Thread: Time Travel... Please Help.

I was having a conversation with my sister about Back to the Future (I'm not having a go at the story, just exercising my brain). Basically, I do not believe you can change your own past, regardless of the abitlity to travel time. She didn't agree. I'm looking for a few more perspectives, from those older, wiser or anybody else too. Is there any ambiguity or huge mistake in the logic I used?

If somebody gave you a Delorean tomorow, and you decided to credit youself with inventing an item from the future (An automotive engine that ran on green house gases say), could you just turn up to your past self?

Picture time as a line from the start of the universe until now. If every time there is more than one outcome, another path is created, ignore the other "branches" of possible realities. This is about changing your own timeline.

Now you take the blueprints to your younger self, and get him the credit. He becomes rich and famous. The past has been influenced by the future.

The problem with that scenario is that if you change your past self, then there is nobody who can become the person who brings the blueprints back in time. There never was the average Joe who stumbled across the Delorean. So who then brought the blueprints back in time.

If you brought them back in time, then told your past self how to get the Delorean to do the same when the time comes, is that changing the past? The future you doesnt differ with the past you when he comes of age. There for the timeline hasnt changed.

NB This is all assuming time travel is possible. If you enter another reality and get them to change your past, there will be no original you to go into another reality. It has already been covered, and is a long winded way of the above example.