Posts Tagged ‘Physics’
“Listening to both sides of a story will convince you that there is more to a story than both sides”*…
Regular readers will have deduced that I am something of a techno-optimist. While I worry that human misapplication (exploitation) of new technologies could create new dangers and/or further concentrate wealth and power in too few hands, I believe that emerging tech could– should– help humanity deal with many of its gravest challenges, certainly including climate change. At the same time, I am disposed to thinking about large issues/problems systemically.
Rianne Riemens shares neither of my enthusiasms; she sounds a critical note on techno-optimism, systems thinking– and more specifically, on the application of the latter to the former…
Today, American tech actors express optimistic ideas about how to fix the Earth and halt climate change. Such “green” initiatives have in common that they capture the world in systems and propose large systemic, and mostly technological, solutions. Because of their reliance on techno-fixes, representatives of Silicon Valley express an ideology of ecomodernism, which believes that human progress can be “decoupled” from environmental decline. In this article, I show how “whole-systems thinking” has become a key discursive element in today’s ecomodernist discourses. This discourse has developed from the 1960s onwards – inspired by cybernetic, ecological and computational theories – within the tech culture of California. This paper discusses three key periods in this development, highlighting key publications: the Whole Earth Catalog of the 1960s, the Limits to Growth report in 1972 and the cyberspace manifestoes of the mid 1990s. These periods are key to understand how techno-fixes became a popular answer to the climate crisis, eventually leading to a vision of the world as an ecosystem that can be easily controlled and manipulated, and of technological innovation as harmless and beneficial. I argue that “whole-systems” thinking offers a naive and misleading narrative about the development of the climate crisis, that offers a hopeful yet unrealistic perspective for a future threatened by climate change, built on a misconception of Earth as a datafied planet.
In “The Techno-Optimist Manifesto” (Citation2023) venture capitalist Marc Andreessen argues why we should all be techno-optimists, especially if we are worried about the future impact of the climate crisis. According to Andreessen, promoting unlimited technological progress is the only option: “there is no inherent conflict between the techno-capital machine and the natural environment”. If we generate unlimited clean energy, we can improve the natural environment, whereas a “technologically stagnant society ruins it” (Andreessen, Citation2023). This is possible, he writes, because technologies enable processes of dematerialization and will eventually lead to material abundance. And, “We believe the market economy is a discovery machine, a form of intelligence—an exploratory, evolutionary, adaptive system” (Andreessen, Citation2023). The manifesto thus conceptualizes technology as immaterial and the capitalist economy as an evolutionary system: it presents techno-fixes as a harmless form of environmental action, and economic growth as an inevitable process that political powers should not interfere with.
The “Techno-Optimist Manifesto” is an example of a form of techno-optimism that places full trust in the potential of capitalist tech companies to help humanity “innovate” its way out of a climate crisis. Andreessen (Citation2023) cites historical figures including Buckminster Fuller, Stewart Brand, Douglas Engelbart and Kevin Kelly as the inspiration for his manifesto, showing that the work of these figures and their communities is being remixed and reappropriated into the future visions of contemporary techno-optimists. In this article, I analyse how the belief in the environmental potential of techno-fixes is engrained in the ideology and history of “Silicon Valley” and is discursively constructed through a language of “whole-systems thinking”. I use the concept of whole-systems thinking as a lens to study how simplified notions taken from whole-systems theory and cybernetics played and still play a key role in techno-environmental discourse in the post-war era in the United States. I zoom in on three key events that help explain the origins and evolution of popular whole-systems thinking: the Whole Earth Catalog community led by Stewart Brand in the 1960s, the Limits to Growth report by the Club of Rome in the 1970s and the cyberlibertarian community in the 1990s. I will show how a new language emerged that used simplified notions of systems-thinking to promote the idea that technology would help understand, manage and save a planet in peril.
