Group items tagged

In 1972, using duct tape and spare parts in the basement on the campus of the University of California, Berkeley, Dr. Clauser and a graduate student, Stuart Freedman, who died in 2012, endeavored to perform Bell’s experiment to measure quantum entanglement. In a series of experiments, he fired thousands of light particles, or photons, in opposite directions to measure a property known as polarization, which could have only two values — up or down. The result for each detector was always a series of seemingly random ups and downs. But when the two detectors’ results were compared, the ups and downs matched in ways that neither “classical physics” nor Einstein’s laws could explain. Something weird was afoot in the universe. Entanglement seemed to be real.

in 2002, Dr. Clauser admitted that he himself had expected quantum mechanics to be wrong and Einstein to be right. “Obviously, we got the ‘wrong’ result. I had no choice but to report what we saw, you know, ‘Here’s the result.’ But it contradicts what I believed in my gut has to be true.” He added, “I hoped we would overthrow quantum mechanics. Everyone else thought, ‘John, you’re totally nuts.’”

the correlations only showed up after the measurements of the individual particles, when the physicists compared their results after the fact. Entanglement seemed real, but it could not be used to communicate information faster than the speed of light.

In 1982, Dr. Aspect and his team at the University of Paris tried to outfox Dr. Clauser’s loophole by switching the direction along which the photons’ polarizations were measured every 10 nanoseconds, while the photons were already in the air and too fast for them to communicate with each other. He too, was expecting Einstein to be right.

Quantum predictions held true, but there were still more possible loopholes in the Bell experiment that Dr. Clauser had identified

For example, the polarization directions in Dr. Aspect’s experiment had been changed in a regular and thus theoretically predictable fashion that could be sensed by the photons or detectors.

Anton Zeilinger

added even more randomness to the Bell experiment, using random number generators to change the direction of the polarization measurements while the entangled particles were in flight.

Once again, quantum mechanics beat Einstein by an overwhelming margin, closing the “locality” loophole.

as scientists have done more experiments with entangled particles, entanglement is accepted as one of main features of quantum mechanics and is being put to work in cryptology, quantum computing and an upcoming “quantum internet

One of its first successes in cryptology is messages sent using entangled pairs, which can send cryptographic keys in a secure manner — any eavesdropping will destroy the entanglement, alerting the receiver that something is wrong.

, with quantum mechanics, just because we can use it, doesn’t mean our ape brains understand it. The pioneering quantum physicist Niels Bohr once said that anyone who didn’t think quantum mechanics was outrageous hadn’t understood what was being said.

In his interview with A.I.P., Dr. Clauser said, “I confess even to this day that I still don’t understand quantum mechanics, and I’m not even sure I really know how to use it all that well. And a lot of this has to do with the fact that I still don’t understand it.”

Before he died, Richard Feynman, who understood quantum theory as well as anyone, said, “I still get nervous with it...I cannot define the real problem, therefore I suspect there’s no real problem, but I’m not sure there’s no real problem.” The problem is not with using the theory — making calculations, applying it to engineering tasks — but in understanding what it means. What does it tell us about the world?

From one point of view, quantum physics is just a set of formalisms, a useful tool kit. Want to make better lasers or transistors or television sets? The Schrödinger equation is your friend. The trouble starts only when you step back and ask whether the entities implied by the equation can really exist. Then you encounter problems that can be described in several familiar ways:

Wave-particle duality. Everything there is — all matter and energy, all known forces — behaves sometimes like waves, smooth and continuous, and sometimes like particles, rat-a-tat-tat. Electricity flows through wires, like a fluid, or flies through a vacuum as a volley of individual electrons. Can it be both things at once?

The uncertainty principle. Werner Heisenberg famously discovered that when you measure the position (let’s say) of an electron as precisely as you can, you find yourself more and more in the dark about its momentum. And vice versa. You can pin down one or the other but not both.

The measurement problem. Most of quantum mechanics deals with probabilities rather than certainties. A particle has a probability of appearing in a certain place. An unstable atom has a probability of decaying at a certain instant. But when a physicist goes into the laboratory and performs an experiment, there is a definite outcome. The act of measurement — observation, by someone or something — becomes an inextricable part of the theory

The strange implication is that the reality of the quantum world remains amorphous or indefinite until scientists start measuring

Other interpretations rely on “hidden variables” to account for quantities presumed to exist behind the curtain.

