In the recent discussion of Many-Worlds and making universes, Jonathan Vos Post asked what science fiction treatments of the idea I like. The answer is pretty much “none,” because most SF treatments are distractingly bad.
For example, last night I finished Neal Stephenson’s Anathem, a whopping huge brick of a book setting up an incredibly imaginative alternate Earth, with a detailed intellectual history paralleling our own. It’s got all sorts of great stuff, but it lost me when it started talking about parallel worlds, because it munges together the Many-Worlds Interpretation of quantum physics, and Multiverse Cosmology in a way that I found distracting.
These are very different theories, dealing with very different things:
The Many-Worlds Interpretation talks (in its popular formulation) about “alternate worlds” in which particular measurements had different outcomes. It’s not quite right to talk about these as separate universes in their own right (really, they’re just different parts of the same universal wavefunction), but that’s the basic idea– there is a branch of the wavefunction corresponding to each of the possible outcomes of any particular measurement, and those branches are inaccessible to one another.
Multiverse Cosmology, on the other hand, posits the existence of other “universes” in which the constants of nature have slightly different values. Depending on which flavor of it you’re dealing with, these may be completely separate parallel worlds (other Big Bangs leading to other universes) or “bubbles” within a single cosmos, stemming from the same Big Bang.
Stephenson blurs the distinction between the two in a way I found annoying. He talks about universes with different physical laws (Multiverse Cosmology) as if they were the same as the different wavefunction branches of Many-Worlds. It’s not critical to the resolution of the plot, but it was annoying to me in a way that hurt my enjoyment of the end of the book. (Which wouldn’t've been that great even if he had gotten the details right, but that’s a topic for another post…)
Of course, Stephenson uses these ideas about as well as anybody else in SF does. Which is why there isn’t much SF about these ideas that I would recommend.