Small is... sort of cute

This little story went on the Guardian site on Friday. The technology isn’t new, but it was a very cute way to introduce the commercialization of it.

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It looks much like any other cover of the children’s magazine National Geographic Kids. Cuddly animals: check. Free Sea Turtle poster: check. Story about rescued hippos: check. Only the lack of colour and the slight graininess makes you think it might be something other than the real thing. But the real reason for these imperfections is that this magazine cover is so small that a single human red blood cell would cover most of it. It measures just 11 by 14 thousandths of a millimetre, and is totally invisible to the naked eye.

This is officially the Smallest Magazine Cover in the World, having been certified as such today by the Guinness Book of Records at the US National Science and Engineering Festival in Washington DC. The image is carved out of a lump of plastic using, as a chisel, a tiny silicon needle 100,000 times sharper than the sharpest pencil tip. The contrast reflects the topography of the surface: the higher it is, the lighter it appears.

The technique was developed over the past five years by physicist Armin Knoll and his colleagues at IBM’s research laboratory in the suburb of Ruschlikon in Zurich, Switzerland. The needle, attached to a bendy silicon strip that scans across the sample surface, is electrically heated so that when it is brought close to the specially developed plastic, the material just evaporates. In this way the researchers can remove blobs of material just five nanometres (millionths of a millimetre) across, paring away the surface pixel by pixel like a milling machine.

By reducing the heat, the tip can be used to take a snapshot of the carved structure it has produced. Surrounded by plastic in a valley, the tip radiates away more heat than if it hovers above a peak, and this heat flow therefore traces out the surface contours.

The IBM team first reported the method in 2010, and I saw it in action in Ruschlikon two years ago. It was a strange experience. Because I was once an editor at the science journal Nature, Knoll and his colleagues decided to write out the journal’s logo for me. On the display screen the letters took shape one by one, each perfectly formed in Times New Roman as if by a rather slow printer. It was hard to believe that each of them was about the height of a single bacterium.

IBM has licensed this technology to a start-up company in Zurich called SwissLitho, founded in 2012 by former IBM scientists Philip Paul and Felix Holzner. The company has developed it into a commercial machine that they call the NanoFrazor, costing around half a million euros. McGill University in Montreal, Canada, has bought the first of them. “It’s a cool tool”, says McGill physicist Peter Grutter. He says that, quite apart from the ability to make tiny structures for electronics, part of the attraction is that, unlike other nanopatterning methods, it’s very easy to find where you are on a surface and so to take images of large areas or to go back and overlay a second pattern.

The National Geographic Kids cover was made by Knoll’s team after running a readers’ poll to select their favourite image. Although Holzner expects the instrument to be mainly used as a research tool for universities like McGill, he suspects that novelty applications like this might prove popular too. It could be used to add security tags to artworks, passports and personalized Swiss watches that would be virtually impossible to forge. Some companies have already used other nanopatterning methods to write the entire Bible on a crucifix for especially devout customers, and even to engrave tiny patterns on the surface of chocolate that scatter light to create different colours. It seems that the Swiss reputation for both precision engineering and fancy confectionery is as secure as ever.

My unexpected internal monologue this week...

[The scene: the foyer of a university theatre. Conference delegates are standing around chatting.]

Look, Michael Frayn is standing over by the coffee on his own! If I don’t go and speak to him, I’ll kick myself afterwards. I mean, I had to stop reading The Tin Men and Towards the End of the Morning in public because I kept embarrassing myself by laughing out loud… And then Copenhagen… Come on, I have to. Don’t know what I’ll say, but anything…

OK, I don’t think that was too great a faux pas to ask what he is working on now. I mean, he said “Nothing!”, but not angrily, and now he’s gone and asked what I am working on! Michael Frayn is interested in that! And I didn’t think he’d even know who I was at all! So yes Michael, I see it as a kind of cultural history and – uh OK, now I get it, this is his very gracious way of deflecting the question, because he doesn’t really want to say what he’s working on. Ah well, keep it going… You see, it’s a book all about the stories we tell when –

That bloke out of the window there looks quite like my neighbour Geoff.

Focus, you fool. You can’t start looking over the shoulder of Michael Frayn, as if you’re hoping to catch the eye of someone else at the meeting who might be more interesting to talk to. This is Michael Frayn! Very funny books! Copenhagen! So, this cultural history that goes back to Plato and –

No, he really looks a lot like my neighbour.

Don’t keep looking, you idiot. Look, you have come to Lincoln for the day. Lincoln is a little town, OK so a city really, with cathedral and all, and the cathedral is fabulous, and the dock front around the campus is nice, but it’s not exactly a place people come to, is it? You have to change at Peterborough, for God’s sake. So you glimpsed a bloke with receding hair and a beard, like 80 percent of all male university lecturers. It’s not actually going to be Geoff, is it? I know he turned out to be in Spain the other week at the same time as you, but is he really going to be strolling through the Lincoln campus just as you glance out of the window? Do you think he is stalking you or something?

So where were we? Oh, Michael is talking to someone else now. Well, I would only have blurted out some silly question about Heisenberg.

[Yes, it was my neighbour Geoff.]

Criticality and phase transitions in biology

My piece just published in New Scientist on phase transitions in biology has had one of the most difficult gestations I’ve ever encountered. No one’s fault, it is just that it’s a very tough job finding the right way to tell a story like this. For one thing, what I came to realise during the editorial process is that, if you talk about criticality, people outside condensed-matter physics are likely to imagine you’re talking about self-organized criticality, and that they don’t generally know that critical points have a long, long history going way back beyond this. Neither, it seems, is the connection between the notion of criticality, with its scale-free phenomena, and phase transitions well known. The real point of the ideas I discuss in this piece is not that there’s something wonderful about being poised at a critical point, on the edge of order and chaos etc., but that it can be useful for a biological system to situate itself near to some phase transition and to draw on the fluctuations and sensitivity to external conditions that this engenders. It doesn’t have to be a critical transition – I am coupling together here the current discussions of near-critical biology with work on first-order phase transitions in protein hydration, where again the value seems to be that one can draw on large fluctuations to attain a big response to a small stimulus. This latter material didn’t make the final cut in New Scientist, and I can see that it made for an even more complicated story. But I do think that there is important common ground between the two ideas. What’s more, no one previously has made the link to Eigen’s ideas about natural selection coming from a phase transition – a notion that he has set out in full in his immense, dense but fascinating recent book, which I reviewed here.

Anyway, this version is based on my original draft, but with some of the later material mixed in. Hopefully it will give some indication of the bigger picture.

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It’s not the midges that were the problem, says Andrea Cavagna, but the kids. You’d think his efforts to record the movements of midge swarms in the public parks of Rome near sunset would be fraught with risks of being eaten alive by the little beasts – but these were a non-biting variety. Keeping away the children who gathered to watch what these folks were up to with their video cameras, generators and thickets of cabling was another matter. That, and the problem of finding a parking space in central Rome.

It’s not easy, he realised, for a physicist to turn field biologist.

The reason why Cavagna, based at Sapienza University in Rome, and his colleagues went midge-hunting sounds strange, perhaps even bizarre. The researchers wanted to know if midges behave like magnets. More specifically, if they act like magnets close to the point where heat flips them between a magnetic and non-magnetic state: a so-called critical phase transition.

Cavagna is one of a small and diverse group of scientists who have begun to suspect that critical phase transitions play vital roles in a wide variety of biological systems. Not only might they underpin the swarming of midges and the flocking of birds, but they might enable neurons in the brain to encode a picture of our environment, some protein molecules to fold up and bind their target molecules, and cell membranes to attract molecules that trigger cell-to-cell messaging. They might even explain how evolution itself works.

It’s good to be critical

Staying alive might seem to be a question of keeping calm and carrying on in the face of whatever comes along. But it’s often important to be able to respond and adapt to challenges rather than stoically riding them out: if you’re a small creature about to be eaten by a big one, you’d better get out of there. The trick is to keep your options open, maintaining easy access to a wide range of actions. It’s a delicate balance: you need stability, but also responsiveness.

