Friday, September 27, 2019

Just how conceptually economical is the Many Worlds Interpretation?

An exchange of messages with Sabine Hossenfelder about the Many Worlds Interpretation (MWI) of quantum mechanics has helped me sharpen my view of the arguments around it. (Sabine and I are both sceptics of the MWI.)

The case for Many Worlds is well rehearsed: it relates to the “measurement problem” and the idea that if you take the “traditional Copenhagen” view of quantum mechanics then you need to add to the Schrödinger equation some kind of “collapse postulate” whereby the wavefunction switches discontinuously from allowing multiple possible outcomes (a superposition) to having just one: that which we observe. In the Many Worlds view postulated by Hugh Everett, there is no need for this “add on” of wavefunction collapse, because all outcomes are realized, in worlds that get disentangled from one another as the measurement proceeds via decoherence. All we need is the Schrödinger equation. The attraction of this idea is thus that it demands no unproven additions to quantum theory as conventionally stated, and it preserves unitarity because of the smooth evolution of the wavefunction at all times. This case is argued again in Sean Carroll’s new book Something Deeply Hidden.

One key problem for the MWI, however, is that we observe quantum phenomena to be probabilistic. In the MW view, all outcomes occur with probability 1 – they all occur in one world or another – and we know even before the measurement that this will be so. So where do those probabilities come from?

The standard view now among Everettians is that the probabilities are an illusion caused by the fact that “we” are only ever present on one branch of the quantum multiverse. There are various arguments [here and here, for example] that purport to show that any rational observer would, under these circumstances, need to assign probabilities to outcomes in just the manner quantum mechanics prescribes (that is, according to the Born rule) – even though a committed Everettian knows that these are not real probabilities.

The most obvious problem with this argument is that it destroys the elegance and economy that Everett’s postulate allegedly possesses in the first place. It demands an additional line of reasoning, using postulates about observers and choices, that is not itself derivable (even in principle!) from the Schrödinger equation itself. Plainly speaking, it is an add-on. Moreover, it is one that doesn’t convince everyone: there is no proof that it is correct. It is not even clear that it’s something amenable to proof, imputing as it does various decisions to various “rational observers”.

What’s more, arguments like this force Everettians to confront what many of them seem strongly disinclined to confront, namely the problem of constructing a rational discourse about multiple selves. There is a philosophical literature around this issue that is never really acknowledged in Everettian arguments. The fact is that it becomes more or less impossible to speak coherently about an individual/observer/self in the Many Worlds, as I discuss in my book Beyond Weird. Sure, one can take a naïve view based on a sort of science-fictional “imagine if the Star Trek transporter malfunctioned” scenario, or witter on (as Everett did) about dividing amoebae. But these scenarios do not stand up to scrutiny and are simply not science. The failure to address issues like this in observer-based rationales for apparent quantum probabilities shows that while many Everettians are happy to think hard about the issues at the quantum level, they are terribly cavalier about the issues at the macroscopic and experiential level (“oh, but that’s not physics, it’s psychology” is the common, slightly silly response).

So we’re no better off with the MWI than with “wavefunction collapse” in the Copenhagen view? Actually, even to say this would be disingenuous. While some Everettians are still happy to speak about “wavefunction collapse” (because it sounds like a complicated and mysterious thing), many others working on quantum fundamentals don’t any longer use that term at all. That’s because there is now a convincing and indeed tested (or testable) story about most of what is involved in a measurement, which incorporates our understanding of decoherence (sometimes wrongly portrayed as the process that makes MWI itself uniquely tenable). For example, see here. It’s certainly not the case that all the gaps are filled, but really the only thing that remains substantially unexplained about what used to be called “collapse” is that the outcome of a measurement is unique – that is, a postulate of macroscopic uniqueness. Some (such as Roland Omnès) would be content to see this added to the quantum formalism as a further postulate. It doesn’t, after all, seem a very big deal.

I don’t quite accept that we should too casually assume it. But one can certainly argue that, if anything at all can be said to be empirically established in science, the uniqueness of outcomes of a measurement qualifies. It has never, ever been shown to be wrong! And here is the ultimate irony about Many Worlds: this one thing we might imagine we can say for sure, from all our experience, about our physical world is that it is unique (and that is not, incidentally, thrown into doubt by any of the cosmological/inflationary multiverse ideas). We are not therefore obliged to accept it, but it doesn’t seem unreasonable to do so.

And yet this is exactly what the MWI denies! It says no, uniqueness is an illusion, and you are required to accept that this is so on the basis of an argument that is itself not accessible to testing! And yet we are also asked to believe that the MWI is “the most falsifiable theory ever invented.” What a deeply peculiar aberration it is. (And yet – this is of course no coincidence – what a great sales hook it has!)

Sabine’s objection is slightly different, although we basically agree. She says:

“Many Worlds in and by itself doesn't say anything about whether the parallel worlds "exist" because no theory ever does that. We infer that something exists - in the scientific sense - from observation. It's a trivial consequence of this that the other worlds do not exist in the scientific sense. You can postulate them into existence, but that's an *additional* assumption. As I have pointed out before, saying that they don't exist is likewise an additional assumption that scientists shouldn't make. The bottom line is, you can believe in these worlds the same way that you can believe in God.”

I have some sympathy with this, but I think I can imagine the Everettian response, which is to say that in science we infer all kinds of things that we can’t observe directly, because of their indirect effects that we can observe. The idea then is that the Many Worlds are inescapably implicit in the Schrödinger equation, and so we are compelled to accept them if we observe that the Schrödinger equation works. The only way we’d not be obliged to accept them is if we had some theory that erases them from the equation. There are various arguments to be had about that line of reasoning, but I think perhaps the most compelling is that there are no other worlds explicitly in any wavefunction ever written. They are simply an interpretation laid on top. Another, equally tenable, interpretation is that the wavefunction enumerates possible outcomes of measurement, and is silent about ontology. In this regard, I totally agree with Sabine: nothing compels us to believe in Many Worlds, and it is not clear how anything could ever compel us.

