Last week I had a blast with reading explanations on Bell's theorem. It was the first time that I've actually understood it. So I wanted to share some websites that explain the theorem in an easy way: 1) Spooky Action at a Distance – An Explanation of Bell’s Theorem by Gary Felder This article is easy to understand and only basic mathematics is used. 2) Does Bell’s Inequality rule out local theories of quantum mechanics? Updated May 1996 by PEG (thanks to Colin Naturman). Updated August 1993 by SIC. Original by John Blanton. This article is more compact than the one before. It introduces a notation often used in discussions, e.g. N(x+, y−). 3) Einstein-Podolsky-Rosen paradox and Bell’s inequalities by Jan Schütz A seminar report introducing the CHSH inequality that is used for experiments. 4) Bell’s Theorem explained A post on the blog Skeptic’s Play that uses set theory to explain Bell’s theorem. 5) Bell’s theorem analogy David M. Harrison uses a classroom analogy to derive Bell’s inequality. 6) Violation of Bell’s theorem Lecture notes by Leonard Susskind also using a Venn diagram. 7) Lecture 17 – Einstein-Podolski-Rosen Experiment and Bell’s Inequality An excellent lecture by Prof. James Binney. You can download the lecture notes here. This lecture assumes that you know some quantum mechanics, e.g. how to calculate probabilities using Dirac’s bra-ket notation. Note: If you have wondered too (like me) about the probability density function [itex]\rho(\lambda)[/itex] read this wiki article on local hidden variables. It explains that [itex]\rho(\lambda)[/itex] describes the probability that the source emits entangled particles with the hidden variable [itex]\lambda[/itex]. 8) Paradigms in Physics: Quantum Mechanics This is an online textbook made available by the Department of Physics, Oregon State University. Have a look at chapter 4 (quantum spookiness). Although they don’t use the term probability density (see note above in 7) it becomes clear now what is meant with [itex]\rho(\lambda)[/itex] . The authors use populations instead. 9) Bell’s Theorem with Easy Math and Bell’s Theorem and Negative Probabilities Two articles by David R. Schneider also known as our DrChinese. 10) John Bell himself presenting his theorem This is a talk given by John Bell at CERN. The youtube video has captions and you can also view a transcript of the talk. Feel free to add more links.