This is disturbing to philosophers as well as physicists. It led Einstein to say in 1952, “The theory reminds me a little of the system of delusions of an exceedingly intelligent paranoiac.”

“Figuring out what quantum physics is saying about the world has been hard,” Becker says, and this understatement motivates his book, a thorough, illuminating exploration of the most consequential controversy raging in modern science.

In a way, the Copenhagen is an anti-interpretation. “It is wrong to think that the task of physics is to find out how nature is,” Bohr said. “Physics concerns what we can say about nature.”

Nothing is definite in Bohr’s quantum world until someone observes it. Physics can help us order experience but should not be expected to provide a complete picture of reality. The popular four-word summary of the Copenhagen interpretation is: “Shut up and calculate!”

Becker sides with the worriers. He leads us through an impressive account of the rise of competing interpretations, grounding them in the human stories

He makes a convincing case that it’s wrong to imagine the Copenhagen interpretation as a single official or even coherent statement. It is, he suggests, a “strange assemblage of claims.

An American physicist, David Bohm, devised a radical alternative at midcentury, visualizing “pilot waves” that guide every particle, an attempt to eliminate the wave-particle duality.

Competing approaches to quantum foundations are called “interpretations,” and nowadays there are many. The first and still possibly foremost of these is the so-called Copenhagen interpretation.

Perhaps the most popular lately — certainly the most talked about — is the “many-worlds interpretation”: Every quantum event is a fork in the road, and one way to escape the difficulties is to imagine, mathematically speaking, that each fork creates a new universe

if you think the many-worlds idea is easily dismissed, plenty of physicists will beg to differ. They will tell you that it could explain, for example, why quantum computers (which admittedly don’t yet quite exist) could be so powerful: They would delegate the work to their alter egos in other universes.

When scientists search for meaning in quantum physics, they may be straying into a no-man’s-land between philosophy and religion. But they can’t help themselves. They’re only human.

If you were to watch me by day, you would see me sitting at my desk solving Schrödinger’s equation...exactly like my colleagues,” says Sir Anthony Leggett, a Nobel Prize winner and pioneer in superfluidity. “But occasionally at night, when the full moon is bright, I do what in the physics community is the intellectual equivalent of turning into a werewolf: I question whether quantum mechanics is the complete and ultimate truth about the physical universe.”

Not only that, but the universe appears to be governed by a kind of cosmic censorship: Regions of extreme gravity—where space-time curves so sharply that Einstein’s equations malfunction and the true, quantum nature of gravity and space-time must be revealed—always hide behind the horizons of black holes.

Dyson, who helped develop quantum electrodynamics (the theory of interactions between matter and light) and is professor emeritus at the Institute for Advanced Study in Princeton, New Jersey, where he overlapped with Einstein, disagrees with the argument that quantum gravity is needed to describe the unreachable interiors of black holes. And he wonders whether detecting the hypothetical graviton might be impossible, even in principle. In that case, he argues, quantum gravity is metaphysical, rather than physics.

The ability to detect the “grin” of quantum gravity would seem to refute Dyson’s argument. It would also kill the gravitational decoherence theory, by showing that gravity and space-time do maintain quantum superpositions.

If gravity is a quantum interaction, then the answer is: It depends. Each component of the blue diamond’s superposition will experience a stronger or weaker gravitational attraction to the red diamond, depending on whether the latter is in the branch of its superposition that’s closer or farther away. And the gravity felt by each component of the red diamond’s superposition similarly depends on where the blue diamond is.

Quantum teleportation — what he called “spooky action at a distance” — can transfer information between locations without actually moving the physical matter that holds it.

This technology could profoundly change the way data travels from place to place. It draws on more than a century of research involving quantum mechanics, a field of physics that governs the subatomic realm and behaves unlike anything we experience in our everyday lives. Quantum teleportation not only moves data between quantum computers, but it also does so in such a way that no one can intercept it.

These entangled systems could be electrons, particles of light or other objects. In the Netherlands, Dr. Hanson and his team used what is called a nitrogen vacancy center — a tiny empty space in a synthetic diamond in which electrons can be trapped.

Traditional computers perform calculations by processing “bits” of information, with each bit holding either a 1 or a 0. By harnessing the strange behavior of quantum mechanics, a quantum bit, or qubit, can store a combination of 1 and 0 — a little like how a spinning coin holds the tantalizing possibility that it will turn up either heads or tails when it finally falls flat on the table.

