The Fly Did Not Push It In

Final round of the 2025 BMW Championship. Tommy Fleetwood’s 27-foot putt stops on the lip of the cup, a fly lands on the ball, and the ball drops. This paper runs the force budget: what the grass was holding back, how little margin it had left, and how much of that margin a 15-milligram fly could possibly use up. The title is the conclusion.

I wrote this in May 2026, before the series started, and corrected it in September 2026.