Physics of Neal Stephenson's Anathem

[mmcirvin]

I just finished reading Anathem, which is enjoyable if huge and somewhat difficult in spots. It gradually turns into a more typical Neal Stephenson novel as it goes on (though the ending is better than most).

Lots of other people have written detailed reviews, and often concentrate on Stephenson's weird alternate-history worldbuilding and use of language, and the initially slow pacing of the novel. I just have a few spoileriffic comments about Stephenson's use of physics:


Of course, the most obviously dodgy thing here, as Stephenson is fully aware, is all the quantum-brain stuff, which will be familiar to anyone who's read a lot of post-1990 hardish SF (and particularly Greg Egan's Quarantine, which has some scenes extremely reminiscent of the adventure near the end of the novel). I'm not a big fan of either Penrose's or Stapp's take on this, but I'm willing to give Stephenson a pass since it's crucial to the central MacGuffin of the novel, since I've committed similar authorial dodginess myself, and since he does put sort of an original twist on it with "Complex Protism", a crazy idea I actually haven't seen before.


That aside, the thing that bothered me the most is that Stephenson seems to genuinely think it's an open possibility that we live in a rotating Godel universe with closed timelike curves traversable by an Orion-style bomb-propelled starship (which, in Stephenson's fictional version, will put you in an alternate timeline if you circumnavigate them). Anathem takes place in another universe entirely, but it eventually turns out that our world is connected to his by this mechanism, so in the story it seems to be a feature of ours too.

Now the Orion isn't capable of really fast interstellar travel, and the book says it was originally supposed to only travel less than a light-year from the alternate-Earth Urnud until mutineers took it around the curve in an attempt at time travel. If it managed to make the trip at all, that means those closed timelike curves are hellaciously short on astronomical scales, and such a cosmology ought to have really obvious optical effects that astronomers don't actually see, such as a pretty bright ghost image of our own Sun (or, given Stephenson's cosmology, I guess it might be the Sun of Tro, the Earth-counterpart one step back down the line from ours).


And then there's all the stuff about "newmatter" and alternate-universe matter. Stephenson (who, you may recall, also posited a fantastical imaginary gold isotope in the Baroque Cycle) seems to think that by altering the conditions of nucleosynthesis, one could produce stable isotopes or variants of the known elements that are not otherwise seen in the universe. His cosmi have slightly different variants of the basic elements, which end up being carried from universe to universe apparently intact.

Nuclear physics wasn't my specialization, but I'm pretty sure that doesn't make sense. The contingencies of nucleosynthesis do have something to do with relative abundances of isotopes, but the ones we see in the world are basically all the ones that are stable, or nearly so. If you had a world with, say, slightly different weak-interaction constants such that the elements had different stable isotopes, and some of that stuff somehow got into our universe and had to deal with our laws of physics, it'd just decay, probably catastrophically. (Asimov was closer to the mark in The Gods Themselves.)

I suppose one could explain away these quibbles by saying that the world Stephenson identifies as Earth isn't really our Earth either. (Sort of like DC Comics' Earth-Prime.) I suppose they never are.

Comments

[mmcirvin.livejournal.com]

...Hmm. I guess you could say the CTCs are hundreds of years long, since that's how long it takes for the ship to make the trip. That's not so bad, but I think it still creates a problem for the astronomical evidence, since you still have those reconverging null geodesics...

[mmcirvin.livejournal.com]

...and that's really still too short anyway. I'd think that to be in the running, a funny model with some critical radius, like Godel's, would have to have that radius be, if not cosmological, at least quite intergalactic, which would put Orions way out of contention.

[sunburn.livejournal.com]

I finished the Baroque Cycle after Anathem, because I'd been saving the last book for some rainy period, and that was a mistake, because I had forgotten too much of the detail from the otehr too books, but it did stand alone.

It took me some time to catch on to the Solomonic Gold's heavier isotope, because they kept saying it was infused with Philosophik Mercury, which was meant as a metaphor, not literally as I was taking it, for the way mercury will.. not sure of the term, but displace? gold, as in a ring. Anyway, the other fantastical element suggested by the Baroque Trilogy was the character of Enoch Root who, though he didn't do a lot of heavy lifting to benefit the plot (mostly lifting a mug at the same tavern-table in Massachusetts for several years), was an immortal being, watching over the Family Waterhouse for 4 centuries, and beyond, perhaps.

Anyway, in addition to reminding me, too, of Quarantine (particularly Fraa Jad's overnight solution of the tile-puzzle), I was amused by Stephenson's terminology for separate lines of experience, narratives, is just the sort of language that would be convincingly real to the postmodernist set, who can't or won't accept that there's material grounding for thoughts and ideas in the world, whether that has been interpreted by a sentient being or not.

[mmcirvin.livejournal.com]

Yeah, the Baroque Cycle actually turned out to be crypto-fantasy set in a secret magic-works world, with a cabal of immortal alchemists pulling strings and actively trying to recede from the world. Of course, it's prefigured in Cryptonomicon, in which Enoch Root appears (but, I confess, I never managed to finish Cryptonomicon; for some reason I found it less engaging than either the Baroque Cycle or Anathem, though most readers seem to have had the reverse experience.)

But that business with the Solomonic Gold was, I think, specifically designed to fake out hard-SF-type readers. Gold amalgamates easily with mercury and there's an unstable heavy isotope of gold that decays to mercury, so I was all set to find out that the gold Newton was trying to get his hands on was just the end product of an Oklo-type natural reactor. But it wasn't, it was magic stuff.

[factitiouslj.livejournal.com]

The thing that bothered me wasn't quite the quantum-brain stuff, but the claim that quantum computers could easily solve the traveling salesman problem by a "try every possibility in parallel" sort of method. This isn't at all a new thing to see in SF, of course, and probably wouldn't have stood out for me if I hadn't been reading Scott Aaronson's blog a lot at the time.

I hadn't thought of that problem with the short closed timelike curves. Sounds like admitting the Earth in the book isn't quite ours isn't enough — that still leaves the issue that astronomers on Arbre should have been able to observe them.

[sunburn.livejournal.com]

It was a great fake-out, because the critical reveal appeared within mere paragraphs of an alarming deviation from recorded history during the trial of the Pyx, a deviation which, thanks to the fictitious gold's alchemical property is steered back on course.

[papersky.livejournal.com]

I really liked that. I was sitting there thinking "A heavier isotope of gold, a heavier isotope of gold -- wait, no, it really is the philosopher's stone and brings people back to life?" Those moments when everything turns inside out are one of the things I love about SF.

[mmcirvin.livejournal.com]

Yeah, quantum computers seem to have a lot of serious limitations even if you allow that you can get one to work, partly because unitarity is a really stringent requirement.

After Anathem I blew through Rudy Rucker's 2006 novel "Mathematicians in Love", and it's interesting how many of the same themes and even plot elements as "Anathem" coincidentally show up in that book even though it's a typically short, wacky Rucker book instead of a huge Stephenson brick. There, the magic computational Macguffin was massively parallel analog computation by physical processes.