Posts Tagged ‘quantum physics’
“Chance, too, which seems to rush along with slack reins, is bridled and governed by law”*…
… though that law can sometimes be less than obvious. Erica Klarreich reports on one creative mathematician’s efforts to help us learn…
In late January, Daniel Litt [pictured above] posed an innocent probability puzzle on the social media platform X (formerly known as Twitter) — and set a corner of the Twitterverse on fire.
Imagine, he wrote, that you have an urn filled with 100 balls, some red and some green. You can’t see inside; all you know is that someone determined the number of red balls by picking a number between zero and 100 from a hat. You reach into the urn and pull out a ball. It’s red. If you now pull out a second ball, is it more likely to be red or green (or are the two colors equally likely)?
Of the tens of thousands of people who voted on an answer to Litt’s problem, only about 22% chose correctly. (We’ll reveal the solution below, in case you want to think it over first.) In the months since, Litt, a mathematician at the University of Toronto, has continued to confound Twitter users with a series of probability puzzles about urns and coin tosses.
His posts have prompted lively online discussions among research mathematicians, computer scientists and economists — as well as philosophers, financiers, sports analysts and anonymous fans. Some joked that the puzzles were distracting them from their real work — “actively slowing down economic research,” as one economist put it. Others have posted papers exploring the puzzles’ mathematical ramifications.
Litt’s online project doesn’t just highlight the enduring allure of brainteasers. It also demonstrates the limits of our mathematical intuition, and the counterintuitive nature of probabilistic reasoning. As Litt wrote, there’s “nothing more exhilarating than posing a multiple-choice problem on which 50,000 people do substantially worse than random chance.”…
The answer to this puzzle, other puzzles, and Litt on what makes a great puzzle, and why simple probability questions can be so deceptively difficult: “Perplexing the Web, One Probability Puzzle at a Time,” from @EricaKlarreich in @QuantaMagazine.
Vaguely related (but also very interesting): “The Bookmaker,” via @annfriedman, who observes: “Leif Weatherby and Ben Recht on Nate Silver and the addiction to prediction: ‘Silver insists that viewing all decisions through this lens of gambling is the underappreciated characteristic of Very Successful People,’ they write. ‘But what Silver willfully ignores is that the successful players in this world aren’t the bettors. They are the bookies and casino owners—the house that never loses.'”
* Boethius, The Consolation of Philosophy
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As we contemplate chance, we might send confirmatory birthday greetings to Carl David Anderson; he was born on this date in 1905. An experimental physicist, he shared the 1936 Nobel Prize in Physics for his discovery (that’s to say, confirmation of the existence) of the positron, the first known particle of antimatter… which had been predicted by mathematician and physicist Paul Dirac, whose “Dirac Equation“– in part a product of its author’s application of probability theory– had predicted (among many other features of quantum theory as we know it) the existence of the particle (and antimatter).
“Few people have the imagination for reality”*…
Experiments that test physics and philosophy as “a single whole,” Amanda Gefter suggests, may be our only route to surefire knowledge about the universe…
Metaphysics is the branch of philosophy that deals in the deep scaffolding of the world: the nature of space, time, causation and existence, the foundations of reality itself. It’s generally considered untestable, since metaphysical assumptions underlie all our efforts to conduct tests and interpret results. Those assumptions usually go unspoken.
Most of the time, that’s fine. Intuitions we have about the way the world works rarely conflict with our everyday experience. At speeds far slower than the speed of light or at scales far larger than the quantum one, we can, for instance, assume that objects have definite features independent of our measurements, that we all share a universal space and time, that a fact for one of us is a fact for all. As long as our philosophy works, it lurks undetected in the background, leading us to mistakenly believe that science is something separable from metaphysics.
But at the uncharted edges of experience — at high speeds and tiny scales — those intuitions cease to serve us, making it impossible for us to do science without confronting our philosophical assumptions head-on. Suddenly we find ourselves in a place where science and philosophy can no longer be neatly distinguished. A place, according to the physicist Eric Cavalcanti, called “experimental metaphysics.”
Cavalcanti is carrying the torch of a tradition that stretches back through a long line of rebellious thinkers who have resisted the usual dividing lines between physics and philosophy. In experimental metaphysics, the tools of science can be used to test our philosophical worldviews, which in turn can be used to better understand science. Cavalcanti, a 46-year-old native of Brazil who is a professor at Griffith University in Brisbane, Australia, and his colleagues have published the strongest result attained in experimental metaphysics yet, a theorem that places strict and surprising constraints on the nature of reality. They’re now designing clever, if controversial, experiments to test our assumptions not only about physics, but about the mind.
