The pre-Newtonian meaning of the word “weight”; a comment on “Kepler and the origins of pre-Newtonian mass” [Am. J. Phys.85, 115–123 (2017)

Abstract

Ever since the beam balance was invented over three millennia ago, it has been used to measure what is now known as mass, but which, until the time of Newton, had always been known as “weight.” Eugene Hecht recently discussed the concept of “mass” from medieval times to Newton's Principia, including the gradual change from philosophical to evidence based scientific thinking, but did not discuss the pre-Newtonian meaning of “weight” which then had the meaning of both weight and mass. The distinction between weight and mass was initiated by Kepler and completed by Newton.