One of the most annoying aspects of science fiction TV and movies is time travel. I’ve got no problem with time travel in general but when the stories get written often writers don’t bother to have it make sense. Usually there are two takes on time travel. “You can’t change the past” or “you can change the past”. The “you can change the past” is further broken down into two categories: “there is only one timeline and changing the past changes this timeline” and “there are many alternate timelines and changing the past creates another alternate timeline”.
All three of these approaches have problems but the biggest problem comes when the writers mix and match them. A recent example is the movie “The Jacket” which was pretty good except they spent the whole movie saying that you can’t change time and at the end they changed time. It was a confusing movie anyway so what the hey.
The all time king of the mix and match is Star Trek. In that Joan Collins episode Kirk couldn’t save her because, “that is the way things have to happen”. Yet there are countless other alternate reality episodes where evil beards are worn and they mess with the time stream to their heart’s delight. Alternate realities abound. Time plays by different rules in different episodes of Trek. Not to mention different series.
The “Butterfly’s Wing” hypothesis says that the beating of a butterfly’s wing can set off a chain of events that creates a hurricane. This is why you have to be careful what you do when you time travel because your actions can have “unforeseen consequences”. But if a butterfly’s wing can cause a hurricane than so can your breathing. Time travelers don’t have to do anything but time travel and they will affect things. This should only matter in the “one timeline” take because in the alternate timeline ones why should anyone care. You can just create a new timeline and then go back to your own. Why be so careful? Pull a Homer Simpson and bash a few thing with a club.
All those different alternate worlds. No one ever explains how all these timelines are created. Usually a person creates one by going back in time and changing things but what about when some crazy accident knocks him into an alternate world where people wear evil beards? Where did that one come from? Did some other time traveler make it? Who knows? The writer don’t usually bother to explain such things.
The answer for a lot of stories is that all of the alternate realities exist at once. They are all there just waiting to be discovered. The TV show “Sliders” is an example of this type. They slide from one reality where England still rules the U.S. to another where women run the world. Of course I have a problem with this too. If all alternate realities exist at once there must be an infinite amount of them. Not just worlds where there are huge dramatic differences; this is a literary conceit. But worlds with mundane, not even noticeable differences. For example, I used to work in Manhattan. I would get of off a bus at 40th and 8th Ave. and walk to 28th and Park Ave. That is about a 20-25 minute walk and I had no set path. I would just follow the lights and cross the streets where I could. There were lots of choices. Can I make this light? Should I dash across or just turn downtown? I bet that if I chose differently at any of those corners it would not have mattered. There are billions of butterfly wing beats and few hurricanes; most small choices don’t matter. But there still would have to be an alternate world where the only difference is that I walked one block further east before turning south. Otherwise everything is the same. Multiply this by many days walking and by many millions of people. Infinite alternate worlds all essentially the same. I bet if you traveled to an alternate world you wouldn’t even notice the difference. Except there would be two of you. Unless the other you traveled to an alternate world too. Wait this is too confusing. Anyway, the odds of finding an alternate world dramatically different would be slim. That would be a real exciting show. Traveling from world to world where everything is the same.
I have always found Robert Heinlein’s “you can’t change time” take the neatest. There are no such thing as time paradoxes. If you go back in time to try and kill your mother before you were born something will stop you. It never happened so you won’t be able to do it. But that doesn’t let a writer “threaten the whole time space continuum”. So most stay away from it. It’s must easier to not sweat the details of time travel. Lazy Bums.