The traditional view of a physicist is someone scribbling unintelligible equations on a chalkboard, with no shortage of Greek letters; and the traditional view of a chemist is someone wearing a white lab coat and goggles, swirling a flask of colored liquid behind an elaborate setup. During my time at Amherst, I have done my fair share of both. I have taken classes from both the chemistry and the physics departments. In that time, I have come to realize that the material overlaps to a much greater degree than I had previously thought. I am referring mostly to things like quantum mechanics, statistical mechanics, and thermodynamics. But of course, the differences, too, abound. While I respect the physics department and physicists to a great extent, I have definitely found my niche in chemistry.

One of the most significant differences is not scientific, rather it is educational. Physics takes a bottom-up approach to teaching, and chemistry takes a top-down. Introductory physics classes teach the fundamentals–Newtonian mechanics and Maxwellian electrodynamics. It makes sense to start here; these represent the start of the field of physics. But most of this material turns out to be useless later on; it is either expanded upon or replaced entirely better theories. Of course it is necessary to understand the basics (and their shortcomings) in order to understand why the current theories and techniques are the way they are. Chemistry is just the opposite. Introductory chemistry classes draw from the most modern theories, teaching to apply the easiest to understand results. Later on, all the gaps are filled in and those results are proved and derived. Upper level physics takes on the attitude “everything you learned last year was wrong, here’s the right way to do it”, while upper level chemistry takes on the attitude “everything you learned last year was right, and here’s where it all came from (and a whole lot more you can do with it)”.

A major scientific difference between physics and chemistry has to do with their goals. Physics seeks to understand the laws and principles governing the behavior of the natural world. They keep looking at smaller and smaller things, postulating theories upon theories, some of which, someday, might be proved. All theories are valid, as long as the math works out. Chemistry observes the behavior of the natural world, and then attempts to understand what it has just seen with a theory or a model. For this reason, while chemists and physicists might agree on a certain theory (I’ll use the example of quantum theory), they have completely different ideas about what to do next. A physicist looks at quantum theory and says, “Aha, hydrogen atom. Good.” and then moves on to quantum chromodynamics, leptons, strange quarks, and lots of other strange things. A chemist looks at quantum theory and says, “But wait, most of the stuff we see is not hydrogen atoms. What then?” and moves on to spectroscopy and perturbation theory. Physics always looks ahead to the next step, often without waiting for experiment to catch up. Chemistry is more cautious–it rigorously tests theory with experiment, and only proceeds when experiment has disproved theory. But more importantly, chemistry is much more interested in the utility of theory than physics is. Now that we’ve got the theory, the chemist asks, how can we use it to predict the behaviors of systems we hadn’t considered before? and the spectroscopist is born. Physics always has its foot on the gas, it won’t pull over for directions even when lost. Physics theory thus has climbed to a point where it is basically inaccessible to someone without extensive training in the particular subfield. This is probably the reason why physics is often seen as the loftiest of the sciences–because it is the most obscure and esoteric. While physics might require much more abstract skills like mathematics, you’d be hard pressed to find a physicist that can interpret the infrared spectrum of an organic molecule.

(A stray thought: Physics is like the wise child in the Passover seder, wanting to know everything, without regard. “What are the statutes, the laws, the ordinances…?” Chemistry is the wicked child–he wants to know what the point is, why we should care. “What does all this mean to you…?”)

I do not necessarily believe that physics is inherently less useful a scientific pursuit than chemistry, nor am I any less interested in the scientific questions it raises. However, for the time being, I’m quite satisfied to study chemistry in school and read about physics in books.

And by the way, chemistry’s got plenty of Greek letters too.