And so he arrived to the bracing sea air of Helgoland \u2014 “far from blossoms and meadows” \u2014 determined to find a mathematical solution.<\/p>\n
<\/p>\n
A birds-eye illustration of Helgoland, which Werner Heisenberg visited in 1925. (Wikimedia Commons: Library of Congress\/CC BY-SA 4.0<\/a>)<\/p>\n A month after this trip to Helgoland, on July 29, Heisenberg submitted a paper<\/a> considered to be the advent of quantum mechanics.<\/p>\n In the years that followed, the greatest minds in physics wrestled with what it all meant.<\/p>\n As a consequence, they discovered some of the strangest pillars of quantum physics.<\/p>\n 1925 was a ‘big year’ in physics<\/p>\n Heisenberg’s musings and subsequent writings were triggered by the concept of “quanta”, which was introduced at the end of the 19th century.<\/p>\n Quanta are discrete packets of energy, and their existence challenged the old view of energy as a continuous phenomenon.<\/p>\n Loading…<\/p>\n Heisenberg managed to come up with a mathematical formulation to make sense of this shift in 1925 with what he called his “matrix mechanics”.<\/p>\n It was the first consistent and logical formulation of quantum mechanics, but it was also incredibly dense.<\/p>\n Meanwhile, Austrian Irish theoretical physicist Erwin Schr\u00f6dinger was also spending stretches of 1925 in seclusion, receiving treatment for tuberculosis at a high-altitude sanatorium in Switzerland.<\/p>\n He was working on his own formulation of quantum mechanics that would later be known as the wave equation.<\/p>\n Erwin Schr\u00f6dinger during a lecture series in 1926. (Supplied: University of Wisconsin-Madison Archives)<\/p>\n The wave equation was easier to grasp than Heisenberg’s matrices, and as a result it’s still used today to understand the behaviour of particles.<\/p>\n “It was a big year,” mathematician and historian Robyn Arianrhod, an affiliate of Monash University, says.<\/p>\n “It was the year quantum mechanics became formalised \u2026 and then all sorts of consequences happened when trying to interpret those two different formalisms.”<\/p>\n That is because it is not always immediately clear what a written equation means when it is applied to the physical world.<\/p>\n Schr\u00f6dinger initially imagined the wave in his wave equation as a physical phenomenon, like a soundwave or an ocean wave.<\/p>\n A page from Schr\u00f6dinger’s notebook with the first record of the wave equation in 1925. (Supplied: Central Library for Physics in Vienna)<\/p>\n But Schr\u00f6dinger’s interpretation of his own equation was wrong.<\/p>\n “Really what the waves are predicting are probabilities,” Dr Arianrhod says.<\/p>\n “It’s a wave of probability telling you all the possible places the particle might be.”<\/p><\/blockquote>\n If you picture a very basic drawing of a wave on a piece of paper, the peaks and troughs will indicate where a particle is more or less likely to be found.<\/p>\n But here’s the strange thing \u2014 until observed, the particle does not have a precise location. It exists in all of those possible locations at once.<\/p>\n This is called superposition.<\/p>\n This concept is often explained through the “Schr\u00f6dinger’s cat” thought experiment, where the cat is both alive and dead at the same time.<\/p>\n “And that was a really interesting and strange idea,” Dr Arianrhod says.<\/p>\n So strange it started a decades-long debate between two titans of physics: Albert Einstein and Danish physicist Niels Bohr.<\/p>\n The Einstein\u2013Bohr debates<\/p>\n The world’s greatest physicists met to discuss this new quantum mechanics at the Solvay Conference on Physics in 1927.<\/p>\n Two camps had emerged, and it was on the sidelines of this conference that they battled it out.<\/p>\n Bohr and his followers accepted we could only ever know statistical likelihoods when it came to the properties of particles.<\/p>\n But Einstein could not accept this \u2014 he did not believe God was “playing dice” with the very building blocks of reality itself.<\/p>\n So during mealtimes, or while walking between the hotel and the conference venue, the two men debated.<\/p>\n Niels Bohr and Albert Einstein discussing the probabilistic nature of quantum mechanics. (Wikimedia Commons: Paul Ehrenfest\/CC BY-SA 4.0<\/a>)<\/p>\n “Every morning, Einstein was like a jack-in-the-box, jumping up with fresh new thought experiments, trying to show the limitations of quantum theory,” Dr Arianrhod says.<\/p>\n “And every time, often after sleepless nights, Bohr found a way of answering those objections.”