Star Trek (the original series), The City on the Edge of Forever. First aired April 6, 1967.
Ultimately, we watch Trek's version of where we're going in order to explore where we are and where we've been. At the beginning of this episode, Spock tells Kirk that the Enterprise which is getting knocked around by turbulence is passing through "ripples in time." And so begins a tightly wound episode that sets the standard for time-travel sci-fi. Star Trek was not the first TV show to attempt to overcome the logical conundrums of time travel, but this episode was arguably the first to get it right. As with every installment of the original series, this one contains some hilariously unsophisticated moments, as when a psychotic Dr. McCoy ludicrously knocks out the transporter chief with a couple of 10-cent karate chops. But its spare, cynical vision of time travel the whole endeavor will lead to nothing but heartbreak could teach something to J.J. Abrams and Damon Lindelof, producers on the new film and also of the eyebrow-furrowing TV show Lost. Both the new Trek and Lost have enough time ripples, eddies and whorls to make your head hurt. At the end of City on the Edge of Forever, Kirk offered simpler (and, for the time, rather risqué) advice: "Let's get the hell out of here." Exactly.