Not a How To Time Travel

This post sort of follows this, this, and this. I don’t have many impractical suggestions of how to time travel. Let me explain.

Time travel is either easy or impossible. It is easy because essentially time is just another dimension of space-time and travel in the other three dimensions is easy and we are already all travelling in time (just in one direction and locally at the same rate). On the other hand, time travel appears to imply paradoxes. Paradoxes of causality worry me less than issues such as conservation of energy/matter.

Causality worries me less because I suspect cause and effect isn’t everything we might think it is. However, if I disappear from one time period and reappear in the next, then my new time period has more matter in it than it did before and worse, that matter will hang around going forward into the future. Perhaps time travel requires some physical exchange of matter between time periods? If so, then what in the universe is keeping track?

A different issue with time travel is the speed of light. Even approaching (but staying within) the speed of light has some weird temporal consequences. Actual time travel would provide ways of in-effect travelling faster than light and likewise FTL travel also implies a degree of time travel. If the speed of light is a hard unbreakable rule of the universe then it follows that time travel is impossible also.

One method of time travel escapes most of these issues: perception. In Kurt Vonnegut’s Slaughter House 5, Billy Pilgrim becomes unstuck in time due to the allied bombing of Dresden in World War 2. However, the time travel here is how he perceives events. Billy’s body isn’t popping in and out of time periods, instead, he is experiencing his life out of sequential order. This kind of mental time travel avoids issues of causality on the grounds that everything has already happened. Events are what they are but perhaps the order in which we experience them is an illusion of the human mind.

Unfortunately for stories, there aren’t many writers who can make a narrative work where no decisions can possibly matter. Which takes me to a topic for another time: how should time travel stories work?

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10 responses to “Not a How To Time Travel”

  1. @Camestros Felapton: Wait, why hasn’t anyone written time travel where conservation of matter/energy is a thing and has to be maintained between timeframes?! WRITE THAT BOOK! 😉 One could do some fun things, depending on how the rules worked.


    • Mass conservation is a thing in a few stories – William Tenn’s The Brooklyn Project and Heinlein’s Door into Summer deal with it in the same odd way, and Flint’s 1632 novels involve a mass for mass swap between eras, as well.

      Liked by 2 people

    • I’m sure somebody must have. The kinetic energy issue would be something else. Mind you it could be a sort of energy source…yes, you couldn’t gain energy but maybe you could swap energy for some form that was more useful.

      Maybe a big battleship that has temporal howitzer – it fires a ~90-100 kilo slug of rock at high speed by sending crew members into the past.


  2. A method of time travel that few seem to consider is just running time backwards. Probably because it’s extremely boring – you just end up starting things over again in the same place with no particular knowledge about the future or the outcome of your choices. However, given that the outcome of some events is essentially random, perhaps if you rewound time and rolled the dice again you might end up with a different present. A ‘keep trying until you end up in a neighbourhood of the multiverse you like’ situation if you will (actually I think there was a Simpsons Little Treehouse of Horrors episode that did this, but not explicitly with time travel).


    • It was a time travel episode (at least the one I’m remembering) – it was a parody of A Sound of Thunder, in which Homer accidentally turns the toaster into a time machine, and keeps altering the present.

      Liked by 2 people

  3. The mass discrepancy resulting from time travel causes pretty well the whole universe to begin to unravel in Bob Shaw’s The Two-Timers. But this proves to be curable.


  4. There’s Larry Niven’s “Svetz” stories, in which time travel is impossible (but they don’t know it) as it sends you into fictitious or legendary worlds. Thus an attempt to retrieve a horse gets a unicorn, etc.


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