Through a discourse analysis of primary sources and literature review I present a critical reading of these events in the light of today’s techno-optimistic environmental discourse. My corpus exists of a number of primary sources, including the aforementioned “Techno-Optimist Manifesto” (2023), Limits to Growth report (Meadows et al., Citation1972), editions of the Whole Earth Catalog and CoEvolution Quarterly, Barlow’s Declaration of the Independence of Cyberspace (1996), texts by Kevin Kelly (Citation1998) and Stewart Brand (Citation2009) and An Ecomodernist Manifesto (Asafu-Adjaye et al., Citation2015). I have discursively analysed these sources for their discussion of systems thinking as well as environmental concerns. By analysing how whole-systems thinking became a popular way of addressing environmental issues, I aim to provide a “post-war genealogy” (Pedwell Citation2022) of the term and critique today’s promises about how tech can save the climate. As Johnston (Citation2020) has argued, tracing the development of a cultural perception of trust in techno-fixes reveals a complex and multi-sided history. I claim that the environmental dimension of techno-optimistic discourses requires a critical reconsideration of the ideological underpinnings of Silicon Valley, described as the “Californian Ideology” by Barbrook and Cameron (Citation1996). I will demonstrate how ecomodernism, including its belief that human progress can be “decoupled” from environmental decline, allows us to better understand, and critique, the environmental ideology of Silicon Valley.
I will first expand on contemporary ecomodernism and present my thesis that “decoupling” nature from culture has come to underlie whole-systems thinking in contemporary techno-optimistic discourse. In the following three sections, I highlight a few historical moments to demonstrate the development of the cultural perception of techno-fixes, specifically as a means of managing the environment. I show how whole-systems thinking became popularized by the Whole Earth community, got incorporated in environmental debates through the Limits to Growth report and is reflected in cyberutopian dreams about immaterial societies. Building on my necessarily brief history, I argue that techno-fixes can be strategically presented as ideal solutions if the world and environment are imagined as simple systems and technology as immaterial and harmless. Finally, I return to contemporary US tech culture and argue that it is shaped by, and co-shapes, the ideology of ecomodernism in which nature and culture are decoupled. I conclude that this worldview expresses itself today in corporate visions, resulting in a false hope about how to innovate our way out of the climate crisis…
Eminently worth reading in full (if in the end, as for me, less as a wholesale rejection of techno-optimism and systems thinking than as a cautionary counterweight): “Fixing the earth: whole-systems thinking in Silicon Valley’s environmental ideology,” from @WeAreTandF.
(image above: source)
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As we tangle with tech, we might pause to remember a man who bridged our understanding of the systems of the world from one paradigm to another: Sir Arthur Stanley Eddington, OM, FRS; he died in this date in 1944. An astrophysicist, mathematician, and philosopher of science known for his work on the motion, distribution, evolution and structure of stars, Eddington is probably best remembered for his relationship to Einstein: he was, via a series of widely-published articles, the primary “explainer” of Einstein’s Theory of General Relativity to the English-speaking world; and he was, in 1919, the leader of the experimental team that used observations of a solar eclipse to confirm the theory.
“Life is teleology par excellence; it is the intrinsic striving towards a goal, and the living organism is a system of directed aims which seek to fulfill themselves”*…
Daniel McShea and Gunnar Babcock argue that everything in the Universe, from wandering turtles to falling rocks, is surrounded by ‘fields’ that guide and direct their movement…
Why do rocks fall? Before Isaac Newton introduced his revolutionary law of gravity in 1687, many natural scientists and philosophers thought that rocks fell because falling was an essential part of their nature. For Aristotle, seeking the ground was an intrinsic property of rocks. The same principle, he argued, also explained why things like acorns grew into oak trees. According to this explanation, every physical object in the Universe, from rocks to people, moved and changed because it had an internal purpose or goal.
Modern science has rejected this ‘teleological’ way of thinking. In the 17th and 18th centuries, scientists and philosophers began to chip away at Aristotle’s seemingly ‘spooky’ notion of intrinsic causes – spooky because they suggested that rocks and creatures were guided by something not entirely material. For those who rejected these Aristotelean explanations, such as Thomas Hobbes and René Descartes, organisms were simply complex machines animated by mechanisms. ‘Life is but a motion of limbs,’ wrote Hobbes in his Leviathan (1651). ‘For what is the heart, but a spring; and the nerves, but so many strings; and the joints, but so many wheels, giving motion to the whole body.’ The heart does not have the goalof circulating blood. It’s just a spring like any other. For many thinkers at the time, this view had real explanatory benefits because they knew something about how machines worked, including how to fix them. It was in this intellectual environment that Newton developed a powerful mechanical worldview, based on his discovery of gravitational fields. In a Newtonian universe, internal purpose doesn’t cause rocks to fall. They just fall, following a law of nature.