While we might expect the injection of philosophy into science to result in something less scientific, in fact, says Cavalcanti, the opposite is true. “In some sense, the knowledge that we obtain through experimental metaphysics is more secure and more scientific,” he said, because it vets not only our scientific hypotheses but the premises that usually lie hidden beneath…
Gefter traces the history of this integrative train of thought (Kant, Duhem, Poincaré, Popper, Einstein, Bell), its potential for helping understand quantum theory… and the prospect of harnessing AI to run the necessary experiments– seemingly comlex and intensive beyond the scope of currenT experimental techniques…
Cavalcanti… is holding out hope. We may never be able to run the experiment on a human, he says, but why not an artificial intelligence algorithm? In his newest work, along with the physicist Howard Wiseman and the mathematician Eleanor Rieffel, he argues that the friend could be an AI algorithm running on a large quantum computer, performing a simulated experiment in a simulated lab. “At some point,” Cavalcanti contends, “we’ll have artificial intelligence that will be essentially indistinguishable from humans as far as cognitive abilities are concerned,” and we’ll be able to test his inequality once and for all.
But that’s not an uncontroversial assumption. Some philosophers of mind believe in the possibility of strong AI, but certainly not all. Thinkers in what’s known as embodied cognition, for instance, argue against the notion of a disembodied mind, while the enactive approach to cognition grants minds only to living creatures.
All of which leaves physics in an awkward position. We can’t know whether nature violates Cavalcanti’s [theorem] — we can’t know, that is, whether objectivity itself is on the metaphysical chopping block — until we can define what counts as an observer, and figuring that out involves physics, cognitive science and philosophy. The radical space of experimental metaphysics expands to entwine all three of them. To paraphrase Gonseth, perhaps they form a single whole…
“‘Metaphysical Experiments’ Probe Our Hidden Assumptions About Reality,” in @QuantaMagazine.
* Johann Wolfgang von Goethe
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As we examine edges, we might send thoughtful birthday greetings to Rudolf Schottlaender; he was born on this date in 1900. A philosopher who studied with Edmund Husserl, Martin Heidegger, Nicolai Hartmann, and Karl Jaspers, Schottlaender survived the Nazi regime and the persecution of the Jews, hiding in Berlin. After the war, as his democratic and humanist proclivities kept him from posts in philosophy faculties, he distinguished himself as a classical philologist and translator (e.g., new translations of Sophocles which were very effective on the stage, and an edition of Petrarch).
But he continued to publish philosophical and political essays and articles, which he predominantly published in the West and in which he saw himself as a mediator between the systems. Because of his positions critical to East Germany, he was put under close surveillance by the Ministry for State Security (Ministerium für Staatssicherheit or Stasi)– and inspired leading minds of the developing opposition in East Germany.
“A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux … is that the vast majority of the mass of the universe seems to be missing”*…
Quantum effects may not be just subatomic, Sabine Hossenfelder suggests; they might be expressed across galaxies, and solve the puzzle of dark matter…
Most of the matter in the Universe is invisible, composed of some substance that leaves no mark as it breezes through us – and through all of the detectors the scientists have created to catch it. But this dark matter might not consist of unseen particle clouds, as most theorists have assumed. Instead, it might be something even stranger: a superfluid that condensed to puddles billions of years ago, seeding the galaxies we observe today.
This new proposal has vast implications for cosmology and physics. Superfluid dark matter overcomes many of the theoretical problems with the particle clouds. It explains the long-running, increasingly frustrating failure to identify the individual constituents within these clouds. And it offers a concrete scientific path forward, yielding specific predictions that could soon be testable.
Superfluid dark matter has important conceptual implications as well. It suggests that the common picture of the Universe as a mass of individual particles bound together by forces – almost like a tinker toy model – misses much of the richness of nature. Most of the matter in the Universe might be utterly unlike the matter in your body: not composed of atoms, and not even built of particles as we normally understand them, but instead a coherent whole of vast extension…
Is dark matter composed of particles? Is it a fluid? Or is it both? Read On: “The superfluid Universe,” from @skdh in @aeonmag.
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As we deconstruct the dark, we might spare a thought for Richard Philips Feynman; he died on this date in 1988. A theoretical physicist, Feynman was probably the most brilliant, influential, and iconoclastic figure in his field in the post-WW II era.
Richard Feynman was a once-in-a-generation intellectual. He had no shortage of brains. (Relevantly to the piece above, in 1965 he won the Nobel Prize in Physics for his work on quantum electrodynamics.) He had charisma. (Witness this outtake [below] from his 1964 Cornell physics lectures [available in full here].) He knew how to make science and academic thought available, even entertaining, to a broader public. (See, for example, these two public TV programs hosted by Feynman here and here.) And he knew how to have fun.
– From Open Culture (where one can also find Feynman’s elegant and accessible 1.5 minute explanation of “The Key to Science.”)
“To create something from nothing is one of the greatest feelings”*…
Something from nothing? Not exactly. As Charlie Wood explains, it’s even weirder…
For their latest magic trick, physicists have done the quantum equivalent of conjuring energy out of thin air. It’s a feat that seems to fly in the face of physical law and common sense.
