The Physics of Star Trek Read Free Page B

us give to travel into the past, relive
     glories, correct wrongs, meet our heroes, perhaps even avert disasters, or simply revisit
     youth with the wisdom of age? The possibilities of space travel beckon us every time we
     gaze up at the stars, yet we seem to be permanent captives in the present. The question
     that motivates not only dramatic license but a surprising amount of modern theoretical
     physics research can be simply put: Are we or are we not
    prisoners on a cosmic temporal freight train that cannot jump the tracks?
    The origins of the modern genre we call science fiction are closely tied to the issue of
     time travel. Mark Twain's early classic
    
    
     A Connecticut Yankee in King Arthur's Court
    
    
     is more a work of fiction than science fiction, in spite of the fact that the whole piece
     revolves around the time-travel adventures of a hapless American in medieval England.
     (Perhaps Twain did not dwell longer on the scientific aspects of time travel because of
     the promise he made to Picard aboard the
    
    
     Enterprise
    
    
     not to reveal his glimpse of the future once he returned to the nineteenth century by
     jumping through a temporal rift on Devidia II, in the episode “Time's Arrow.”) But H. G.
     Wells's remarkable work
    
    
     The Time Machine
    
    
     completed the transition to the paradigm that Star Trek has followed. Wells was a graduate
     of the Imperial College of Science and Technology, in London, and scientific language
     permeates his discussions, as it does the discussions of the
    
    
     Enterprise
    
    
     crew.
    Surely among the most creative and compelling episodes in the Star Trek series are those
     involving time travel. I
    have counted no less than twenty-two episodes in the first two series which deal with this
     theme, and so do three of the Star Trek movies and a number of the episodes of
    
    
     Voyager
    
    
     and
    
    
     Deep Space Nine
    
    
     that have appeared as of this writing.
    Perhaps the most fascinating aspect of time travel as far as Star Trek is concerned is
     that there is no stronger potential for violation of the Prime Directive. The crews of
     Starfleet are admonished not to interfere with the present normal historical development
     of any alien society they visit. Yet by traveling back in time it is possible to remove
     the present altogether. Indeed, it is possible to remove history altogether!
    A famous paradox is to be found in both science fiction and physics: What happens if you
     go back in time and kill your mother before you were born? You must then cease to exist.
     But if you cease to exist, you could not have gone back and killed your mother. But if you
     didn't kill your mother, then you have not ceased to exist. Put another way: if you exist,
     then you cannot exist, while if you don't exist, you must exist.
    There are other, less obvious but equally dramatic and perplexing questions that crop up
     the moment you think about time travel. For example, at the resolution of “Time's Arrow,”
     Picard ingeniously sends a message from the nineteenth to the twenty-fourth century by
     tapping binary code into Data's severed head, which he knows will be discovered almost
     five hundred years later and reattached to Data's body. As we watch, he taps the message,
     and then we cut to LaForge in the twenty-fourth century, as he succeeds in reattaching
     Data's head. To the viewer these events seem contemporaneous, but they are not; once
     Picard has tapped the message into Data's head, it lies there for half a millennium. But
     if I were carefully examining Data's head in the twenty-fourth century and Picard had not
     yet traveled back in time to change the future, would I see such a message? One might
     argue that if Picard hasn't traveled back in time yet, there can have been no effect on
     Data's head. Yet the actions that change Data's programming were performed in the
     nineteenth century regardless of