment. On Stardate 3134.0, an Enterprise landing crew is beamed down to a planet to rescue their temporarily psychotic physician, gone mad because of a cordrazine drug-induced accident (in Ellison’s original script drug abuse led to an onboard murder, for which the convicted crewman was condemned to spend the rest of his life on this barren planet). While on the planet, the landing crew investigates an anomalous source of energy causing “ripples” in the fabric of time. The crew comes upon an arch-shaped rock structure that Spock’s tricorder readings indicate is on the order of ten thousand centuries (one million years) old. Surging with power, it appears to be the single source of the time ripples. Kirk’s rhetorical inquiry of “What is it?” produces a response: “I am the guardian of forever. I am my own beginning, my own ending.” Spock, in his archetypical omniscience explains: “A time portal, Captain. A gateway to other times and dimensions.”
Acknowledging Spock’s correct analysis, the “guardian” gives them a centuries-long glimpse into history, “a gateway to your own past, if you wish.” What they witness is every historian’s fantasy—a replay of history with the opportunity to go back and relive the past. “Strangely compelling, isn’t it?” Kirk queries. “To step through there and lose oneself in another world.” But as they ponder the imponderable, the still drug-crazed physician, Dr. McCoy, appears from behind a rock and leaps through the time portal, which promptly terminates its historical replay. “Where is he?” Kirk asks. The guardian replies: “He has passed into . . . what was.” A landing-party member who was in contact with the ship at the moment McCoy jumped through the time portal suddenly loses all communications. “Your vessel, your beginning, all that you knew is gone,” explains the guardian. McCoy, in the manner of the increasingly popular “what if” genre of historical thought experiments, in something akin to the matricide problem of time travel, altered the past in a manner that erased the Enterprise from history. (Why the landing crew would remain is not explained, nor is the matricide paradox resolved, for if you go back in time and kill your mother before you were born, then you erase yourself from the continuum that allowed you to alter that original past. If McCoy changed the past in such a way that the Enterprise and her crew no longer existed, then he could not have jumped through the time portal to erase that history.)
Matricide paradox aside (which it must be for time travel scenarios to exist in science fiction), the solution is that Kirk and Spock must return to the past just before McCoy jumped through the portal and prevent him from doing whatever it was he did to alter the future. Exactly when they should jump