“You can’t extract energy directly from the vacuum because there’s nothing there to give,” said William Unruh, a theoretical physicist at the University of British Columbia, describing the standard way of thinking.
But 15 years ago, Masahiro Hotta, a theoretical physicist at Tohoku University in Japan, proposed that perhaps the vacuum could, in fact, be coaxed into giving something up.
At first, many researchers ignored this work, suspicious that pulling energy from the vacuum was implausible, at best. Those who took a closer look, however, realized that Hotta was suggesting a subtly different quantum stunt. The energy wasn’t free; it had to be unlocked using knowledge purchased with energy in a far-off location. From this perspective, Hotta’s procedure looked less like creation and more like teleportation of energy from one place to another — a strange but less offensive idea.
“That was a real surprise,” said Unruh, who has collaborated with Hotta but has not been involved in energy teleportation research. “It’s a really neat result that he discovered.”
Now in the past year, researchers have teleported energy across microscopic distances in two separate quantum devices, vindicating Hotta’s theory. The research leaves little room for doubt that energy teleportation is a genuine quantum phenomenon.
“This really does test it,” said Seth Lloyd, a quantum physicist at the Massachusetts Institute of Technology who was not involved in the research. “You are actually teleporting. You are extracting energy.”…
“Physicists Use Quantum Mechanics to Pull Energy out of Nothing,” from @walkingthedot in @QuantaMagazine.
Vaguely related (and fascinating): “The particle physics of you.”
* Prince
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As we demolish distance, we might send insightful birthday greetings to Brain Cox; he was born on this date in 1968. A physicist and former musician (he was keyboardist for Dare and D:Ream), he is a professor of particle physics in the School of Physics and Astronomy at the University of Manchester, and a fellow at CERN (where he works on the ATLAS experiment, studying the forward proton detectors for the Large Hadron Collider there).
But Cox is most widely known as the host/presenter of science programs, perhaps especially the BBC’s Wonders of the Universe series, and for popular science books, such as Why Does E=mc²? and The Quantum Universe— which (he avers) were inspired by Carl Sagan and for which Cox has earned recognition as the natural successor to David Attenborough and Patrick Moore.
Science is too important not to be a part of a popular culture.
“There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”*…
Some observations are best considered “interesting, if true”; some, a la Karl Popper, “true, until false”… Consider this very recent paper in Nature…
Theories of scientific and technological change view discovery and invention as endogenous processes, wherein previous accumulated knowledge enables future progress by allowing researchers to, in Newton’s words, ‘stand on the shoulders of giants.’ Recent decades have witnessed exponential growth in the volume of new scientific and technological knowledge, thereby creating conditions that should be ripe for major advances. Yet contrary to this view, studies suggest that progress is slowing in several major fields. Here, we analyse these claims at scale across six decades, using data on 45 million papers and 3.9 million patents from six large-scale datasets, together with a new quantitative metric—the CD index—that characterizes how papers and patents change networks of citations in science and technology. We find that papers and patents are increasingly less likely to break with the past in ways that push science and technology in new directions. This pattern holds universally across fields and is robust across multiple different citation- and text-based metrics. Subsequently, we link this decline in disruptiveness to a narrowing in the use of previous knowledge, allowing us to reconcile the patterns we observe with the ‘shoulders of giants’ view. We find that the observed declines are unlikely to be driven by changes in the quality of published science, citation practices or field-specific factors. Overall, our results suggest that slowing rates of disruption may reflect a fundamental shift in the nature of science and technology.
The full paper: “Papers and patents are becoming less disruptive over time” @Nature
One notes that the quote above– from Lord Kelvin, at the turn of the twentieth century– immediately preceded a couple of decades in which physics was radically redefined and advanced by Planck, Einstein, Bohr, et al. (In fairness to Kelvin, consider this suggestion that his point was more subtle.) As we look forward, we might ponder the ways in which the reorganization of disciplines, the rise of research in other cultures (less constrained by the mores of “conventional” research), the use of AI, and/or some as yet unknown dynamic could challenge the phenomenon– “a narrowing in the use of previous knowledge”– to which the authors attribute diminishing disruption.
[Source of the image above]
* Lord Kelvin, in an address to the the Royal Institution in April of 1900
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As we ponder progress, we might send advanced birthday greetings to Wilhelm Wien; he was born on this date in 1864. A physicist, his work helped move past Kelvin’s log-jam. In 1893, he used theories about heat and electromagnetism to deduce Wien’s displacement law, which calculates the emission of a blackbody (a surface that absorbs all radiant energy falling on it) at any temperature from the emission at any one reference temperature. His colleague Max Planck colaborated with Wien, then extended the thinking in what we now know as Planck’s law, which led to the development of quantum theory.
Wien received the 1911 Nobel Prize for his work on heat radiation.
Just before Kelvin’s speech (in 1898) Wien identified a positive particle equal in mass to the hydrogen atom– what we now know as a proton. Wien, in the techniques he used, laid the foundation of mass spectrometry.
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