Researchers believe these devices could one day speed the creation of new medicines, power advances in artificial intelligence and summarily crack the encryption that protects computers vital to national security. Across the globe, governments, academic labs, start-ups and tech giants are spending billions of dollars exploring the technology.

Although it cannot move objects from place to place, it can move information by taking advantage of a quantum property called “entanglement”: A change in the state of one quantum system instantaneously affects the state of another, distant one.

“It does not work that way today. Google knows what you are running on its servers.”

The information also cannot be intercepted. A future quantum internet, powered by quantum teleportation, could provide a new kind of encryption that is theoretically unbreakable.

“We know nothing about the intrinsic quality of physical events,” he wrote, “except when these are mental events that we directly experience.”

I think Russell is right: Human conscious experience is wholly a matter of physical goings-on in the body and in particular the brain. But why does he say that we know nothing about the intrinsic quality of physical events except when these are mental events we directly experience? Isn’t he exaggerating? I don’t think so

I need to try to reply to those (they’re probably philosophers) who doubt that we really know what conscious experience is.The reply is simple. We know what conscious experience is because the having is the knowing: Having conscious experience is knowing what it is. You don’t have to think about it (it’s really much better not to). You just have to have it. It’s true that people can make all sorts of mistakes about what is going on when they have experience, but none of them threaten the fundamental sense in which we know exactly what experience is just in having it.

If someone continues to ask what it is, one good reply (although Wittgenstein disapproved of it) is “you know what it is like from your own case.” Ned Block replies by adapting the response Louis Armstrong reportedly gave to someone who asked him what jazz was: “If you gotta ask, you ain’t never going to know.”

So we all know what consciousness is. Once we’re clear on this we can try to go further, for consciousness does of course raise a hard problem. The problem arises from the fact that we accept that consciousness is wholly a matter of physical goings-on, but can’t see how this can be so. We examine the brain in ever greater detail, using increasingly powerful techniques like fMRI, and we observe extraordinarily complex neuroelectrochemical goings-on, but we can’t even begin to understand how these goings-on can be (or give rise to) conscious experiences.

1966 movie “Fantastic Voyage,” or imagine the ultimate brain scanner. Leibniz continued, “Suppose we do: visiting its insides, we will never find anything but parts pushing each other — never anything that could explain a conscious state.”

His mistake is to go further, and conclude that physical goings-on can’t possibly be conscious goings-on. Many make the same mistake today — the Very Large Mistake (as Winnie-the-Pooh might put it) of thinking that we know enough about the nature of physical stuff to know that conscious experience can’t be physical. We don’t. We don’t know the intrinsic nature of physical stuff, except — Russell again — insofar as we know it simply through having a conscious experience.

We find this idea extremely difficult because we’re so very deeply committed to the belief that we know more about the physical than we do, and (in particular) know enough to know that consciousness can’t be physical. We don’t see that the hard problem is not what consciousness is, it’s what matter is — what the physical is.

This point about the limits on what physics can tell us is rock solid, and it arises before we begin to consider any of the deep problems of understanding that arise within physics — problems with “dark matter” or “dark energy,” for example — or with reconciling quantum mechanics and general relativity theory.

Those who make the Very Large Mistake (of thinking they know enough about the nature of the physical to know that consciousness can’t be physical) tend to split into two groups. Members of the first group remain unshaken in their belief that consciousness exists, and conclude that there must be some sort of nonphysical stuff: They tend to become “dualists.” Members of the second group, passionately committed to the idea that everything is physical, make the most extraordinary move that has ever been made in the history of human thought. They deny the existence of consciousness: They become “eliminativists.”

no one has to react in either of these ways. All they have to do is grasp the fundamental respect in which we don’t know the intrinsic nature of physical stuff in spite of all that physics tells us. In particular, we don’t know anything about the physical that gives us good reason to think that consciousness can’t be wholly physical. It’s worth adding that one can fully accept this even if one is unwilling to agree with Russell that in having conscious experience we thereby know something about the intrinsic nature of physical reality.

