Comment on “A Scratch-Guide Model for the Motion of a Curling Rock”.

For several years, there has been disagreement in the literature over the “scratch-guiding mechanism” first published by Nyberg et al. (Wear 301:583–589, 2013) in 2013 and recently quantified by Penner (Tribol Lett 67:35.1–35.13, 2019) in 2019. According to this proposal, the lateral motion of curling rocks can be influenced by pre-existing scratches on the ice. In particular, it is argued that scratches made by the front of the running band can “push” the back of the running band to the left or to the right, depending on their orientation. We offer here a critique of the Penner paper (Penner in Tribol Lett 67:35.1–35.13, 2019), alluding inter alia to recently published experimental results (Shegelski and Lozowski 10.1177/1754337118821575, 2019), which clearly demonstrate that scratches made by the running band of a curling rock have no influence on the trajectories of a subsequent rock travelling over those scratches. We also point out some apparent inconsistencies and deficiencies in the Penner model itself. [ABSTRACT FROM AUTHOR]