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Quantum-Theory Wars Reference Frames, of Holding Mutually Opposing Views and of Being Free to Ramin Skibba Explores a History of Unresolved Change One’S Mind

Quantum-Theory Wars Reference Frames, of Holding Mutually Opposing Views and of Being Free to Ramin Skibba Explores a History of Unresolved Change One’S Mind

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are led away to their doom”. He says what you wouldn’t expect; if Dyson has a pattern, perhaps it is contra- riety. He prefers the students at Haver- ford College, a liberal-arts university in Pennsylvania — who are “ostentatiously ill-dressed, uncombed, and unwashed” — to Princeton’s “pampered” ones. He con- tradicts himself. His wartime job at the UK Royal Air ’s Bomber Command, analysing the effect of Allied firebomb- ing on German cities, left him “All these with a “perma- adventures in nently bad con- this strange new ”. Yet he world are still understood the unreal to me.” joy of German sailors who torpedoed Allied fuel tankers because he felt “elation” when the fire- bombing succeeded. In the late 1950s, he worked with the defence contractor General Atomic in La Jolla, California, on a project he thought would be “legendary”: a - ship called Orion, ill-advisedly powered by nuclear explosions. Because building it required nuclear testing, he publicly opposed the Nuclear Test Ban Treaty; after Orion was defunded, he supported the treaty. Later, he became president of the anti-nuclear-proliferation Federation of American . He proposed the ‘no first use’ policy on nuclear weapons, (left) with in the late , when was in its infancy. while admiring his theoretical- friend for standing against the treaty. Dyson’s contradictions might seem confusing, but I can hear him politely and methodically explaining the rationality of seeing from different Quantum-theory reference frames, of holding mutually opposing views and of being free to Ramin Skibba explores a history of unresolved change one’s mind. questions beyond the interpretation. The one Dysonian pattern for which the letters hold unequivocal evidence is delight. He uses the word often and ll hell broke loose in physics some cultural, political and invokes it even more: “Today I discov- 90 years ago. Quantum theory economic factors — ered a little theorem which gave me some emerged — partly in heated clashes he explores alterna- intense moments of pleasure. It is beauti- Abetween Albert Einstein and Niels Bohr. tive explanations. ful and fell into my hand like a jewel from It posed a challenge to the very of Had events played the sky.” In the book’s last letter, he writes science, and arguably continues to do so, by out differently in the to his sister about being robbed and hit severely straining the relationship between 1920s, he asserts, our on the head. Preparing to die, he notices theory and the nature of reality. Adam view of physics might the sunlight on the bushes and thinks, “life Becker, a science writer and astrophysicist, be very different. has been good to me and this death is also explores this tangled tale in What Is Real?. Becker lingers ARCHIVES/AIP/SPL VISUAL EMILIO SEGRE What Is Real?: The good, with the bright and the green Becker questions the hegemony of the Unfinished Quest on the 1927 Solvay bushes”. Copenhagen interpretation of quantum for the Meaning of Conference in Maybe with some people, you don’t mechanics. Propounded by Bohr and Werner Quantum Physics Brussels, where 29 look for patterns. You just enjoy their Heisenberg in the 1920s, this theory holds ADAM BECKER brilliant scientists multivariate company. ■ that physical systems have only , Basic: 2018. gathered to discuss rather than specific properties, until they’re the fledgling quantum Ann Finkbeiner is a freelance science measured. Becker argues that trying to parse theory. Here, the disagreements between writer in Baltimore, Maryland, and how this interpretation reflects the world Bohr, Einstein and others, including Erwin author of The Jasons. She blogs at www. we live in is an exercise in opacity. Showing Schrödinger and , came to a lastwordonnothing.com. that the evolution of science is affected by head. Whereas Bohr proposed that entities e-mail: [email protected] historical events — including sociological, (such as ) had only probabilities if

