We've been teased mercilessly with the prospect of time travel by literature (The Time Machine, Slaughterhouse-Five), movies (Back to the Future, Bill and Ted's Excellent Adventure) and even television (Quantum Leap). But so far, the concept has remained limited strictly to fiction. The advantages to being able to travel through time are clear (meeting Napoleon, watching the moon landing), and the disadvantages have been pretty well chronicled too (i.e. really screwing things up). As much as we all would like to see time travel become a reality, some things are probably best left to the imagination.