Still Spinning: The Moser Spindle at Sixty

SummarySummaryThe 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.MSC:: 05C15 Additional informationNotes on contributorsVeselin JungićVeselin Jungić (MR Author ID: 670836) is a Teaching Professor in the Department of Mathematics, Simon Fraser University, and a Canadian 3M National Teaching Fellow. Most of his research is in Ramsey theory and the field of mathematics education and outreach.Notes1 This paper was originally submitted in 2021, which explains the reference to “sixty” in the title.2 Note that the online version of this article has color diagrams.3 Moser brothers established this fact in 1961 ∼ [9].