In fact, Chad Orzel suggests that the right way to look at the MWI might be as a mathematical formalism that makes no claims about reality consisting of multiple worlds – a kind of quantum book-keeping exercise, a bit like the path integrals of QED. I’m not quite sure what then is gained by looking at it this way relative to the standard quantum formalism – or indeed how it then differs at all – but I could probably accept that view. Certainly, there are situations where one interpretational model can be more useful than others. However, we have to recognize that many advocates of Many Worlds will have none of that sort of thing; they insist on multiple separate universes, multiple copies of “you” and all the rest of it – because their arguments positively require all that.

Here, then, is the key point: you are not obliged to accept the “other worlds” of the MWI, but I believe you are obliged to reject its claims to economy of postulates. Anything can look simple and elegant if you sweep all the complications under the rug.

Thursday, September 05, 2019

Physics and Imagination

This essay appears in Entangle: Physics and the Artistic Imagination, a book edited by Ariane Koek and produced for an exhibition of the same name in Umea, Sweden.

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It would seem perverse, almost rude, not to begin a discussion of imagination in physics with Einstein’s famous quote on the topic, voiced during a newspaper interview with the writer George Viereck in 1929:
“I'm enough of an artist to draw freely on my imagination, which I think is more important than knowledge. Knowledge is limited. Imagination encircles the world.”

For a fridge-magnet inspirational quote to celebrate the value of imagination, you need look no further. But context, as so often with Einstein, is everything. He said this after talking about the 1919 expedition led by the British physicist Arthur Eddington to observe the sky during a total solar eclipse off the coast of Africa. Those observations verified the prediction of Einstein’s theory of general relativity that starlight would be bent by the gravitational field of a massive body like the sun. Einstein told Viereck that “I would have been surprised if I had been wrong.” Viereck – a fascinating figure in his own right, who had previously interviewed (and showed some sympathy for) Adolf Hitler and wrote a psychological and gay-inflected Wildean vampire novel in 1907 – responded to that supremely confident statement by asking: “Then you trust more to your imagination than to your knowledge?”

You could say that Einstein’s reply was a qualified affirmative. And this seems very peculiar, doesn’t it, for a “man of science”?

The story dovetails with Einstein’s other well-known response to the eclipse experiment. Asked by an assistant (some say a journalist) how he should have felt if the observations had failed to confirm his theory, he is said to have responded “Then I would feel sorry for the dear Lord. The theory is correct.”

Compare that with the statement of another celebrated aphoristic physicist, the American Richard Feynman:
“It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.”

Who is right? Einstein trusting to imagination, intuition and artistry, or Feynman to the brutal judgement of empiricism? If we’re talking about scientific methodology, Feynman is right in spirit but nonetheless displaying the limitations of the physicist’s common “naïve realist” position about science, which assumes that nature delivers uncomplicated, transparent answers when we put to it questions about our physical theories. Yet Einstein’s general relativity was a theory so profoundly motivated and so conceptually satisfying, despite the mind-boggling shift it demanded in conceptions of space and time, that it could not be lightly tossed on the scrapheap of beautiful ideas destroyed by ugly facts.

So the sensible way to have handled a discrepancy with observed “facts” like those collected by Eddington in his observations of the positions of stars during an eclipse would have been to wonder if the observations were reliable. Indeed, Eddington was later accused of cherry-picking those facts to confirm the theory, perhaps motivated by his Quaker’s desire to bring about international reconciliation after First World War had triggered the ostracising of Germany. (It seems those charges were unfounded.) Nature doesn’t lie, but experimentalists can blunder.

*

There’s a deeper reason to valorize Einstein’s claim about imagination in physics. What I feel he is really saying is that imagination precedes knowledge, and indeed establishes the precondition for it. You might say that when the shape of imagination sufficiently fits the world, knowledge results.

We have never needed more reminding of this. In his unfinished magnum opus Novum Organum the seventeenth-century English philosopher Francis Bacon presented knowledge as the product obtained when raw facts – observations about the world – are fed into a kind of science machine (what we might now call an algorithm) and ground into their essence. It was an almost mechanical process: you first collect all the facts you can, and then refine and distil them into general laws and principles about the way the world works. Bacon never completed his account of how this knowledge-extraction process was meant to work, but at any rate no one in science has ever successfully used such a thing, or even knows what it could comprise.

Yet Bacon’s vision threatens to return in an age of Big Data – especially in the life sciences, where the availability of information about, say, genome sequences or correlations between genes and traits has outstripped our ability to create theoretical frameworks to make sense of it. There’s a feeling afoot not only that data is intrinsically good but that knowledge has no option but to fall out of it, once the mass of information about the world is large enough.

Physicists have received advance warning of the limitations of that belief. They have their own knowledge machines: sophisticated telescopes and particle detectors, say, and most prominently the Large Hadron Collider and other particle colliders capable of generating eye-watering quantities of data about the interactions between the fundamental constituents of the world. But they already know how little all this data will help without new ideas: without imagination.

For example? There are some good reasons to believe that if physics is going to penetrate still further into the deep laws of nature, it needs a theoretical idea called supersymmetry. So far, all we know about the particles and forces of nature is described by a framework called the Standard Model, which contains all the ingredients seemingly needed to explain everything seen in experiments in particle physics to date. But we know that there’s more to the universe than this, for many reasons. For one thing, the current theory of gravity – Einstein’s general relativity – is incompatible with the theory of quantum mechanics used to describe atoms and their fundamental particles. Supersymmetry – a putative connection between two currently distinct classes of particle – looks like a promising next step to a deeper physics. Yet so far, the LHC’s high-energy collisions have offered no sign that it’s true.

