{"id":4649,"date":"2007-09-28T10:28:38","date_gmt":"2007-09-28T10:28:38","guid":{"rendered":"http:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/"},"modified":"2007-09-28T10:28:38","modified_gmt":"2007-09-28T10:28:38","slug":"locality-and-causality-and-epr","status":"publish","type":"post","link":"https:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/","title":{"rendered":"Locality and Causality and EPR"},"content":{"rendered":"<!DOCTYPE html PUBLIC \"-\/\/W3C\/\/DTD HTML 4.0 Transitional\/\/EN\" \"http:\/\/www.w3.org\/TR\/REC-html40\/loose.dtd\">\n<html><head><meta http-equiv=\"content-type\" content=\"text\/html; charset=utf-8\"><meta http-equiv=\"content-type\" content=\"text\/html; charset=utf-8\"><\/head><body><p>There are few parallels in human endeavor than the very deep and profound argumentative disagreement between Neils Bohr and Albert Einstein on the very nature of Quantum Mechanics.  While Bohr was in the Copenhagen Interpretation gang, Einstein was looking for the hidden variables.<\/p>\n<p>Einstein wrote a paper with Podolsky and Rosen enunciating the EPR paradox.  It was a thought experiment.  This is how it is described in wikipedia:<\/p>\n<blockquote>\n<p>The EPR paradox draws on a phenomenon predicted by quantum mechanics, known as <a href=\"http:\/\/en.wikipedia.org\/wiki\/Quantum_entanglement\" title=\"Quantum entanglement\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">quantum entanglement<\/a>, to show that measurements performed on spatially separated parts of a quantum system can apparently have an instantaneous influence on one another. This effect is now known as \"<a href=\"http:\/\/en.wikipedia.org\/wiki\/Nonlocality\" title=\"Nonlocality\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">nonlocal behavior<\/a>\" (or colloquially as \"quantum weirdness\" or \"spooky action at a distance\").<\/p>\n<\/blockquote>\n<p>Broadly, the thought experiment in very simple terms can be described thus:<\/p>\n<p>Hiesenberg\u2019s uncertainty principle says motion and position cannot be measured with accuracy at the same time.  So, you cannot know the exact location of the electron.  However, if two electrons were brought together and went towards each other, they will be repelled \u2013 while adhering to the conservation of momentum \u2013 both together will have the same momentum combined after the \"collision\" as they had before the collision.  After the collision, if one were to measure the position and momentum of electron 1 at different times (in keeping with Hiesenberg\u2019s principle), one could due to correlation from conservation of momentum, calculate the exact measurement of electron 2 <em>without <\/em>disturbing it!<\/p>\n<p>Interestingly, Einstein and co. devised EPR paradox to refute QM by bringing in classical bearings on it.  However the opposite happened.  It helped establish how actually QM violated the classical laws.  Here is the explanation:<\/p>\n<blockquote>\n<p>Although originally devised as a thought experiment that would demonstrate the <a href=\"http:\/\/en.wikipedia.org\/wiki\/Incompleteness_of_quantum_physics\" title=\"Incompleteness of quantum physics\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">incompleteness of quantum mechanics<\/a>, actual <a href=\"http:\/\/en.wikipedia.org\/wiki\/Bell_test_experiments\" title=\"Bell test experiments\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">experimental results<\/a> refute the <a href=\"http:\/\/en.wikipedia.org\/wiki\/Principle_of_locality\" title=\"Principle of locality\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">principle of locality<\/a>, invalidating the EPR trio\u2019s original purpose. The \"<a href=\"http:\/\/en.wikipedia.org\/wiki\/Spooky_action_at_a_distance\" title=\"Spooky action at a distance\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">spooky action at a distance<\/a>\" that so disturbed the authors of EPR consistently occurs in numerous and widely replicated experiments, though the validity of these experiments does remain in debate. Einstein never accepted quantum mechanics as a \"real\" and complete theory, struggling<sup><span title=\"This claim needs references to reliable sources\u00a0since September 2007\">[<em><a href=\"http:\/\/en.wikipedia.org\/wiki\/Wikipedia:Citing_sources\" title=\"Wikipedia:Citing sources\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">citation needed<\/a><\/em>]<\/span><\/sup> to the end of his life for an interpretation that could comply with relativity without implying \"God playing dice\", as he condensed his dissatisfaction with quantum mechanics\u2019s intrinsic randomness and counter-intuitivity.<\/p>\n<p>The EPR paradox is a <a href=\"http:\/\/en.wikipedia.org\/wiki\/Physical_paradox\" title=\"Physical paradox\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">paradox<\/a> in the following sense: if one takes quantum mechanics and adds some seemingly reasonable conditions (referred to as <a href=\"http:\/\/en.wikipedia.org\/wiki\/Principle_of_locality\" title=\"Principle of locality\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">locality<\/a>, <a href=\"http:\/\/en.wikipedia.org\/wiki\/Philosophical_realism\" title=\"Philosophical realism\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">realism<\/a>, <a href=\"http:\/\/en.wikipedia.org\/wiki\/Counter_factual_definiteness\" title=\"Counter factual definiteness\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">counter factual definiteness<\/a>, and completeness), then one obtains a <a href=\"http:\/\/en.wikipedia.org\/wiki\/Contradiction\" title=\"Contradiction\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">contradiction<\/a>. However, quantum mechanics by itself does not appear to be internally inconsistent, nor \u2014 as it turns out \u2014 does it contradict relativity. As a result of further theoretical and experimental developments since the original EPR paper, most physicists today regard the EPR paradox as an illustration of how quantum mechanics violates <a href=\"http:\/\/en.wikipedia.org\/wiki\/Classical_physics\" title=\"Classical physics\" class=\" decorated-link\" target=\"_blank\" rel=\"nofollow\">classical<\/a> intuitions.