It’s not the physics picture of matter that’s the problem; it’s the ordinary everyday picture of matter. It’s ironic that the people who are most likely to doubt or deny the existence of consciousness (on the ground that everything is physical, and that consciousness can’t possibly be physical) are also those who are most insistent on the primacy of science, because it is precisely science that makes the key point shine most brightly: the point that there is a fundamental respect in which ultimate intrinsic nature of the stuff of the universe is unknown to us — except insofar as it is consciousness.

There are two problems. One is that quantum mechanics, as it is enshrined in textbooks, seems to require separate rules for how quantum objects behave when we’re not looking at them, and how they behave when they are being observed

Why are observations special? What counts as an “observation,” anyway? When exactly does it happen? Does it need to be performed by a person? Is consciousness somehow involved in the basic rules of reality?

Together these questions are known as the “measurement problem” of quantum theory.

The other problem is that we don’t agree on what it is that quantum theory actually describes, even when we’re not performing measurements.

We describe a quantum object such as an electron in terms of a “wave function,” which collects the superposition of all the possible measurement outcomes into a single mathematical object

But what is the wave function? Is it a complete and comprehensive representation of the world? Or do we need additional physical quantities to fully capture reality, as Albert Einstein and others suspected? Or does the wave function have no direct connection with reality at all, merely characterizing our personal ignorance about what we will eventually measure in our experiments?

For years, the leading journal in physics had an explicit policy that papers on the foundations of quantum mechanics were to be rejected out of hand

An alternative algorithm is known that could have let the conventional computer be more competitive, or even win, by exploiting what Neven called a “bug” in D-Wave’s design. Neven said the test his group staged is still important because that shortcut won’t be available to regular computers when they compete with future quantum annealers capable of working on larger amounts of data.

“For a specific, carefully crafted proof-of-concept problem we achieve a 100-million-fold speed-up,” said Neven.

“the world’s first commercial quantum computer.” The computer is installed at NASA’s Ames Research Center in Mountain View, California, and operates on data using a superconducting chip called a quantum annealer.

Google is competing with D-Wave to make a quantum annealer that could do useful work.

Martinis is also working on quantum hardware that would not be limited to optimization problems, as annealers are.

Government and university labs, Microsoft (see “Microsoft’s Quantum Mechanics”), and IBM (see “IBM Shows Off a Quantum Computing Chip”) are also working on that technology.

“it may be several years before this research makes a difference to Google products.”

“If we replace ‘human judgments’ with ‘physical measurements,’” Wang and colleagues write, “and replace ‘cognitive system’ with ‘physical system,’ then these are exactly the same reasons that led physicists to develop quantum theory in the first place.”

then there is the mishandling of time. The physicist Lee Smolin's recent book, Time Reborn, links the crisis in physics with its failure to acknowledge the fundamental reality of time. Physics is predisposed to lose time because its mathematical gaze freezes change. Tensed time, the difference between a remembered or regretted past and an anticipated or feared future, is particularly elusive. This worried Einstein: in a famous conversation, he mourned the fact that the present tense, "now", lay "just outside of the realm of science".

Recent attempts to explain how the universe came out of nothing, which rely on questionable notions such as spontaneous fluctuations in a quantum vacuum, the notion of gravity as negative energy, and the inexplicable free gift of the laws of nature waiting in the wings for the moment of creation, reveal conceptual confusion beneath mathematical sophistication. They demonstrate the urgent need for a radical re-examination of the invisible frameworks within which scientific investigations are conducted.

we should reflect on how a scientific image of the world that relies on up to 10 dimensions of space and rests on ideas, such as fundamental particles, that have neither identity nor location, connects with our everyday experience. This should open up larger questions, such as the extent to which mathematical portraits capture the reality of our world – and what we mean by "reality".

Is nature really this weird? Or is this apparent weirdness just a reflection of our imperfect knowledge of nature?

The answer depends on how you interpret the equations of quantum mechanics, the mathematical theory that has been developed to describe the interactions of elementary particles. The success of this theory is unparalleled: Its predictions, no matter how “spooky,” have been observed and verified with stunning precision. It has also been the basis of remarkable technological advances. So it is a powerful tool. But is it also a picture of reality?

Does the wave function directly correspond to an objective, observer-independent physical reality, or does it simply represent an observer’s partial knowledge of it?

If there is an objective reality at all, the paper demonstrates, then the wave function is in fact reality-based.

