Time in a Bottle of Ink

In fiction, one of the hardest devices to use well is time travel.

Most who make the attempt at coherent time travel stories use a parallel time model. As in, time operates on different threads alongside each other, and you can jump from thread to thread, each having a different future depending on which thread you travel (the time traveler's presence splits the thread into yet another outcome, etc.). Which automatically means there are duplicates of all of us, living our alternate universe lives simultaneously, and this is how it is often depicted, as in you can't show your time-traveling self to your other self or you'll freak out and the universe will explode. (An exception being the movie The Butterfly Effect, where there were duplicates of everyone except the time traveler.) Examples of using duplicate selves in time travel: Harry Potter & The Prisoner of Azkaban (did OK), an episode of Doctor Who (1st season--fun, but not exactly sound), and most recently, the TV show Heroes (here, the time traveler met his duplicate self, and started traveling time with him, resulting in one of his selves being killed... it's fun, but not sure it's consistent). The hard part is resolving what happens to the duplicates when the time traveling is done (or if one of you dies)? Is it still you or is it someone else? (Heroes obviously decided it's someone else.)

In time travel stories, you often hear about the Butterfly Effect. The quickest references are the adage that talks about a butterfly flapping its wings, causing a tornado somewhere else; or the Ray Bradbury story about time travel, called A Sound of Thunder, where the guy steps off the designated path in the time of dinosaurs, and crunches a butterfly under his boot, which results in a dramatic change in the future he once knew. In fact, this story appears in a pretty good anthology of time travel-themed fiction called The Best Time Travel Stories of the 20th Century (Harry Turtledove, ed.).

Some, like HG Wells in his novel The Time Machine, opt to view time travel more like a destination. The character saw what things were like, had an effect on the present time he was in, but didn't seem to have an effect on future events directly, since when he returned to tell the story to his friends, nothing had changed as a result of his travels.

Many, many writers have used time travel to tell a story, and several have done a passable job (especially if the rest of the story and characters are awesome, like in Doctor Who), while some fail utterly. Time travel, because there are only theories about it, is a nasty temptation for use as a literary device. I say nasty, because it's deceptively tricky--the whole concept is dependent on certain assumptions of the properties of time and space, and those are very easy to contradict, especially when you're trying to push a story forward while moving backward.