Mechanistic explanations, however, struggled to explain how life develops. How does a grass seed become a blade of grass, in the face of endless disturbances from its environment? Long after the mechanistic revolution, the philosopher Immanuel Kant confronted the stubborn problem of teleology and despaired. In 1790, he wrote in the Critique of Judgment that – as commonly paraphrased – ‘there will never be a Newton for a blade of grass.’ Less than a century later, with the publication of On the Origin of Species (1859), Charles Darwin seemed to crack the problem of biological teleology. Darwin’s ideas about natural selection appeared to explain how organisms, from grass seeds to bats, were able to pursue goals. The directing process was blind variation and the selective retention of favourable variants. Bats who sought moths and had an ever-improved capacity to track and catch them were favoured over those who were less goal directed and therefore had lesser capabilities. Though natural selection seemed to illuminate what Descartes, Hobbes and Kant could not, Darwin’s theory answered only half the problem of teleology. Selection explained where teleological systems like moth-seeking bats come from but didn’t answer how they find their goals.
So, how do goal-directed entities do it, moment by moment? How does an acorn seek its adult form? How does a homing torpedo find its target? Mechanistic thinking struggles to answer these questions. From a mechanical perspective, these systems look strangely future oriented. A sea turtle, hundreds of miles out to sea, can find the beach where it was born, a location that lies in its future. A developing embryo, without any thought of the future, constructs tissues and organs that it will not need until much later in life. And both do these things persistently: carried off course by a strong current, the sea turtle persistently finds a trajectory back toward its natal beach; despite errors in cell division and gene expression, an embryo is able to make corrections as it grows into its adult form. How is this possible?
Even though mechanistic thinking has failed to solve this teleological problem, it still dominates scientific thought. Today, we invoke mechanism to explain almost everything – including human goal-directed behaviour. To explain the growth of an acorn, we look to mechanisms in its genes. To explain the ocean voyages of a sea turtle, we look to mechanisms in its brain. And to explain our own thoughts and decisions, we focus on neural pathways and brain chemistry to explain decision-making. We explain behaviour in terms of evolutionary needs, such as survival or reproductive success. We may even think of our genes as ‘blueprints’. For some 20th-century thinkers, such as the US psychologist Burrhus Frederic Skinner, human brains are purely mechanistic. Skinner denied that people have goals at all. More recently, the primatologist Robert Sapolsky, based at Stanford University, and others have painted a mechanistic picture of us that denies we have free will.
And yet, despite centuries of rejection, teleology has not been banished. Most of us still have a deep intuition that there is more to our thinking and action than mere mechanisms. The feeling of being in love isn’t just the mechanical outcome of neurochemistry. We want to believe it is driven by our wants and intentions. Some of us, especially if moved by religious or spiritual impulses, might even see goals in the larger universe: ‘I am here for a purpose,’ you might think to yourself. For many, a world of pure mechanism seems insufficient. And beyond our intuitions about teleology, there are countless areas of science where teleological explanations are commonly deployed, even without any explicit recognition of them. Consider the debate over which parts of a genome are ‘functional’ (ie, they perform roles that are beneficial to an organism) and which are ‘non-functional’ (ie, useless remnants of evolution). The very idea that a gene can either be functional or non-functional implies that certain genes aim towards certain results, or have certain purposes for the organism, while others have no ends and are merely purposeless junk. So, even beyond our intuitions, teleology is so deeply entwined with science that there will be no getting rid of it anytime soon.
So, caught between modern science and our intuitions about teleology, we seem to have only two ways of explaining the apparent goal directedness in some systems: teleology or mechanism. Both are troublesome. Both are inadequate. In recognition of this problem, philosophers of biology and others have, in recent decades, been struggling to find an alternative. We believe we have found it: a third way that reconciles Aristotelian thinking about goal directedness with the mechanistic view of a Newtonian universe. This alternative explains the apparent seeking of all goal-directed entities, from developing acorns and migrating sea turtles to self-driving cars and human intentions. It proposes that a hidden architecture connects these entities. It even explains falling rocks.
We call it ‘field theory’…
Eminently worth reading in full: “Elusive but everywhere,” from @aeonmag.
* Carl Jung
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As we grapple with goals, we might recall that it was on this date in 184i that James Braid first saw a demonstration of “animal magnetism,” which led to his study of the subject he eventually called “hypnotism” and his contributions to the development of hypnotherapy. Details here.