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they weren’t observed, Einstein argued that they had independent reality, prompting his famous claim that “ does not play dice”. Books in brief Years later, he added a gloss: “What we call science has the sole purpose of determining Work: The Last 1,000 Years what is.” Suddenly, — Andrea Komlosy, trans. Jacob K. Watson & Loren Balhorn Verso (2018) the idea that confirmed scientific theories Employment outside the home became the globally dominant form roughly reflect reality — was at stake. of work only after 1900. Yet in policy and discourse, it has eclipsed Quantum phenomena were phenomenally older, more informal modes of production. Social historian Andrea baffling to many. First was –particle Komlosy probes the joins between them in this sweeping chronicle, duality, in which can act as particles and from 1250 — the dawn of globalization and urbanization — to today, particles such as electrons interfere like light when international corporations threaten labour standards. This is a . According to Bohr, a system behaves as book teeming with insights, from the contempt for manual labour in a wave or a particle depending on context, but ancient Greece to the historical tendency for all kinds of subsistence you cannot predict which it will do. tasks to be “housewife-ized” into unpaid domestic labour. Second, Heisenberg showed that uncertainty, for instance about a particle’s position and , is hard-wired into The Ascent of John Tyndall physics. Third, Bohr argued that we could Roland Jackson University Press (2018) have only probabilistic knowledge of a system: A leading light in climate science, germ theory and , in Schrödinger’s thought experiment, a cat in Victorian researcher John Tyndall seemed a man for all . He a box is both dead and alive until it is seen. discovered the greenhouse effect and why the sky is , and as a Fourth, particles can become entangled. For public intellectual, hobnobbed with and example, two particles might have opposite Hermann von Helmholtz, and poet Alfred Tennyson. This splendid spins, no how far apart they are: if you monument of a biography by Roland Jackson tracks Tyndall’s rise measure one to be spin up, you instantly know from rural Ireland to laboratorial glory days in Britain and Europe. The that the other is spin down. (Einstein called experimentalist’s obscurity now, Jackson avers, may be down in part to this “spooky at a distance”.) his death in 1893: he just missed the era of relativity and the quantum. Becker explains how these challenge locality, and . In the classical world of billiard balls, projec- Microbia tiles and apples falling from trees, they were Eugenia Bone Rodale (2018) never problems. At the age of 55, journalist Eugenia Bone returned to university to take Sifting through the history, Becker shows a microbiology course, reasoning that “humility is the entry point for how Bohr, as an anti-realist, brought to studying nature”. The microbial of life came into focus. Bone’s his side many rising physicists, including is an exquisitely observant, often amusing voyage from the origins Heisenberg, and . of life to antibiotic resistance, punctuated by scientific revelations. Einstein, however, persistently argued that (The compound geosmin, produced by Streptomyces bacteria, gives the Copenhagen interpretation was incom- soil its sweet smell; bacteria nucleate rain; a quadrillion microbes plete. He conjectured that there might be pack part of a cow’s stomach.) The devil’s in the detail, Bone finds, but hidden variables or processes underlying what enchants is the connectivity of this ‘hidden’ ocean. quantum phenomena; or perhaps ‘pilot waves’, proposed by de Broglie, govern the behaviour of particles. In 1932, mathemati- Elastic: Flexible Thinking in a Constantly Changing World cian produced a proof Leonard Mlodinow Pantheon (2018) that there could be no hidden variables in Physicist Leonard Mlodinow revels in the neuroscientific. Here he . Although mathemati- extends his explorations with an in-depth study of agile creative cally correct, it was revealed to be flawed dec- thinking in a hectic age. Among the psychological factors Mlodinow ades later. But the damage had been done: the isolates are a yen for novelty, and the capacity to reconcile diverse potentially viable alternatives conceived by ideas. He plunges deep into the human brain, marshalling Einstein and de Broglie remained relatively compelling research both on brain basics and on outlier issues such unexplored. The Copenhagen interpretation as mental blocks. Perhaps most gripping is his take on the “default had taken hold by the , and textbooks network” — the brain structures that govern richly creative activities today state that Bohr’s view ‘won’. such as daydreaming, the “dialogue we have with ourselves”. Thus, the can be seen as a stand-off between two mathematically equivalent but fundamentally different Wild Moms : Bohr’s instrumentalist view of Carin Bondar Pegasus (2018) quantum physics and Einstein’s realist one. Biologist and broadcaster Carin Bondar’s tour of the vagaries of In science, a dominant determines motherhood in the animal kingdom is a thrills-and-spills survey, which experiments are done, how they’re from brood parasitism to breeding. The diversity of interpreted and what kind of path a research evolutionary solutions to maternality is mind-bending. We learn, programme follows. for instance, how baby koalas ingest their mothers’ faeces to But what if a picks the wrong para- inoculate their gut microbiomes, and that female gastric-brooding digm? Becker shows how, in the 1950s and frogs vomited up their froglets. Ultimately, however, this is less a 1960s, a handful of physicists dusted off the synthesized narrative than a biological litany. Barbara Kiser

