# Randomness and Bell's Inequality [Audio only] | Two Minute Papers #31 ## Метаданные - **Канал:** Two Minute Papers - **YouTube:** https://www.youtube.com/watch?v=674DL39dOOQ - **Дата:** 10.12.2015 - **Длительность:** 5:22 - **Просмотры:** 5,202 ## Описание In this episode, we discuss what makes an event random, and how incredible it is what Bell's theorem (or inequality) has to say about truly random events. Note: "local" means that information from the hidden variable doesn't travel faster than light. __________________________ The paper "On the Einstein Podolsky Rosen Paradox" is available here: http://www.drchinese.com/David/Bell_Compact.pdf http://homepages.physik.uni-muenchen.de/~vondelft/Lehre/09qm/lec21-22-BellInequalities/Bell1964.pdf Subscribe if you would like to see more of these! - http://www.youtube.com/subscription_center?add_user=keeroyz The thumbnail image was created by Giovanni Arteaga (CC BY 2.0) - https://flic.kr/p/8M11b6 Splash screen/thumbnail design: Felícia Fehér - http://felicia.hu Károly Zsolnai-Fehér's links: Patreon → https://www.patreon.com/TwoMinutePapers Facebook → https://www.facebook.com/TwoMinutePapers/ Twitter → https://twitter.com/karoly_zsolnai Web → https://cg.tuwien.ac.at/~zsolnai/ ## Содержание ### [0:00](https://www.youtube.com/watch?v=674DL39dOOQ) Segment 1 (00:00 - 05:00) dear fellow Scholars this is 2minute papers with car here when using cryptography we'd like to safely communicate over the internet in the presence of third parties to be able to do this and many other important applications we need random numbers but what does it exactly mean that something is random randomness is the lack of any patterns and predictability people usually use coin flips as random events but is a coin flip really random if we had a really smart physicist who can model all the forces that act upon the coin he would easily find out whether it's going to be heads or tails strictly speaking a coin flip is therefore not random what about random numbers generated with computers are a collection of processing units that run programs if one knows the program code that generates the random numbers they are not random anymore because it doesn't happen by chance and it is possible to predict John F nyman famously said anyone who considers arithmetical methods of producing random digits is of course in a state of sin for as has been pointed out several times there's no such thing as a random number there are only methods to produce random numbers and a strict arithmetic procedure of course is not such a method some websites offer highquality random numbers that are generated from atmospheric noise practically speaking this of course sounds SS adequate enough if someone wants to break the encryption of our Communications they would have to be able to model the physics and initial conditions of every single Thunderbolt which means processing millions of discharges per day this is practically impossible so it seems reasonable to say that random events are considered random because of our ignorance not because they are strictly speaking unpredictable you just need to be smart enough and the notion of Randomness Fades away in the light of your intelligence or so it seemed for physicists for a long time imagine if someone who has never heard about magnetism would see many magnets attracting each other and some added magnet powder this person would most definitely say It's Magic happening however if you know about magnetism you know that things don't happen randomly there are very simple laws that can predict all this movement in this case magnetic forces we can Loosely call a hidden variable so we have a phenomenon that we cannot predict and we are Keen to say it's random in reality it is not there is just a hidden variable that we don't know of that is responsible for this Behavior we have the very same phenomenon if we look inside of an atom Quantum level effects happen according to the physics of extremely small things and we again find behaviors that seem completely random we know some of the trends just like we know which roads in our city are expected to have a huge traffic jam every morning but we cannot predict where every single individual car is heading we have it the same way with extremely small particles we are Keen to say that a behavior seems completely random because nothing that we know or measure would explain it other people would immediately say wait you don't know everything maybe these Quantum effects are not random as there may be hidden things hidden variables that you don't know of which make up for the behavior we can't just say this or That Is Random it is much more likely that our knowledge is insufficient to predict what is happening as electromagnetic forces seemed magical to scientists a few hundred years ago so is quantum mechanics completely random or does it only seem random it is probably one of the most difficult questions ever asked how can you find out that something you measure that seems random is really completely random and not just the act of forces that you don't know of and hold on to your chair because this is going to blow your mind a simple and intuitive statement of Belle's theorem states that no physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics this means that he proved that the behavior scientists experience in quantum mechanics are really random they cannot be explained by any Theory you could possibly make up simple one or complicated doesn't matter this Discovery is absolutely insane you can definitely prove that a crappy Theory someone quickly made up doesn't explain a behavior but how can you prove that it is completely impossible to build such a theory that does no matter how hard you try how smart you are you can't do it this is such a mind-bogglingly awesome theorem and please note that we definitely lose out on some details and generality because of the fact that we use intuitive words to discuss these results as opposed to the original ### [5:00](https://www.youtube.com/watch?v=674DL39dOOQ&t=300s) Segment 2 (05:00 - 05:00) derivation with Co variances between measurements on our imaginary list of the Wonders of the World Monuments created not by the hands but the minds of humans this should definitely be among the best of them thanks for watching and for your generous support and I'll see you next time --- *Источник: https://ekstraktznaniy.ru/video/14907*