“In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move.”*…
In the face of cosmologists who are trying to combine string theory with the theory of cosmic inflation to understand the universe-as-we-find-it, Neil Turok suggests a much simpler explanation. Frank Landymore reports…
Our understanding of the universe, as advanced as it is, remains riddled with paradoxes and huge question marks. Physicists have come up with some pretty heady ideas to explain them — we’ll get to those later — but there just might be a far “simpler” solution to all those holes in cosmology.
As Higgs Chair of Theoretical Physics at the University of Edinburgh Neil Turok explains in an essay for The Conversation, there could be a “mirror” universe that existed before the Big Bang and is a reflection of our own, moving backward in time.
It’s a trippy concept to wrap your head around, but simpler on the physics side of things. It would neatly balance out some of the asymmetries we observe in the universe, provide an answer to dark matter, and supplant some of what Turok would characterize as clumsier leading theories in cosmology, like cosmic inflation and string theory.
“Picturing the big bang as a mirror neatly explains many features of the universe which might otherwise appear to conflict with the most basic laws of physics,” wrote Turok, who published his team’s findings in the journal Annals of Physics. “The progress we have already made convinces me that, in all likelihood, there are alternatives to the standard orthodoxy — which has become a straitjacket we need to break out of.”
The physical laws of the universe should exhibit charge, parity, and time reversal — collectively known as CPT — symmetry, which essentially means every physical interaction can be mirrored. So to break down its implications: every particle should have an anti-particle of the opposite charge, every space has its inversion, and time can be reversed.
Except that’s not what we actually observe. Time only goes forward, and there are more particles than anti-matter particles. As far as we can tell, our universe is not symmetrical.
But: “Our mirror hypothesis restores the symmetry of the universe,” Turok argued. He compared it to looking at your reflection: “The combination of you and your mirror image are more symmetrical than you are alone.”
Extrapolating our universe backward in time through the Big Bang, “we found its mirror image, a pre-bang universe in which (relative to us) time runs backward and antiparticles outnumber particles,” Turok wrote.
This could also solve the mystery of dark matter, an invisible substance thought to make up 85 percent of all matter in the universe. Under the mirror hypothesis, weak, subatomic particles called neutrinos would be the ideal candidate to explain it.
Since we’ve only observed left-handed neutrinos, perhaps yet-unseen right-handed could even exist in the mirror universe.
What’s more, this could also tidily explain why the universe appears to be so uniform and flat. The prevailing theory is that a period of accelerated, faster-than-light expansion called cosmic inflation was responsible for shaping how the universe is today — but we’re yet to observe the large gravitational waves this would have produced.
With a handy mirror universe, however, “statistical arguments explain why the universe is flat and smooth and has a small positive accelerated expansion, with no need for cosmic inflation,” Turok wrote.
Of course, there’s a lot more needed to bear out this intriguing hypothesis. But Turok argues that, even if disproven, it demonstrates that there could be more straightforward explanations than what the Standard Model offers…
A mirror of our own, going backwards in time: “Physicist Says There’s Another Universe Hiding Behind the Big Bang,” from @futurism.
Turok’s full essay– longer and more detailed, but very accessible– is here.
* Douglas Adams, The Restaurant at the End of the Universe
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As we size up symmetry, we might send lofty birthday greetings to another ponderer of the cosmos, Carl Edward Sagan; he was born on this date in 1934. An astronomer, cosmologist, astrophysicist, astrobiologist (his contributions were central to the discovery of the high surface temperatures of Venus), he is best remembered as a popularizer of science– via books like The Dragons of Eden, Broca’s Brain and Pale Blue Dot, and the award-winning 1980 television series Cosmos: A Personal Voyage (which he narrated and co-wrote), the most widely-watched series in the history of American public television (seen by at least 500 million people across 60 different countries).
He is also remembered for his contributions to the scientific research of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.
(Readers can enjoy a loving riff on Cosmos here.)
“What happens when you get to the end of things?”*…
Charlie Wood introduces a remarkable new collection in Quanta…
A couple of years ago, I was chatting about black holes with Dan Harlow of the Massachusetts Institute of Technology when he made a casual comment that left a deep impression on me. I asked if some new work he’d been doing strengthened the case that space-time was “emergent.” Without missing a beat he replied, “Sure, if it needed strengthening.”
