Terminator Genisys opens on July 1st and, while I am cautiously optimistic that it will be good, I am certainly going to use the opportunity to discuss the use of time travel in entertainment.

I’m no quantum physicist – sorry to disappoint – so I’ll be giving a bit of a layman’s take on the three most frequently used types of time travel. Of course there have been many other types used here and there, but I’ll be focusing on the ones that seem to be the most recurrent. The Terminator film franchise had really made use of all three types, which is why I’ll be using that as a jumping off point.

I will be referring to the theories here as the the Infinite Loop, the Running River and the Parallel Timelines theory.  Not exactly scientific terminology but I find them to be fitting, so let’s just roll with it.

The Terminator goes with the Infinite Loop theory, which essentially states that time is a circle. Everything that will ever happen has already happened and will happen again and again and again. Specifically in this case, John Connor sends Kyle Reese back in time to protect his mother Sarah Connor from a Terminator sent back to kill her by Skynet, and then Reese ends up becoming John’s father.

The suggestion here is that Reese was always John’s father, and so the future and the past have always been set in stone. By the end of the movie, Judgment Day – the nominal nuclear destruction of the human race – has not been averted. So, humanity is blasted, John Connor leads the rebellion against the machines, Skynet sends a Terminator back in time, John sends Reese back in time to protect his mother, and the events of the film continue on an infinite cycle.

The Infinite Loop is typically used in tragic stories, as it plays with the notion of unavoidable fate always trumping free will. This is why it’s the theory favored by the fairly nihilistic Rust “time is a flat circle” Cohle in True Detective, and Battlestar “all of this has happened before and all of this will happen again” Galactica.

T2 switches gears and uses “no fate but what we make” as it driving mantra. I’m going to skip the details of the film since, if you haven’t seen it, then I’m sure you’ve already stopped ready this blog post. The bottom line is that Sarah Connor, the super annoying preteen version of her son John, and a Terminator fresh off a babyface turn (wrasslin’ reference alert) decide to go ahead and stop Judgment Day from ever happening.

It’s not made clear whether they succeeded in the theatrical release, but several of the home video versions have a deleted epilogue where an elderly Sarah Connor is playing with her grandkids in a park. All of which suggests that Judgment Day was, in fact, averted.

This is the Running River theory, called such since a good analogy for it is that, if a river’s course is diverted at any point, then every point that flows after that affected point is changed as well. However, it is still the same river. This theory is used in stories with happier endings, as it illustrates that we can change our future for the better. The best example of this is perhaps Back To The Future, wherein Marty McFly changes his family’s life for the better after a brief, reverse-Oedipal wracked, visit to his parents’ past.

Terminator 3 flipped back to the Infinite Loop theory and, while I wouldn’t mind blogging about how that movie get a bad rap and is actually pretty good, it would be superfluous to go further into it.

Terminator Salvation, also better than its reputation though still not especially good, doesn’t really have much to do with time travel. As such, I’m going to twist the facts here to get to my last point. It could be interpreted as saying that the future (or the present, I suppose) may not be the same as it once was. In fact, it may be an entirely different timeline.

Parallel Timelines have long been the theory of choice for ongoing stories. DC  and Marvel Comics have had several “Event Series” and one or two movies that stemmed from this version of time travel. Buffy The Vampire Slayer had a great episode titled Dopplegangland, where a vampire version of Willow crosses over the the “Prime” timeline.  That’s a good specific example of why comic books favor his method – because it allows for different versions of characters to interact with one another. It also enables them with to do things with – and to – famous characters that they otherwise couldn’t (for primarily economic reasons).

The broader explanation for Parallel Timelines is that anytime someone goes back in time and changes something, a whole new future is created from that point forward. The original timeline still exists, adhering to the Infinite Loop rules, but the new timeline essentially falls under Running River rules. But, again, that timeline has not been changed. A new one has simply been created.

Looper, an awesome time travel movie that you should see if you haven’t yet, sits on the fence between Parallel Timelines and Running River, but I always interpreted it more as the former than the latter. The underseen Source Code is a better pure example of Parallel Timelines, where soldier/lab rat Colter Stevens is continually sent back in time to try and stop a terrorist attack on a  train. This theory can be bittersweet, as it allows for a happy ending in one timeline, but you know that things still turn out crappy in the others.

The Parallel Timelines theory of time travel actually plays off of a similar philosophical theory. The philosophy states that, to keep it as brief as possible, every decision that every living being makes creates its own distinct timeline. I’m rather fond of this theory, but it would take another couple thousand words to get into.

To bring things full circle, or back to the start of this particular Infinite Loop, Terminator Genisys opens on July 1st and I’m going to check it out. Looks like they’re throwing together a grab bag of every time travel theory mentioned above, and so it may be an unholy mess. But I’m never one to pass on a time travel movie, so I’ll be there.

Thanks for indulging my crackpot take, I’ll be back soon with some news about my own works, so keep readin’!