What this research implies is that we are not just hearing different “stories” about the electron, one of which may be true. Rather, there is one true story, but it has many facets, seemingly in contradiction, just like in “Rashomon.” There is really no escape from the mysterious — some might say, mystical — nature of the quantum world.

We should be careful to recognize that the weirdness of the quantum world does not directly imply the same kind of weirdness in the world of everyday experience.

This is why, in fact, we are able to describe the objects around us in the language of classical physics.

I suggest that we regard the paradoxes of quantum physics as a metaphor for the unknown infinite possibilities of our own existence.

One common strategy for thinking about this is to suggest that what we used to call the whole universe is just a small part of everything there is, and that we live in a kind of bubble universe, a small region of something much larger

Newton realized there had to be some force holding the moon in its orbit around the earth, to keep it from wandering off, and he knew also there was a force that was pulling the apple down to the earth. And so what suddenly struck him was that those could be one and the same thing, the same force

That was a physical discovery, a physical discovery of momentous importance, as important as anything you could ever imagine because it knit together the terrestrial realm and the celestial realm into one common physical picture. It was also a philosophical discovery in the sense that philosophy is interested in the fundamental natures of things.

There are other ideas, for instance that maybe there might be special sorts of laws, or special sorts of explanatory principles, that would apply uniquely to the initial state of the universe.

The basic philosophical question, going back to Plato, is "What is x?" What is virtue? What is justice? What is matter? What is time? You can ask that about dark energy - what is it? And it's a perfectly good question.

right now there are just way too many freely adjustable parameters in physics. Everybody agrees about that. There seem to be many things we call constants of nature that you could imagine setting at different values, and most physicists think there shouldn't be that many, that many of them are related to one another. Physicists think that at the end of the day there should be one complete equation to describe all physics, because any two physical systems interact and physics has to tell them what to do. And physicists generally like to have only a few constants, or parameters of nature. This is what Einstein meant when he famously said he wanted to understand what kind of choices God had --using his metaphor-- how free his choices were in creating the universe, which is just asking how many freely adjustable parameters there are. Physicists tend to prefer theories that reduce that number

You have others saying that time is just an illusion, that there isn't really a direction of time, and so forth. I myself think that all of the reasons that lead people to say things like that have very little merit, and that people have just been misled, largely by mistaking the mathematics they use to describe reality for reality itself. If you think that mathematical objects are not in time, and mathematical objects don't change -- which is perfectly true -- and then you're always using mathematical objects to describe the world, you could easily fall into the idea that the world itself doesn't change, because your representations of it don't.

physicists for almost a hundred years have been dissuaded from trying to think about fundamental questions. I think most physicists would quite rightly say "I don't have the tools to answer a question like 'what is time?' - I have the tools to solve a differential equation." The asking of fundamental physical questions is just not part of the training of a physicist anymore.

The question remains as to how often, after life evolves, you'll have intelligent life capable of making technology. What people haven't seemed to notice is that on earth, of all the billions of species that have evolved, only one has developed intelligence to the level of producing technology. Which means that kind of intelligence is really not very useful. It's not actually, in the general case, of much evolutionary value. We tend to think, because we love to think of ourselves, human beings, as the top of the evolutionary ladder, that the intelligence we have, that makes us human beings, is the thing that all of evolution is striving toward. But what we know is that that's not true. Obviously it doesn't matter that much if you're a beetle, that you be really smart. If it were, evolution would have produced much more intelligent beetles. We have no empirical data to suggest that there's a high probability that evolution on another planet would lead to technological intelligence.

a bunch of particles can share these states at the same time, effectively becoming instances of the same particle. And so: entanglement.

possible to strip away all of this indeterminateness

wave functions are very fragile, subject to a “collapse” in which all of those possibilities become just a single particle at a single point at a single time.

physicists have observed a very peculiar behavior of electrons in supercooled baths of helium. When an electron enters the bath, it acts to

two probabilities can be isolated from each other, cordoned off like quantum crime scenes

it’s possible to take a wave function and isolate it into different parts. So, if our electron has some probability of being in position (x1,y1,z1) and another probability of being in position (x2,y2,z2), those two probabilities can be isolated from each other, cordoned off like quantum crime scenes

when a macroscopic human attempts to measure a quantum mechanical system: The wave drops away and all that’s left is a boring, well-defined thing.

trapping the chance of finding the electron, not pieces of the electron

using tiny bubbles of helium as physical “traps.

repel the surrounding helium atoms, forming its own little bubble or cavity in the process.