Harlow isn’t the only physicist with serious doubts about what reality is made of. For more than a decade now, Nima Arkani-Hamed of the Institute for Advanced Study has been delivering a polished lecture arguing that space-time is “doomed.” Time and again, I’ve heard theorists in high-energy physics make similar-sounding statements, and I’ve always been struck by their confidence. We don’t have the faintest idea what the next theory of physics will look like, whether it will involve strings, loops, triangles or something entirely new that no one has thought to propose. And yet so many theorists seem rather convinced that whatever it will be, it won’t involve space or time.
Why? What does that statement mean? What would it look like to do physics without referring to space or time? I’ve spent most of this year trying to find out. The results have just been published in “The Unraveling of Space-Time,” a massive package that includes articles, videos and interactive animations from me and my colleagues Mark Belan, Emily Buder, Amanda Gefter and Joseph Howlett.
Over the course of more than 40 interviews with nearly 30 physicists, I learned that there are many ways to define emergent space-time. But at the most basic level, “emergent space-time” means that space and time are the outputs of a theory instead of the inputs. A classic analogy is heat. To explain why a teacup cools, scientists of the 1700s put heat into their theory of the world as a substance that repels itself and naturally spreads out. But this “caloric theory” was ultimately replaced by thermodynamics, a theory where a primary input is molecules that buzz around with some energy. As molecules crash into each other, their energy spreads, and we now recognize this process as the origin of heat transfer. Heat is an output — a prediction — of thermodynamics. It is an emergent phenomenon.
Space-time is the ultimate input. If physics is largely about predicting what happens where and when, you need a stage upon which things can happen. Albert Einstein became a household name for revealing that this stage acts like a fabric that bends in ways we experience as gravity. He described in spectacular detail how space-time behaves, much as 19th-century scientists described how heat behaves with caloric theory. The idea that space-time is emergent is the idea that space-time will eventually go the way of heat, water, air and so many other substances before it; we will someday understand it to be the inevitable consequence of the behavior of simpler entities. Call them the “atoms” of space-time.This week’s series explores the mind-bending notion of emergent space-time from a number of angles. There is, of course, the why of it all. This mostly boils down to the strange things that happen when Einstein’s theory of space-time collides with quantum mechanics, the theory of the subatomic world. When we combine features from both theories, we see that any experiment that tries to probe reality a little too closely will get thwarted by the appearance of a black hole, an enigma that undermines the familiar picture of space-time in its own way.
For this and other reasons, physicists are pushing to escape our familiar space-time, often referred to as the “bulk,” in search of alien environments conducive to new ways of doing physics.
Where else might one do physics, if not in the bulk? A few ideas are being developed, including one that goes by the name of holography. This is roughly the idea that any gravitational system — even the entire universe — can have an alternative description as a collection of quantum particles moving around a flat surface. From these gravity-free surfaces, a bulk world with gravity somehow pops out. It’s a remarkable theoretical claim, and over the past few years, holographers have developed a suite of tools that have helped them decode the bulk from the behavior of these surface particles.Another research program, spearheaded by Arkani-Hamed, has even more ambitious aims — getting both space-time and quantum mechanics as outputs from even more alien inputs. His group has recently developed an entirely new language for making predictions, one that makes no reference to space-time. Instead, it uses only geometric shapes and primitive counting tasks.
Is space-time, at least in its current form, definitely doomed? The idea tortured one of the pioneers of gravitational theory, John Wheeler. And today, the end of space-time is even more widely accepted. Most of the theorists I spoke with struggled to think of colleagues in the quantum gravity community who would defend space-time as a fundamental ingredient of reality. However, some researchers are pursuing alternatives. I spoke at length with Latham Boyle about patterns in particle physics that have led him and his collaborators to the more conservative notion that space-time might come in two “sheets.”
The various proposals under development are unlikely to see experimental tests this century, so a conclusive answer doesn’t seem near. But if it were someday established that space-time does break down, what would that mean for us?
On a practical level, not much. Einstein’s fabric of space-time is so sturdy that little short of a black hole would put a noticeable dent in it. But at a conceptual level, it’s hard to imagine a more dramatic rethinking of reality. When Democritus suggested that matter emerges from tiny barbed “atoms” more than 2,000 years ago, he couldn’t possibly have foreseen that parts of his proposal would ultimately be realized in the form of quantum theory — a framework asserting that reality is an ocean of overlapping waves of possibility that resolve into fixed objects only in certain situations.
