“What if?” is a very popular question. It’s arguably the basic question for most works of fiction. But here we’ll talk about one variation: “what if something happened differently?”. As we talked about in the first half of this series, time travel jumps up and down the timeline of a story, causing closed loops and paradoxes. But what if the timeline breaks into two or more possibilities? Then you have alternate universes – where something in the past of a story is changed (the “point of divergence”) and everything afterwards is different.
This is popular for resolving time travel paradoxes, sometimes with a handwave misapplying the many-worlds interpretation of quantum mechanics. But it’s also popular in its own right, spawning long lists of related tropes and whole forums and wikis for discussion. There is both alternate history of reality, and alternate universe fic of other fictional stories. So what problems are there with such stories?
Butterflies & Butterfly Nets
The butterfly effect was originally named from discussions of weather forecasting. The basic idea is that while climate is relatively predictable, daily weather is a boundly-chaotic system. Even the slightest difference in initial conditions, like a butterfly flapping its wings, can dramatically change everything that follows. This is also known as “for want of a nail”.
For alternate universe fic and alternate histories, the butterfly effect is almost always not respected. That’s because it is hard to trace out causality in complex systems, even in retrospect. For example, if Star Trek: Voyager had cast a different actor as Seven-of-Nine, Barack Obama might not currently be president of the USA. The causality for that one goes like this: Jeri Ryan played Seven-of-Nine. She was then married to Jack Ryan. They eventually divorced, in part because of the stresses from frequent travel between Los Angeles and Chicago. Five years later, Jack Ryan was running against Obama for the Illinois seat in the US Senate. Jack Ryan was compelled to release the records of the divorce proceedings during the campaign. Various unflattering things about him in those documents led to him being compelled to resign from the race. Obama went on to win a landslide victory against Alan Keyes, who was brought on by the Republicans as a last-minute replacement.
It is hard to write an appropriately chaotic timeline, especially for something as complex as the history of a planet with more than seven billion people on it. And so authors invoke butterfly nets (or “in spite of a nail”), constraining their timelines to be artificially similar to each other. Thus we have good Spock and evil Spock; several dozen versions of Superman; and going back in time more than a hundred years changes the personality of a dictator but doesn’t erase every person currently in the world and replace them with different people.
The last deserves special mention. Part of the appeal of alternate universe fic (and a lot of alternate history) is “I have this cool character. What would they do in a different situation?” . In TV and film this also saves on casting. So butterfly nets are invoked to get the same set of characters, even when they should have been butterflied away entirely if the point-of-divergence was long before they were born.
One of the most notable offenders here is Star Trek. Despite 200 years or more of divergent history between the main Star Trek universe and the Mirror Universe, almost all of the characters exist in both – same names, same faces, same genomes, although far different personalities. This makes no sense. e.g. Ben Sisko was conceived by the Prophets/wormhole aliens to be their emissary. Since there is no emissary in the Mirror Universe, how is he there? And how did his father and mother and all ancestors back at least 8 generations exist, exchange gametes, and give the exact patterns of genes and environment that produced Sisko? The same argument applies to Spock, who only has the goatee so you can tell which one of him is evil.
In terms of total number of offending doppelgangers, comic books probably win. Consider the Crisis on Infinite Earths line, which was an attempt to clean up the various DC properties and all of the different alt universe versions of them – well over 100. And a bunch of new ones have been written since then. The Marvel comics have their own multiverse, with dozens of alternate universes in it. Comic book canon is very messy.
Economics of Parallel Worlds
Characters and butterfly nets aside, let’s consider the economics of alternate universes. First, there must be some way of getting from one world to another – be it a special communications device, a broken transporter, magic powers, or vaguely-described biological technology. As with time machines, the convention is usually to arrive at the same spot that you left from in a geocentric reference frame. This ignores length-of-day variations and perturbations to Earth’s orbit. Or you do some navigation and portal yourself anywhere you want. You may go “cross-time”, from one alternate universe to another, or also forward and backward in time.
I’ve written before about what you would want to do if alternate universes actually existed and were accessible. But this is rarely done. Charlie Stross’ Merchant Princes series is an example. In a European-Middle-Ages-like alternate North America, an extended family clan develops around carriers of a mutation that lets them walk themselves and a person-load of cargo between worlds a couple of times a day. This started in the 1800’s, and they established a credit base in our world by securely transporting bullion and on their side by rapid transit and limited technology imports. But the clan is not properly using their skills. Rather than going public and getting a load of money and bringing teachers and tech from our side to their side, they barely break even making money as cocaine mules. This holds even after some of them have been schooled in business, engineering, or medicine on our side. After a while, the whole plot kind of unravels. Rachel and I have considered a somewhat similar setting, based around the concept of world-walkers but done correctly. Things change very dramatically very quickly, as the walkers tie together a network of thousands of worlds by hauling petabytes of data back and forth until technology replicates their skill.
If there is time-travel as well as cross-time travel, you can engineer branches in the timeline (or you will can have). Subject to the limits of chaos and history before the point-of-divergence, you can build alternate universes to-order. Consider the ethics of that.
The idea goes back to A Connecticut Yankee In King Arthur’s Court, although Twain was writing satire. In some sense, it is the goal in the Terminator series: Skynet wants to engineer a timeline without humans, the humans want to engineer one without Skynet. But the most extreme case I know is a series by John Barnes, The Timeline Wars. Two large alliances of timelines are playing a massive game of Achron against each other, going back and creating alternate universes that support them (including some of the timelines that will provide the resources of the teams that went back in time to create those timelines). Their agents try to subvert the timelines that the other side has split off, either to ensure that the future turns out as it was going to or to split the line again and give an equal balance. The rival sides build massive generators to have sent agents further back in time, to gain an edge. Things end when a timeline that was spawned by agents going back to the Roman Republic and teching it up finally reveals itself and its Sufficiently Advanced Technology. The problem with this of course is the same as that with regular time travel: infinitely long time along one set of world-lines, looping through the time portal, leading to the heat death of the universe.
Good thing time travel is impossible.