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theories of Einstein and de Broglie and turned them into a fully fledged interpreta- tion capable of shaking up the status quo. argued that particles in quan- tum systems existed whether observed or not, and that they have predictable positions and deter- “Becker reminds mined by pilot us that we need waves. John Bell humility as then showed we investigate that Einstein’s the myriad concerns about interpretations locality and that explain the incompleteness same data.” in the Copen- hagen interpretation were valid. It was he who refuted von Neumann’s proof by revealing that it ruled out only a narrow class of hidden-variables theories. The scientific community greeted Bohm’s ideas coolly. A former mentor, J. Robert Oppenheimer, said: “if we can- not disprove Bohm, then we must agree to ignore him”. And, as Becker shows, Bohm’s leftist views led to an appearance before the House Un-American Activities Committee, and subsequent ostracization. Bohm’s contemporary, physicist Hugh Everett, delivered another challenge to the Copenhagen interpretation. In 1957, Everett set out to resolve the ‘’ in quantum theory — the con- tradiction between the probabilistic nature of particles at the quantum level and their ‘collapse’, when measured, into one state at A Pan Am shuttle prepares to dock at the international Space Station V in this classic scene from the film. the macroscopic level. Everett’s many-worlds interpretation posited no collapse. Instead, probabilities bifurcate at the moment of measurement IN RETROSPECT into parallel — such as one in which Schrödinger’s cat is alive and another in which it’s dead. Although an infinite number of untestable universes 2001: A Space Odyssey seems unscientific to some, many physi- cists today view the theory as important. Fifty years on, the masterful science-fiction film looks The book has a few minor short­comings. Becker gives too much space to recent more prophetic than ever, reflects Piers Bizony. applications building on Bell’s research, and too little to new developments in the of science. Yet he, like cosmolo- n 1968, film-maker Stanley Kubrick 2001: A Space Festival audience: gist Sean Carroll in his 2016 The Big Picture and his screenwriting colleague, Odyssey “A f t e r 2001, science (R. P. Crease Nature 533, 34; 2016), does science-fiction author Arthur C. Clarke, DIRECTOR: STANLEY fiction is dead.” make an explicit case for the importance of Ipresented 2001: A Space Odyssey. Half a KUBRICK; CO-WRITER: The narrative was ARTHUR C. CLARKE philosophy. That’s a key call, with influen- century later, this unprecedentedly detailed Metro-Goldwyn-Mayer: ambitious, to say tial scientists such as Neil deGrasse Tyson speculation about our place in the cosmos 1968. the least. Prehistoric dismissing the discipline as a waste of . and our evolving relationship with apemen have a mind- What Is Real? is an argument for technology is regarded as one of the great altering encounter with an alien black keeping an open mind. Becker reminds landmarks in cinema. monolith. Four million years later, a giant us that we need humility as we investigate The influence of 2001 on the design spacecraft is sent to Jupiter on a mysteri- the myriad interpretations and narratives of subsequent space-film hardware and ous mission. On board are two astronauts, that explain the same data. ■ special effects has been pervasive. How- three hibernating scientists and a seemingly ever, in terms of artistic and philosophical sentient computer, HAL 9000. Hovering Ramin Skibba is an astrophysicist turned bravura, it has been a harder act to follow. above Jupiter, another monolith waits. science writer based in San Diego, California. In 2007, director Ridley Scott (of Blade Monoliths aside, 2001 was prescient e-mail: [email protected] Runner and Alien fame) told a Venice Film in almost all its detailed of

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