If the void itself emerges from something, that something will be at least as alien. Just as individual molecules don’t themselves have a well-defined notion of heat, the base level of reality could lack marquee features of our existence that we take for granted. Places. Times. The ability to influence only nearby objects. The requirement that causes precede effects. Physicists are already finding that these notions seem unlikely to be present in a more precise accounting of the world. They seem to be the approximate outputs of something stranger.“One of the most spectacular aspects of these new findings is the emergence of causality can only happen in the approximate description,” Elliott Gesteau, a quantum gravity researcher at the California Institute of Technology, told me over Zoom earlier this year. If there is gravity, he continued, “which is what we have in our world, then this causal structure is only approximate and must break down.”…
Are we on the verge of a new physics? “Why Space-Time Looks Doomed,” from @walkingthedot in @QuantaMagazine.
The full interactive collection is here, and eminently worth reading in full.
* John Wheeler
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As we wrestle with reality, we might spare a thought for a physicist whose work helped move the questions we face forward– Max Karl Ernst Ludwig Planck; he died on this date in 1947. A theoretical physicist, he is best remembered as the originator of quantum theory. It was his discovery of energy quanta that won him the Nobel Prize in Physics in 1918.
“Those who are not shocked when they first come across quantum theory cannot possibly have understood it”*…
A scheduling note: your correspondent is headed onto the road for a couple of weeks, so (Roughly) Daily will be a lot more roughly than daily until September 20th or so.
100 years ago, a circle of physicists shook the foundation of science. As Philip Ball explains, it’s still trembling…
In 1926, tensions were running high at the Institute for Theoretical Physics in Copenhagen. The institute was established 10 years earlier by the Danish physicist Niels Bohr, who had shaped it into a hothouse for young collaborators to thrash out a new theory of atoms. In 1925, one of Bohr’s protégés, the brilliant and ambitious German physicist Werner Heisenberg, had produced such a theory. But now everyone was arguing with each other about what it implied for the nature of physical reality itself.
To the Copenhagen group, it appeared reality had come undone…
[Ball tells the story of Niels Bohr’s building on Max Planck, of Werner Heisenberg’s wrangling of Bohr’s thought into theory, of Einstein’s objections and Erwin Schrödinger’s competing theory; then he homes in on the ontological issue at stake…]
Quantum mechanics, they said, demanded we throw away the old reality and replace it with something fuzzier, indistinct, and disturbingly subjective. No longer could scientists suppose that they were objectively probing a pre-existing world. Instead, it seemed that the experimenter’s choices determined what was seen—what, in fact, could be considered real at all.
In other words, the world is not simply sitting there, waiting for us to discover all the facts about it. Heisenberg’s uncertainty principle implied that those facts are determined only once we measure them. If we choose to measure an electron’s speed (more strictly, its momentum) precisely, then this becomes a fact about the world—but at the expense of accepting that there are simply no facts about its position. Or vice versa…
…A century later, scientists are still arguing about this issue of what quantum mechanics means for the nature of reality…
[Ball recounts subsequent attempts to reconcile quantum theory to “reality,” including Schrödinger’s wave mechanics…]
… Schrödinger’s wave mechanics didn’t restore the kind of reality he and Einstein wanted. His theory represented all that could be said about a quantum object in the form of a mathematical expression called the wave function, from which one can predict the outcomes of making measurements on the object. The wave function looks much like a regular wave, like sound waves in air or water waves on the sea. But a wave of what?
At first, Schrödinger supposed that the amplitude of the wave—think of it like the height of a water wave—at a given point in space was a measure of the density of the smeared-out quantum particle there. But Born argued that in fact this amplitude (more precisely, the square of the amplitude) is a measure of the probability that we will find the particle there, if we make a measurement of its position.
This so-called Born rule goes to the heart of what makes quantum mechanics so odd. Classical Newtonian mechanics allows us to calculate the trajectory of an object like a baseball or the moon, so that we can say where it will be at some given time. But Schrödinger’s quantum mechanics doesn’t give us anything equivalent to a trajectory for a quantum particle. Rather, it tells us the chance of getting a particular measurement outcome. It seems to point in the opposite direction of other scientific theories: not toward the entity it describes, but toward our observation of it. What if we don’t make a measurement of the particle at all? Does the wave function still tell us the probability of its being at a given point at a given time? No, it says nothing about that—or more properly, it permits us to say nothing about it. It speaks only to the probabilities of measurement outcomes.
