Functional MRI (fMRI) detects the seconds-long rushes of oxygenated blood to areas of the brain that are engaged with whatever the subject is thinking or doing at the time. The technique is being increasingly used to develop semantic models—how the concept of, say, an object that we see or an emotion that we feel is represented neurally in the brain. Robert Mason and Marcel Just at Carnegie Mellon University now extend those studies to physics concepts. Momentum, entropy, magnetic field, and other abstract concepts are qualitatively different from concrete nouns, action verbs, and numbers, and aren’t what the brain was built for. The researchers' study focused on nine right-handed participants, all upperclassmen or graduate students in physics or engineering. The individuals first were asked to list two or three properties to describe each of 30 physics terms; "velocity" properties, for example, might include "vector" and "motion." Next came the scans, during which the terms were displayed in random order multiple times, and the participants actively thought about each in turn. Afterward, the participants were asked to split the terms into four to six groups and give each category a name. When Mason and Just correlated the fMRI maps, both for the same individual and for different individuals, they found consistent neural signatures that could be described by five factors. One was trivial: the length of the word. But aided by the participants' categorizations and property descriptions, the researchers could assign semantic physics interpretations to the other factors: causal motion (pink regions in the figure) registered strongly for terms such as "gravity" and "torque"; periodicity (green), for "sound waves" and "diffraction"; mathematical representation (red), for "acceleration" and "heat transfer"; and energy flow (blue), for "heat transfer" and "electric field." Moreover, the activated regions variously fall within parts of the brain known to process relevant fundamental aspects such as visualization and rhythm. (R. A. Mason, M. A. Just, Psychol. Sci., in press, available here.)