What’s more, there’s nothing in the Standard Model that seems to account for the “dark matter” that astrophysicists need to invoke to explain what they see in the cosmos. This mysterious substance is believed to pervade the universe, invisibly, being felt by ordinary matter only through its gravitational influence. Without something like dark matter, it is hard to make sense of the observed forms and motions of galaxies: how they rotate without shedding stars like a water sprinkler. The reasons to believe in dark matter – and moreover to believe it exceeds the mass of ordinary visible matter by a factor of about five – are very strong. Yet countless efforts to spot what it consists of have failed to offer any clues. Huge quantities of data constrain the choices, but no evidence supports any of the theories proposed to explain dark matter.

These are – there is no avoiding the issue – failures of imagination. Supersymmetry and dark matter are wholly imagined theories or entities, but the collective imagination of physicists has not yet made them vivid enough to be revealed or disproved. It is possible that this is because they are imaginary in the more literary sense: they exist only in our minds. And they are not alone; dark energy (which causes the universe to expand at an increasing rate) and string theory (one candidate for a theory that would unite gravity and quantum mechanics) are other components of the physicist’s imaginarium waiting to be verified and explained or to be dismissed as unicorns, as the ether, as the philosopher’s stone.

A single observation – one experiment revealing a discrepancy with a definite theoretical prediction, or one sighting of a new kind of particle – could change the situation. Maybe it will. But it is equally possible that we will need ultimately to concede defeat, and to extent the imagination of physics into new territory: for example to accept, as some are already arguing, that what we call “dark matter” is a symptom of another physical principle (a modification to the theory of gravity, say) and not a true substance.

There’s nothing embarrassing or damning in all this. It’s not that physics itself is failing. The situation is just business as usual in science: to have mysteries awaiting explanation, even ones of this magnitude, is a sign of health, nor sickness. For individual physicists whose reputations hang (or seem to) on the validity of a particular idea, that’s scant comfort. But for the rest of us it’s nothing short of exhilarating to see such deep and broad questions remaining open.

*

The real point is that imagination in physics is what the paths to the future, to new knowledge, are built from. Actual knowledge – things we can accept as “true”, in the sense that they offer tried and tested ways of predicting how the world behaves – has been assembled into an edifice as wonderful and as robust as the Gothic cathedrals of stone, the medieval representations of the physical and spiritual universe. But at the point where knowledge runs out, only imagination can take us further. I think this is what Einstein was driving at.

The invitation is often to suppose that this imagination operates only at the borders of physical theory: at, you might say, the cliff-face of physics that tends to dominate its public image, where we find exotica like string theory, black holes, cosmology and the Higgs boson. But physics, perhaps more than any other science, has a subtle, fractal-like texture in which gaps in knowledge appear everywhere, at all scales. Imagination was needed to start to understand that strange state of matter made of grains: powders and sand, part fluid and part solid. It is currently blossoming in a field known as topological materials, in which the electrical and magnetic properties are controlled by the abstract mathematical shapes that describe the way electrons are distributed, with twists akin to those in the famous one-sided Möbius strip. It was imagination that prompted physicists and engineers to make structures capable of acting as ‘invisibility shields’ that manipulate and guide light in hitherto inconceivable ways. In all these cases, as in science more broadly, the role if the imagination is not so much to guide us towards answers as to formulate interesting and fruitful new questions.

What does this imagination consist of? We’d do well to give that question more attention. I would suggest that it is, among other things, a way of seeing possibilities: a rehearsal of potential worlds. That’s what justifies Einstein’s comparison to the work of the artist: imagination, as Shakespeare put it, “bodies forth the forms of things unknown.” The scientist’s theories, as much as the poet’s pen, “turns them to shapes and gives to airy nothing a local habitation and a name.” That name could be “general relativity” – why not?

What’s the source, though? Many ideas in fundamental physics grow from what might seem the rather arid soil of mathematics. Supersymmetry and string theory are predicated in particular on the conviction that the deepest principles of the physical world are governed by symmetry. What this word means at the level of fundamental theory might seem less apparent to the outsider than what it implies in, say, the shape of a Grecian urn or the pattern of wallpaper, but at root it is not so very difference: symmetry is about an equivalence of parts and their ability to be transformed one into another, as a left hand becomes a right through the mirror reflection of the looking glass.

Well, it might seem arid, this mathematics. But imagination is as vital here as it is in art. What mathematicians value most in their colleagues is not an ability to churn out airtight proofs of abstract theorems but a kind of creativity that perceives links between disparate ideas, an almost metaphorical way of making connections in which intuition is the architect and proof can come later. Both mathematicians and theoretical physicists commonly speak of having a sense that they are right about an idea long before they can prove it; that proof is “just the engineering” needed to persuade others that the idea will hold up.

Let’s be cautious, though, about making “engineering” the prosaic, plodding part of science though. The common perception is that theorists do the dreaming and experimentalists just build the apparatus for putting dreams to the test. That’s just wrong. For one thing, it’s typically experiment that drives theory, not the other was around: it’s only when we have new instruments for examining the world that we discover gaps in our understanding, demanding explanation. What’s more, experiment too is fuelled by imagination. No one tries to see something unprecedented – farther out into space (which means, because light’s speed is finite, farther back in time), or into the world of single atoms, or into the spectrum of radiation outside the band of light our eyes can register – unless they have conjured up images of what might be there. Sure, you need some existing theory to guide your experimental goals, to show potentially fruitful directions for your gaze; but no one sails into uncharted territory if they think all they’ll find is more of the same, or nothing at all. “If you can’t imagine something marvellous, you are not going to find it”, says physics Nobel laureate Duncan Haldane. “The barrier to discovering what can be done is actually imagination.” And the power and artistry of the experimenter’s imagination comes not just from dreaming of what there is to be found in terra incognita, but also from devising a means to travel there.

