All about time-travel

On his blog, Stephen Gallagher considers various ways of using time-travel in scripts and stories.

The most obvious form is the 'paradox romp' like Back to the Future, where something in the past gets changed, and repairs have to be made to safeguard the present as we know it. There's a '70s Czech comedy called Tomorrow I shall Wake Up and Scald Myself with Tea that involves defeated Nazis trying to go back and give the H-bomb to Hitler. The Terminator is one of these, inverting the concept so that the aim is to prevent an unpleasant future rather than preserve the timeline. NBC's Journeyman featured the same kind of action on a weekly basis, with Kevin McKidd going back to change individual lives for the better. Which is laudable but not half as much fun as killer robots. In Harlan Ellison's Star Trek episode City on the Edge of Forever, Kirk has to watch Joan Collins get hit by a car knowing that if he saves her, Hitler gets atomic weapons (again).