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Volume 16: Pages 264-276, 2003

Newton on Mass and Force: A Comment on Max Jammer's Concepts of Mass (1961; 2000)

Ed Dellian

Bogenstr. 5, D‐14169 Berlin, Germany

The concepts of mass and force, as understood in contemporary physics, mean qualities of matter. The somewhat mysterious quality “mass” is said to appear in two or even three different ways: inertial mass, active gravitational mass, and passive gravitational mass. Generally, Isaac Newton is thought to have first introduced the concept and its different appearance as inertial or gravitational mass to theoretical physics, while Albert Einstein is highly praised for having shown the indiscriminate equivalence of both concepts. A look into Newton's Principia of 1687, however, helps us to see that Newton neither understood mass as a quality, but rather as only another name for a quantity of matter (which quantity he defined not in words, but mathematically), nor ever explicitly or implicitly taught any distinction between an “inertial” and a “gravitational” aspect of matter. So it seems that to rely on Newton's authentic teaching could perhaps not only relativize Einstein's merit as to the simplification of the concept of mass but also be proof against Jammer's depressing conclusion “that the notion of mass, although fundamental to physics, is still shrouded in mystery” [Concepts of Mass in Contemporary Physics and Philosophy (Princeton University Press, Princeton, NJ, 2000)]. Accordingly, the paper aims at showing some quite surprising insights into the realm of modern physics — from the Newtonian view on the closely related, but different, entities mass and force.

Keywords: Newton's Principia — the key to understanding mass, force, and more

Received: August 25, 2003; Published online: December 15, 2008