It seems anomalous to pick apart a time travel story for not making sense. Time travel itself doesn’t make sense. And all time travel stories have holes somewhere (my own included).
However, there’s a time travel rule at the heart of the Back to the Future trilogy and the Bruce Willis movie Looper (occasionally rearing its befuddling head in other stories as well) that has always bugged me.
It’s the rule that says that when a time traveller goes back in time and changes the past, those changes affect the time traveller.
The rule doesn’t make sense. It didn’t make sense in Back to the Future or Looper. It didn’t make sense when the rule’s existence was hinted at in Travellers or Star Trek Voyager either (more on these later).
Now, don’t get me wrong. If you want to use this rule in your writing, go right ahead. The fact that other time travel writers have used it has given me something to talk about. And like I say, you can always find nonsenses in a time travel story. That’s part of the fun. And even though Back to the Future uses this rule, that doesn’t stop it from being my favourite movie trilogy of all time.
The Grandfather Paradox in action
The rule that changing the past affects the time traveller who’s changed it is a manifestation of the Grandfather Paradox. The Grandfather Paradox is described as: if you go back in time and kill your own grandfather before your mother or father is conceived, you erase your own existence. And if you erase your own existence, you can’t go back in time and make those changes in the first place. This in turn means your grandfather would still be alive and you’d still be born after all. Hence, a paradox. It’s self-contradictory, each possibility negating itself.
So, when Marty McFly starts disappearing on stage in Back to the Future, we’re seeing the Grandfather Paradox in action (or at least the first part of it—it’s a bit difficult to do the actual paradox portion of it and still have a story). It’s one of the more literal interpretations of the Grandfather Paradox, the whole film being predicated on the idea that if George McFly and Lorraine Baines don’t hook up, time-travelling son Marty will vanish—because he was never born.
Why disappearing Marty doesn’t work
There’s nothing wrong with these crucial stakes at the centre of Back to the Future: If George and Lorraine don’t get together, the McFly siblings are never born and the future we see at the beginning of the movie gets erased. What doesn’t make sense is that these alterations would affect the version of Marty that has already time-travelled.
If you want to follow that rule, Marty should have disappeared the moment he got run over by his grandfather’s car in 1955. That was the moment he changed the past and Lorraine started falling for him instead of George. At that point Marty’s future was already erased, which was why he and Doc had to get things back on track. So why didn’t he disappear straight away?
The same goes for Old Biff in Back to the Future Part II. He travels back to 1955 and gives his younger self a sports almanac that enables him to get rich from gambling. From that moment on Old Biff has completely rewritten his own history and should disappear immediately. But he doesn’t disappear until later, after he’s made a further trip in the DeLorean. The disappearance itself only happens in a deleted scene, although we do see him struggling and in pain pre-vanishing, much like Marty on stage in the first film.*
And don’t even get me started on that photograph. Doc and Marty realise that Marty’s future has been changed when they see the gradual vanishing of Marty’s siblings in a photograph of the three of them from the future. Why is it happening gradually? If you want to follow this rule, the moment Marty gets run over, all three people in that photo should disappear instantly.
To be fair, writer Bob Gale has acknowledged the lack of logic as to why the McFly siblings disappear gradually instead of all at once. He’s also acknowledged the even more obvious problem of why the picture itself didn’t disappear—since it almost certainly wouldn’t have been taken if the three people in it didn’t exist!
Why Old Seth losing body parts doesn’t work
In Looper, Old Seth comes back in time and causes changes that lead his younger self to get captured by Abe. Abe’s men cut an address into Young Seth’s arm, then start severing his body parts.
These effects start appearing on Old Seth. The address appears as a scar on his arm. Then, as he’s on his way to the address, his fingers start disappearing, followed by his nose, legs and arms.
While all this makes for an exciting and disturbing scene, logically it doesn’t work. Nor does Old Joe vanishing at the end of the film after Young Joe commits suicide. And it doesn’t work for the same reasons as disappearing Marty and Biff in Back to the Future.
Why? Well, let’s start with Seth. The moment Young Seth is kidnapped, his life is entirely rewritten. This should, based on the film’s own rules, erase Old Seth. But it doesn’t. Old Seth doesn’t disappear. He keeps on heading for the address, just sans the body parts that are currently being lopped off his younger self.
We have the same problem with Old Joe. The moment he comes back in time and starts interacting with his younger self, he’s completely changed his own future. The writers acknowledge this by having Old Joe start to manifest new memories of Young Joe’s actions, but that’s not enough. Old Joe only disappears when Young Joe commits suicide, but the Old Joe that has come back in time had already had his life rewritten—why would Young Joe’s death be the thing that suddenly makes all the difference? He should have disappeared the moment his timeline changed.
Why the rule itself doesn’t work
The fact that Old Joe, Old Seth, Future Marty and Future Biff don’t all disappear the moment their younger selves’ lives are rewritten is indicative of a fundamental problem with the rule itself.
The disappearing rule treats the time traveller and the time traveller’s younger self as the same person. Therein lies the problem. As soon as Future You changes the timeline of Past You, Past You becomes a different You. (Got that? Whose heads are hurting?)
So, Young Seth becomes a different Seth the moment he is kidnapped and starts having his limbs removed. This Seth will no longer grow to become the Old Seth that would’ve travelled back in time.
And yet Looper treats both Seths as if they are still the same man, hence why we see the effects of what they’re doing to Young Seth happening to Old Seth. This is a nonsense. Old Seth is now a man from an alternate timeline, a timeline that no longer exists, a timeline in which he was not a paraplegic. Old Seth and Young Seth are now two totally different people with totally different lives, and so nothing that happens to Young Seth should have any effect on Old Seth.
