Reply #57: Ah, an excellent reference to one of my favorite shows!

[JTG of the PRB]

The paradox encountered by Fry in Futurama is what they call a predestination paradox. The events that happened when he traveled back in time happened exactly as they were supposed to happen, and had anything else happened from what DID happen, the future would have been changed.

The examples you spoke of are from one of the two trains of thoughts regarding time travel. Those possibilities exist in a Universe that will automatically cancel out or negate any changes in the timeline. The predestination paradox is one of those - one traveling back in time will create and change history so that the historical outcomes are exactly what they were supposed to be and nothing else. Another idea along those lines says that there is a slippage created by the Universe that may allow you to go back to the time you intended, but either in a situation or a location that will entirely prevent you from accomplishing your mission.

The article on Wikipedia talks about this time slippage, giving the example that if you were to travel back in time with the intent of killing Hitler, your trip through time may very well be successful, but you would find yourself on a Montana farm in late April, 1945 - in the right time but too far away to accomplish your intended goal of killing Hitler.

I've been poking around this Wikipedia article all night. My brain is starting to hurt, so I think it's time for me to go to bed too. For anybody interested in learning more than you ever needed to know about time travel theories and paradoxes, here is the link:

http://en.wikipedia.org/wiki/Time_travel