Tuesday, July 21, 2015

Advanced Arithmancy: Isn't that just P-Chem?


Advanced Arithmancy is not mentioned in the books (as far as I’m aware), but it does show up in the movie adaptation of Harry Potter and the Prisoner of Azkaban. In a couple of previous posts I tried to make a case of why Hogwarts or some other school of magic should hire a chemistry professor – namely me. As someone who teaches Physical Chemistry I would like to make a case of why I would be suitable for Advanced Arithmancy.


Let’s start with basic Arithmancy. The term comes from the Greek words arithmos and manteia, meaning number and divination respectively. So says Wikipedia. “Arithmancy is thus the study of divination through numbers.” Numerology remains quite popular today as it did in times past. Even Hermione, who rejected Divination class with Trelawney as being “wooly”, seems to think there is something more concrete in Arithmancy class with Professor Vector. But can you really divine the future with numbers?

In Newtonian mechanics, if you know the positions and velocities of all particles in a system at any instant, you can predict the future behavior of all those particles. The caveat is that they must obey Newton’s laws. There are three problems: (1) Knowing all the positions and velocities is a tall order but possible, at least in theory, (2) particles at the level of atoms are governed by quantum mechanics, and (3) for any “real” system of interest, there are likely to be external influences that must be taken into account.

This is where Physical Chemistry, or P-Chem, comes in. It turns out that for an ensemble of particles, you can make good predictions using the “laws” of quantum mechanics. The field of statistical mechanics then allows you to derive thermodynamic quantities. Why is thermodynamics important? It tells you, at least for equilibrium thermodynamics, where things are headed given where you are now. And you don’t need to know the individual details of all particles. The thermodynamic quantities allow you to make macro-scale future predictions without needing to know everything that’s going on at the micro- or nano-scopic level. That, in principle, helps overcome the first two problems. A year of P-Chem (required of Chemistry majors) should give students a headstart in this area. Now, it’s not going to be easy – but it will be very interesting. And at the end of the course, students can even get the famous bumper sticker that says “Honk if you passed P-Chem”. These were quite popular some years ago but I haven’t seen many recently. The third problem is more complicated but a follow-up class, perhaps Double Advanced Arithmancy, could cover the fundamentals of non-equilibrium thermodynamics.

So can numbers predict the future? This is what scientists are attempting in many areas. Probably the most familiar are large-scale simulations of the earth and its environment – that show up non-stop on the Weather Channel. Closer to my field, simulations are run to predict the properties of new catalysts, advanced materials, and biochemical evolution. We build mathematical models, estimate the “present” conditions, and using the “laws” of quantum and/or classical mechanics we can predict the future of something not yet physically seen or built.

But what most of us care about from a Divination point of view is “what is going to happen to me in the future”? That’s not so easy to tell. Like a single quantum particle, perhaps an individual’s “future is not set” (I admit to recently watching Terminator Genisys). We seem to do reasonably in making some macro-level predictions for ensembles of particles (or individuals), but what if these individuals started to collude in ways that were not represented in our models. Do we know what all the feedbacks might be? Maybe that might be the heart of quantum mechanics. (Or at least I’m a quantum mechanic at heart.) Sounds like another class: Triple Advanced Arithmancy. Is there a Hogwarts College, I wonder? Maybe I could help start one.

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