American Scientist

In high school, my classmates and I learned that many things come in threes. In trigonometry class, we naturally were introduced to the properties of figures with three sides and three angles. In civics class, we were told that there are three branches of the U.S. government: the legislative, the executive, and the judiciary. In Latin class, we translated the opening sentence of Caesar’s Gallic Wars—“Gallia est omnis divisa in partes tres”—as “All Gaul is divided into three parts.” And in physics class, we learned about Newton’s three laws of motion and also that there are three classes of levers (class 1, class 2, and class 3), each with three points of interest: the fulcrum, the load, and the effort, but with the positioning of the load and effort varying with respect to the fulcrum in each class of lever.