Metaphysics- Time Travel: Star Trek vs. Terminator

How many movies/TV shows have time travel as a plot device? LOTS! Some do it better than others and some muck it all up (Lost). Taking the above-mentioned movies shows in account let’s see what makes for good time travel and whether or not any of the compare to what would likely happen in time travel.
Let’s start with the best of the three: Star Trek. (Spoiler Alert for those who haven’t seen the movie yet, though there’s no excuse to have not seen it yet.) In the movie, a black hole is opened by which two star ships are sucked through and sent into the past. These ships alter the course of events creating a “parallel reality” as spoken by one of the characters. After a brief scene where the crew discusses this occurrence, the aspect of time travel isn’t brought up again, which is a good thing. This is the best way to handle time travel in cinema, establish the way time travel works in this particular mythology and move on from there. Dwelling on the nuances of time travel leads only to trouble (Lost).
In Star Trek, traveling back through time and altering events creates a “split” from the “normal” timeline that does not interact with each other.
On to Terminator. We all know the story; the machines in the future send back a terminator to murder the mother of the leader of the human resistance before he is born in an attempt to preemptively end the war. However, the terminator ultimately fails and in their attempt they inadvertently cause the leader of the resistance to be conceived. What’s suggested here is that all the events in the past are determined (can’t be changed), further, that the events in the past already incorporate the intrusion of people from the future.
So, in Terminator, there is only one continuous timeline by which there can be no deviation and that all people and sentient artificial life are confined to this timeline despite being able to jump to different segments of it.
The difference between time travel in each of these movies illustrates well the difference in thought with regards time, free will, and identity. Given these two films we have to two possible theories regarding how time functions: in one scenario (Star Trek) time is like a tree branch, forking off into limitless paths or the other scenario (Terminator) time is unmoveably linear, regardless of jumping to different parts of the linear path, branching is impossible. In the former, time is undetermined, it can be changed, in the latter time is determined.
So, how does this effect free will? Well, taking a very broad definition of free will (the ability to do more than one action in a given time frame) the Star Trek thesis argues that we have a very robust free will, we can freely choose to do one action among many and that these actions affect the flow of future events. In the Terminator thesis we have a very narrow form of free will, that we are only likely able to do one action for every time frame and that decision making and deliberation are likely self-delusions.
As regards identity, the Star Trek thesis suggests that our future identity is non-finite, whereas Terminator suggests that our future identity is finite.
So, now that we’ve lain out what the central differences and their implications are on these two theories of time travel, what does science say about any of these? Well, I’ll use as my primary source, Stephen Hawking. We won’t go into whether or not time travel is feasible, but rather his discussion on what time actually is. Perhaps you remember your high school chemistry class, so when I talk about the second law of thermodynamics you might remember what that is. If you don’t, that’s ok, I’ll remind you: the second law of thermodynamics states that all systems move towards randomness, the technical term for this is entropy. Simply put, entropy is the reason why messes don’t clean themselves, why the Mona Lisa is falling apart, why you’re going to die someday. Literally, the universe is falling apart, nothing lasts, and everything is struggling towards the most random state of existence. This is lucky for us, the most random state for, say… oxygen molecules is to be as dispersed throughout our atmosphere as possible, we’d be in big trouble if all the oxygen in the world decided to hover over Alaska, exclusively.
So, what does randomness have to do with time? Well, Hawking argues that entropy points in one direction, toward randomness, and that time always points with entropy. This makes sense, if you think about it, we get older as time passes, as time passes we get older, getting older is merely the process of our bodies breaking down, undergoing entropy. Hawking argues that if entropy went in reverse, we would likely experience time in reverse, under this view, time doesn’t really exist, what we call “time” is actually just us following along the course of decay.
Where does all of this lead us? If you read my post regarding identity continuity, you may guess which of these theories I endorse. We are not temporally whole beings at any given moment; our temporal identity stretches from our beginning to our end. Think of entropy as gravity and think of yourself as being in a free fall from an airplane, regardless of whether or not you struggle or wag your arms, you’re going to continue going in one direction and you’re eventually going to hit the ground.
I’ll illustrate my conclusion with one of my favorite examples. Let’s say you and I are golfing and I have to make a one foot put. Unfortunately for me, I got cocky and miss the put. Angrily I tell you that I “Could have made that put,” upon which you respond, “No I couldn’t have.” One of us is right and it’s not me. I could put the ball in the exact same spot and sink it 100 times and not have demonstrated that I “Could have made that put.” Why not? Because in order to validate that claim I would have to reverse the flow of entropy and restore the universe to the exact same state it was in when I missed the put. But in so doing, I would have to restore my state of mind to the cocky state of mind from which I missed the shot. I can’t make that shot because I didn’t make that shot.
Time doesn’t branch, the past cannot change because it did not change, and once I, or anyone else, do something, that something is fixed and immobile, such is entropy. Now, I am not going to claim that this sufficiently disproves the doctrine of free will, that I’ll leave for another post (I think I can show that free will doesn’t exist, it’s just going to be really long.)
So, if John Connor has been born, there’s nothing those damn machines can do about it.