When I speak of dreams, I don’t just mean it metaphorically, nor just in the sense of waking reverie. To judge from the testimony of scientists themselves, dreams can function as sources of inspiration. True, we should be a little wary of that; the notion of receiving insight in a dream became a romantic trope in the nineteenth century, and careful historical analysis often reveals some hard and very deliberate graft, as well as a very gradual process of understanding, behind scientific advances that were recast retrospectively as dream-revelations. But it happens. Several contemporary physicists have attested to insights that came to them in dreams, as the conscious mind that has been long pondering a problem loosens its bonds on the margins of sleep and admits a little more of the illogic on which imagination thrives.

All the same, we shouldn’t think that the physicist’s imagination always works in the abstract, in the realm of pure thought. Very often, it takes visual form: finding the right symbolic representation of a problem, such as Feynman’s famous “diagrams” for studying questions in the field of quantum electrodynamics (in essence, the theory of how light and matter interact), can unlock the mind in ways that more abstract algebraic mathematics or calculus can’t. Pen and paper can be the fuel of the imagination. As Cambridge physicist Michael Cates (incumbent of the chair previously held by Stephen Hawking and Isaac Newton) has said, “I need a piece of paper in front of me and I’m pushing symbols around on the page… so there’s this interaction between processing in your head and moving symbols around.” Never underestimate the traditional blackboard as a tactile, erasable aid to the imagination. The productivity of such aids is no surprise. Ask a child to think of a story, and it’s ne easy matter. Give them a doll’s house full of figurines, and they’re away.

*

Yet whether it is theoretical or experimental, this imagination in science (as in art) is not idle fantasy. It is a condensation of experience: it takes what you know and plays with it. I do mean “plays”: imagination is nothing if not ludic. But it is also the very stuff of thought. One interpretation of cognition, in the context of artificial intelligence, is that it is largely about figuring out the possible consequences of actions we might make in the world: an “inner rehearsal” of imaginary future scenarios. Imagination in science extends that process beyond the self to the world: given that we know this, mightn’t things also be arranged like that?

It’s much more than a guess, then, and as Shakespeare hints, has almost the power of an invocation. Truly, the scientific imagination can invoke into being something that was not there before. Isaac Newton was cautious about his “force of gravity”, knowing that he risked (and indeed incurred from his arch-rival Gottfried Leibniz) accusations of occultism. Yet all the same this “force” became – and remains – a ‘thing’ in physics, even if we can regard it as a figure of speech, a convenient conceptual tool that general relativity invites us to regard otherwise as curvature of spacetime. It’s a process entirely analogous to the way Shakespeare goes on to speak, in A Midsummer Night’s Dream, of how correlation leads us to imagine causation:
Such tricks hath strong imagination,
That if it would but apprehend some joy,
It comprehends some bringer of that joy.

In this way we’re reminded that imagination shares the same etymological root as “magic” – which, in the age just before the time of Isaac Newton, did not necessarily mean superstitious agency but the “hidden forces” by which natural magicians comprehended and claimed to manipulate nature. In that regard Newton wasn’t, as John Maynard Keynes claimed, the “last of the magicians”, in the sense of his having a belief in occult forces (such as gravity, acting invisibly across space). No, if that was Newton’s “magic” then today’s physicists share a conviction in it, for any model in physics awards imagination this role of employing imagined causative agencies – things we might not perceive directly but which manifest through their effects, such as dark matter, dark energy, or the Higgs field – to explain what we see.

Now, though, physics places demands on the imagination as never before. I’m struck by how dark matter and dark energy, say, commandeer known concepts (mass, energy) that may or may not turn out to be appropriate. Even more challenging are efforts to provide some physical picture of quantum mechanics, the kind of physics generally used to describe atoms and fundamental particles. These objects don’t seem to conform to our intuitions derived from the everyday world of rocks and stones, tennis balls and space rockets. They can, for example, sometimes display behaviour we associate not with particles but with waves. They appear to be able to influence one another instantaneously over long distances; they are said to exist “in several states or places at once.”

Yet these descriptions are attempts – often clumsy, sometimes misleading – to make quantum mechanics fit into the forms of our conventional “classical” imagination. Arguments and misperceptions follow, or a disheartening decision to draw a veil over quantum improprieties by calling them “weird”. We can and should do better, but this will require a reshaping, an expansion, of our imaginative faculties. We have to develop a kind of intuition that is not constrained by our daily experience – because if there’s one thing we can be sure about in quantum mechanics, it’s that it demands the possibility of phenomena that lie outside this experience.

To venture into unknown territory, where imagination is at a premium, is a risk. To put it bluntly, your imagination is more likely to lead you astray than toward the truth. It is no magical guarantor of insight. Will you take that risk? Mathematical physicist Jon Keating has put the problem succinctly: “[How can we] encourage people to make them feel more comfortable with the failure that comes with most creative and imaginative ideas?” Unless we get better at that, educationally or institutionally, science will suffer.

And it’s very possible that physicists won’t alone accomplish the feats of imagination needed to crack their hardest problems. They may need to find inspiration from philosophy, art, literature, aesthetics. Imagination doesn’t recognize categories and boundaries – it is a power that aims to encircle the world.