In 2010 two physicists suggested how this might be possible. Thierry Mora (now at the École Normale Superieure in Paris) and Bill Bialek at Princeton University argued that many biological systems, from flocking birds to neural networks, might be “poised close to a critical point”. The idea drew on a well-established notion from statistical physics: the critical phase transition, where a system of many interacting components switches suddenly from one global state of organization to another, typically from an orderly to a disorderly state. The magnetic transition of iron, where it changes from having the magnetic orientation of its atoms random and disorderly to all lined up as the material is cooled, is the classic example. The switch happens abruptly at the so-called critical point – for iron, at a temperature of 1,043 Kelvin.

What have magnets got to do with biology? The point is that the critical transition of a magnet isn’t anything to do with magnetism per se. It is an outcome of the fact that each atom is interacting (here via magnetic forces) with its neighbours, and that they all have to come to some ‘collective decision’ about how to organize themselves. Because of that collective aspect, phase transitions happen all at once when a threshold value of some control parameter such as temperature is surpassed. They occur in all manner of physical systems, from superconductors and the Big Bang to polymer mixtures. So why not in biology?

The proposal of Mora and Bialek didn’t spring from nowhere. It echoes suggestions made in the 1990s that many natural systems, including some in biology (such as mass extinctions), display ‘self-organized criticality' (SOC), meaning that they undergo disruptions and fluctuations at all possible scales of size. The archetypal example of SOC was a pile of sand, which can have avalanches of all sizes as new grains are added at the top of the slope. This wide range of fluctuations scales is just what is found at an ordinary critical point – for example, a magnet at its critical point is a patchwork of domains of all different sizes with different magnetic orientations.

But, says Cavagna, it was never really clear that SOC had a deep connection to the older notion of critical phase transitions. The key feature of SOC is that it is indeed ‘self-organized’, which means that it will return to the critical state after a disturbance like an avalanche. So there’s no actual phase transition at all. “It’s just a point of great instability”, Cavagna says – and not one that is reached, like a true phase transition, by tuning a parameter like temperature. What’s more, says Bialek, “there was a huge amount of ideology about why criticality was a good thing in biology” – but no good argument for why. These two researchers and others are now trying to clarify what advantages criticality might convey on a wide range of biological systems, regardless of whether it is achieved by self-organization, natural selection or something else.

A critical magnet is poised on a knife-edge, where the smallest nudge can tip it into becoming wholly magnetic or non-magnetic. This knife-edge character of traditional (rather than self-organized) critical points means that it is all but impossible for a system to stay there. But the proposal of Mora and Bialek is that biological systems might benefit from operating close to critical points. This could provide access to a wide range of fluctuations involving different configurations of its components. The striking thing about near-criticality is that the rarity of specific, seemingly unlikely configurations is exactly compensated for by the fact that there are many more variants of such states than there are of common ones. “There’s a small number of very common configurations, a large number very rare configurations, and everything in between”, says Mora. “Being close to a critical point means that you're as likely to find yourself in any of these configurations.” As a result, he says, “being critical may confer the necessary flexibility to deal with complex and unpredictable environments.”

Another key feature of a critical system is that it is extremely responsive to disturbances in the environment, which can send rippling effects throughout the whole system. “At the critical point, everything is about to go crazy”, says physicist Jim Sethna of Cornell University. “So you get massively more sensitive behaviour.” That, Sethna says, can help a biological system to adapt very rapidly to change. The sensitivity stems from the long-ranged correlations in the behaviour of the system’s components that develop near criticality: a tweak here has an influence right over there, so that each component can ‘feel’ what all the others are doing.

Crucially, this flexibility and adaptiveness is achieved not by some incredibly complex and fragile set of interactions between the components, but taking advantage of the universal and robust characteristics of all systems made up of many interacting components. If a system evolves to be close to critical, says Sethna, it then has something like a set of general-purpose knobs that can allow it to adapt to environmental changes without having to reconfigure genomes.

Recent work by physicists Amos Maritan and Jayanth Banavar and their coworkers gives a clearer picture of why criticality in particular is useful. They have calculated how a system of agents that can gather information about their environment, and whose fitness depends on their ability to locate the source of environmental stimuli, evolves over time. They found that such a collection of evolving cognitive agents settles naturally into a critical state. “Being poised at criticality provides the system with optimal flexibility and evolutionary advantage to cope with and adapt to a highly variable and complex environment”, says Maritan.

In effect, this critical state allows the system to ‘sense’ what is going on around it: to encode a kind of ‘internal map’ of its environment and circumstances, rather like a river network encoding a map of the surrounding topography. “A key ingredient to the success of a living system is its ability to capture relevant information from the richly varying external world, synthesizing its most prominent features into manageable maps”, says Maritan. If this is indeed a feature of a near-critical state, the activity of neurons would be expected to operate in such a state just as Mora and Bialek proposed, because what our brains ‘show us’ will then be a good approximation to what is really ‘out there’.

There’s now mounting evidence that brains really are organized this way. One signature of criticality would be long-ranged correlations between the ‘spiking’ activity of neurons – something that Bialek and his coworkers have found in their models of neural networks. These correlations mean that the state of each neuron is to some degree encoded in the state of the rest of the network, providing a mechanism for error correction and recovery of lost information.

And it’s not just all theory. Dante Chialvo of the National Council for Scientific and Technological Studies in Buenos Aires, Argentina, and colleagues have shown that dynamics characteristic of a critical state in the activity of the human brain can account for some of the key features seen in MRI brain imaging, such as the coherent operation of many neurons clustered together in space. And Nir Friedman of the University of Illinois at Urbana-Champaign and his coworkers have found that avalanches in the firing of neurons show the same kind of size–probability relationship as those in self-organized critical sand-piles. It’s not hard to imagine that this apparently general operating principle of neural networks might bring some structure to the mass of data soon to emerge from the large-scale projects recently launched in the US and Europe to map out the connectivity of the human brain.

Superfluid starlings

Responsiveness has an obvious utility to a herd or flock of animals looking out for predators: if a few individuals spot one, the rest of them can gain that information almost at once. And they do – just think of schools of fish darting around in unison to avoid sharks.

It was this sort of flocking behaviour that partly stimulated Mora and Bialek’s proposal in the first place. Theoretical modelling of flocking over the past decade or so has shown that coordinated motion requires each animal simply to respond to its nearest neighbours’ movements by trying to align itself. This is similar to the way magnetic atoms get aligned, and in fact some flocking models are directly analogous to models of magnetism. Mora, Bialek, Cavagna and their collaborators have recently shown that the graceful, orderly motion of flocks, familiar from watching starlings at twilight, is most easily maintained if the flock is close to a critical point. Further from this point, a flock might stay coordinated but loses the ability to respond quickly and coherently to outside disturbances such as predators.

In other words, says Cavagna, flocking isn’t just about orderly motion. Too much of it and you end up regimented like a crystal, slow to respond to anything. The responsiveness comes instead from the correlations between individuals – how one affects another.

Fine in theory. But do real flocks work this way? In a happy confluence of ideas and observations, Cavagna and his coworkers in Rome began their studies of flocking in 2010 just as Mora and Bialek were presenting their ideas on biological criticality. The Italian team found that flocks of starlings have scale-free correlations in the velocity fluctuations of individual birds. In other words, if one bird in the flock changes course, others will tend to do so too almost instantaneously, no matter how far apart they are.

Cavagna and colleagues placed video cameras on top of the National Museum of Rome in the city centre, which overlooks a major roosting site for starlings in winter. They filmed the birds during their flocking displays at dusk, and then used computer-vision methods to turn the footage into records of the three-dimensional movements of individual birds in the flock, which typically contained between a hundred and several thousand birds. They analysed this data to figure out how each bird deviated from the average velocity of the entire flock, and to measure the correlations: how closely these deviations for any pair of birds shadow each other as the distance between the pair increases.

“We found that correlation was very strong”, Cavagna says. In other words, the birds seem to be tuned into one another’s movements even over scales beyond which they can see each other. The influence of one bird is transmitted to others far away through neighbour-to-neighbour interactions, in just the same way as the magnetic poles of atoms of iron in a magnet can ‘speak’ indirectly over long distances close to the critical point.

