He called it a book that manages to explain relativity and a lot more without resorting to a single bit of mathematics (except for asking you to grasp the not-too-onerous concept that the velocity of light, a constant 186,000 miles per second, is a product of its frequency and wavelength). After all, Mr. Zukav writes, "The fact is that physics is not mathematics. Physics, in essence, is simple wonder at the way things are and a divine (some call it compulsive) interest in how that is so. Mathematics is the tool of physics, stripped of mathematics, physics becomes pure enchantment."