Tuesday, August 13, 2019

Still trying to kill the cat

Some discussion stemming from Erwin Schrödinger’s birthday prompts me to set out briefly why his cat is widely misunderstood and is actually of rather limited value in truly getting to grips with the conundrums of quantum mechanics.

Schrödinger formulated the thought experiment during correspondence with Einstein in which they articulated what they found objectionable in the view of QM formulated by Niels Bohr and his circle (the “Copenhagen interpretation”, which should probably always be given scare quotes since it never corresponded to a unique, clearly adduced position). In that view, one couldn’t speak about the properties of quantum objects until they were measured. Einstein and Schrödinger considered this absurd, and in 1935 Schrödinger enlisted his cat to explain why. Famously, he imagined a situation in which the property of some quantum object, placed in a superposition of states, determines the fate of a cat in a closed box, hidden from the observer until it is opened. In his original exposition he spoke of how, according to Bohr’s view, the wavefunction of the system would, before being observed, “express this by having in it the living and the dead cat (pardon the expression) mixed or smeared out in equal parts.”

This is (even back then) more careful wording than the thought experiment is usually afforded today, talking specifically about the wavefunction and not about the cat. Even so, a key problem with Schrödinger’s cat if taken literally as a thought experiment is that it refers to no well defined property. In principle, Schrödinger could have talked instead about a macroscopic instrument with a pointer that could indicate one of two states. But he wanted an example that was not simply hard to intuit – a pointer in a superposition of two states, say – but was semantically absurd. “Live” and “dead” are not simply two different states of being, but are mutually exclusive. Then the absurdity is all the more apparent.

But in doing so, Schrödinger undermined his scenario as an actual experiment. There is not even a single classical measurement, let alone a quantum state one can write down, that defines “live” or “dead”. Of course, it is not hard to find out if a cat is alive or dead – but it is very hard to identify a single variable whose measurement will allow you to fix a well defined instant where the cat goes from live to dead. Certainly, no one has the slightest idea how to write down a wavefunction for a live or dead cat, and it seems unlikely that we could even imagine what they might look like or what would distinguish them.

This is then not, at any rate, an experiment devised (as is often said) to probe the issue of the quantum-classical boundary. Schrödinger gives no indication that he was thinking about that, except for the fact that he wanted a macroscopic example in order to make the absurdity apparent. It’s now clear how hard it would be to think of a way of keeping a cat sufficiently isolated from the environment to avoid (near-instantaneous) decoherence – the process by which “quantumness” generally becomes “classical” – while being able to sustain it in principle in a living state.

Ignoring all this, popular accounts typically take the thought experiment as a literal one rather than as a metaphor. As a rule, they then go on to (1) misunderstand the nature of superpositions as being “in two states at once”, and (2) misrepresent the Copenhagen interpretation as making ontological statements about a quantum system before measurement, and thereby tell us merrily that, if Bohr and colleagues are right, “the cat is both alive and dead at the same time!”

My suspicion is that, precisely because it is so evocative, Schrödinger’s thought experiment does not merely suffer from these misunderstandings but invites them. And that is why I would be very happy to see it retired.

Of course, there is more discussion of all these things in my book Beyond Weird.

Thursday, April 25, 2019

A Place That Exists Only In Moonlight: a Q&A with Katie Paterson

I have a Q&A with Katie Paterson in the 25 April issue of Nature. There was a lot in Katie’s comments that I didn’t have room for there, so here is the extended interview. The exhibition is wonderful, though sadly it only runs for a couple more weeks. This is science-inspired art at its finest.



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Scottish artist Katie Paterson is one of the most scientifically engaged of contemporary artists. Her work has been described as “combining a Romantic sensibility with a research-based approach, conceptual rigour and coolly minimalist presentation.” It makes use of meteorites, astronomical observations, fossils and experiments in sound and light to foster a human engagement with scales in time and space that far exceed our everyday experience.

Many of her works have astronomical themes. All the Dead Stars depicts, on a sheet of black etched steel, the location of around 27,000 stars that are no longer visible. For the Dying Star Letters (2011-) she wrote letters of condolence for every star newly recorded has having “died” – a task that got ever more challenging with advances in observing technologies. And History of Darkness (2010-) is an ongoing archive of slides of totally dark areas of the universe at different epochs and locations.

For Future Library (2014-2114), 100 writers including Margaret Atwood and David Mitchell will write stories (one is commissioned each year since 2014) that will be kept in sealed storage until 2114, when they will be printed on paper made from 1,000 trees being planted in a forest in Norway. Paterson has said of the project that “it questions the present tendency to think in short bursts of time, making decisions only for us living now.”

Some of your works speak to concerns about degradation of the environment and the onset of the Anthropocene – Future Library, for example, and the Vatnajökull project (2007-8) that relays the live sound of meltwater flowing within an Icelandic glacier to listeners who dial in on mobile phones. Do you think that what can seem like an overwhelming problem of environmental change on scales that are hard to contemplate can be made tangible and intelligible through art?

Future Library has a circular ecology built into it: words become enmeshed in growing trees, which, fed by water and light, a century later will become books. It’s a gathering, and the trees spell out time. The artwork is made with simple materials, people, nature and words, and its connected to feelings and senses. The phone call I set up to the glacier was an intimate one-to-one experience; listening to a graveyard of ice. The crisis of global warming does not feel intimate when it’s screeching at us through screens and graphs – yet of course it is. Our planet is disappearing. Humans understand suffering, the cycle of birth and dying. We need a contemporary approach to what Stephen Hawking called ‘Cathedral thinking’: far-reaching vision that is humanly relatable.

David Mitchell sees an optimistic message in Future Library (as well as an exercise in trust): it is, he says, “a vote of confidence in the future. Its fruition is predicated upon the ongoing existence of Northern Europe, of libraries, of Norwegian spruces, of books and of readers.” How confident are you that the books will be made?