What’s more, these observations showed that realignment of the birds’ orientation as the flock changes direction spreads much faster than the standard theories of collective movement permit. This behaviour can be explained by adding an extra ingredient to the theory: a ‘symmetry rule’ which reflects the fact that all directions of flight are equivalent. With this included, it turns out that the movement of the flock becomes mathematically equivalent to that of a superfluid such as liquid helium, which can flow essentially without losing any energy through viscous drag. In other words, a flock of birds can be considered a kind of living superfluid.

Midges don’t exhibit the orderly swarming motions of birds and fish. Might they, nevertheless, display the long-ranged correlations expected on the disordered side of a critical phase transition? “Some biologists insisted there is no collective behaviour in midges”, Cavagna says, and he expected his observations to confirm that view. But after painstakingly filming the midges swarming around park landmarks, reflected in the setting sun, he and his coworkers couldn’t avoid the conclusion that there were very strong correlations here too.

“It’s physically exhausting work”, Cavagna says: lugging all the equipment into a park, filming for several hours, then immediately going back to the lab well after dusk to download the data. “Still, at least it was summer, and the Roman parks are lovely.” Filming birds is harder, he says, since they only flock in the cold winter.

But why would evolution tune midges to behave that way, given that predation isn’t an issue for them? Cavagna thinks that this might be looking at the question the wrong way. Perhaps they can’t help being near-critical. The researchers found that the reach of the correlations was always about the same size as the swarm: the bigger the swarm, the longer the correlations. So maybe the swarm size isn't an adaptation, but is a side-effect of some other factor that determines how the midges interact. This factor - the range of neighbouring midge interactions, say - sets the correlation distance for midge motions, so that if the swarm gets bigger than that size, it will automatically shed midges.

Quick drying

The idea that biology makes use of phase transitions and their associated correlations and fluctuations could go far deeper than these large-scale networks and communities, and might be applied even at the level of individual cells and molecules. Protein molecules, for example, often carry out their functions as enzymes by switching from one shape to another. That needs to happen easily when the right signal is given, for example when another molecule binds to the protein to activate it. These conformational changes are, like phase transitions, cooperative, meaning that they involve interactions between all the component parts. Tweak this bit of a protein, and the whole thing tips into a new shape.

Cooperative transitions have also long been thought to govern the way protein chains fold up into their functional shapes in the first place. But recently David Chandler at the University of Berkeley at California and his coworkers have argued that both this process and the way several protein molecules stick together into many-component assemblies could be controlled by a transition that occurs not in the protein itself but in the water that surrounds it. They believe there may be an abrupt ‘drying transition’ in which all the water suddenly exits from the space between two water-repelling parts of proteins. Chandler argues that these drying transitions, which have been seen in computer simulations of some proteins, draw on the strong fluctuations that exist in the water, whereby the water molecules organize themselves into ever-changing regions of high or low density – not unlike a midge swarm, in fact. These fluctuations make it easier for the gap between the protein segments to tip over from a ‘wet’ to a ‘dry’ state, just as they make it easier for a critical magnet to tip over into a magnetic or non-magnetic state. Not all, or even most, proteins seem to fold or aggregate via these drying transitions. But Chandler and colleagues argue that most of them may be fine-tuned by evolution to be close to such a transition, some lying on one side of that boundary and some on the other.

Drying transitions have also been found in computer simulations of the docking of small molecules into the ‘binding cavities’ of the enzymes they activate. Some proteins in thermophilic organisms, which thrive in hot environments, have cavities lined with water-repelling chemical groups that seem poised right on the brink of expelling the water and becoming dry at the organism’s normal working temperature. The docking of the ‘plug’ into its ‘socket’ would be made easier by this ease of emptying. Meanwhile, some protein channels that sit in cell walls and regulate the flow of other molecules or ions in and out are also poised to undergo drying transitions within their conduit pores, so that they can be easily switched from an ‘open’ state (where the water-filled pore lets dissolved substances pass) to a ‘closed’ state (where the pore is dry and denies passage).

Another benefit of being close to a phase transition has been suggested by Sethna and his colleagues. Some biological membranes are patchworks in which different types of lipid molecule are segregated into liquid-like ‘rafts’, phase-separated like immiscible droplets of oil and water. Because these patches have a wide range of fluctuating sizes, rather like the domains of a near-critical magnet, Sethna’s team argued that they are close to a critical phase transition at which the molecules become fully miscible.

They say that the value here is not in the phase transition itself, but in the domain size fluctuations that accompany it. Such fluctuations in immiscible fluids were shown in the 1980s to give rise to a force analogous to the so-called Casimir force that pulls together two closely spaced metal plates in a vacuum. The normal Casimir force is caused by electromagnetic fluctuations in the vacuum, themselves a consequence of quantum physics: because the size of these fluctuations is restricted between the plates, this produces a pressure that draws them together. Likewise, constraints on the ‘near-critical’ fluctuations of lipid patches between protein molecules embedded in the membrane give rise to a ‘critical Casimir’ attraction that might help molecules to bind together and trigger chemical reactions involved in cell signalling. In effect, says Sethna, it means that proteins at the membrane surface can talk to each other via the lipid rafts. “Here again criticality allows the system to access structures over a wide range of scales”, says Mora.

The physics of evolution

Phase transitions and criticality might turn out to be important in the operation of gene networks, which currently seem absurdly baroque and yet somehow generate stable and robust organisms. Bialek and coworkers recently reported an indication of criticality in the gene regulatory network that determines the spatial patterning of the fruit fly embryo – the so-called gap gene network. They found long-ranged correlations in the fluctuations of gene expression levels at well-separated parts of the embryo. It’s possible that these critical-like fluctuations might help to improve the signal-to-noise ratio of the information transmission in the regulatory network.

Mora and Bialek have suggested that phase transitions in the ‘information space’ that relates a protein’s structure to its shape and function through the collective interactions of its chemical building blocks might account for the appearance of distinct ‘families’ of protein structures. This would imply that the evolution of protein sequences (and hence gene sequences) is significantly constrained by the limited number of ‘stable states’ in sequence space – in other words, that nature’s profusion is regulated by an order even deeper than natural selection.

In fact, not only does evolution seem likely to make use of phase transitions – it might actually be one. Chemist Manfred Eigen, who won the 1967 Nobel Prize for his work on fast chemical reactions, has argued that natural selection appears in a system of self-replicating, information-bearing entities as an abrupt phase transition at certain threshold values of the rates of replication and mutation. In other words, it is not just ‘something that happens’ in reproducing systems, but is a physical law that arises from the way information itself is organized. In Eigen’s theory, neutral selection – in which mutations get fixed in a population even though they have no adaptive benefit – injects fluctuations analogous to those at a critical point. These are essential to prevent natural selection from getting ‘stuck’ in minor valleys of the evolutionary landscape – or as a physicist might say, to prevent the system settling into a metastable phase, which is provisionally stable but not the optimal arrangement of the components. That would fit with the recent suggestion of evolutionary biologist John Tyler Bonner at Princeton University that the random fluctuations of neutral evolution could account for the immense variety of forms found in organisms such as diatoms.

Criticality and the critics

“I knew from the beginning that I wanted to do something in between physics and biology”, says Bialek. The question is, he says, “can you talk about these things that biologists usually study in the way that physicists do?” He suspected “that there’s some collection of phenomenon that people didn’t realise were related to each other, or some part of the biological world that nobody has looked at from a physicists’ point of view” – in other words, the big question was “whether aspects of particular [biological] models can be derived from some more general principle.” If Bialek and Mora are right, criticality could emerge as one such general principle.

But these ideas have yet to be embraced by most biologists, whose agenda is often now dominated by fine details rather than a search for over-arching principles. Getting these ideas a hearing in biology is likely to be a struggle. “There’s a big difference in culture”, says Sethna. “Biologists tend to be skeptical of anything that involves a lot of math.” In an effort to bridge this ‘two cultures’ divide, in 2010 Bialek spearheaded an interdisciplinary centre called the Initiative for the Theoretical Sciences at the City University of New York, where he is now director. Here physicists can discuss these ideas with neuroscientists, ecologists and other biologists – Cavagna was recruited as a visiting professor last year, and has been collaborating with Bialek and Mora to refine the understanding of critical flocking. But it will take time and patience, both to figure out how widely phase transitions and criticality really are used in biology, and to persuade life scientists that, as Sethna puts it, cells, and perhaps proteins, animals and entire ecosystems, “do a lot of interesting physics.”

