Time Travel

[Mr. Morden]

I assume that even the slightest change in the world from before I was born would result in a timeline in which I never existed.  I mean, even if my parents still met, married, and had kids, my existence depends on a very specific sperm cell meeting a very specific egg.  Wouldn't the tiniest change in the past have resulted in a different combination?

So assuming that we're dealing with time travel rules in which when you go back in time you can "change" history and create a new timeline, if I went back in time 50 years, did something as simple as go to a local restaurant to order dinner, then return to the present, wouldn't I return to a world in which none of the people I know today exist?  That would be because the people I briefly interacted with at that restaurant would have had days that unfolded slightly differently, leading to some of them having kids at a slightly different time, with a different DNA combination, cascading through the lives of everyone around the world.  What do you think?