We have put many methods in place to ensure that the books will be made. Each tree is marked on a computerized system, and the foresters take great care. We are investigating the likely methods of making ink in 100 years’ time. The city of Oslo has taken this artwork to their heart, and even the king and queen of Norway are involved. We have a Trust whose mandate is to “compassionately sustain the artwork for its 100 year duration.” Yes, Future Library is an exercise in trust. This year’s author Han Kang described the project as having an undercurrent of love flowing through it. It concerns me, and certainly says something about our moment in time, that we even question whether it will be possible to make books in just 100 years. We have clearly reached a crisis.

You have said “Time runs through everything I make.” Your work deals with the scales of distance and time that astronomers and geologists have to consider routinely, but which far exceed human intuition. How can we cope with that?

I find professions that routinely deal with long timescales fascinating. For the foresters in Future Library, 100 years is normal. Geologists work across time periods where major extinctions become plots on a map. Astronomers work with spans of time that go beyond everything that has ever lived. However, this routineness may blur the immensity of the concepts at hand. All the same, we can unearth materials fallen from space and comprehend that they go back far beyond humanity’s time on earth. Our technologies are advanced enough to look to a time beyond the Earth’s existence, approaching the Big Bang. Humans have devised and created these images, yet they exceed our capacity to understand them.
For me the route to a different kind of understanding of time is through the imagination. That’s the space that provides the most freedom and openness. My art attempts to deal directly with concepts that I can’t get to otherwise. Perhaps mathematical languages enable something similar. My journey in astronomy has been a search for connection: understanding that we are not separate from the universe, but are intrinsically linked.

Your work Light Bulb to Simulate Moonlight (2008) does exactly what it says on the tin. The bulb was created in collaboration with engineers at OSRAM. Can you explain how it was made?

I approached Dieter Lang, innovation manager and lighting engineer at OSRAM, and asked him to adapt the methods they use to make ‘daylight bulbs’ to recreate moonlight. I wanted to create a whole lifetime of moonlight – a bulb that lasts the length of an average human life. Dieter took light measurements under a full moon in the countryside outside Munich. I’d always imagined the futility of trying to recreate something as ineffable as moonlight, yet I was happy with the result – the light bulbs burn very brightly, a yellowy-blue tinged light, which changes according to your distance to it, just like the moon.



Do you see projects like the “dead stars” works or History of Darkness as attempts to connect us to the vastness of deep space and time? Or might they in fact suggest the futility of trying to keep track of all that has happened in the observable cosmos?

It oscillates somewhere in between. History of Darkness has futility written into it, capturing infinite darkness from across space and time. Each slide could contain millions of worlds, and learning that these images refer to places beyond human life and even the Earth may expand our relationship to these phenomena, and enhance the sense of our fallibility. All the Dead Stars was made in 2009. I’d like to update it in years to come – it might become an expanse of white dots, as telescopes become even more powerful and abundant.
I’m always drawn to the idea of the universe as deep wilderness. No matter how extensive our research and advanced technologies become, we can never ever truly access the great beyond. I read that our ‘cosmic horizon’ is around 42 billion light years away. What lies beyond, whether finite or infinite, will forever remain outside our understanding. Creating artwork is as much my own way of grappling with the “divine incommensurability” of our position in the universe, as much as an attempt to communicate it with others.

In Earth-Moon-Earth (Moonlight Sonata Reflected from the Surface of the Moon) (2007), you encoded Beethoven’s sonata in Morse code, broadcast it to the surface of the moon in radio waves, and reconstructed the partial score from the reflections. That evidently required some powerful technology. And in 2014 an ESA mission to the Space Shuttle enabled your project of returning a fragment of meteorite to earth orbit. How do these collaborations with scientific institutions come about?

Earth-Moon-Earth was created with “moon bouncer” radio enthusiasts: underground groups of people sending messages to each other via the moon. I simply wrote them letters. While studying at the Slade [art school in London] I wandered into the Rock & Ice Physics Laboratory next door [in University College London]. They allowed me to play my glacial ice records in their walk-in freezers. That was when I found out quite how easy it was to approach others in different fields. With the moonlight bulb I simply called round a number of lighting companies till I came across the right person. The map of the dead stars involved hundreds of researchers. Some scientists are far more involved than others, from sharing data (NASA gave me the recipe for the scent of Saturn’s moon) to developing the artworks very closely with myself and my studio. [Astronomers] Richard Ellis and Steve Fossey have played an enormous role. I tend to approach people who are experts in niche fields, such as type 2a supernova, and I ask to draw on their specialization. It’s their passion, so they are generally receptive. This can be a chance to share their knowledge in a way that they haven’t been asked to before, that will become manifest in an artwork engaging with totally different audiences. Of course there can be bafflement, but so far it’s been overwhelmingly positive.
Recently, for the first time researchers from came to me. I received a message from a group of scientists working on a mission proposal to NASA, inviting me to join their team as a ‘space-artist/co-investigator’ inquiring into cosmic dust. I’m extremely happy about this, not only for the creative potential but because the scientists have shown genuine concern that an artist might have something of value to contribute to their research. The group understands that art can be a way to share their knowledge through a different, more experiential, channel.

Your concepts clearly draw on – and indeed derive from – new scientific discoveries and techniques. For example, The Cosmic Spectrum (2019) is a large rotating colour wheel on which segments show the “average colour” of the Universe (as perceived by the human eye) from the Big Bang until the present, partly using data from the 2dF Galaxy Redshift Survey. How do you stay abreast of the latest scientific developments, and what do you tend to look for in them?