Theatre of the Invisible

I gave this talk yesterday at the meeting Performing Science: Dialogues Across Cultures at the University of Lincoln. It seemed brief enough to put up here. _____________________________________________________

The actor David Garrick had a set-piece during his performances of Hamlet, the role for which he was most famous, that electrified London theatre audiences in the eighteenth century. It came when the ghost enters at the start of the play. According to the St. James Chronicle in 1772, “As no Writer in any Age penned a Ghost like Shakespeare, so, in our Time, no Actor ever saw a Ghost like Garrick.” The German scientist Georg Christoph Lichtenberg wrote that “His whole demeanour is so expressive of terror that it made my flesh creep even before he began to speak.”

Garrick is shown in the midst of this tour-de-force in a contemporaneous print (Figure 1). Doesn’t it seem here as if his hair is actually rising from his scalp? And in fact, it really is. But not even Garrick could raise his hair at will. He achieved the spine-tingling effect (which goes by the splendid name of horripilation) with the aid of a London wig-maker named Perkins, who created a mechanical wig powered by hydraulics.



Figure 1 David Garrick as Hamlet, on seeing his father’s ghost in Act I. Mezzotint after a painting by Benjamin Wilson, 1756.

This wasn’t just a cheap trick. Garrick’s approach to what was then seen as naturalistic performance was informed by a Cartesian view of human physiology, in which the body was regarded as a kind of hydraulic mechanism driven by fluids called animal spirits that were pumped around the organs and limbs. Within this view, an artificial hydraulic wig was little different from the way real horripilation was thought to work by a rush of fluids to the head. Like all emotion, it was simply a matter of biomechanics.

But there is another defence of Garrick’s potentially absurd ‘fright wig’: he needed all the help he could get, because he’d set himself the task of conjuring the illusion of the ghost by gesture alone. Whereas previously the dead king was generally played by an actor, Garrick insisted that he should be invisible: a disembodied voice whose presence was seen only by the actors. But theatrical invisibility is a difficult trick – as film makers later discovered, it needs visible signifiers to sustain the illusion.

Garrick’s choice represented a decision not just about staging but about what the ghost in Hamlet – on which the plot of course turns – truly means. It is a statement about how the entire play should be interpreted. Because we’re then forced to ask: is this a real spirit, or just a figment of Hamlet’s tortured mind?

Partly this is a question about the significance of ghosts in Shakespeare’s time. But I want to locate this issue of the visibility of his ghosts within a wider debate about appearance, illusion and spectacle in theatre. Because it is my contention that, from the eighteenth to the early twentieth centuries in particular, science – and particularly optical science – became strongly linked to theatre, stage magic and the advent of cinema, in ways that were as much thematic as they were instrumental.

Ghosts were a common, even clichéd sight on the Elizabethan stage. They served as narrators, popping up to fill in a bit of back-story. As such, they were no cause for alarm in either implication or appearance, being represented by a sort of Jack-in-the-box puppet, or else by an actor with whitened face, dressed in clothes made of furry leather. They were a device borrowed from the plays of Seneca, which supplied a model for the revival of tragedy during the Renaissance. The Senecan ghost typically appeared in the prologue, calling for an act of revenge that motivated the play’s tragic plot.

But the ghost in Hamlet is no glove puppet. He’s made to sound hardly less terrible to the audience than he is to Hamlet and his friends: the sight “harrows me with fear and wonder”, gasps Horatio. That’s what Shakespeare did to the theatrical ghost: he made it real, humanized, haunting and disquieting. His spirits are really spooky, and in some ways they represent a supernatural stage presence that has never been equalled.

The Senecan ghost is merely a “bit of dramatic machinery”. But ghosts in Shakespeare, and in some of the Jacobean plays that came after, leave the audience guessing. Indeed, they leave the characters guessing: what sort of apparition is this? This is a question about what ghosts meant in the popular superstition of the time. The answer wasn’t simple, but we can at least say that it was determined largely by your religion. Catholics believed that the souls of the dead reside for a time in Purgatory before being admitted (if they warrant it) to heaven. This gave souls a period in which to haunt the living. But Protestants rejected the idea of Purgatory – which makes it puzzling how a dead soul can feature in what is undoubtedly a Protestant play. Might, then, the ghost be a demon masquerading as the king, to provoke Hamlet into acts of slaughter and, indirectly, Ophelia into sinful suicide?

This was the choice, it seems: ghosts were either dead souls, or they were demons – or maybe angels. All were real entities; as the Shakespeare scholar Robert Hunter West has said, when these plays were first performed “Englishmen were seriously aware in a way that we are not of an invisible world about them.” Around this time there was a vigorous debate about the meaning and status of ghosts, and several learned books were published that attempted to provide them with a taxonomy.

One of the most influential was by the theologian Noel Taillepied, called A Treatise of Ghosts. Taillepied claimed that the souls of the departed may be returned to earth by God to deliver a message. Shakespearian ghosts indeed do always have motives and messages to impart, and sometimes only the intended recipients can see them, or at least hear them. The notion of a ghost who, like Banquo in Macbeth, haunts the guilty party alone was well established in folk tradition. If we are inclined to attribute this now to the fevered imaginings of a guilty conscience, we shouldn’t imagine that Shakespeare was in contrast blindly literal – the powers of invocation and agency attributed to the imagination in the late Renaissance leave no clear distinction between a ghost being a projection of the mind and an objective phenomenon.

Ghosts didn’t, as one might expect, go out of fashion with the alleged rationalism of the Enlightenment. Certainly in popular superstition they remained as present as ever, as the famous Cock Lane Ghost of London in the mid-eighteenth century attested. That case ended in a prosecution for fraud, after investigation by a committee that included Samuel Johnson. But Johnson himself remained a firm believer in ghosts, even if not in this particular one.

What changes in our perceptions of the spirit world is not the question of whether it exists but of what it means. In the nineteenth century, the rise of spiritualism saw ghosts become sources not so much of terror as of consolation: mediums offered the opportunity to speak with the souls of the departed loved ones. And what is most striking in this period, certainly for the purposes of this meeting, is how ideas about invisible beings and unseen spirit worlds co-evolve with the development of science and technology, and also with the traditions of the theatre.

For one thing, spiritualist séances were undoubtedly pieces of theatre in themselves, designed to astonish and confound their audiences and prepared with a great deal of stagecraft (Figure 2). Here is an account by William Crookes, one of the many scientists who tried to subject spiritualism to scientific investigation, of a séance conducted in 1871 by the famous medium Douglas Home:

"At first we had rough manifestations, chairs knocked about, the table floated 6 inches from the ground and then dashed down, loud and unpleasant noises bawling in our ears and altogether phenomena of a low class. After a time it was suggested that we should sing, and as the only thing known to all the company, we struck up ‘For he’s a jolly good fellow’. The chairs, tables and things on it kept up a sort of anvil accompaniment to this. After that D. D. Home gave us a solo – rather a sacred piece – and almost before a dozen words were uttered Mr Herne was carried right up, floated across the table and dropped with a crash of pictures and ornaments at the other end of the room. My brother Walter, who was holding one hand, stuck to him as long as he could, but he says Herne was dragged out of his hand as he went across the table."

The group was subsequently treated to accordions playing themselves, floating lights, books dashed about and disembodied hands stroking their faces. The effect must surely have been overwhelming – both exciting and frightening, and doubtless calculated to inhibit objective assessment.



Figure 2 Victorian séances involved many strange goings-on that relied on carefully prepared and executed illusionistic trickery.

