Towards a Taxonomy of Time Travel

By Brenda Clough

clock I am writing a time travel novel.  A very complicated subject, with a considerable literary history!  In an effort to organize my unlucky characters’ thinking on it, I began to draft a Taxonomy, illustrated by examples that with luck we will all  know.  Is some major category missing? Can you name other movie or book examples?  Let me know!

1. Time travel can change the past

A. Changes appear instantly; old time line is immediately overwritten

(A1) BackTo The Future – Marty feels changes physically (disappearing hand) as the possibility of his non-existence becomes more likely, but his memories are never altered in any way. We don’t get to see what would have happened if he HAD disappeared. Would his actions in keeping his parents from conceiving him have been undone, creating a paradox or would this new timeline retain his (residual-alt-timeline) actions up to his disappearance?

A2) Looper – Time traveler feels the change physically AND mentally as, or right after it happens, but the current timeline retains his (residual-alt-timeline) actions up to that point. Characters around the time traveler see AND remember the changes to the traveler. (Someone could have witnessed Old Seth becoming disfigured just as we did.)  For a full-of-spoilers but highly detailed analysis of how the time travel works in this movie, go here. You see why writing a time travel novel is turning my hair white?

B. Changes don’t appear until you get back to the/your present (A Sound of Thunder by Ray Bradbury, in which an accidental change in the past makes the present a world of intelligent reptiles).  Old time line is replaced with new.

B1) The time traveler loses his old memories and only remembers the new altered reality. (As I recall this is how it worked in Time After Time by Jack Finney.)

B2) New memories coexisting with old memories. I think this is what The Butterfly Effect movie was like, right?

C. Changes appear but retain a residual effect (you can kill your grandfather, then disappear, but grandpa remains dead)

C1) There will be a duplicate of the time traveler if time traveler tries to go back to the future because it won’t be the same future reality.

C2) When returning to the future, duplicate disappears and time traveler is the only version but the future is still foreign to the traveler. (Timecop?)

C3) It is branching; every change you make creates a new different future.  In theory therefore you could go and shop around all the different futures, looking for the one you like best. (There have been novels with thise theme, can’t recall one.)

2. Time Travel cannot change the past

A. Purely tourism; all you can take is photos.  C.S. Lewis describes a story which he did not name, in which when the time traveler goes back raindrops penetrate like bullets, since nothing, not even the path of a raindrop, can be altered in the past.
B. Minor souvenirs can be taken back.

3. Time travel sometimes changes the past

A. Only big alterations have an impact (shooting Hitler has effect, shooting his janitor, no)

B. Even tiny alterations have an impact (Butterfly effect) and so you must be very careful what you do to the past, lest you destroy your present. (This is the angle I used in Revise The World.)

4. Time travel is an endless and intrinsic loop where effects create the causes that leads to the effects.

A) Cause – effect cycle has no origin.

A1) Harry Potter and the Prizoner of Azkhaban. There are several delicious loopy moments in this but I’ll pick one. Harry fights the dementors but is overcome by their numbers, Harry thinks his father comes to fights them off. A few hours later Harry travels back in time to arrive at the same moment when he see himself fighting the dementors in vein. Waits for his father to arrive and help the past Harry than realises it was himself that helped fight them off. An intrinsic loop where effect creates the cause creating the same effect.

B) Time travel object appear to have no origin.

B1) ABC’s Lost series. The Compass paradox. Richard gives John a compass in the 2000s. John travels back in time to 1950s. Gives Richard the compass. Richard waits half a century, giving the compass back to john. Compass has no origin of production but is ageing with every loop.

4. Time travel is one-way

A) Psychic time travel one-way.  A good example would be Replay by Ken Grimwood.

B) Physical time travel one-way.  I can’t name a specific work, somebody help me here.  But I recall generally works in which unlucky time travelers are stranded in the far past, cooking trilobites over a campfire.  And, of course! Titus Oates makes a one-way trip to the futre in Revise.




Towards a Taxonomy of Time Travel — 13 Comments

  1. Time Machines Repaired While-U-Wait, a near-future novel by Australian author K. A. Bedford (published by Edge in Canada, 2008) has lots of minor and major problems caused by people using hard-SF time machines to travel to the past/s and the future/s – lots of branching time-lines, with the central character Al ‘Spider’ Webb on occasions seeing himself murdered, go back/forwards to try and save himself and others, and meeting an older, sadder, wiser version of himself. Spider is a time machine repair technician, and very cynical about the use of time machines. there’s a government department in charge of regulating time travel, with a special section dedicated to fixing up temporal messes.