I discovered [astronomer] Ivan Baldry’s work on the cosmic spectrum several years ago. Many of my ideas sit on the back burner for years and manifest themselves at later stages. I don’t feel on top of scientific developments, but sometimes just one experience has enough potency to carry projects through years later.
I’m drawn to current investigations into the sunsets on Mars caught by NASA’s Mars Curiosity rover – but equally by botanical records from bygone eras, or the ray of light in a Florentine cathedral that marks the solstice built centuries ago. Sometimes just looking at titles on the shelves of science libraries can be enough to evoke compelling images. My inspirations have been wide and varied: from looking through telescopes to extremely distant galaxies, to tending a moss garden in a Zen monastery (a universe in itself). I’ve always drawn inspiration from artists, writers, musicians and thinkers whose work has a cosmic dimension: for example, raku ceramicists molding ‘the cosmos in a tea bowl’.

Some of your works exist only as the ongoing collection of ideas in the book A Place That Exists Only in Moonlight (2019). Occasionally they find a striking resonance with concepts that, for a cosmologist or physicist say, might almost seem like a thought experiment or research proposal: “A reset button for the universe pressed only once”, say, or “The speed of light slowed to absolute stillness”. Do you ever find that the scientists you collaborate with or encounter are inspired by your ideas into asking new questions or conducting new investigations themselves?

A Place that Exists Only in Moonlight arose out of a period of heavy production. I wanted to find a ‘lighter’ approach, which is the creative core of everything for me; just the ideas themselves. The book contains artworks to exist in the mind, many of which refer to suns, stars, moons, planets, earthly and cosmic matter. The cover is printed with cosmic dust: a mixture of moondust, dust from Mars, shooting stars, ancient meteorites and asteroids. I wanted the reader to be able to hold and touch the material the words describe, while taking them in. The Ideas are like thought experiments, Zen koans, Gedankenexperiment. In a way that’s true of all my artworks. What time is it on Venus? What texts will be read by unborn people? Is it possible to plant a forest using saplings from the oldest tree on earth, can we make ink to be read only under moonlight? I’m always curious. I will post copies of the book to everyone I have worked with, and I would be very happy indeed if they chose to conduct new investigations themselves.

A Place That Exists Only in Moonlight, an exhibition that pairs Paterson’s works with studies of light, sky and landscapes by J. M. W. Turner, is at the Turner Gallery in Margate, UK, until 6 May.

Monday, April 15, 2019

Out of the ashes of Notre Dame



There is no positive spin to put on the fire that has gutted Notre Dame Cathedral, and it could sound idiotic to think otherwise. This was one of the masterpieces of the Gothic era, a place where – as Napoleon allegedly said of Chartres – an atheist would feel uneasy (although this atheist instead felt moved and inspired). I don’t yet know the extent of the damage, but it is hard to imagine that the thirteenth-century northern rose window will have survived the inferno, or that the west front of the building, which has been called “one of the supreme architectural achievements of all time”, will emerge intact. Even if the building is eventually restored – and I am sure it will be – one might wonder what will be the point of a twenty-first-century facsimile, bereft of the spirit and philosophy that motivated the original construction.

And yet… The Gothic cathedrals already undermine notions of “authenticity”. In past ages, they weren’t seen as buildings that had to be maintained in some “pristine” state at all costs. Ever since they were erected, they were modified and redesigned, sometimes with very little care for their integrity. This happened at Notre Dame in the seventeenth century, when the flame of Gothic had long gone out. There was a fashion for plonking grotesque, kitsch marble sculptures in place of medieval statuary, which was indeed the fate of Notre Dame’s high altar. The vandalism went on through the eighteenth century – and that was even before the Revolutionaries did their worst, melting down metal bells, grilles and reliquaries and then using the cathedral as a kind of warehouse. The Gothic revival of Viollet-le-Duc in the nineteenth century had better intentions but not always better taste.

This was ever the way, even in the Middle Ages: bishops would decide that their cathedral had become old-fashioned, and would commission some new extension or renovation that as often as not ended up as a jarring clash of styles. The notion of conservation and a “respect for the old” simply didn’t exist.

And that’s even before we consider the ravages of unintentional damage. Many of the wonders of Gothic architecture only came about as a result of fire in the first place. That is how we got Chartres: thanks to a fire in 1194 that destroyed the building commissioned in the 1020s (after the cathedral before that was burnt down). The conflagration was devastating to the morale of the local people: according to a document written in 1210, they “considered as the totality of their misfortune the fact that they, unhappy wretches, in justice for their own sins, had lost the palace of the Blessed Virgin, the special glory of the city, the showpiece of the entire region, the incomparable house of prayer”. Yet look what they got in its place.

And they had no hesitation in putting a positive spin on it. Another early thirteenth-century account asserted that this was God’s will – or the Virgin’s – all along: “She therefore permitted the old and inadequate church to become the victim of the flames, thus making room for the present basilica, which has no equal throughout the entire world.”

And so it went on throughout the Middle Ages and beyond: the astonishing edifices of the Gothic masters fell or burnt down, got neglected or half-dismembered, were subjected to undignified “improvement”, were ransacked or, later, bombed. Chartres has had catastrophic fires too: no one seems now too bothered that the original roof and allegedly wonderful timberwork beneath it were consumed by flames in 1836, or that the replacement we see today was originally intended only to be temporary.

What happened today at Notre Dame is truly a tragedy. But we shouldn’t forget that these magnificent buildings have always been works in progress, always in flux. Perhaps, in mourning what was lost, we can see it as an opportunity to marvel again at the worldview that produced it: at the ambition, the imagination, the profound union of technical skill and philosophical and spiritual conviction. And we can consider it a worthy challenge to see if we can find some way of matching and honouring that vision.

