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Thinking about other universes (or, the trouble with infinities)

December 8, 2011 8 comments

I’ve been mulling over another subject that was suggested by the recent NOVA miniseries “The Fabric of the Cosmos,” hosted by physicist Brian Greene based on his book of the same name.  I felt some of the ideas it put across were too fanciful, putting sensationalism over plausibility or clarity, and one of them was the topic of its concluding episode, “Universe or Multiverse?”

The premise of that episode was that, if the Big Bang happened as the result of localized symmetry-breaking in an ever-inflating realm of spacetime, then our universe could be just one “bubble” in a perpetually expanding cosmic foam, with other universes being separate “bubbles” with their own distinct physics and conditions, forever out of reach because the space (how many dimensions?) between us and them is forever expanding.  Now, that’s okay as far as it goes.  It’s a somewhat plausible, if untestable, notion given what we currently know.  But what Greene chose to focus on was a rather outre ramification of this: the idea that if the multiverse is infinite, if there’s an infinite number of other universes alongside ours, then probability demands that some of them will be exact duplicates of our universe, just happening by random chance to have the exact same combination of particles and thus producing the same galaxies, stars, planets, species, inviduals, etc. — kinda like how the famous infinite number of monkeys banging on an infinite number of typewriters will inevitably produce all great literature by chance.  Thus, so the claim went, there could be other universes out there that are essentially parallels to our own with duplicates of ourselves, except maybe for some minor variations.  (Or maybe universes where duplicate Earths and humans exist in different galaxies, or where a duplicate Milky Way coexists with a different configuration of galaxies, or all of the above.)

Note that this is entirely different from the concept of parallel timelines, the usual way of generating alternate Earths in science fiction.  Parallel timelines aren’t separate universes, despite the erroneous tendency of SF to use the terms interchangeably.  They’re coexisting quantum states of our own universe.  The idea is that just as a single particle can exist in two or more quantum states at the same time, so can the entire universe.  These alternate histories would branch off from a common origin, and thus it’s perfectly reasonable that they’d have their own Earths and human beings and the same individuals, at least if they diverged after those individuals were born.  And there’s at least the remote possibility of communication or travel between them if nonlinear quantum mechanics could exist.  What we’re talking about here is something else altogether, literal other universes that just happen by random chance to duplicate ours because it’s inevitable if there’s an infinite number of universes.  While parallel timelines would be facets of the same physical universe we occupy, and would thus essentially be overlapping each other in the same place, these duplicate universes would be unreachably far away, except maybe by some kind of FTL or wormhole technology if such a thing could ever exist.  And they might predate or postdate our own universe by billions of years.

But I think it was a flawed conceit to dwell on that aspect of the multiverse idea, and I have my problems with the reasoning employed.  For one thing, it’s purely an ad hoc assumption that the multiverse is infinite rather than finite.  If it’s finite, then there’s no guarantee that there would be other universes that exactly duplicate ours.  Certainly there could be ones with compatible physical laws, with their own stars and galaxies and planets and life forms, but odds are they’d be different planets, different species, different individuals.  No duplicate Earth, no duplicate Lincoln or Kennedy or Jet Li.

And if the multiverse is infinite, then sure, you could argue that with an infinite number of tries, it’s inevitable that our universe would be exactly duplicated somewhere.  But the flip side to that argument is that if there’s an infinite number of universes, then the odds that any given universe would duplicate ours would be n divided by infinity, or effectively zero.  In practical terms, if we found a way to visit other universes via wormholes or something, then we could search for an infinite amount of time before finding one that had its own Earth and human race and history duplicating ours except for having more goatees or whatever.  Thus, by any realistic standard, such duplicates would be effectively nonexistent. (This is the problem with infinity as a concept in science — it tends to lead to absurdities and singularities.  Physicists generally try to avoid infinities.)  So while that result (the existence of duplicate universes) might be a logically sound consequence of the premise of an infinite multiverse, it’s also a trivial result, one that has no practical meaning and can’t be proven or falsified.  So it’s not science, just sophistry.  It’s angels dancing on the head of a pin.  And that makes it a waste of time to focus on in a program that’s supposed to be about science.

