Still Spinning: The Moser Spindle at Sixty

Abstract

Summary The Moser spindle, a seemingly simple geometric object with seven vertices and 11 line segments of unit distance, was first introduced in the early 1960s. This article shows that the Moser spindle still plays a major role in the search for solutions to some of the most intriguing open problems in discrete geometry. Specifically, the problem of finding the chromatic number of the plane and the problem of finding the fractional chromatic number of the plane.