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Bell's Theorem Proves That Our World is Quantum, it Cannot Be Mechanical

A Great explanation of Bell's theorem and the Bell inequality. Bell's theorem proves that our world is quantum in nature and cannot ever be explained by mechanical physics. John Stuart Bell derived the Bell inequality and provided a fascinating answer to the EPR paradox initially posed by Albert Einstein, Boris Podolsky and Nathan Rosen on the concept of quantum entanglement. Bell posed Bell's theorem, or the Bell inequality to answer the question of quantum entanglement. This is Physics Made Simple. I am going to illustrate Bell’s theorem with a spin-the-wheel toy and two ways to play the game so you can get a clear understanding of the physics behind Bell’s theorem. 0:00 Bell's inequality explained 0:34 Quantum entanglement of two particles 1:10 particles in the state of Schrödinger's cat 1:40 explanation #1 of quantum entanglement 2:02 explanation #2 of quantum entanglement: locality and realism 2:38 John Stuart Bell's contribution 3:45 Spin the wheel toy game and explanation 4:46 the quantum version of the spin-the-wheel-toy game 5:28 explaining the effect of entanglement in the game EXCERPT OF THE VIDEO "Albert Einstein, Boris Podolsky and Nathan Rosen proposed a thought experiment in 1935 on the concept of quantum entanglement. This lead John Stuart Bell to find what we know today as the Bell inequality or Bell’s theorem. The Bell inequality and Bell’s theorem are very famous but hard to explain without using difficult math. This is Physics Made Simple. I am going to illustrate Bell’s theorem with a spin-the-wheel toy and two ways to play the game so you can get a clear understanding of the physics behind Bell’s theorem. Particles are entangled when they are generated, interact or share spatial proximity in such a way that we cannot describe their quantum states independently. Einstein, Podolsky and Rosen propose a thought experiment where we create two entangled particles, for example with the system above. We then move the two particles very far apart. Here we observe something fascinating. Particles are in a quantum state: like with Schrödinger’s cat, we can only if it is alive or not by opening the box. As long as we don’t look, the cat and the particle are in an unknown state. This explanation was criticized by Albert Einstein as “spooky action at a distance”. The quote became famous because it summarizes so well what we observe. But let’s continue to the second explanation of quantum entanglement The second explanation is that there is some hidden information that predetermined the result of the measurements before we performed it. The second explanation used the assumptions of “realism” and “locality”. ,“Realism” means that the property exists whether we measure it or not, it is just there. “Locality” means that information cannot travel faster than the speed of light and particles are only influenced by their environment, If the second explanation, then quantum mechanics is incomplete because it doesn’t entirely describe the particle’s properties. This is what we call “hidden local variables”. John Stuart Bell improved this line of thinking with Bell’s theorem. If we perform independent measurements on each particles, then they each contain “hidden variables”. Because they each contain half of that information, it creates a constraint on their correlation that is known as the **Bell inequality**. BUT Bell then shows that quantum physics correlations that violate this inequality. Since we see that quantum physics “works” with our experiments, something must be wrong in the reasoning. The only way to make the Bell inequality work is to assume that the “hidden variables” of the particles are not local. There is something that lets particles interact instantaneously, with information travelling at an infinite speed. Let’s say I have a spin the wheel toy And I’m playing with Albert and Marie They have to guess on which half the spin will land on. The trick is that Albert and Marie each to decide how to split the wheel. They pick an angle to represent their choice. So basically, if the spin lands within degrees of that angle, so half the circle, they win. In the easy cases, they can both choose the same angle. So they will always win together or lose together. ... " #physics #quantumphysics #physicsmadeeasy