Besides, it’s boring.  The show presented us with the prospect that there could be an infinite number of possible forms for universes to take, whole other sets of physical laws, an unlimited range of possibilities… and all they wanted to talk about was duplicates of the world we already know?  What a staggering failure of imagination — or what a staggering triumph of self-absorption.  I would’ve been far more interested in hearing about the endless variety of universes that weren’t just like ours.  Why not dazzle the viewers with some discussion about what physics would be like in a universe with more than three spatial dimensions?  Or one with a higher or lower speed of light?  That would’ve been so much cooler and more enlightening than the silly, dumbed-down examples they gave, like Earth with a ring around it or Brian Greene with four arms.

I suppose the one appeal of the infinite-monkeys premise is metafictional: You can use it to argue that if every remotely possible combination or interaction of particles is inevitable, then every fictional universe really happens somewhere.  So, for instance, I could claim that my various fictional universes — my default/Only Superhuman universe, the Hub universe, the “No Dominion” universe, whatever else I might eventually get published — all coexist in the greater multiverse, and their different physical rules, different principles of FTL and whatever, could be explained by subtle variations in the laws of physics of their distinct universes (and yet somehow don’t prevent the fundamental interactions, dark energy, and so forth from having the exact same values so that stars and planets and life can form the same way).  And it’s handy for fans who want to believe that, say, a crossover between Star Trek and Transformers, or Star Wars and Firefly, or whatever might be possible despite the huge differences in those universes’ histories and physics.  But I’m not sure I find it desirable.  To me, if there’s some planet in some unreachably distant universe that exactly duplicates Earth’s evolution and history, and has a duplicate of myself who’s writing this post at this equivalent point in his Earth’s orbit (which might be billions of years in the past or future relative to my “now,” if such a thing could even be meaningfully measured), I wouldn’t really think of him as me, or his Earth as being my Earth.  So it wouldn’t really feel to me that those other fictional universes connected to my world’s history, and that would make them less meaningful.

Or would it?  I mean, just going in, I know these fictional universes don’t have the same physical laws as our universe, that the specific characters or alien races or whatever that exist in them don’t exist in our world.  So I know going in that they’re already separate realities from my own.  Their versions of Earth and its history may correspond almost exactly to ours, yet they’re still separate entities.  So maybe it’s no worse to think of my various written worlds (blog name drop!) as coexisting realms in an infinite multiverse than it is to think of them simply as independent fictional constructs.

And sure, sometimes I think it would be nice to have some sort of grand unified theory linking my universes together.  I already tend to think of “No Dominion” as being in a parallel quantum timeline of my Default universe, because it has no visible discrepancies in physics or cosmology and has a lot of similar technological and social developments; it’s just that some technologies develop decades too early to be compatible with my published or soon-to-be-published Default-universe fiction.  That won’t work for something like the Hub, though, since it has distinct differences in physical law.  And yeah, I admit I’ve tried to think of a way to fit my universes together into a unified multiverse, at least in passing.  I suppose the “infinite monkeys” idea could give me a means to do that.

But I don’t think I find it appealing, because it just multiplies the variables to such an insane degree.  If these universes are just infinitely separated samples of an infinitely expanding metacosmos, then that doesn’t really unify them in any way, does it?  They’re so far apart, so mutually unreachable, that the “connection” doesn’t really count as a connection at all.  (After all, given the underlying physical premise, there’s no realistic chance of any kind of wormhole link or inter-universe crossover anyway.)  It’s a trivial and useless result fictionally for the same reasons it is physically.  And if they’re specks in an infinite sea of universes, it makes them all feel kind of irrelevant anyway.  So why even bother?  It’s simpler just to treat them as distinct fictional constructs and not bother trying to unify them.  Besides, even if I know intellectually that the humanity and Earth and Milky Way of my fictional universes aren’t the same as my own, it’s more satisfying to pretend they are, to construct a satisfying illusion for the readers that they’re reading about an outgrowth of our own reality, than to pretend that they’re some totally separate duplicates in universes unreachably distant from ours.  No point going out of my way to create a premise that alienates me and my audience from the universes they’re reading about.  Granted, judging from some conversations I’ve had in the past, there are some people out there who wouldn’t have a problem with that.  But it doesn’t really work for me.

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