  2. I think the Company novels by Kage Baker fall somewhere between 3A and 3B with a dash of 4. They try to make the changes unobtrusive by affecting only the little things/people and they can go backwards, but forward only up to their starting point. It’s not that the big things can’t be changed, but they might be discovered and then would lose their cash cow which leads me to believe this world’s logic system contains 1B2 as well, otherwise, how would they be discovered?

  3. Stephen King’s 11/22/63 is an interesting study in time-travel effects, because the time travel is linked to a specific location, and sometimes big things change (the protagonist intends them to) and sometimes they don’t. Being King, he throws in a fascinating amount of history about the Kennedy assassination and Oswald, the man. But what I most enjoyed (I listened to this as an audiobook) was the loopiness of his set up. There was ample opportunity to think about what should be changed, and to go back and fine tune — and not in any predictable way, either. My husband and I enjoyed talking about the things we liked (and didn’t) for quite a while after listening to the book.

    • Thanks for bringing this up. The “rules” or taxonomy aren’t evident until the end, so I wasn’t quite sure how to mention it myself. But yes, very loopy, and the idea that you can keep trying until you get it right is both liberating and exhausting.

  4. Well, since I wrote this post I have finished writing the novel, which is titled THE RIVER TWICE for reasons that you can readily deduce. It is clearly a 1C3. I feel so much more organized now.

  5. Are Poul Anderson’s Time Patrol stories C’s? In that, if you go back in time and kill your grandfather, you still exist, but without a parent.

  6. An example of physical time travel one-way is Julian May’s ‘Saga of the Exiles’ book quartet where a time portal in Europe takes people six million years back to the past.

    A lot of misfits go through and the govt is happy because a) It gets rid of the malcontents and b) The timeline hasn’t been affected, so no worries, right?

  7. While conceptualizing a time travel tae myself, I decided to go with the universe simply not caring about causality. The laws of physics apply the moment objects interact. There is no mechanism in nature that checks why something is there so really physics doesn’t care wether there is a reason you exist or not and where you come from. All it cares about is: You’re there. Any changes in your past won’t affect you because there is nothing in nature that keeps check for consistency.

  8. I’ve reviewed 189 time travel books over at my blog, mostly middle grade and young adult– here’s the list

    I’ve never tried to wrap my head too much around the various paradoxes and causalities involved, because it makes my head hurt! But I am rather interested in the authorial intent–I mentally divide them into catagories depending on the reason for the time travel–character growth through time travel, chance to write historical fiction from a different slant, didactic time travel, and simply thought experiments for the plotting fun of it.

  9. The philosopher David Lewis argued that a time traveller could do nothing that would lead to a paradox. The very fact of this person traveling in time entails that whatever they did, they would fail to kill their own grandfather. I think in Terry Pratchett’s the Last Continent the Archchancellor has this attitude.
    And yet, David Lewis also believes in the universe of infinite possible worlds.
    Another endless loop story is Heinlein’s By His Bootstraps. Many philosophers think that endless loops are actually the most theoretically consistent types of timetravel.

  10. The Door Into Summer by Heinlein has the protagonist wondering if the time-machine guy sent more people back than he admits to — and if Leonardo was in fact a man of the future trying to explain through drawings possibilities for the future. But he had no infrastructure, so Leonardo’s trip was one-way. the protagonist, on the other hand, can use cryo-sleep to figure out a way to return for revenge of a type, and still get back to his own time.

    One of my favorite time travel stories, sad but lovely, is “Ripples in the Dirac Sea” where time travel can only happen in the span of your lifetime — but you can go anywhere on Earth in that span. The machine can go multiple ways, but only within your lifetime — and it’s only a time machine, so it can gain you time but not space, which becomes critically important.

    Brave woman, weaving together a time travel story!

  11. Robert Heinlein’s “–All You Zombies–” is a Type 4 story — I think. I really need to re-read it, and chart out all the transitions. It’s about a temporal recruiter, so he goes back and forth a lot! O. Henry’s stories are straightforward compared to the twists in this one.