<\/p>\n After the Solvay Conference, it was assumed Bohr had won the debate. After all, the equations of quantum mechanics worked.<\/p>\n “Although everybody thought Bohr had won, Bohr himself kept puzzling over these ideas,” Dr Arianrhod says.<\/p>\n For years, the men swapped letters and thought experiments, trying to figure out how a particle could be in a superposition of every possible state until observed.<\/p>\n How could observing a particle alter the particle? Don’t particles have inherent properties, whether they’re observed or not?<\/p>\n It was this observer effect, and Einstein’s attempts to undermine it, that led us to the strangest phenomenon of all: entanglement.<\/p>\n Accidental discovery of entanglement<\/p>\n There’s a famous paper in physics<\/a> known as the Einstein\u2013Podolsky\u2013Rosen (EPR) paradox.<\/p>\n In it, the authors present a thought experiment to demonstrate a problem with the observer effect.<\/p>\n “Say you’ve got a red and a green jelly bean and each is in a sealed box,” Dr Arianrhod says.<\/p>\n “If observer one opens their box and finds a green jelly bean, then observer two knows the colour of their jelly bean in the other box will be red.”<\/p>\n You can imagine an entangled pair of particles as quantum mechanical jelly beans. (Getty Images: CSA-Printstock)<\/p>\n Easy enough to understand. However, if these are quantum mechanical “entangled” jelly beans, things get more complicated.<\/p>\n According to quantum mechanics, neither jelly bean has an inherent colour. They exist in a superposition of both red and green until they are observed.<\/p>\n “All we can say for sure is that each jelly bean has a 50 per cent chance of being red and each has a 50 per cent chance of being green,” Dr Arianrhod says.<\/p>\n If observer one looks inside their box and discovers a red jelly bean, observer two’s jelly bean will instantaneously be green.<\/p>\n “And this means that the second jelly bean’s colour is determined by the first observer. It’s not pre-existing,” Dr Arianrhod says.<\/p>\n The EPR paper concluded: “No reasonable definition of reality could be expected to permit this.”<\/p>\n Bohr responded to the EPR paper, disagreeing with Einstein’s conclusion. And that was that.<\/p>\n “The question was essentially put aside for decades,” theoretical physicist Eric Cavalcanti of Griffith University says.<\/p>\n “Anyone who tried to ask questions about the foundations of quantum mechanics was told to shut up and calculate.<\/p>\n “Worrying about philosophy was considered to be a waste of time.”<\/p><\/blockquote>\n However, 30 years after the EPR paper was published, a physicist from Northern Ireland, John Stewart Bell, decided it warranted a closer look.<\/p>\n The test that proved Einstein wrong<\/p>\n Einstein could not accept what he called “spooky action at a distance”.<\/p>\n He thought there must be “hidden variables” that determine the colour of the jelly bean, not the observer who simply opened a box and looked inside.<\/p>\n So Bell devised a theorem<\/a> to test Einstein’s idea.<\/p>\n John Bell came up with a theorem that tested the limits of Einstein’s hidden variables theory. (Wikimedia Commons: CERN\/CC BY-SA 4.0<\/a>)<\/p>\n He found that if you held to Einstein’s view of the world, there would be a limit to how much you could know about an entangled pair of particles at any time.<\/p>\n For example, you might be able to discover the colours of your jelly beans, but finding out their momentum would be a step too far.<\/p>\n The implication was if you breached this upper limit, you proved Einstein wrong.<\/p>\n It was doing this that snared Alain Aspect, John Clauser and Anton Zeilinger the 2022 Nobel Prize in Physics.<\/p>\n They broke the upper limit, proving that quantum mechanics \u2014 in all its weirdness \u2014 was sufficient to explain the behaviour of particles.<\/p>\n Alain Aspect explaining his experiment from 1982, which violated Bell’s inequality.\u00a0 (Wikimedia Commons: J\u00e9r\u00e9my Barande\/CC BY-SA 4.0<\/a>)<\/p>\n Although Professor Aspect’s experiments proved Einstein’s view of the world wrong, he did not gloat about it.<\/p>\n “When people say, ‘Oh, you showed Einstein wrong’, I say, ‘Come on, I showed Einstein was great,'” he said in response to the award.<\/p>\n After all, if Einstein had not asked all those follow-up questions, it is unclear where we might be in our understanding of particle physics, and our use of entanglement in quantum technology.