Addition and multiplication In our study of **oscillating** systems we shall have occasion to use one of the most remarkable, almost astounding, formulas in all of mathematics. From the physicist's point of view we could bring forth this formula in two minutes or so, and be done with it. But science is as much for intellectual enjoyment as for practical utility, so instead of just spending a few minutes, we shall surround the jewel by its proper setting in the grand design of that branch of mathematics called elementary algebra.

— Richard Feynman, Robert B. Leighton, ?Matthew Sands (1963),

Alcmaeon was, says [J.] Wachtler, the first who attempted to explain the phenomenon of sound and our perception of it by reference to the structure of the ear itself. Empedocles to some extent follows or agrees with him. ...Empedocles teaches that hearing is caused by the impact of the air-wave against the cartilage which is suspended within the ear, **oscillating** as it is struck, like a gong.

— John Isaac Beare,