That an electron (or other particle) can be in many places at the same time is strange enough, but the notion that those possibilities can be captured and shuttled away adds a whole new twist.

wave function isn’t a physical thing. It’s mathematics that describe a phenomenon.

The electron, upon measurement, will be in precisely one bubble.

“No one is sure what actually constitutes a measurement,”

Is consciousness required? We don’t really know.”

Around 100 years ago, quantum mechanics was a purely theoretical topic, only developed to understand certain properties of atoms

But today, quantum mechanics is the basis of our use of all semiconductors in computers and mobile phones

Despite these direct and indirect benefits, most theoretical physicists have a very different motive for their work. They simply want to improve humanity’s understanding of the universe. While this might not immediately impact everyone’s lives, I believe it is just as important a reason for pursuing fundamental research

It somehow seems that every new level of understanding we achieve comes in tandem with new, more fundamental questions. It is never enough to know what we now know. We always want to continue looking behind newly arising curtains. In that respect, I consider fundamental physics a basic part of human culture.

She became a science journalist. At first it was a lark, a way to get free press passes to conferences where she and her father could ask questions of the greatest minds in quantum mechanics, string theory and cosmology. But within a short time, as she started getting assignments, journalism became a calling, and an identity.

Tracking down the meaning of nothing — and, by extension, secrets about the origin of the universe and whether observer-independent reality exists — became the defining project of their lives. They spent hours together working on the puzzle, two dark heads bent over their physics books far into the night.

she has an epiphany — that for something to be real, it must be invariant — she flies home to share it with her father. They discuss her insight over breakfast at a neighborhood haunt, where they make a list on what they will affectionately call “the IHOP napkin.” They list all the possible “ingredients of ultimate reality,” planning to test each item for whether it is “real,” that is whether it is invariant and can exist in the absence of an observer.

their readings and interviews reveal that each item in turn is observer-dependent. Space? Observer-dependent, and therefore not real. Gravity, electromagnetism, angular momentum? No, no, and no. In the end, every putative “ingredient of ultimate reality” is eliminated, including one they hadn’t even bothered to put on the list because it seemed weird to: reality itself

What remained was an unsettling and essential insight: that “physics isn’t the machinery behind the workings of the world; physics is the machinery behind the illusion that there is a world.”

In the proposal, she clarifies how cosmology and quantum mechanics have evolved as scientists come to grips with the fact that things they had taken to be real — quantum particles, space-time, gravity, dimension — turn out to be ­observer-dependent.

In school, one learns about “the scientific method”—usually a straightforward set of steps, along the lines of “ask a question, propose a hypothesis, perform an experiment, analyze the results.”

That method works in the classroom, where students are basically told what questions to pursue. But real scientists must come up with their own questions, finding new routes through a much vaster landscape.

Since science began, there has been disagreement about how those routes are charted. Two twentieth-century philosophers of science, Karl Popper and Thomas Kuhn, are widely held to have offered the best accounts of this process.

For Popper, Strevens writes, “scientific inquiry is essentially a process of disproof, and scientists are the disprovers, the debunkers, the destroyers.” Kuhn’s scientists, by contrast, are faddish true believers who promulgate received wisdom until they are forced to attempt a “paradigm shift”—a painful rethinking of their basic assumptions.

Working scientists tend to prefer Popper to Kuhn. But Strevens thinks that both theorists failed to capture what makes science historically distinctive and singularly effective.

Sometimes they seek to falsify theories, sometimes to prove them; sometimes they’re informed by preëxisting or contextual views, and at other times they try to rule narrowly, based on t

Why do scientists agree to this scheme? Why do some of the world’s most intelligent people sign on for a lifetime of pipetting?

Strevens thinks that they do it because they have no choice. They are constrained by a central regulation that governs science, which he calls the “iron rule of explanation.” The rule is simple: it tells scientists that, “if they are to participate in the scientific enterprise, they must uncover or generate new evidence to argue with”; from there, they must “conduct all disputes with reference to empirical evidence alone.”

, it is “the key to science’s success,” because it “channels hope, anger, envy, ambition, resentment—all the fires fuming in the human heart—to one end: the production of empirical evidence.”

Strevens arrives at the idea of the iron rule in a Popperian way: by disproving the other theories about how scientific knowledge is created.

