All Physics Is Not Particle Physics

A wag of my finger at the Corporate Masters, for their new article about traffic jams, with the subhead “For particle physicists who study phase transitions, a traffic jam is simply a solid made up of idling cars.” In the body of the article, we find:

While the concept of critical density has been repeatedly demonstrated using computer simulations–drivers are surprisingly easy to model as a system of interacting particles–it wasn’t until last year that this theory of traffic was experimentally confirmed. A team of physicists at Nagoya University wanted to see how many cars could maintain a constant speed of 19 mph around a short circular track. It turned out that the critical number was 22: Once that density was reached, tiny fluctuations started to reverberate around the track, which caused the occasional spontaneous standstill. As the scientists note, this is actually a pretty familiar scenario for particle physicists, who are used to studying phase transitions, such as the transformation of liquid water into solid ice. In this case, the critical threshold is temperature, which triggers clusters of molecules to slow down and form a crystal lattice, which then spreads to nearby molecules. A traffic jam is simply a solid made up of idling cars.

Neither of these explanations require the word “particle” in front of “physicists.” While it’s undoubtedly true that some particle physicists study exotic phase transitions, the vast majority of physicists working on phase transitions are not particle physicists– they work in condensed matter physics, and statistical mechanics. Look at the author list of the Nagoya University paper— none of the institutional affiliations are suggestive of particle physics.

There’s a really deplorable trend in science journalism to discuss physics as if particle physics were the whole of physics, as if every person with a physics degree lies awake nights wondering about the Higgs Boson. In fact, particle physicists don’t even constitute a plurality within physics— condensed matter physicists outnumber them by a significant margin. Most people with physics degrees study something other than particle physics.

While it’s very nice to see Seed acknowledging that there is interesting work done by physicists in other fields, turning around and calling it “particle physics” undoes whatever good was done by noting them in the first place. “Particle” is not a random intensifying adjective attached to indicate that some individual physicists are really smart. “Particle physicists” are a very specific subset of physicists, the ones whose experiments cost a billion dollars and whose theories are unmoored from petty constraints like data. Reflexively putting “particle” in front of “physicist” makes about as much sense as reflexively putting “pharmaceutical” in front of “chemist” or “disgraced” in front of “politician”– it might cover most of the examples you run into in the news, but it’s insulting to the exceptions.

(I should note that the Nagoya traffic experiment is pretty cool– you can watch the video on YouTube, and read the New Scientist article that goes with it. It’s not particle physics, though, not by any stretch.)