Crucially, this means that what we see depends on what and how we measure. There are situations for which quantum mechanics predicts that we will see one outcome if we measure one way, and a different outcome if we measure the same system in a different way. And this is not, as is sometimes implied (this was the cause of Heisenberg’s row with Bohr), because making a measurement disturbs the object in some physical manner, much as we might very slightly disturb the temperature of a solution in a test-tube by sticking a thermometer into it. Rather, it seems to be a fundamental property of nature that the very fact of acquiring information about it induces a change.
If, then, by reality we mean what we can observe of the world (for how can we meaningfully call something real if it can’t be seen, detected, or even inferred in any way?), it is hard to avoid the conclusion that we play an active role in determining what is real—a situation the American physicist John Archibald Wheeler called the “participatory universe.”..
… Heisenberg’s “uncertainty” captured that sense of the ground shifting. It was not the ideal word—Heisenberg himself originally used the German Ungenauigkeit, meaning something closer to “inexactness,” as well as Unbestimmtheit, which might be translated as “undeterminedness.” It was not that one was uncertain about the situation of a quantum object, but that there was nothing to be certain about.
There was an even more disconcerting implication behind the uncertainty principle. The vagueness of quantum phenomena, when an electron in an atom might seem to jump from one energy state to another at a time of its own choosing, seemed to indicate the demise of causality itself. Things happened in the quantum world, but one could not necessarily adduce a reason why. In his 1927 paper on the uncertainty principle, Heisenberg challenged the idea that causes in nature lead to predictable effects. That seemed to undermine the very foundation of science, and it made the world seem like a lawless, somewhat arbitrary place….
… One of Bohr’s most provocative views was that there is a fundamental distinction between the fuzzy, probabilistic quantum world and the classical world of real objects in real places, where measurements of, say, an electron with a macroscopic instrument tell us that it is here and not there.
What Bohr meant is shocking. Reality, he implied, doesn’t consist of objects located in time and space. It consists of “quantum events,” which are obliged to be self-consistent (in the sense that quantum mechanics can describe them accurately) but not classically consistent with one another. One implication of this, as far as we can currently tell, is that two observers can see different and conflicting outcomes from an event—yet both can be right.
But this rigid distinction between the quantum and classical worlds can’t be sustained today. Scientists can now conduct experiments that probe size scales in between those where quantum and classical rules are thought to apply—neither microscopic (the atomic scale) nor macroscopic (the human scale), but mesoscopic (an intermediate size). We can look, for example, at the behavior of nanoparticles that can be seen and manipulated yet are small enough to be governed by quantum rules. Such experiments confirm the view that there is no abrupt boundary of quantum and classical. Quantum effects can still be observed at these intermediate scales if our devices are sensitive enough, but those effects can be harder to discern as the number of particles in the system increases.
To understand such experiments, it’s not necessary to adopt any particular interpretation of quantum mechanics, but merely to apply the standard theory—encompassed within Schrödinger’s wave mechanics, say—more expansively than Bohr and colleagues did, using it to explore what happens to a quantum object as it interacts with its surrounding environment. In this way, physicists are starting to understand how information gets out of a quantum system and into its environment, and how, as it does so, the fuzziness of quantum probabilities morphs into the sharpness of classical measurement. Thanks to such work, it is beginning to seem that our familiar world is just what quantum mechanics looks like when you are 6 feet tall.
But even if we manage to complete that project of uniting the quantum with the classical, we might end up none the wiser about what manner of stuff—what kind of reality—it all arises from. Perhaps one day another deeper theory will tell us. Or maybe the Copenhagen group was right a hundred years ago that we just have to accept a contingent, provisional reality: a world only half-formed until we decide how it will be…
Eminently worth reading in full: “When Reality Came Undone,” from @philipcball in @NautilusMag.
See also: When We Cease to Understand the World, by Benjamin Labatut.
* Niels Bohr
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As we wrestle with reality, we might spare a thought for Ludwig Boltzmann; he died on this date in 1906. A physicist and philosopher, he is best remembered for the development of statistical mechanics, and the statistical explanation of the second law of thermodynamics (which connected entropy and probability).
Boltzmann helped paved the way for quantum theory both with his development of statistical mechanics (which is a pillar of modern physics) and with his 1877 suggestion that the energy levels of a physical system could be discrete.
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