I’ve remarked several times that I think condensed matter physics gets slighted in public discussions of the field, especially relative to its usefulness. Particle physics gets all sorts of press, but in practical terms, it is essentially useless– whether CERN or Fermilab locate the Higgs boson or not will make absolutely no difference in the lives of the average person. Condensed matter physics, on the other hand gets basically no press, despite the fact that modern technological civilization would be impossible without an understanding of condensed matter physics.
(I should note here that my own background is in atomic, molecular, and optical physics, shading towards quantum optics, so I’m not saying this as a disgruntled condensed matter physicist. Quantum optics is also slightly over-represented in the media, relative to the practical impact it has, but not nearly as badly as high-energy physics.)
It’s not hard to see why this happens. I have an undergraduate solid state physics book (Kittel) sitting on my desk, and about 25 pages in, it switches to the “reciprocal lattice” description of materials, a mathematical abstraction that no longer maps neatly onto the ordinary description of the world in terms of positions and momenta of individual particles. It’s hard to tell coherent stories about the behavior of objects when you’re working at that level of abstraction. Quantum optics and particle physics have a fair bit of mathematical overhead, but at the end of the day, you can still boil them down into stories about individual particles doing comprehensible things– they’re weird stories, but there’s still a narrative structure.
The fundamental problem, here, is that condensed matter physics is dealing with huge numbers of particles– 1023 or thereabouts. And dealing with more particles is extraordinarily difficult. Quantum optics and particle physics deal with one particle at a time, which is the only problem we know how to solve.
OK, strictly speaking, you can do exact solutions for two interacting particles. But you generally do that by using a mathematical trick to make the two particle system look like a one-particle system. For example, if you’re dealing with two objects orbiting their common center of mass (a planet and its satellite, or a single electron and a positive nucleus), you can replace the two-particle system with a one-particle system in which a particle of a slightly lower mass orbits a fixed point. We know how to solve that problem.
As soon as you add a third particle, though, analytical solutions become impossible. There are some approximation techniques that you can use to get close to the right answer, but there’s no way to construct a function that will always work to describe the three-particle system. There’s no approximation you can use to get it down to just one particle, or even to two particles.
If the three-body problem is impossible, you can understand why the 1023-body problem requires so much mathematical overhead. Actually, in many ways, a system with huge numbers of particles is easier to work with than a system of three particles, provided you’re willing to deal with statistical averages over the whole ensemble. You can get the bulk properties of a material without needing to know what each of the individual particles in the system is doing. This is the key realization that makes thermodynamics work, and something similar goes on in condensed matter.
The price you pay for this, though, is that it becomes extremely difficult to tell a non-mathematical story about the physics that gives rise to those bulk properties. That’s not to say that there aren’t useful narratives about those fields– people in those fields talk about them using narrative in the same way that particle physicists and quantum opticians do– it’s just that the stories they tell involve the behavior of more abstract objects, that are several steps removed from the microscopic physics. That makes it really hard to tell a compelling story to someone who isn’t familiar with the mathematical language.
(Similar problems crop up in high energy theory, as well– the double-well picture explaining the Higgs is a good example, in which abstract things are moving in some potential whose origin is a little murky. They’re not really central to the popular-level explanations, though.)
It’s a tough problem. Given the essential role of condensed matter systems in the technology we rely on every day, it seems like there ought to be a market for popular-level explanations of this stuff. It’s really amazingly difficult to explain at a pop-science level, though. Or, at least, it seems that way to me, my entire background in the subject being one grad-school class in Solid State, that I didn’t do very well in.
(In a similar vein, there’s remarkably little popular literature about chemistry, for similar reasons. Once you get more than a handful of atoms together, you need to start using abstract tricks to make useful predictions, and it becomes extremely difficult to follow. So you get a lot of writing about more basic stuff (physics) and more complicated stuff (biology), because it’s easier to construct compelling stories out of small numbers of particles and cute fuzzy animals.)
I’d love to see good explanations of condensed matter physics at a popular level. A really good general audience cond-mat blog would be fantastic. I don’t know of one, though. Doug Natelson is the best I know of, but as his most recent post notes, it’s really hard.
Anyway, pointers to blogs and books, or suggestions of cool ways to understand condensed matter would be welcome. Particularly if you can suggest an angle that might make it make sense to the dog.