How an SAT question became a mathematical paradox. Head to https://brilliant.org/veritasium to start your free 30-day trial, and the first 200 people get 20% off an annual premium subscription. Special thanks to our Patreon supporters! Join this list to help us keep our videos free, forever: https://ve42.co/PatreonDEB I invented Snatoms, a molecule modeling kit where the atoms snap together magnetically. Try it at https://ve42.co/SnatomsV Huge thanks to Dr. Doug Jungreis for taking the time to speak with us about this SAT question. Thanks to Stellarium, a wonderful free astronomy simulator – https://ve42.co/Stellarium Thanks to Newspapers.com, a database of historical newspapers – https://ve42.co/Newspapers ▀▀▀ References: Summary of this problem by MindYourDecisions – https://www.youtube.com/watchv=kN3AOMrnEUs More cool math about this problem by Kyle Hill – https://www.youtube.com/watchv=_zCDbB9wvrc Discussion of a solar day by MinutePhysics – https://www.youtube.com/watchv=nZMMuv0Ltyo Murtagh, J. (2023). The SAT Problem That Everybody Got Wrong. Scientific American – https://ve42.co/SATSciAm United Press International (1982). Error Found in S.A.T. Question. New York Times – https://ve42.co/SAT-NYT Yang (2020). What's the hardest SAT math problem that you've seen Quora – https://ve42.co/SATQuora Coin rotation paradox via Wikipedia – https://ve42.co/CoinParadox Simmons, B. (2015). Circle revolutions rolling around another circle. MathStackExchange. – https://ve42.co/CircleRoll Sidereal time via Wikipedia – https://ve42.co/SiderealWiki Solar Time vs. Sidereal Time via Las Cumbres Observatory – https://ve42.co/SiderealLCO Images & Video: Zotti, G., et al. (2021). The Simulated Sky: Stellarium for Cultural Astronomy Research - https://ve42.co/Stellarium Newspapers from 1980s - 1990s via Newspapers.com – https://ve42.co/Newspapers SAT Practice Test via the College Board – https://ve42.co/PracticeSAT Revolution Definition via NASA – https://ve42.co/RevolutionNASA