And as Crookes’ case shows, many scientists were taken in by all this – not simply because they were credulous, but because they surely wanted to believe. And also because some of them felt that they had more reason than ever to do so. The invention of the telegraph in the 1830s and 40s showed that it was possible to send messages instantly over immense distances, even spanning the Atlantic once the cables had been laid in the 1860s. With the appearance of the telephone a decade later, it became possible to hear voices directly over such a distance. And in the 1890s, the development of radio broadcasting by Marconi and Oliver Lodge meant that these signals didn’t even need a wire to convey them – they could be sent through the invisible ether. Many scientists figured that, if it was possible to hear the voice of someone who wasn’t physically present, it was not so hard to imagine that one might also hear the voices of those who were not even alive. Spiritualism was even sometimes called celestial telegraphy, and wireless broadcasting led people to suspect that the ether was a vast, invisible sea filled with all manner of voices, coming from who knew where. Rudyard Kipling made this analogy in his 1902 short story “Wireless”, in which some early radio hams pick up random messages from ships offshore while in the same building a man feverish from consumption acts as a human receiver for snatches of poetry by Keats that he picks up from some unknown and perhaps long dead source.

These speculations got another boost from the discovery of X-rays in 1895 (Figure 3) – an invisible form of radiation like light, but of a shorter wavelength. Perhaps thoughts might be transferred from person to person, or from the dead to the living, by similar invisible rays sent through the ether?



Figure 3 The X-ray image taken by Wilhelm Röntgen of his wife’s hand, c.1895.

And as this image shows, the technology of photography, devised in the 1830s, could make these invisible rays visible – this is the rather spooky image taken by the discoverer of X-rays, Wilhelm Rontgen, of his wife’s hand, and when she saw it she is said to have exclaimed “I have seen my death!” From its earliest days, photography seemed to be as much about revealing the invisible as documenting the visible. Because the surface of glass plates used to hold the emulsion could preserve faint images of an earlier exposure, some early photographers found that ghostly figures sometimes appeared in their images when the plates were reused. It was soon decided that these were spirits, and ghost photography because a lucrative business in the late nineteenth century. One of the first entrepreneurs of this business was an American named William Mumler, who set up a ‘spirit photography’ business in Boston and New York (Figure 4).



Figure 4 Abraham Lincoln’s shade consoling his widow, in a “spirit photograph” taken by William Mumler. The Lincolns were enthusiasts of Spiritualism, and were said to have conducted séances in the White House.

Even when scientists explained how such double exposures were easy to fake, it did little to diminish the popularity of the genre, for in its mysterious ability to capture the instant and to solidify intangible light photography seemed virtually a supernatural medium itself. Didn’t it, after all, convey a weird kind of immortality – and paradoxically, by doing so, remind the sitter that death awaits us all?

It’s quite natural that one of the first uses of photography would be to make invisible beings visible. For optical technology has always been closely allied with magic, and also with the theatre. It was long thought capable of revealing what went otherwise unseen, particularly spirits, souls and demons. The camera obscura, the forerunner of the photographic camera, in which natural scenes are projected through a small opening into a darkened space (Figure 5), was known since at least the eleventh century, and was popularized in the sixteenth century manual of natural magic by the Italian Giambattista della Porta (who was also a popular dramatist). By the early seventeenth century mountebanks were using such devices to astonish audiences.



Figure 5 The camera obscura, as depicted in Athanasius Kircher’s Great Art of Light and Shadow (1646).

Looking-glasses that produce figures “at a distance in the air” also featured in the magic lantern, an early form of projector that became a stalwart device of optical natural magic. It was described by the Jesuit inventor and mystical philosopher Athanasius Kircher in 1646: light is passed through an image painted onto glass and then through a lens before falling onto a screen (Figure 6). By the time Kircher was writing, magic lanterns were becoming commercialized. The Danish mathematician Thomas Walgensten traveled across Europe selling these lanterns and using them purportedly to summon ghosts.



Figure 6 The magic lantern, as shown by Kircher.

The magical stage spectacles of the late eighteenth century straddled this ambiguous boundary. The German illusionist Johann Georg Schröpfer held séances in his Leipzig coffee shop in which he used the magic lantern, projected onto smoke, to summon ghosts. Schröpfer’s performances were perhaps the first ‘entertainment séances’, and his techniques were copied by the German Paul Philidor, whose popular public displays in the early 1790s were unashamedly eye-catching and became known as “phantasmagoria” (Figure 7). Subsequently, Étienne Gaspard Robertson used magic-lantern back-projection in his “Fantascope” shows, in which, by mounting the device on wheels, he could make the projection grow rapidly larger or smaller so that ghouls and demons might seem to rush upon the terrified audience.



Figure 7 An advertising bill for the Phantasmagoria show of Paul Philidor in 1801.

Robertson explicit sought to scare his public with visions of ghosts and devils (Figure 8): he was in effect producing the first horror films. He was in fact a professor of physics with a special interest in optics, who realised the commercial potential of optical trickery when he attended one of Philidor’s extravaganzas. And although he made no pretence of possessing magical abilities, he exploited his specialist knowledge while artfully keeping his audiences guessing about what they were seeing.



Figure 8 The light show of Étienne Gaspard Robertson amazes and terrifies an audience in the early nineteenth century.

The most famous illusionistic ghost of the stage also comes from this collusion of science demonstration and pure theatre. In the mid-nineteenth century, the Royal Polytechnic Institute in London put on magic and séance shows to show how paranormal activities could be faked. One of the lecturers was the chemist and science popularizer John Henry Pepper, who later set up his own “Theatre of Popular Science and Entertainment” at the Egyptian Hall in London. Pepper collaborated with the engineer Henry Dircks in the late 1850s to create a technique for projecting the reflection of a hidden actor onto a huge, slanted sheet of glass: a semi-transparent apparition perfect for depicting ghosts (Figure 9). Plays featuring ‘Pepper’s ghost’, including Hamlet, Macbeth and A Christmas Carol, became sensations throughout Europe and the US.



Figure 9 Pepper’s ghost.

The Egyptian Hall was the centre of theatrical magic and scientific illusion in the nineteenth century. Perhaps the most famous residency was that of John Nevil Maskelyne, a watchmaker who began the foremost dynasty of British stage magicians (and who was, incidentally, the inventor of the pay toilet) (Figure 10). In 1905 Maskelyne and a group of other British magicians founded the Magic Circle, dedicated to the art of stage magic and illusion. Like many of these stage magicians, Maskelyne was also a debunker of spiritualists and mystics claiming special powers.



Figure 10 A playbill for the illusion and magic show of John Nevil Maskelyne in the late nineteenth century.

This role of illusionism is clear from Albert Allis Hopkins’ now classic 1898 manual of magic, in which the American amateur magician Henry Ridgely Evans proclaimed that “Science has laughed away sorcery, witchcraft, and necromancy.” Hopkins shows how stage magicians of the Victorian era made avid use of the newest scientific discoveries. He said that X-rays, discovered only two years before the book was published, “are now competing with the most noted mediums in the domain of the marvellous.” Hopkins describes a trick in which a man dining alone is suddenly cast into darkness, whereupon he vanishes and the audience sees, seated across the table, a glowing skeleton, lit up by a hidden X-ray generator (Figure 11).



Figure 11 A glowing, macabre dinner guest is conjured up using X-rays (from the generator on the right) to stimulate luminescence from a skeleton painted in a phosphorescent material, as depicted in Albert Hopkins’ 1898 book of stage magic.

The elaborate illusionism of the theatrical light-show found a new home in the early days of cinematography. In the late 1880s Thomas Edison began to create a kind of electrical magic lantern called the Kinetoscope that projected a series of still images in rapid succession to create the illusion of movement. In 1894 he opened a Kinetoscope parlour in New York, where for a few cents one could watch the first motion pictures, each lasting a minute or so. Meanwhile, the Lumière brothers turned the magic lantern into a portable, manually operated movie projector called the Cinématographe that threw the image onto a screen. A Parisian audience watched the first public screening in 1895.

In the audience for that premiere was the Frenchman George Méliès, who had developed his own form of illusionistic magic at the Paris theatre he owned. He promptly bought a movie camera and started making films himself. Many of these used his existing stage tricks, supplemented by the new illusionistic possibilities that cinematography offered. He made 78 films in 1896 alone, and over 500 during the next two decades. Several of them were ghost films, sometimes aimed more at slapstick than chills (Figure 12).



Figure 12 A scene from George Méliès’ comedy The Apparition, or Mr Jones’ Experience with a Ghost (1903).

