THOUGH YOU WOULDN’T KNOW IT from what I write. I could never write a time travel story, though, because I have too hard a time with the possibility.
In order to accept time travel, one must accept one or the other possible models of time — one as a continuum — without discrete ticks of the cosmic clock. Or of time as a series of discrete, quantum events, with ticks of the cosmic clock analogous in time to a Euclidean point in space — defining a discrete and unique locus with no dimension.
If time is a continuum, you could never land anywhen for certain, because there never is a discrete quantum moment which can be defined as any when, which would require a certain conservation of events. Every branching of events — every time a particle goes one direction rather than another, a new universe is created in which that probability eventuated. Things get too messy and probabilities end up merging when they’re too close to each other, which sort of obviates the quantum nature of things.
The notion of the conservation of events is, to the best of my knowledge, original to me. It means that the probability of any given event or sequence of events is directly proportional to the number of individual beings or objects (in the case of objects, to their mass and in the case of beings to the influence they have on still other beings) affected by the event. And that, with events above a certain moment — probability weighting — the number of subsidiary events which must be altered or prevented grows ever larger, the greater the probability. In other words, it does no good to go back and kill Hitler in order to prevent the Holocaust or World War II — some other figure will rise to take his place. But you may be able to save the life of his loyal Alsatian shepherd dog from death in the bunker in April 1945, if you can find just the right combination of events to tip the odds in her favor — killing any number of historical figures won’t do it.
This combination also works “sideways,” as you may call it — for the creation and meeting of parallel worlds or universes. Of course, there are an infinite number of possible branchings for any given either-or choice, all the way from the subatomic level up to the movement of civilizations or people’s lives. But each branching of a quark’s path does not create or fail to create a whole civilization or that civilization’s end in a war. Branchings between what might be considered discrete world lines are usually caused by historic cusps — whether this king or that one is the one whose kingdom is the first to develop agriculture, animal husbandry, the domestication of cats, the brewing of beer, with all the civilizational changes that follow in train with those choices. Like that public TV series, Connections. And world lines with similar sequences of probability branchings made will tend to cluster around the moment of those probabilities, conserving events of greater moment across world lines and possibly several lines at once. So there will be several lines in which the Irish discovered America, but the Vikings were the first to plant settlers there among the Indians, while the Spanish were the first successful colonists. In others, it will be the Dutch, the Italians, the Portuguese and the English, in still others, the Chinese — coming from the West — colonize the Americas long before the Irish set out westward in their coracles. The variations among these, such as are found in alternate history fiction cause similar world branchings, but tend to cluster around key events of greater relative moment.
This is the model I use in building the world of the Baby Troll Chronicles. I would love to hear from y’all with your thoughts on the matter.