Wednesday, December 12, 2018

How to write a science best-seller

Everyone knows how science writing works. Academic scientists labour with great diligence to tease nuanced truths from theory and experiment, only for journalists and popularizers to reduce them to simplistic sound bites for the sake of a good story.

I’ve been moved to ponder that narrative by the widespread appearance on Christmas science/non-fiction books lists of two books by leading science academics: Steven Pinker’s Enlightenment Now and Robert Plomin’s Blueprint. I reviewed both books at length in Prospect, and my feelings about both of them were surprisingly similar: they have some important and valuable things to say, but are both infuriating too in terms of what they fudge, leave out or misrepresent.

I won’t recapitulate those views here. Plomin has taken some flak for the genetic determinism that his book seems to encourage – most recently from Angela Saini in the latest Prospect, whose conclusion I fully endorse: “Scientists… should concentrate on engaging with historians and social scientists to better understand humans not as simple biological machines but as complex, social beings.” Pinker has been excoriated in one or two places (most vigorously, and some would say predictable, by John Gray) for using the “Enlightenment” ahistorically as a concept to be moulded at will to fit his agenda (not to mention his simplistic and obsolete characterization of Nietzsche).

What both books do is precisely what the caricature of science journalism above is said to do, albeit with more style and more graphs: to eschew nuance and caveats in order to tell a story that is only partly true.

And here’s the moral: it works! By delivering a controversial message in this manner, both books have received massive media attention. If they had been more careful, less confrontational, more ready to tell a complex story, I very much doubt that they would have been awarded anything like as much coverage.

Now, my impression here – having spoken to both Pinker and Plomin – is that they both genuinely believe what they wrote. Yes, Pinker did acknowledge that he was using a simplified picture of the Enlightenment for rhetorical ends, and in conversation Plomin and I were broadly in agreement most of the time about what genetic analyses do and don’t show about human behaviour. But I don’t think either of them was setting out cynically to present a distorted message in order to boost book sales. What seems to be happening here is more in the line of a tacit collusion between academics keen to push a particular point of view (nothing wrong with that in itself) and publishers keen to see an eye-catching and controversial message. And we have, of course, been here before (The God Delusion, anyone?).

Stephen Hawking’s book Brief Answers to the Big Questions was also a popular book choice for 2018 that, in a different way, often veered towards the reductively simplistic, though it seemed to fall only to me (so far as I was able) and my esteemed colleague Michael Brooks to point that out in our reviews.

It seems, then, increasingly to be the job of science writers and critics, like Angela and Michael, to hold the “specialists” to account – and not vice versa.

I could nobly declare that I decline to adopt such a tactic to sell my own books. But the truth is that I couldn’t do it even if I wanted to. My instincts are too set against it. For one thing, it would cause me too much discomfort, even pain, to knowingly ignore or cherry-pick historical or scientific facts (which isn’t to say that I will sometimes get them wrong), or to decline to enter areas of enquiry that might dilute a catchy thesis. But perhaps even more importantly, I would find simplistic narratives and theses to be just a bit too boring to sustain me through a book project. What interests me is not winning some constructed argument but exploring ideas – including the fascinating ideas in Enlightenment Now and Blueprint.

Wednesday, October 31, 2018

Musical illusions

Here's the English version of my column on music cognition for the current issue of the Italian science magazine Sapere.

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“In studying [optical] illusions”, writes Kathryn Schulz in her book Being Wrong, “scientists aren’t learning how our visual system fails. They are learning how it works.” What Schulz means is that normal visual processing is typically a matter of integrating confusing information into a plausible story that lets us navigate the world. Colour constancy is a good example: the brain “corrects” for variations in brightness so that objects don’t appear to change hue as the lighting conditions alter. The famous “checkerboard shadow” illusion devised by vision scientist Edward Adelson fools this automatic recalibration of perception.


Adelson’s checkerboard illusion. The squares A and B are the same shade of grey.

In this regard as in many others, auditory perception mirrors the visual. The brain often rearranges what we hear to create something that “makes more sense” – with the same potential for creating illusions. Psychologist of music Diana Deutsch has delved deeply into the subject of musical illusions, some of which are presented on a CD released by Philomel in 1995. Several of these have to be heard through stereo headphones: they deliver different pitches to the left and right ears, which the brain reassigns to create coherence. For example, in the “scale illusion” the notes of two simultaneous scales – one ascending, one descending – are sent alternately to each ear. But what one hears is a much simpler pattern: an ascending scale in one ear, descending in the other. Here the brain is choosing to perceive the more likely pattern, even though it’s wrong.

Another example reveals the limitations of pitch perception. A familiar tune (Yankee Doodle) is played with each note assigned a random octave. It sounds incomprehensible. The test shows that, in deciphering melody, we attend not so much to absolute pitch class (a C or D, say) as to relative pitch: how big pitch jumps are between successive notes. Arnold Schoenberg’s twelve-tone serialism ignored this, which is why the persistence of his “tone rows” is often inaudible.

Perhaps the strangest thing about optical illusions is that we enjoy them, even if – indeed, because – we find them perplexing. Instead of being upset by the brain’s inability to “get it right”, we are apt to laugh – not a common response to wrongness, although it’s actually how a lot of comedy works. You might, then, expect to find musical illusions put to pleasurable use in music, especially by jokers like Mozart. But they are rather rare, maybe because we simply won’t notice them unless we see the score. Something like the scale illusion is used, however, in the second movement of Rachmaninov’s Second Suite for Two Pianos, where two sets of seesawing notes on each piano are heard as two sets of single repeated notes. It seems likely that Rachmaninov (not noted for jocularity) wasn’t just having fun – it’s merely easier to play these rapid quavers using pitch jumps rather than on the same note.