Tensors — In words of one syllable

Albert Einstein in his new book (“The Evolution of Physics,” by Albert Einstein and L. Infeld, New York, 1938, Simon and Schuster, page 226) says, “Modern physics is simpler than the old physics and seems, therefore, more difficult and intricate.” That is, while the reasoning becomes simpler the necessary groundwork becomes more extensive. So it is with the tensor, for its power lies in the simplification it affords. Like every progressive innovation in symbolic mathematics, it involves a condensation of reasoning. But the obscurity of the symbolism tends to increase in proportion to the gain in compactness. The brevity of the tensor, its best quality, is the greatest source of difficulty for the student. We are dealing here with one of those abstract physico-mathematical concepts which are usually well understood only after long acquaintanceship and patient application. A great many of us are trying vainly to cover too much ground in a single step.