There must always be an explanation. When none is found, one is made up. When natural phenomena cannot be explained by other means, they are said to be magical. The same phenomena would be explained in scientific societies through science. They are understood, tamed and therefore not very frightening. But to those who do not have access to a scientific explanation, these phenomena seem strange and potentially dangerous. Not that they necessarily look dangerous but they are unknown and the meaning which is made up may make them frightening.
Equations are an example of these things which may look like magic. When they are explained, when they become familiar, they no longer appear so fierce. Unfortunately, very often books and instructors make equations mysterious by not explaining or deriving them. Even some simple equations are provided without explanations. In some cases the derivation is short and based on very straightforward concepts. The inverse-lever rule for phase diagrams, for instance, can be derived in a few lines from the conservation of mass. It is not a lot of trouble and allows students to advance to civilization.
A side effect is that students do not necessarily know which equations are purely empirical (and thus cannot be derived) and which can be derived.
© Mathieu Bouville, May 7 th 2003