Given this genealogy of cinema, it is no surprise that marvels soon took over. Films of ghostly and supernatural phenomena weren’t simply an early genre of cinema – they were its natural subject, for the motion picture should properly be seen not so much as “celluloid theatre” but as celluloid magic. Jacques Derrida seemed to discern this when in 1982 he called cinema “the art of ghosts, a battle of phantoms.”

What ought we to conclude from all of this?

First, that the first marriage of science and theatre happened in the arena of the magical and the illusory, and in particular in the disputed area where science and folk belief have vied for authority over the invisible.

Second, that science and technology have long had a performative aspect that was particularly prominent in the late eighteenth and the nineteenth centuries, and which involved a delicate interplay between explanation, mystification and spectacle, of the kind that I sense still persists in the Royal Institution Christmas Lectures.

Third, cinema should perhaps be a stronger part of this discourse, in the sense that its relationship to theatre, particularly in terms of its genesis, becomes much clearer once we acknowledge the close associations with optical technologies and illusionism.

And finally, I think, we should be reminded here of the role of imagination, which, both in science and in theatre, is needed to span the gulf of what isn’t known or cannot be expressed. Imagination is rarely spoken of today in science, but in a famous 1870 essay “Scientific Use of the Imagination”, John Tyndall argued that via the imagination “we can lighten the darkness which surrounds the world of our senses.” It is in its capacity to permit and depict imaginative leaps that theatre can help to illuminate and perhaps even extend some of the meanings of science.

Is music just about sex?

This piece (after editing) has just gone live on BBC Future. I don’t want to knock this PRSB paper, which reports intriguing findings. But please, journalists, a bit of proportion, even (especially?) with this steamy subject matter. For one thing, what exactly is it you will be imagining if I were to say to you “I’m going to play you a piece of music, and I want to imagine you having sex with the composer…”?

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Humans have made music for more than 40,000 years – the age of the earliest known instruments, flutes made from hollow animal bones. But no one knows why. Of all the theories that have been proposed, one of the most enduring and alluring comes from Charles Darwin, who suggested that it’s all about sex. “Musical notes and rhythm”, he wrote in The Descent of Man (1871), “were first acquired by the male and female progenitors of mankind for the sake of charming the opposite sex.”

Darwin’s idea was motivated partly by analogy with bird song, which does indeed often function to attract mates. But not only is there still debate about whether bird song qualifies as “music” in the same sense as human song, but there has been little reason to suppose that humans too use music primarily for courtship.

Now psychologist Benjamin Charlton of the University of Sussex in Brighton, England, offers some evidence to support this sexual-selection hypothesis. He has found that women’s sexual preferences for composers changes during their menstrual cycle, and that they prefer composers of more complex music – who might be construed as more capable mates – at the most fertile point of the cycle [1].

OK, don’t all shout at once – yes, there is a lot to argue over here. But let’s start at the beginning: what’s so special about music?

In answering that question, two things stand out. First, there are no cultures known that lack music – even if they lack a written language. It is as close to a universal human trait as you could hope for. Second, music – unlike, say, cooking, farming, talking, raising a family – doesn’t obviously have any benefit. Of course, it does have a benefit: we love it, it makes us joyful or transports us into tears, rapture and dance. But there’s no obvious, tangible result of music that we can definitely link to any evolutionary advantage.

It’s no wonder, then, that the question of the origins of music has excited such passionate debate. There is evidently something here that is crucial to human existence – we seemingly can’t do without music – but it’s awfully hard to say why, not least because music began way before recorded history. There is no shortage of ideas [2]. Some think that music began as a way of fostering social cohesion, a ‘tribal’ role that still persists today. Others say that it began in the sing-song of mother-to-infant communication, an exaggeration of tones called “motherese” that people all over the world practice. Others think that music and language were once merged into a composite form of communication dubbed “musilanguage”, from which music split as a vehicle of the emotions while language became all about semantic meaning.

But Darwin’s notion of music as an agent of sexual selection remains a favourite, not least because it has his name attached. Darwin regarded sexual selection as an adjunct of natural selection: it was “survival of the sexiest”, regardless of whether the sexual attributes had any other survival benefits. In this view, skill at singing and making music functioned like the peacock’s tail: useless, even an impediment, but attention-catching.

But it’s conceivable that such sexual displays do offer honest clues about the bearer’s “good genes”. The male peacock might be saying “I’m so ripped that I can survive even when encumbered with this absurd thing.” Likewise, a musician able to make complex and beautiful music might be displaying his or her (but usually his) superior skills of cognition, dexterity, stamina and all-round fabulousness. Falling for a musician then makes good evolutionary sense.

The link between sex and music might seem indisputable. Rock musicians have gaggles of sexually available fans at the height of their fertility, and no one made the guitar more explicitly phallic than Jimi Hendrix. (This is no modern phenomenon – Franz Liszt’s recitals set women swooning too.) There’s some anecdotal reason to think that music production declines after sex – Miles Davis attested that musicians are often celibate before big concerts, to retain their ‘edge’. And in case you’re thinking that being a musician didn’t do much for the survival prospects of Hendrix, Jim Morrison or Kurt Cobain, bear in mind that – as Darwin himself pointed out – some male birds drop dead from exhaustion when singing in the breeding season. It’s worth the risk for the sake of becoming a sexual beacon (and after all, Hendrix did father three children).



A sexual-selection origin of music might also help to explain the apparent impulse towards diversity, creativity and novelty, for many male songbirds also develop large repertoires and variety in an effort to produce the most alluring mating signal. And doesn’t the excess of the peacock’s tail – the result of a well-attested runaway tendency in selection of sexual characteristics – seem to speak to the towering stacks of amplifiers and speakers, the pyrotechnics, the outrageous costumes? In short, mightn’t it explain the phenomenon that is Kiss?



But this is part of the problem with Darwin’s idea: it is just too alluring, inviting “evidence by anecdote”. These aren’t much more than Just So stories, and culturally specific ones at that. Songs in pre-literate cultures are by no means the tribal equivalents of ‘Let’s Spend the Night Together’: those of the Australian Aborigines, for example, express the singer’s feelings as a member of the community. Most Western music in the Middle Ages was practised by (supposedly) celibate monks. And in some African societies, musicians are regarded as lazy and unreliable, and so poor marriage material. (Hmm… Pete Doherty, anyone?)

Besides, hard scientific evidence for sexual selection in music is been scant and equivocal. For example, one study in 2000 reported that, in classical concerts, there were significantly more women in the seats nearer the (predominantly male) orchestras than in the back rows – a genteel form, it was suggested, of the female hysteria that greeted the Beatles in concert [3].

If women do pick sexual partners on the basis of creative or artistic traits, one would expect changes in their preferences during peak fertility (irrespective of whether baby-making is actually on the agenda). A study in 2006 did find that men apparently showing higher “creative intelligence” were favoured at this time [4]. Charlton reasoned that the complexity of a male composer’s music might be considered an indicator of his creativity and capacity for learning complex behaviour, and so this too might affect female sexual choice. He has previously found that ovulation doesn’t seem to affect women’s preferences for complexity of music per se [5]. But what about the composers themselves?

Charlton recruited a group of 1,465 adult women participants for his web-based survey, and divided them into those at low and high risk of conception at the time of testing, based on what they reported about their reproductive cycle. He played them several short melodies, composed for the experiment, of varying degrees of complexity. First he asked some of the participants to rate the melodic complexity, to ensure that they could do this reliably. Then he asked a different group which of the supposed (male) composers of a pair of melodies of different complexity they would prefer as a short- or long-term sexual partner. A significant number showed a greater preference for the “more complex” composer – but only in the high-conception-risk group, and only as a short-term partner (implying sex right now, when the chance of conception is high).

Now, numbers are numbers: it seems that something connected to the reproductive cycle was indeed changing preferences in that situation. But what? The findings, Charlton says, “support the contention that women use (or ancestrally used) the ability of male composers to create complex music as criteria for male choice.” That would in turn suggest that musical complexity itself arose from an “arms race” in which male musicians increasingly strove to prove their prowess and woo a mate. Charlton suggests that future work might examine whether the sexual preferences also work for a reversal of sexes, with women making the music. It would be interesting to find out, although there is no reason to suppose that sexual selection is gender-symmetrical, and in fact in general it is not. The fact that most music is produced by men [6] is actually what you’d expect for sexually selective trait [7] (although that’s not to say that it’s an explanation).

