The Terminator

Somehow I managed not to see this movie in the 22 years since it was made. While waiting around for the start of Super Bowl XL, I caught it on one of the cable stations.

Not a bad flick, but what I found interesting was the closed temporal loop in the plot. Kyle teaches Sara about fighting the cyborgs, Sarah will teach their son John, who in turn will eventually teach Kyle. It’s a closed loop; nobody actually creates the knowledge.

This is one of the paradoxes of time travel and probably the strongest argument against it being possible as it can lead to impossible situations, and even impossible objects. Consider the example of the young MIT scientist who inherits a gold ring from his elderly landlady. The young scientist then discovers a means of time travel, travels back in time and meets a young girl that he falls in love with. Stricken that he has to return to the future and never see her again, he gives her the gold ring. She, of course, turns out to be the elderly landlady.

This is another closed temporal loop and there are two problems with this story. The first problem is who the heck made the ring? The second is what’s going on with the entropy of the ring? It should be increasing over time until it eventually wears out, which would mean that the loop is not exactly the same each time and will eventually break with unpredictable results.

So, be a little careful if you think you’ve figured out a way to travel through time.