The problem isn’t that Popper and Kuhn are completely wrong. It’s that scientists, as a group, don’t pursue any single intellectual strategy consistently.

Exploring a number of case studies—including the controversies over continental drift, spontaneous generation, and the theory of relativity—Strevens shows scientists exerting themselves intellectually in a variety of ways, as smart, ambitious people usually do.

“Science is boring,” Strevens writes. “Readers of popular science see the 1 percent: the intriguing phenomena, the provocative theories, the dramatic experimental refutations or verifications.” But, he says,behind these achievements . . . are long hours, days, months of tedious laboratory labor. The single greatest obstacle to successful science is the difficulty of persuading brilliant minds to give up the intellectual pleasures of continual speculation and debate, theorizing and arguing, and to turn instead to a life consisting almost entirely of the production of experimental data.

Ultimately, in fact, it was good that the geologists had a “splendid variety” of somewhat arbitrary opinions: progress in science requires partisans, because only they have “the motivation to perform years or even decades of necessary experimental work.” It’s just that these partisans must channel their energies into empirical observation. The iron rule, Strevens writes, “has a valuable by-product, and that by-product is data.”

Science is often described as “self-correcting”: it’s said that bad data and wrong conclusions are rooted out by other scientists, who present contrary findings. But Strevens thinks that the iron rule is often more important than overt correction.

Eddington was never really refuted. Other astronomers, driven by the iron rule, were already planning their own studies, and “the great preponderance of the resulting measurements fit Einsteinian physics better than Newtonian physics.” It’s partly by generating data on such a vast scale, Strevens argues, that the iron rule can power science’s knowledge machine: “Opinions converge not because bad data is corrected but because it is swamped.”

Why did the iron rule emerge when it did? Strevens takes us back to the Thirty Years’ War, which concluded with the Peace of Westphalia, in 1648. The war weakened religious loyalties and strengthened national ones.

Two regimes arose: in the spiritual realm, the will of God held sway, while in the civic one the decrees of the state were paramount. As Isaac Newton wrote, “The laws of God & the laws of man are to be kept distinct.” These new, “nonoverlapping spheres of obligation,” Strevens argues, were what made it possible to imagine the iron rule. The rule simply proposed the creation of a third sphere: in addition to God and state, there would now be science.

Strevens imagines how, to someone in Descartes’s time, the iron rule would have seemed “unreasonably closed-minded.” Since ancient Greece, it had been obvious that the best thinking was cross-disciplinary, capable of knitting together “poetry, music, drama, philosophy, democracy, mathematics,” and other elevating human disciplines.

We’re still accustomed to the idea that a truly flourishing intellect is a well-rounded one. And, by this standard, Strevens says, the iron rule looks like “an irrational way to inquire into the underlying structure of things”; it seems to demand the upsetting “suppression of human nature.”

Descartes, in short, would have had good reasons for resisting a law that narrowed the grounds of disputation, or that encouraged what Strevens describes as “doing rather than thinking.”

In fact, the iron rule offered scientists a more supple vision of progress. Before its arrival, intellectual life was conducted in grand gestures.

Descartes’s book was meant to be a complete overhaul of what had preceded it; its fate, had science not arisen, would have been replacement by some equally expansive system. The iron rule broke that pattern.

by authorizing what Strevens calls “shallow explanation,” the iron rule offered an empirical bridge across a conceptual chasm. Work could continue, and understanding could be acquired on the other side. In this way, shallowness was actually more powerful than depth.

it also changed what counted as progress. In the past, a theory about the world was deemed valid when it was complete—when God, light, muscles, plants, and the planets cohered. The iron rule allowed scientists to step away from the quest for completeness.

The consequences of this shift would become apparent only with time

In 1713, Isaac Newton appended a postscript to the second edition of his “Principia,” the treatise in which he first laid out the three laws of motion and the theory of universal gravitation. “I have not as yet been able to deduce from phenomena the reason for these properties of gravity, and I do not feign hypotheses,” he wrote. “It is enough that gravity really exists and acts according to the laws that we have set forth.”

What mattered, to Newton and his contemporaries, was his theory’s empirical, predictive power—that it was “sufficient to explain all the motions of the heavenly bodies and of our sea.”