Yet while Charlton’s findings are intriguing, there are many reasons not to jump to conclusions. For example, the most complex music, according to some measures [8], is Indonesian gamelan, which is among the most social, devotional and non-sexualized of all world music.



There is little reason to think that music has displayed a steady trend towards greater complexity. And it is very hard to untangle a listener’s preferences for a composer from their preferences for the actual music. The latter in general shows a peak of ‘preferred complexity’, beyond which preference declines (as the Beatles’ music got steadily more complex, their sales declined [9]). And this is even before we get into the murky issue of how cultural overlays will colour the assumptions that women might make about fictitious composers, based on a tiny snippet of ‘their’ tunes. More work required, then – or in other words, if music be the food of love, play on!

References
1. B. D. Charlton, Proceedings of the Royal Society B, advance online publication (2014). [Here] [Be patient - this might take a while to become live on the PRSB site...]
2. N. L. Wallin, B. Merker & S. Brown (eds), The Origins of Music. MIT Press, Cambridge, 2000.
3. V. A. Sluming & J. T.Manning, Evolution and Human Behavior 21, 1-9 (2000). [Here]
4. M. Haselton & G. Miller, Human Nature 17, 50-73 (2006). [Here]
5. B. D. Charlton, P. Filippi & W. T. Fitch, PLoS ONE 7, e35626 (2012). [Here]
6. G. F. Miller, in ref. 1, p. 329-360. [preprint available here]
7. D. M. Buss & P. Schmitt, Psychological Review 100, 204-232 (1993). [Here]
8. H. D. Jennings, P. Ch. Ivanov, A. M. Martins, P. C. da Silva & G. M. Viswanathan, http://arxiv.org/abs/cond-mat/0312380 (2003).
9. T. Eerola, T. & A. C. North, in Proceedings of the 6th International Conference of Music Perception and Cognition, eds C. Woods, G. Luck, R. Brochard, F. Seddon & J. Sloboda. Keele University, 2000.

Whatever happened to beautiful instruments?

Have scientific instruments lost their soul? In preparing a schools talk for next week on beautiful experiments, I have been perusing the images online at the very fabulous Museo Galileo in Florence, where I once spent a very happy afternoon. Here are just a few of the very lovely instruments and apparatus that scientists used to use, which are far more beautiful than they really had any call to be. These days scientists have to make do with stuff like this:

which no doubt does the job, but does it inspire you? Below is what I’d like to see return – not the devices themselves, but the spirit in which they were made. Why shouldn’t labs be beautiful?

Hey hey mama

It gladdens my heart to see Jimmy Page with his double-neck guitar on the pages of a science magazine, even in Italian. So it is with the March-April issue of Sapere, where the second of my “music instinct” columns has now appeared. Here it is.

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Attempts to explain how music moves us generally have only one big idea on which to draw. But it’s a good one, and is surely a big part of the answer. When in 1956 the musicologist and composer Leonard Meyer published his book Meaning and Emotion in Music, he was one of the first people to move beyond the cool, formal analysis of musical structure and try to get at why music can make us dance, jump for joy, or break down in tears.

Meyer suggested that it’s all to do with setting up expectations and then violating or postponing their resolution. We think the music is going to do one thing, but it does another – or perhaps it does what we expect, but not quite when we expect it. The unexpected creates a feeling of tension, which might be experienced as excitement. And if that tension is then released, say by the final closing chord of a piece, we feel all the more satisfaction from the delayed gratification. Even the simple rallentando slowing at the end of a Chopin prelude will work that magic.

I’ll give several examples in the forthcoming columns of how this violation of expectation can be played with to raise the emotional temperature, sometimes with exquisite results. Here I want to look at rhythm. This is one of the easiest ways to set up an expectation, because we expect rhythm almost by definition to be repetitive and predictable.

So when it isn’t, we get a thrilling shock. The classic example is Stravinsky’s Rite of Spring, in particular the “Dance of the Adolescents” section. A repeated chord beats away in an insistent pulse – but with an emphasis that shifts with every bar, first on the second beat of the bar, then the first, first again, then second… We never guess when it is coming, so each time it delivers an electrifying jolt.

These unexpected emphases enliven all sorts of music – in jazz, they appear as syncopation, where the beat seems to jump in early and make the rhythm swing. But there are other ways of playing with rhythmic expectation too. Take Led Zeppelin’s song “Black Dog”, where the instrumental riff sounds easy until you try to play it. What’s going on – have they added an extra beat or something? But no, John Bonham’s drums are still ticking away four beats to the bar. The surprising complexity comes from the fact that the guitar riff doesn’t actually fit into this four-beat bar – it has an extra half note. So as it is repeated, it begins and ends in a different place in each bar. The result of these imperfectly overlapping rhythmic structures is disorientating where you think it should be simple. That way, it forces us to pay attention and gives the song a kind of coiled tension and urgency. Stravinsky, I like to think, would have approved.

Particle Fever is aptly named

Here’s the thing. Director and former particle physicist Mark Levinson has made a film, Particle Fever, about the finding of the Higgs particle by the LHC. That’s good news. And it sounds appealing – no omniscient narrator, just the scientists telling the tale. And there are plenty of female physicists in it. But… Here is Levinson on why his background was useful for doing this job: “In some senses, physics hadn’t changed that much since I got out of it in the 80s, because they didn’t have the LHC.” There’s a word missing in that sentence, Mark: “particle”. Particle physics hasn’t changed that much – and to say so is not a great endorsement of your former discipline. But this equating of “physics” with “particle physics” not only plays along with the media myth that the only thing worth noting in physics is what is going on at CERN, but also explains outbursts like this one I received from a (non-particle) physicist recently: “Perhaps the poster child for overselling science should be high-energy physics. They oversold the most expensive toys that physicists have ever produced: high-energy particle accelerators… their arrogance when they talk about ‘the god particle’ and ‘the most important problems’ is disappointing.” I’ve heard similar things from other frustrated physicists. Perhaps Levinson is not now a spokesperson for the particle-physics community, but he does it no favours in this remark.

And it’s evidently not a one-off slip. Later he suggests that there is some fundamental division (in physics) between theorists and experimentalists, along the following lines: “A theorist can wake up in the morning, suddenly erase an equation and rewrite it. An experimentalist, meanwhile, has been working on building a machine for 10 years to prove that theory.” This is not remotely true outside of particle physics – not only could most experimental physicists ill afford to spend 10 years working on building a machine (even if they had to) without having their funding dry up, but most physicists I know work on theory and experiment at the same time.

It is hard not to feel a churl if you express some reservations about the jamboree around the Higgs – but when you see that this circus has apparently convinced some outsiders that the discovery of the Higgs was the most important event in science in the past 100 years, it seems right to feel a twinge of concern. That’s part of the reason I wrote this article. CERN is a blast, the Higgs news was mighty fine, and Peter Higgs deserved the Nobel. But can we please keep a sense of proportion, both about the importance for physics and the whole issue of what physics is?

As for Levinson, he redeems himself by planning – if I read the signs right – to make a film about Denis Noble’s book The Music of Life. I look forward to that.

The physics of marathons

Here, just in time for the London Marathon, is my latest piece for BBC Future. And now I know where the cover of Critical Mass came from.

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Around 40,000 people will run the London Marathon on 13 April this year. But if you’re a serious long-distance runner, don’t come with high expectations. “I have to admit to being completely frustrated by the congestion and for 18-19 miles was just dodging people and being held up”, one participant grumbled after the 2012 event. “I had to overtake a lot of people and ended up with bruised forearms from all the elbows”, said another. “People couldn't let you past for a lot of the way.”

There’s no getting away from it – mass running events like this are likely to be congested. But could the crowding problems be reduced, without restricting the number or calibre of participants? The issue here differs rather little from one that has received far more attention: how to optimize traffic flow on our roads. And while the stakes on the road are much higher – congestion comes at considerable cost in pollution, economic losses and personal inconvenience, while a collision could leave you with far worse than a bruised arm – nonetheless there can also be real dangers from bottlenecks and jams in marathons.

