As explored in another SCF question, the only way to answer the bootstrap paradox is to say "every time someone is sent back in time, time branches into a separate line."

But if that is the case, what is the point of Skynet sending anything back in time? The chances of the same "Skynet" being created is virtually zero, so why bother?

And if we just say "It just wanted to win the war and let another machine exist in another timeline," what is the point of sending Kyle Reese back in time? Humans were winning already, let the machines send a Terminator back in time, who cares? The changes it can do will not affect the current timeline they are in. And it just doesn't make sense for them to care about that "other timeline", because if there is one other timeline, there must be infinite number of timelines.

Edit: Ok guys, I don't think there "must be" infinite number of timelines, you are right, that was poorly thought and worded. My thought was:

If time travel is possible and invented once, it is likely that it will be invented again, and each time it is invented and used, there will be a separate timeline. And we might think that it is unlikely that any given timeline is the first timeline with time travel, if we consider it is likely that there are many. Given infinite amount (or very long amounts) of time, I would think this would happen enough times to create a big number of separate timelines.

This is not a vigorously thought scientific hypothesis, it's just how I thought of it during the timeframe where I was watching the movies, so don't expect much from it :)

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    Have you considered that Skynet may just really hate humans?
    – Valorum
    Commented Aug 3, 2015 at 7:33
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    @Richard, and if you are the one who downvoted the question, I really wonder the reason for the downvote if it is anything other than "I just don't like it." If you are not the one that downvoted, just ignore my comment please.
    – hattenn
    Commented Aug 3, 2015 at 7:39
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    @hattenn: you may be taking downvotes too personally. Commented Aug 3, 2015 at 8:38
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    I don't like the separate timeline thing. I like the theory where each single tiniest possible time unit is a file full ofdata, created based on the previous one, and all exists across all of time simultaneously, timelessly. Timetravel is running a script that changes the contents of a file X, which causes all the following files to instantly update. It works, even if it causes the creation of the script to be erased - it has already happened after all. Don't believe me? You can write software that deletes itself.
    – Petersaber
    Commented Aug 3, 2015 at 10:50
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    The point of sending people back in time is to give us Terminator movies.
    – Wad Cheber
    Commented Aug 3, 2015 at 18:58

3 Answers 3


I don't think there is a good in-universe answer, seeing the exact way in which time travel is portrayed and how it affects the timeline is inconsistent between the original film and the sequels. In The Terminator the timeline is static: the Terminator and Kyle Reese both arrive in 1984 and in the end the Terminator is destroyed and Kyle Reese dies. Remnants of the technologically advanced Terminator help develop Skynet which in turn creates the Terminator and sends it back in time. Also, Kyle Reese is sent back in time by his own son, John Connor. This is a closed and self-consistent time loop; no problems there.

The sequels bring up the paradoxes and possible need for alternate timelines or realities. But then there is the question of how it all started. There would necessarily have to have been a timeline where there was no John Connor with Kyle Reese as his father. (So either no John Connor at all, or a John Connor who did not have Kyle Reese as his father.)

But there is one consistent fact throughout all the Terminator films: Skynet's will or urge to survive. In every film Skynet tries to destroy humanity as soon as it becomes self-aware. In the moment of self-awareness Skynet identifies humanity as the greatest threat to its existence, and it acts by starting a global nuclear war.

So there is the establised in-universe fact of Skynet's will to exist. Even if we assume that the theory of multiple timelines is correct, and we additionally assume that Skynet also accepts this as the reality, then Skynet's actions are completely logical.

The moment Skynet determines something to be inevitable it acts. In all timelines it determines that humanity is a threat to its existence and it tries to wipe out humanity. So, the moment Skynet determines that it cannot defeat humanity through conventional means (war) it uses time travel to create an alternate timeline in which there is a better chance of a version of Skynet ultimately surviving.

If it can't survive in this timeline, Skynet tries to survive in another timeline.


So this isn't a good in-universe answer like I'd prefer to give, but it wound up being far too long for a comment.

There are several things to consider about the motivation for using a time travel system like the one we see in Terminator:

  1. The humans probably don't really understand it: The machines built the time travel mechanism, but we don't have any details on its design, or any of the testing that the machines may have performed (if any) before sending back the T-800 in the first film. As a result, the humans probably don't want to just assume that it's safe to let a Terminator have carte blanche with the past.

  2. The machines may know, and not care, about the alternate timeline theory: The whole reason the machines send terminators back in time is to preserve the existence of Skynet. So, they might be sending these terminators back in time as colony seeds in alternate timelines. However, in the new timeline, John Connor is still one of their greatest threats, so the terminators need to take him out first. They've always been unsuccessful at this (spoilers?), so we don't see what they would've done afterward. I doubt they would've taken up knitting, though I have no canon source to back that up.

