Next Week's Talk: Time Travel

Anyway, the idea of these Discussion Meetings is for us all to discuss, not for me to pontificate (good excuse, eh?). So I'll start off by making a few general and controversial statements. It's then up to you to disagree with me. I also hope you'll have plenty of stories to retell, because (and here comes controversial statement number 1) Time Travel stories, probably more than those of any other subgenre, are all about plot. Characterization, literary merit (whatever that means - Jo will tell us later in the term!), and extrapolation of technology or society, are all secondary to the 4-dimensional twists of the plot. Maybe this explains why many of the best Time Travel stories are short stories.

Controversial statement number 2: a time travel story isn't really a time travel store unless it involves travel into the past. We all travel forward in time at a rate of 24 hours every day, and there's nothing really special about speeding up that rate. Whenever you fall asleep, perhaps. You can achieve a longer leap forward with cryonic suspension, such as in the film, Forever Young, where Mel Gibson, frozen in 1939, is accidentally resuscitated in 1992 and has to learn about answerphones. As a decent chap, as of course everyone was in 1939, Jamie Lee Curtis falls for him, and it all gets very soppy, so I'll leave it there.

If you want to get really ambitious, you can use the time dilation effect, either by travelling close to the speed of light, or passing through an intense gravitational field, such as close to a black hole. Poul Anderson's Tau Zero takes this to extremes: after an accident, a spaceship is forced to accelerate continuously, allowing them to outlive the Big Crunch and another Big Bang.

But none of these are proper Time Travel stories. Jumping into the future offers a convenient mechanism for the protagonist to see what that future might be like (and that can be very interesting in itself), but gives no scope for doing anything unusual with Time, and critically, has no possibility for paradox. Embarrassingly, my stipulation that a Time Travel story requires travel into the past, disqualifies the seminal and probably most famous "Time Travel" story of all. In H.G. Wells' The Time Machine, the Traveller does eventually go back in time when he returns to the present, but this is a postscript to the main story, which involves Wells' ideas on the evolution of humanity and human society.

Since we're always trying to encourage people to write for Sfinx, I'll now tell you how to write a Time Travel story.

You need a mechanism to travel back in time

1. All you need to do is travel faster than the speed of light. Then you arrange for for your superluminal device to transport you between a rapidly-moving spaceship and the earth, and bob's your uncle, you'll return from your jaunt before you set out. Tachyon is a good buzzword to use at this point (all it means is a superluminal particle).
2. If you think your reader too smart for that one, you can always arrange to fall into a black hole. Since no one really knows what happens then, particularly if there's a singularity involved, you can have the laws of physics break down in any way you like. The problem, of course, is that you'd probably be converted to neutronium by the tidal forces on your way in, unless you found a really big black hole to play with. I'm sure I left one around here somewhere.
3. This is all ignoring the gravitational physicists who keep coming out with papers suggesting ways you really could travel round a closed causal spacetime path (if I got that right, that's General Relativity-speak for travelling back in time). If I were you, I'd give this method a miss. The engineering requirements are a little extreme such as structures weighing more than the rest of the Universe.
4. If all else fails, you can always use the mad scientist or magician dabbling in forces that no mere mortal (protagonist included) can understand. The Anubis Gates by Tim Powers is a good example of this. Excellent book too.

You need a theory of time

1. Just can't be done. You seek out your mother, but she's in hiding. You murder the little girl, and as you mount the gallows you see her identical twin watching you. Just as you cock the pistol, a meteorite strikes you down. Whatever you do, History (with a capital H) conspires against you.
2. A variation on this theme is The end of the Universe. A paradox would cause the universe to be destroyed. This thesis is carefully and thoughtfully examined in the Back to the Future films.
3. Fixed past. Perhaps one can travel backwards in time, but can't change anything at all. One is entirely an observer, unable to move a blade of grass (eg. a novel by Brian Aldiss - I think it was An Age).
4. Alternate worlds. When you kill your mother, a parallel world where you never lived is created (or revealed). Don't get me started on Alternate worlds, or I'll start talking about Quantum Mechanics and how it proves that I am immortal.
5. The Time Police prevent you. Silly idea.
6. Although not much use for Time Travel stories, Larry Niven has made an interesting argument. Suppose that Time Travel were possible, with a single, malleable, timeline. This is an inherently unstable situation. As long as people go back in time and change the past, they will inevitably affect themselves, even if only slightly. These small changes are cumulative - eventually a timeline will come about where that person never invented the time machine, or didn't use it. This is the only stable state: where no one ever used a time machine. Since systems tend to evolve towards a stable state, this has probably happened. Ie. Time Travel is possible, but never practiced.

The Plot

Could one fix up all one's past misfortunes and lead the perfect life? Oddly, this always seems to lead to one being the instrument of one's own misfortune.

How would you recognise other Time Travellers without alerting everyone else? Ken Grimwood's fantasy, Replay, is an entertaining example.

I'll gladly tell you more about any of the stories I've mentioned (and could bore you with many more), but it's your turn now.