How (Not) to Define Inertial Frames

Australasian Journal of Philosophy, vol. 103, pp. 869–886

Abstract

It is nearly impossible to open a textbook on Newtonian mechanics without encountering the concept of inertial frames: the frames that are privileged by the theory’s dynamics. In this paper, I argue that extant definitions of inertial frames are unsatisfactory. I criticize two common definitions of inertial frames: law-based definitions, according to which inertial frames are simply those in which the laws are true, and structure-based definitions, according to which inertial frames are those that are ‘adapted’ to spatiotemporal structure. I then offer a new, symmetry-based definition of inertial frames. This definition offers a non-conventional way of specifying the dynamically privileged frames. The result clarifies the foundations of Newtonian mechanics and accounts for the empirical success of coordinate-dependent formulations of it.

Authors 1

1. Caspar Jacobs corresponding Aachen

   Leiden University

   Affiliation as printed

   Leiden University