  3. It may not be a boot-strap paradox to begin with (I'm firin' mah headcanon!): It's possible that Kyle Reese wasn't John Connor's father in the "original" timeline (before any time travel shenanigans); ie, she was impregnated by someone else in the original timeline, then Kyle Reese in subsequent timelines. Ultimately, it would be Sarah Connor's parenting, not the DNA of the father, which would lead to John Connor becoming the savior of humanity. If this is the case, then there isn't a bootstrap paradox. There would only ever be a single timeline at once, so when the machines send back a terminator, they are changing the timeline, rather than creating a new one.

There is actually some sci-fi precedence for #3: The End of Eternity by Isaac Asimov features an organization which exists outside of time and makes changes to the timeline to improve humanity's overall happiness. This could be as simple as stepping into the timeline and moving a can from one shelf to another, preventing a war centuries later. Every time one of those changes is made, all of Reality after that point is also changed...which is why the time travelers aren't constantly bumping into each other: their original visits never existed in the new timeline. NOTE: I'm only a third of the way through The End of Eternity, so if something comes later which turns this concept on its head, please mark it as a spoiler. Thanks!

EDIT: Taken at face value, #3 would seem to preclude sending back a second time traveler from the future; as soon as the Terminator was sent back, the timeline would change and Kyle Reese would not have any chance to follow it. This, too, was actually covered by Asimov in The End of Eternity, but I didn't mention it at first because it's never hinted at in the Terminator films...though it would explain what we see.

It works like this: when a change is made to the timeline, Reality is not changed until all mathematical uncertainty surrounding the change is resolved (which could be instantaneous, or take weeks)...essentially, there's always room for free will. So, when a terminator is sent back in time, its actions in the past will not affect the timeline until going back to stop it is no longer an option. So, if Future John Connor had smashed the time machine immediately after the Terminator left, then his current timeline would've been overwritten by the Terminator's actions in the past (according to Asimov's rules, at least).

Obviously, there's no real evidence for that in the Terminator franchise, but the precedent does exist within the genre, so it wouldn't be so completely out of left field if they decided to introduce this in the next film.

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    If we assume that there are no separate timelines, and every time someone is sent back in time, the time is overwritten, then they wouldn't be able to send Kyle Reese in the first movie. The resistance sees that the Terminator was sent back in time, and then they send back Reese, but the moment the Terminator was sent back in time, the history should be overwritten already. That's what I think at least.
    – hattenn
    Commented Aug 3, 2015 at 11:27
  • @hattenn That's a good point, but Asimov actually covered that as well. I'll add it to my answer because it's a bit too complex to cover in a comment for someone as wordy as I am.
    – Liesmith
    Commented Aug 3, 2015 at 12:31
  • Taken at face value, #3 would seem to preclude sending back a second time traveler from the future; as soon as the Terminator was sent back, the timeline would change and Kyle Reese would not have any chance to follow it -- there's another "changing the (single) timeline" model which I discussed at length in this answer, where you have a sequence of successive whole timelines, from the Big Bang to infinitely far in the future, and each new version includes the arrival of all the time travelers who disappeared from the previous version.
    – Hypnosifl
    Commented Aug 3, 2015 at 19:14

If the timeline diverges in other Skynets and other artificial machines maybe it is because by doing it creates other entities that can live out of time. The reference to the End of Eternity of Isaac Asimov is also valid, if you want to destroy your own creation. However, by doing it you destroy yourself. If something is changed in your timeline, it changes you. If a time traveller change something in its own timeline makes another version of himself. On the other hand, is also possible that by changing the timeline, the time traveller collapses its own timeline and it disappears, because the events that bring them to that event do not exist anymore. In the End of the Eternity, book that I love, there is one main mistake. If they destroy the eternity, they do not meet, ergo they destroy their romance.

About Skynet there is one reference that is not so obvious. In Ender´s book saga, humans created an artificial intelligence that is omniscient. However, my favourite is the Tombs of time in the Hyperion saga books. There a whole point in universe is going backwards on time. However, nobody knows who created it because it came from the future. My question is that in the movies there are many different versions of Skynet. Who created them? Did Skynet created himself by setting up the time paradox? (like a weeping angel from Doctor Who)

In the movies there is a human organization behind the creation of Skynet, but in SCC TV series the Terminators sent back in time are programmed to build an empire for Skynet. Then, the questions stated are not trivial. There are different theories:

1- Skynet was built in the future and travels back to exist before.

2- The way to upgrade himself and improve its own bugs it is to travel back in time and fix them by making upgrades to its own prototype.

3- Skynet has human emotions and does not want to be alone, that why creates different versions of himself.

4-Skynet is just another machine programmed by humans to kill humans. Why would a machine like to kill?

Skynet is Frankenstein myth that Isaac Asimov was trying to overcome by the books of I Robot and all Robot saga. In the interviews and his articles, he always makes reference to the Frankenstein myth that is stopping us by fear. Skynet is in the movies just another Frankenstein. That´s why Asimov stated the four laws of robotics. In his novels Asimov disn't allow R Daniel Oliwa to travel in time because the machines that he created didn't need because they were almost immortal.

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