The SAT Question Everyone Got Wrong

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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.

I invented Snatoms, a 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

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References:
Summary of this problem by MindYourDecisions – https://www.youtube.com/watch?v=kN3AOMrnEUs
More cool math about this problem by Kyle Hill – https://www.youtube.com/watch?v=_zCDbB9wvrc
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
Revolution Definition via Merriam-Webster – https://ve42.co/RevolutionWebster
Earth motion animation via NASA – https://ve42.co/OrbitNASA
Satellite animation via NASA – https://ve42.co/SatNASA

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Directed by Emily Zhang
Written by Emily Zhang and Gregor Čavlović
Edited by Peter Nelson
Animated by Ivy Tello and Fabio Albertelli
Filmed by Derek Muller
Produced by Emily Zhang, Gregor Čavlović, and Derek Muller

Thumbnail by Ren Hurley
Additional video/photos supplied by Getty Images and Pond5
Music from Epidemic Sound
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https://www.youtube.com/watch?v=FUHkTs-Ipfg