The film also treats both Joes as the same man. But the moment Old Joe escapes from Young Joe, the course of Young Joe’s life changes. Since Old Joe doesn’t immediately disappear, it must mean that Old Joe is now a different, separate entity from his younger self, originating from an alternate timeline in which he moved to Shanghai, became a hitman and married his wife. A timeline that no longer exists.
Similarly, the changes that Marty and Doc make to the timeline in 1955 should mean that the yet-to-be-conceived Marty is a new entity, separate from his original time-travelling 1985 self. In fact, Marty and Doc’s timeline changes actually cause a very different version of the McFly family to emerge. George is no longer a wimp and a loser and Lorraine is no longer overweight and an alcoholic. Both are happy, fit and successful.
But this means their children, including Marty, would’ve turned out differently too. We actually have two Marty McFlys now. We have the original, from a timeline that now no longer exists, in which he was born to wimp George and depressed Lorraine. And then we have the new version, born to a brave George and a happier Lorraine. (We are given the highly unlikely scenario that the new version, who Original Marty sees briefly when he returns to the future, still ends up in that car park with Doc and the Libyans in the exact same fashion as before—but that’s a problem for another day.) Following the disappearing rule, the existence of New Marty means that Old Marty has been erased and should disappear.
But he doesn’t. Old Marty persists. Just like Old Joe and Old Seth persist, despite their younger selves’ lives having dramatically changed course.
That means three things.
1. Old Marty, Old Joe and Old Seth are now separate entities from alternate timelines.
2. None of them would be affected by what happens to their younger selves.
3. None of the disappearing makes sense.
Hinting at the disappearing rule
Early in the TV series Travellers, there is an episode in which the travellers manage to prevent the impact of an asteroid, one of the key disasters that would trigger the future apocalypse and, in turn, give rise to the traveller program. The travellers take this to mean that if successful their existences will be erased, and that they should disappear on the spot.
But they’ve already been changing the past and altering the future, and nobody’s disappeared. No traveller over the course of the series just vanishes despite originating from a now deleted timeline. So the characters should’ve realised that they’re now new entities that will persist regardless of what they do. (The fact that they don’t disappear apparently doesn’t lead anyone to guess this; they just think that they haven’t changed the future enough to cause them to disappear.)
Then there’s the anomalous expectations of the Borg Queen in Star Trek Voyager’s Endgame. In that episode, Admiral Janeway comes back in time to bring Voyager home early. The moment she makes contact with her past self, the timeline changes course. And then she comes aboard, furnishing Past Voyager with juicy titbits about the future and taking them back to the Borg nebula—none of which originally happened.
At no point during any of these interactions does Admiral Janeway disappear, start to disappear or behave as though she’s in danger of disappearing. And this is despite the fact that the timeline she’s come from no longer exists. Whether Admiral Janeway is able to help Voyager get home or not, her past self and crew are already on a new path simply by virtue of her being there. (Hence why Captain Janeway makes the very good point that a lot of the grimness the Admiral’s predicting might not happen now.)
The fact that Admiral Janeway doesn’t ever disappear indicates that she must now be a separate and distinct entity from her younger self. That Admiral Janeway and Captain Janeway might go back to Earth or just continue travelling together is a perfectly reasonable possibility as the episode goes along. Same as Original Marty and New Marty existing together in 1985.
And then the Borg Queen goes and ruins it all.
The scene goes like this. Admiral Janeway has just unleashed a deadly and crippling pathogen that’s killing the Borg. The Queen sends a ship in pursuit on Voyager. The Queen says this to Admiral Janeway:
“Captain Janeway is about to die. If she has no future, you will never exist, and nothing you have done here today will happen.”
Frankly she deserved to die just for that comment.
Killing Captain Janeway wasn’t going to cause Admiral Janeway to “never exist”. If doing anything to Captain Janeway was going to have any effect on Admiral Janeway, we would’ve seen it already. In fact, we would’ve seen it the moment the admiral came through the rift.
Yet we didn’t. Unlike Old Joe in Looper, there wasn’t even any suggestion that the admiral had suddenly garnered new memories. Everything presented before the Borg Queen’s comment indicated that Admiral Janeway and Captain Janeway were two different women from two different timelines. And the Borg Queen (or, more accurately, the writers) should’ve known this.
So there you have it folks. This is why the disappearing rule doesn’t work. Or, at least, why it doesn’t work in those particular stories. (Of course, if anyone has any examples of stories where they think it has worked, I’m all ears.)
Meantime, I’m off for a lie down. To quote Abe in Looper, this time travel shit just fries your brain like an egg.
* Of course, the whole sequence of events with Old Biff has an even more fundamental problem. When we see Old Biff struggling and in pain, it’s after he’s back in the normal 2015. But he’s changed the past. The 2015 he went back to should have been the alternate one, after his younger self has become rich and corrupt and taken over Hill Valley. Doc explains this later when Marty suggests returning to 2015 to stop Old Biff from time-travelling: “We can’t! Because if we travel into the future from this point in time, it will be the future of this reality.” Ooops.
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From my first reading of THE TIME MACHINE in 1956, I’ve believed those who travel in time do so because they were meant to and go where sent. No Butterfly Effect, and no alternate timelines except in our daydreams. Free Will and Choice are illusions created by Destiny.
Yes, that is another popular approach to time travel – that you can’t change the past. “Lost” did this. “Whatever happened, happened.”
It’s a strong theme in Audrey Niffenegger’s “The Time Traveler’s Wife”. I must admit I’m quite a strong supporter of the idea!