# In Predestination, what is the purpose of the 50 year rule?

I've been able to deconstruct and understand most of the logic within the world of Predestination. However, the one thing that didn't seem to really get explained was the rule that things get weird if you travel more than 50 years in either direction of 1981. Is this an arbitrary rule within their universe, or does it tie into the story in a way that I may have missed?

In more spoiler-y words:

Does the 50 year limit have to do with the protagonist's paradox timeline (i.e. 100 years is roughly the length of 2 generations from birth to death), or does the 50 year limit apply to everyone?

The explanation given in the film according to WikiQuote

John: This time period. Okay. So how far can you travel, then?

Temporal Agent: Travel beyond 53 years of zero point, either direction, will result in the temporal wake disintegrating.

John: Zero point?

Temporal Agent: The invention of time travel.

John: And when's that?

Temporal Agent: It will be in 1981.

So it seems to apply to "everyone" as it applies to a specific point in time (the invention of time travel in 1981)

• That's kind of a bummer, given how seamlessly everything else fits together, but thanks for finding the exact quote! Commented Oct 5, 2015 at 22:29
• @NonsenseSynapse well, the logic "fits" together into a paradox ;) Commented Oct 6, 2015 at 9:02
• @EdmundYeung99 100% agree that this is the canon answer. You might like to read my fan-theory answer below for the film if a single minute change were made. Commented Apr 29, 2017 at 21:27
• @NonsenseSynapse I agree. And (having just re-watched the film) I managed to create a much more satisfying answer if you make a single minute change to the film. See below for my idea :) Commented Apr 29, 2017 at 21:29

EdmundYeung99's answer is as much of an answer as exists in the film, and is in every sense the 'correct' answer. However ...

Having just re-watched the film, I have just constructed a non-canon fan-theory that can work if you make one tiny change to the film that otherwise has no effect, and gives a much more satisfying answer....

Time Travel's Zero-Point is 1981.

In the film, Agent Doe takes John to the Temporal Bureau, and leaves him there in August 1985. Shortly after (the next day?) John is given his first Field Kit and

becomes Agent Doe.

That date, August 1985, doesn't tie into anything, AFAICS. There are no references to any of John's early missions at the TB, nor any other reference to when he became an Agent.

Supposing you make a single character change to the film: change the last digit on the clock to a '1'. Now John becomes Agent Doe in the same year that Time Travel is invented.

From there it isn't much of a leap to suggest that:

The very existence of (Jane/John/Agent Doe/Fizzle Bomber) is the fundamental source of Time Travel. That (continuing the theme of John's circular life) Time Travel exists solely because this closed temporal loop exists ... which of course only exists because Time Travel exists.

That explains the 1981 start point. To get the 53-year limit ...

one could assert/guess that the Fizzle Bomber is maybe 53 years old (in terms of his personal linear TimeLine) when he dies. It doesn't seem to far off visually. And have a nice feel to it.

Obviously all of this is completely made-up and does require a tiny change to the film. But I think it's rather nice :)

• Interesting theory. I like it! The 53-year limit definitely felt to me like it was too close to a human age to be a coincidence. Commented Feb 5, 2018 at 23:53