The really annoying thing about time travel stories

I’ve always wanted to invent a time machine so I could whip back in time to stop Hitler before he did anything evil. Of course there are a couple of problems. First is I’d be joining the back of a LOOONG queue. The other is that our friend Albert Einstein tells us it’s impossible.

But even if a time machine could be built, nobody’s really figured out what it entails. Here’s the deal.

The Horsehead nebula, Barnard 33, as seen by Hubble. Wonderful, wonderful imagery.
The Horsehead nebula, Barnard 33, as seen by Hubble. Wonderful, wonderful imagery.

Science fiction is rife with stories about time travel, variously either as social commentary, H. G. Wells style, or as cautionary tales – witness Ray Bradbury’s wonderful A Sound of Thunder. Invent a time machine, go back in time and change the past – and you’d better watch out.

Of course, if things change so you don’t exist, then you can’t have invented the time machine. Which means you didn’t go back in time. Therefore you do exist, so you did invent the time machine and… Yah.

Or there’s Harry Harrison’s hilarious Technicolour Time Machine, about a movie maker who uses a time machine to cut production costs on his period drama by going back to the actual period. What I’m getting at is that there’s a gaping great hole in all of this. And it’s an obvious one.

Suppose you COULD time travel. Suppose you’d built a machine to do it. You decide to whip back twelve hours. And promptly choke to death in the vacuum of deep space.

Nikolai Tesla with some of his gear in action. Public domain, from http://www.sciencebuzz.org/ blog/monument-nearly-forgotten-genius-sought
OK, so it’s not a time machine, but this is what one SHOULD look like. Nikolai Tesla, being spectacular with AC electricity (he’s reading a book, centre left). Public domain, from http://www.sciencebuzz.org/ blog/monument-nearly-forgotten-genius-sought

What gives? The problem is that everything in space is moving. Earth is rotating. Earth also moves around the Sun, which itself is orbiting the galaxy, which itself is moving as part of the Local Group, and so forth. We don’t notice or even think about it because we’re moving with the Earth. If we take Earth as our reference point, it’s fixed relative to us. And that leads us to imagine that  time machines are NOT moving through space – Wells, in particular, was quite explicit that his time machine was fixed and time moved around it.

But actually, a time machine that did this – that stayed ‘still’ relative to Earth would have to move through space, because Earth is moving.

Let’s reverse that for a moment. What say your time machine doesn’t move in space at all. You move back and forth through time, but your absolute spatial position is fixed. Not relative to Earth, but relative to the universe.

You leave your lab and leap back 12 hours. Earth won’t be there – it won’t have arrived. Leap forward 12 hours – same thing, only Earth’s moved away. If you’ve only moved a few seconds, you might find yourself plunging from a great height (aaaargh!). Or buried deep in the Earth (choke).

So for a compelling time-machine story you need to have a machine that not only travels anywhere in time, but also anywhere in space. And, of course, any relative dimensions associated with both. That’s right. A machine that travels anywhere through time and relative dimensions in space.

Heeeeeey, wait a minute

Copyright © Matthew Wright 2014

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19 thoughts on “The really annoying thing about time travel stories

  1. ‘A machine that travels anywhere through time and relative dimensions in space. Heeeeeey, wait a minute…’

    Y’see, someone’s got there before you! How did they manage that?

    Of course, the whole space and time thing might just be a manifestation of energy in other dimensions, in which case nothing is actually moving anywhere, it just looks that way to our three dimensional eyes and measuring devices.

    Chris

    1. That’s definitely possible – there’s some exciting development along those very lines at the moment – suggesting quantum superposition may actually be something a lot more mundane, reflecting interactions between multiple universes.

  2. I would like to find a good time travel story, but I feel like most of them would be kind of cheesy . . . a lot like syfy movies (which some people love, I’m not judging).

    1. Hah heh! Excellent! And of course then there’s also the problem of having a one-shot time machine that takes you back to do the deed, but being a bit rusty over exactly WHEN Hitler started and ending up arriving in Berlin around mid-afternoon on 30 April 1945…

  3. You got there before I did, Matthew. I was thinking that, naturally, you need the time vortex to fix that problem… And yes, poor Rory had to put Hitler in a cupboard, which sort of did his head in.

    1. It’s a while since I saw the episode. Quite cool given that the ‘go back in time to kill Hitler’ is probably the No. 1 time-travel trope – inevitably, The Doctor and crew had to have fun with that one!

  4. Okay, so you are able to go back and assassinate Hitler in the early 30s and (best case scenario) eliminate the entire Nazi movement. Uh oh. There’s a great chance you’ll no longer exist. Suddenly all those men who went to war—regardless of whether they lived or died—don’t go anywhere. Economies are altered. Virtually everyone is changed in some small way. Those whose paths aren’t changed collide with those whose paths are changed, thus changing all paths eventually. Timing changes and suddenly that same egg and sperm don’t meet. Goodbye.

    1. That is indeed the dilemna, though I suspect odds are on that if the entire Nazi heirarchy were knocked off in 1933, others would have arisen to take their place and probably done something similar. As Lord Vansittart pointed out in 1944, the real issue the west faced in dealing with Germany wasn’t specifically the Nazis, it was the ‘Reich’ mentality that went back 70 years or so, of which the Nazis were the latest symptom. An interesting thought which generates a possible ‘alternative history’ scenario that hasn’t been much explored – a Second World War, still driven by a ‘dark Germany’, but minus the special evil of the Nazis…

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