Descartes would have found this attitude ridiculous. He had been playing a deep game—trying to explain, at a fundamental level, how the universe fit together. Newton, by those lights, had failed to explain anything: he himself admitted that he had no sense of how gravity did its work

Strevens sees its earliest expression in Francis Bacon’s “The New Organon,” a foundational text of the Scientific Revolution, published in 1620. Bacon argued that thinkers must set aside their “idols,” relying, instead, only on evidence they could verify. This dictum gave scientists a new way of responding to one another’s work: gathering data.

Quantum theory—which tells us that subatomic particles can be “entangled” across vast distances, and in multiple places at the same time—makes intuitive sense to pretty much nobody.

Without the iron rule, Strevens writes, physicists confronted with such a theory would have found themselves at an impasse. They would have argued endlessly about quantum metaphysics.

ollowing the iron rule, they can make progress empirically even though they are uncertain conceptually. Individual researchers still passionately disagree about what quantum theory means. But that hasn’t stopped them from using it for practical purposes—computer chips, MRI machines, G.P.S. networks, and other technologies rely on quantum physics.

One group of theorists, the rationalists, has argued that science is a new way of thinking, and that the scientist is a new kind of thinker—dispassionate to an uncommon degree.

As evidence against this view, another group, the subjectivists, points out that scientists are as hopelessly biased as the rest of us. To this group, the aloofness of science is a smoke screen behind which the inevitable emotions and ideologies hide.

At least in science, Strevens tells us, “the appearance of objectivity” has turned out to be “as important as the real thing.”

The subjectivists are right, he admits, inasmuch as scientists are regular people with a “need to win” and a “determination to come out on top.”

But they are wrong to think that subjectivity compromises the scientific enterprise. On the contrary, once subjectivity is channelled by the iron rule, it becomes a vital component of the knowledge machine. It’s this redirected subjectivity—to come out on top, you must follow the iron rule!—that solves science’s “problem of motivation,” giving scientists no choice but “to pursue a single experiment relentlessly, to the last measurable digit, when that digit might be quite meaningless.”

If it really was a speech code that instigated “the extraordinary attention to process and detail that makes science the supreme discriminator and destroyer of false ideas,” then the peculiar rigidity of scientific writing—Strevens describes it as “sterilized”—isn’t a symptom of the scientific mind-set but its cause.

The iron rule—“a kind of speech code”—simply created a new way of communicating, and it’s this new way of communicating that created science.

Other theorists have explained science by charting a sweeping revolution in the human mind; inevitably, they’ve become mired in a long-running debate about how objective scientists really are

In “The Knowledge Machine: How Irrationality Created Modern Science” (Liveright), Michael Strevens, a philosopher at New York University, aims to identify that special something. Strevens is a philosopher of science

Compared with the theories proposed by Popper and Kuhn, Strevens’s rule can feel obvious and underpowered. That’s because it isn’t intellectual but procedural. “The iron rule is focused not on what scientists think,” he writes, “but on what arguments they can make in their official communications.”

Like everybody else, scientists view questions through the lenses of taste, personality, affiliation, and experience

geologists had a professional obligation to take sides. Europeans, Strevens reports, tended to back Wegener, who was German, while scholars in the United States often preferred Simpson, who was American. Outsiders to the field were often more receptive to the concept of continental drift than established scientists, who considered its incompleteness a fatal flaw.

Strevens’s point isn’t that these scientists were doing anything wrong. If they had biases and perspectives, he writes, “that’s how human thinking works.”

Eddington’s observations were expected to either confirm or falsify Einstein’s theory of general relativity, which predicted that the sun’s gravity would bend the path of light, subtly shifting the stellar pattern. For reasons having to do with weather and equipment, the evidence collected by Eddington—and by his colleague Frank Dyson, who had taken similar photographs in Sobral, Brazil—was inconclusive; some of their images were blurry, and so failed to resolve the matter definitively.

it was only natural for intelligent people who were free of the rule’s strictures to attempt a kind of holistic, systematic inquiry that was, in many ways, more demanding. It never occurred to them to ask if they might illuminate more collectively by thinking about less individually.

In the single-sphered, pre-scientific world, thinkers tended to inquire into everything at once. Often, they arrived at conclusions about nature that were fascinating, visionary, and wrong.

How Does Science Really Work?Science is objective. Scientists are not. Can an “iron rule” explain how they’ve changed the world anyway?By Joshua RothmanSeptember 28, 2020