The young Huygens solves the problem of elastic collisions

Christiaan Huygens was probably the first person to solve the problem of elastic collisions. He did this in the 1650s when he was only in his early twenties. The first formal publication of his general rule for the outcome of a head-on hard collision was in March 1669 in the Journal des Sçavans. Our present paper describes in detail Huygens' work on elastic collisions. We focus particularly on how Huygens' instinct for symmetry led him to a solution in the center-of-gravity reference frame. He readily transformed this solution to other frames using what we now call the Galilean velocity transformation. Huygens' symmetry approach is quite different from the modern description of collisions using Newtonian action and reaction forces.