Writing stories about time travel is one of the most challenging, but also one of the most satisfying undertakings I know. There are so many different models of how time travel might work, based on the many competing physical [...]]]>

“Time is but the stream I go a-fishing in” – David Henry Thoreau

Writing stories about time travel is one of the most challenging, but also one of the most satisfying undertakings I know. There are so many different models of how time travel might work, based on the many competing physical theories of how space and time are structured, that it is a complete smorgasbord for the sci-fi writer. And each different cosmology has its own, fascinating paradoxes and implications.

When I came to write TimeSplash, I had just finished writing another time travel book, Time & Tyde (which is still unpublished, by the way). In that book, I had used a model of time that was strictly in accordance with general relativity. Time was ‘just’ another dimension. If you follow Einstein, time travel is allowed but the Universe is completely predetermined and therefore travelling backwards is merely unravelling the forward travel so nothing could be done in the past that had not already been done. Other major views are that time travel is prohibited by the Universe (Stephen Hawking) or that time travel is allowed but you cannot (for some unknown reason) ever create a paradox (ie it would be impossible ever to shoot your grandmother – Kip Thorne). I chose the Kip Thorne interpretation and had a lot of fun with it (in a dark, psychological thrillery sort of way.)

So I was ready for something very different when it came to TimeSplash. I started as far away from the physics of time travel as I could possibly go (given that physical reality has me on a pretty tight leash most of the time) and asked myself, “What if time was just the way it feels and the way ordinary people like to describe it? What if time flows, like a river, that there really is a timestream, and what if there could be currents and eddies in this stream?” And, if time is a river, where are we on it? Is the present special? Or is it just another point in the stream?

So I made a decision: The forward edge of the Universe’s flow through time is the present, and once the past has been ‘made’ it cannot be undone. This is consistent with some of the more ‘out there’ cosmologies (Cahill and Klinger suggest that the Universe is constantly self-assembling out of chaos, the present is therefore like a wave front moving us through time) so I was quite happy to give it a go and see where it led. And once you start imagining a river – an actual river, broad, deep, calm, inexorable – other analogies suggest themselves. Time travel, for example, might be like lobbing a brick backwards from where we are in the present to an earlier point in the river. If you did this, time travellers might make a splash when they re-enter the stream. After all, the past has been made and the travellers would not belong there. But just keep that analogy going. What happens when you lob a brick into a river? There is a splash, yes, but the river keeps flowing on. It takes away the turbulence, it carries it downstream. Pretty soon, the river is smooth and steady again, as if the anomaly has been straightened out and everything is back the way it was. Time, the past, would be self-repairing. Whatever anomaly or paradox was created, it would be fixed. The original past, the past we know, would be preserved.

By this time in my speculation, I was pretty excited, because I’d seen two great possibilities for a story. Firstly, if the disturbance created by the splash was big enough, it might flow all the way downstream to the present. At that point it would have nowhere else to go, there would be no more chance for it to be corrected and for the stream to heal itself. A big enough splash would affect the present – strangely, perhaps – because what would a splash in time consist of unless it was acausality and space-time distortions? – but also the effect might be dangerous if it were big enough. Secondly, if you can go back in time, create acausal disturbances, and return, it might actually be fun. Acausality, space-time distortions might be pretty trippy things to experience – as long as they were mild enough.

And there was the rub.

What if kids got hold of this technology? What if they used it to lob themselves back in time to experience trippy anomalies? What if they started making bigger splashes, deliberately creating paradoxes, say, so that the turbulence flowed all the way to the present and their friends could also enjoy it? What if a whole party culture evolved around timesplashing, with the heroes of the scene – the ‘bricks’ – creating big splashes so that hundreds or thousands of partying kids could feel the backwash? And then, what if one of those bricks took it too far? What if people started dying, whole towns started being wrecked?

The actual science of time travel in TimeSplash is glossed over. Essentially, the ‘lobbing a brick into a river’ analogy is about all there is to it. A way has been found to hurl material back through time, where it can remain for a period dependent on how far back it has gone. In the normal course of such an event, only small disturbances to to the earlier flow are created, which are wiped out as the flow moves inexorably forward. The material of spacetime is, however, somewhat elastic. It can be disturbed but it will return to its original configuration. Imagine a 4D lattice of points (spacetime events) connected by elastic links which are directional along the line of causality. Pull one of the points backward to meet one of its antecedents and then snip the lines leading out of the antecedent. This is analogous to shooting your own grandmother and creates a paradox because some things which exist no longer have any cause. The more influential a person (or thing for that matter) has been, the more acausality will ensue from going back to halt their progress through time. The elastic mesh metaphor (spacetime as a crystal lattice) explains how the Universe ‘knows’ how influential a particular person or event has been, and why some paradoxical events will lead to much bigger disturbances than others. Disturbing a point in the lattice, or removing forward-pointing links, changes the stresses across the whole network. A reasonable assumption is that this effect would increase exponentially the farther back you go because (generally speaking) forward links will increase exponentially.

A cool idea about time travelling, as the extreme sport focus for a whole, fringe youth culture, is one thing. Having the material for a novel is another. I still needed a story, and I needed to build a world for the story to take place in. Most of all, I needed some cool characters, with complicated relationships and motivations to hang the whole thing on. But I think I’ll leave all that for other posts.