Mathematicians Explain Sports: Hockey
Offsides as an arbitrary condition on how you parametrize your position relative to the puck.
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Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2017-06-28-mathematicians-explain-sports-to-each-other--mathematicians-explain-sports-hockey/ (CC BY-NC 4.0)Transcript
Hockey: "What's 'offsides'?" "It's this sort of arbitrary condition on how you parametrize your position, based on the puck's position with respect to time. Should I walk you through it?" "Nah, sounds like technical details."