Name: Your Daily Equation #21: Bell's Theorem and the Non-locality of the Universe
Duration: 51 min
Description: Brian Greene works through Bell's argument in a single sitting. The start jumps to 'John Bell's breakthrough' (25:00), followed by a worked inequality example (29:40), the experiments (35:37) and loopholes (45:24); the earlier chapters on EPR (6:32) and 'the untestable debate' (20:54) retell Part 1. The title's 'non-locality' is one reading of the result, which Part 7 weighs against the others.

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21Unit 5 · Entanglement & RealityBell's Theorem & the End of Local Realism

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Interview · World Science Festival
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Alain Aspect in a long-form World Science Festival conversation. At 29:33 he takes up Bell's inequality and Bohm's hidden variables, at 33:19 switching the polarizer orientations while the photons were in flight, and at 37:19 how his experiments improved on Clauser and Freedman's: this section's story, told by the man who ran the Orsay experiments.
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Lecture · MIT
Lecture 24: Entanglement: QComputing, EPR, and Bell's Theorem
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A full MIT 8.04 lecture by Allan Adams. The first part previews quantum computing (the no-cloning theorem, met briefly in Part 5 and fully in Chapter 24, and the Deutsch–Jozsa algorithm of Chapter 23); the last part is devoted to the EPR experiment and Bell's inequality, the ideal bridge from this chapter to the next. Best watched after the lesson.
- Ch 20
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Lecture · Nobel Prize
Nobel Prize lecture: Alain Aspect, Nobel Prize in Physics 2022
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"From Einstein's doubts to quantum technologies": Alain Aspect on his Orsay experiments of the early 1980s, which tested Bell's inequality with fast-switching polarizers, and on how entanglement went from philosophical puzzle to technological resource.
- Ch 20
- Ch 21
Lecture · Nobel Prize
Nobel Prize lecture: John Clauser, Nobel Prize in Physics 2022
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- Ch 20
- Ch 21
Lecture · Nobel Prize
Nobel Prize lecture: Anton Zeilinger, Nobel Prize in Physics 2022
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IBM's Qiskit team builds Bell's inequality from scratch for newcomers, in the wake of the 2022 Nobel Prize. Watch for the moment an argument about 'reality' turns into an inequality that an experiment can check; today you will meet it as a single number, S.
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Explainer · YouTube
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Space Time's account of the 2022 prize goes deeper into why Bell's idea needed half a century of ever more careful experiments before physicists considered the case closed. Best watched after Parts 5 and 6, when the loopholes will make sense.
- Ch 21
Explainer · YouTube
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Made with 3Blue1Brown, this reaches the same contradiction by a different road: three polarising filters and a Venn diagram that pre-written answers cannot satisfy. Compare its counting argument with the CHSH card argument in Part 3.
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Explainer · YouTube
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From 25:17, Henning Weier of the company qutools runs a live experimental demonstration of a Bell-inequality violation, so you see the correlations of this section measured on real equipment rather than computed on paper. The same lecture discusses possible loopholes at 49:47 and asks at 1:22:31 whether local realism fails.
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