Newton’s example of the two globes

Abstract

At the end of the Scholium Newton includes a long paragraph about two globes revolving around their center of gravity and held together by a tensed cord. It has been interpreted as a thought experiment (Sect. 6.2) meant to show how the properties of true circular motion defined as absolute motion can be determined in a three-dimensional empty universe. I start by showing that this reading of Newton’s example as a bona fide thought experiment is riddled with interpretation problems and that it is less straightforward than so far assumed (Sect. 6.3).