<\/p>\n “Bohr’s instinct was right,” Dr Arianrhod says.<\/p>\n “But Einstein’s desire to look for fundamentals actually led him to find one of the most bizarre properties of quantum mechanics of all.”<\/p><\/blockquote>\n What comes next?<\/p>\n This year, physicists travelled to Helgoland<\/a>, tracing Heisenberg’s footsteps to mark the 100-year anniversary of his fateful trip.<\/p>\n The United Nations declared<\/a> 2025 the International Year of Quantum Science and Technology.<\/p>\n And yet the question that Einstein asked way back in the beginning \u2014 what does this all mean? \u2014 continues to nag theoretical physicists.<\/p>\n Einstein repeatedly challenged Bohr with thought experiments. (Wikimedia Commons: Paul Ehrenfest\/CC BY-SA 4.0<\/a>)<\/p>\n What does it mean for particles to be in a superposition of states, or entangled? What does it mean for observers to alter a particle?<\/p>\n The maths might work, but it can not make meaning.<\/p>\n Part of the problem, Dr Cavalcanti says, is that “we have a lot of answers, but we don’t know which one is right”.<\/p>\n “And each paints a completely different picture of reality.”<\/p>\n One is the Many Worlds<\/a> theory, which argues the wave of probabilities does not collapse after observation. All probabilities continue to exist, playing out in parallel universes.<\/p>\n The Holy Grail of physics: The quest to find quantum gravity<\/a><\/p>\n There’s a 100-year-old conundrum in physics that we’re still yet to untangle, and it has to do with the very nature of space-time itself.<\/p>\n “There’s a branch in which you chose to quit your job and there’s a branch where you chose to keep your job,” Dr Cavalcanti says.<\/p>\n Then there’s QBism<\/a>, which puts the observer’s subjective beliefs at the heart of measurement. Your expectations influence the observations you make.<\/p>\n And then the de Broglie\u2013Bohm theory, which allows faster-than-light interactions between particles, breaking Einstein’s theory of relativity.<\/p>\n There are dozens of interpretations out there, each weirder than the next. Any one of them could be true.<\/p>\n “Will we ever know? To Bohr, it didn’t matter. He didn’t really need to know, but Einstein did,” Dr Arianrhod says.<\/p>\n “There will always be people who want to know. Whether or not nature is going to reveal those secrets is anyone’s guess.”<\/p>\n Listen to <\/strong>The Centenary of Quantum Mechanics<\/strong><\/a> and subscribe to <\/strong>The Science Show podcast<\/strong><\/a> for more mind-bending science.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"In 1925, a young German physicist fled to the treeless island of Helgoland in the North Sea to…\n","protected":false},"author":2,"featured_media":300094,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3845],"tags":[110994,18419,111006,23755,30222,111008,111003,111004,110996,3284,23391,82694,59672,111010,110997,110998,110995,111002,111007,98774,111000,111001,74,111005,35305,17844,11112,6462,70,4945,16,15,110999,111009],"class_list":{"0":"post-300093","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-100-years","9":"tag-18419","10":"tag-alain-aspect","11":"tag-albert-einstein","12":"tag-anniversary","13":"tag-anton-zeilinger","14":"tag-bell-theorem","15":"tag-bells-inequality","16":"tag-bohr","17":"tag-computing","18":"tag-einstein","19":"tag-entanglement","20":"tag-epr","21":"tag-erwin-schrodinger","22":"tag-heisenberg","23":"tag-helgoland","24":"tag-hundred-years","25":"tag-john-bell","26":"tag-john-clauser","27":"tag-nobel","28":"tag-observer-effect","29":"tag-paradox","30":"tag-physics","31":"tag-prize","32":"tag-quanta","33":"tag-quantum-mechanics","34":"tag-quantum-physics","35":"tag-schrodinger","36":"tag-science","37":"tag-superposition","38":"tag-uk","39":"tag-united-kingdom","40":"tag-wave-equation","41":"tag-werner-heisenberg"},"share_on_mastodon":{"url":"","error":"Validation failed: Text character limit of 500 exceeded"},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/300093","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/comments?post=300093"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/300093\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media\/300094"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media?parent=300093"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/categories?post=300093"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/tags?post=300093"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/p>\n
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