<\/p>\n<\/blockquote>\n<p>The most basic dichotomy was thus between principle of locality itself within the context of causality.  <\/p>\n<\/body><\/html>\n","protected":false},"excerpt":{"rendered":"<p>There are few parallels in human endeavor than the very deep and profound argumentative disagreement between Neils Bohr and Albert Einstein on the very nature of Quantum Mechanics.  While Bohr was in the Copenhagen Interpretation gang, Einstein was looking for the hidden variables.<\/p>\n<p>Einstein wrote a paper with Podolsky and Rosen enunciating the EPR paradox.  It was a thought experiment.  This is how it is described in wikipedia:<\/p>\n<blockquote>\n<p>The EPR paradox draws on a phenomenon predicted by quantum mechanics, known as <a href=\"http:\/\/en.wikipedia.org\/wiki\/Quantum_entanglement\" title=\"Quantum entanglement\">quantum entanglement<\/a>, to show that measurements performed on spatially separated parts of a quantum system can apparently have an instantaneous influence on one another. This effect is now known as &quot;<a href=\"http:\/\/en.wikipedia.org\/wiki\/Nonlocality\" title=\"Nonlocality\">nonlocal behavior<\/a>&quot; (or colloquially as &quot;quantum weirdness&quot; or &quot;spooky action at a distance&quot;).<\/p>\n","protected":false},"author":1517,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[64],"tags":[],"class_list":["post-4649","post","type-post","status-publish","format-standard","hentry","category-sciences"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Locality and Causality and EPR<\/title>\n<meta name=\"description\" content=\"There are few parallels in human endeavor than the very deep and profound argumentative disagreement between Neils Bohr and Albert Einstein on the very nature of Quantum Mechanics. While Bohr was in the Copenhagen Interpretation gang, Einstein was looking for the hidden variables. Einstein wrote a paper with Podolsky and Rosen enunciating the EPR paradox. It was a thought experiment. This is how it is described in wikipedia:   The EPR paradox draws on a phenomenon predicted by quantum mechanics, known as quantum entanglement, to show that measurements performed on spatially separated parts of a quantum system can apparently have an instantaneous influence on one another. This effect is now known as &quot;nonlocal behavior&quot; (or colloquially as &quot;quantum weirdness&quot; or &quot;spooky action at a distance&quot;).\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Locality and Causality and EPR\" \/>\n<meta property=\"og:description\" content=\"There are few parallels in human endeavor than the very deep and profound argumentative disagreement between Neils Bohr and Albert Einstein on the very nature of Quantum Mechanics. While Bohr was in the Copenhagen Interpretation gang, Einstein was looking for the hidden variables. Einstein wrote a paper with Podolsky and Rosen enunciating the EPR paradox. It was a thought experiment. This is how it is described in wikipedia:   The EPR paradox draws on a phenomenon predicted by quantum mechanics, known as quantum entanglement, to show that measurements performed on spatially separated parts of a quantum system can apparently have an instantaneous influence on one another. This effect is now known as &quot;nonlocal behavior&quot; (or colloquially as &quot;quantum weirdness&quot; or &quot;spooky action at a distance&quot;).\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/\" \/>\n<meta property=\"og:site_name\" content=\"Drishtikone\" \/>\n<meta property=\"article:published_time\" content=\"2007-09-28T10:28:38+00:00\" \/>\n<meta name=\"author\" content=\"Desh Kapoor\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Desh Kapoor\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/\",\"url\":\"https:\/\/www.patheos.com\/blogs\/drishtikone\/2007\/09\/locality-and-causality-and-epr\/\",\"name\":\"Locality and Causality and EPR\",\"isPartOf\":{\"@id\":\"https:\/\/www.patheos.com\/blogs\/drishtikone\/#website\"},\"datePublished\":\"2007-09-28T10:28:38+00:00\",\"dateModified\":\"2007-09-28T10:28:38+00:00\",\"author\":{\"@id\":\"https:\/\/www.patheos.com\/blogs\/drishtikone\/#\/schema\/person\/e24bcebf9da3425dd595b71543245311\"},\"description\":\"There are few parallels in human endeavor than the very deep and profound argumentative disagreement between Neils Bohr and Albert Einstein on the very nature of Quantum Mechanics. While Bohr was in the Copenhagen Interpretation gang, Einstein was looking for the hidden variables. Einstein wrote a paper with Podolsky and Rosen enunciating the EPR paradox. It was a thought experiment. This is how it is described in wikipedia: The EPR paradox draws on a phenomenon predicted by quantum mechanics, known as quantum entanglement, to show that measurements performed on spatially separated parts of a quantum system can apparently have an instantaneous influence on one another. 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