This is why Martin Treiber of the Technical University of Dresden has set out to devise computer models that can predict the flows of participants in marathons and mass cross-country skiing events. Treiber has previously developed models for understanding road traffic flows, and he says that these can be adapted in relatively straightforward ways to capture the essential details of how runners and skiers behave en masse.

One of the first attempts to model traffic flow was made in the 1950s by James Lighthill, an expert on fluid flow, and his collaborator Gerard Whitham of Manchester University. They considered the traffic as a kind of liquid flowing down a pipe, and looked at how the flow changes as the fluid gets denser. At first the flow rate – the amount of stuff you can pump through the pipe in a given time – increases as the density increases, since you simply get more stuff through in the same period of time. But if the density becomes too high, there’s a risk of blockages occurring, and then the flow rate plummets – you have a jam.

Treiber’s model of a marathon, described in a preprint, invokes this same principle that the flow rate first increases and then decreases as the density of runners increases, thanks to an abrupt switch from free to congested flow. He assumes that there is a range of different preferred speeds for different runners, which each sustains throughout the race. With just these ingredients, Treiber can calculate the flow rate of runners, knowing the ‘carrying capacity’ at each point on the route. For example, when the route narrows at bottlenecks, so that the maximum ‘free flow’ rate is lower, the model predicts how congestion might develop and spread elsewhere.

This allows Treiber to figure out how congestion might depend on the race conditions – for example, for different starting procedures. Some marathons start by letting all the runners set off at once (which means those at the back have to wait until those in front have moved forward). Others assign runners to various groups according to ability, and let them start in a series of waves.

Treiber has applied the model to the annual Rennsteig half-marathon along a hiking trail in the Thüringian Forest of central Germany, which attracts around 6,000 participants. In 2013, because the police were no longer willing to close a road to ensure that runners could cross safely, the traditional route had to be altered. It could pass either over a 60m wooden hiking bridge or through a tunnel. Treiber used his model to predict the likely congestion incurred in the various options. If the bridge were to be used, it was important to ensure it did not get too overloaded with runners – a danger if bottlenecks ahead of the bridge spill back onto it. The model predicted that a mass start would certainly risk this, but so, to a lesser degree, would wave starts (which the Rennsteig uses). Only by moving the starting point further back from the bridge could the danger be avoided – and even then, if some of the numbers assumed in the model were only slightly inaccurate, there was still a risk of jams reaching the bridge.

Treiber and his coworkers found that no dangerous congestion seemed likely for the tunnel route. The run organizers consulted with Treiber’s team, and eventually chose this option. They also adopted the team’s recommendation for a wave start with delays of about 150 seconds between waves.

Treiber and his coworkers have adapted his model to describe mass skiing events such as the cross-country Vasaloppet hosted each year in Sweden, a 90-km race that draws around 15,000 participants. This is a more complicated situation to model. Partly that’s because the speed of the skiers can depend quite dramatically on the slope of the course, especially when it is uphill. Treiber built this explicitly into his model, deducing the gradient of the course from Google Maps and applying rules that describe how speed depends on slope. He also included lane-changing rules, since the entire course is divided into well-defined lanes. His computer simulations predicted that massive jams, delaying participants by up to 40 minutes, would form where the route has a steep uphill gradient – just as is seen in the real event. The Vasaloppet has a mass start – but Treiber says that if it could be persuaded to adopt a wave start, with 5-minute delays between waves, all the jams would disappear. Whether the organizers will accept this “wisdom for the crowd” remains to be seen.

Sceptical hauntings

The aforementioned A Natural History of Ghosts by Roger Clarke (which I highly recommend) informs me that Einstein once wrote “Even if I saw a ghost, I wouldn’t believe it.” I know what he means. I once had an experience that can only reasonably be called paranormal, and I don’t believe it. The fact is, though, I don’t disbelieve it either. I don’t see how I can. It remains a mystery, and I can only say that I have almost no idea how to interpret it – which, to be honest, is something I rather like, even if it leaves me feeling a little like the protagonist in Alan Lightman’s novel Ghost.

As a teenager, Clarke went hunting for ghosts around the Isle of Wight, where he lived at what I suspect must have been much the same time as I did. But perhaps the grand manor houses where he seems to have spent his childhood were not the only or even the best places to search. I don’t actually recall the exact, or even the approximate location of the house in which, aged around 15, I had my weird experience, but I think it was in Shanklin, and I do know that it was an unremarkable terraced house probably dating from no further back than the 1950s. It belonged to a relative, maybe an aunt, of one of the friends with whom I had gone to a party, and who had bravely agreed to lend their floor to three teenaged boys after they had undoubtedly consumed more alcohol than was wise or even legal. It was around Christmas time, and I remember there was a decorated tree in the living room (definitely a “living room”, nothing as refined as a “sitting room”) where we laid out our sleeping bags.

So yes, we had been drinking, but not into a stupor, and I remember feeling fairly coherent when we turned out the lights in the early morning. There may well be a perfectly rational and natural explanation for all of this, but I won’t accept that it was simple inebriation.

This “haunting” was entirely within my own mind, which is why I am kind of happy to regard it as a mental phenomenon of some sort. But it was like none I have had before or since. As a child and young person I was plagued by nightmares, but I never knew any other occasion when I awoke from them doubting that this is all they were. What happened as I was sleeping was nothing like a nightmare. For a start, I was fully aware of where I was: lying in a sleeping bag next to my friends on a borrowed floor. But what I felt – and it came upon me quite suddenly – was that I was being taken over and possessed by an incredibly malign force. And it had the character of a personality, one that was raging wildly. I could hear a voice in my head, intoning words that I couldn’t recognize but which sounded to be spoken in something approaching a Scottish accent, and utterly fearsome and demonic. Here’s the worst thing: I could feel my whole body inside my sleeping bag, and it felt as though it was being emptied out, shrivelling up into a dry husk as this “thing” took it over.

Then I woke up, and in an almost parodic manner I sat bolt upright, eyes wide open, and said “Ah!”. I was terrified. But there were by friends, sleeping soundly next to me. I have not the slightest suspicion that this was any kind of prank played by them, and I don’t see how they could have created the mental effect anyway.

Well, I suppose I thought, that was a very scary experience indeed. But here I am, in this mundane little house, and there’s evidently nothing strange going on here. So after a time, I lay down and went back to sleep.

That was a mistake. I’d scarcely nodded off when the whole thing happened again: the same fury and sense of malevolence, the same feeling that I was being possessed and crushed within my own body. That’s the way to put it: as though any shred of my own self was to be pulverized out of existence.

And again I “awoke with a start”, in that phrase that children’s writers seem unable to do without. This time, sitting upright and seeing everything as before, I thought: sod it, I am not going to risk going back to sleep. I’ll sit the night out. But I couldn’t. At some point I drifted back into slumber.

This time it started differently: not with that sense of frantic raving and anger, but insidiously, as though this “thing” had decided this time that I would be more effectively eliminated by stealth. But I knew it was happening, just as I knew I was lying there helpless. Then I “heard” a distinct phrase in my head, and I can only suppose it was the voice of some part of me. It said this: “What do you think it wants?”

I have never forgotten those words, especially because they were evidently regarded as a provocation. The moment they “sounded”, the “thing” returned in full, furious force, and there I was again, becoming this shrivelled husk.

But I woke up again. And this time I’d really had enough. I was beside myself with fear. Why didn’t I wake up one of my friends? What, a teenager, admitting to his mates that he was scared he was being possessed? No, I wasn’t going to risk that. Instead I was determined that this time I’d stay awake until dawn. And I nearly did, because I remember that there was the first dim light starting to appear through the curtains, and the birds were starting to tweet, when I fell asleep again, this time into an untroubled slumber.

So there you have it. I was too confused, too shy and embarrassed, to say anything in the morning or to make any enquiries about the house or the people who lived there. I wish I had, but there you go.

All this ghost business comes from the research I have been doing for my next book, Invisible. And I remember reading somewhere in the course of that research about a well attested brain disturbance that can create the sensation of a weight pressing on the chest – purportedly an explanation for some nocturnal “manifestations” that have been described through the ages, perhaps like the one depicted so provocatively in Fuseli’s famous image. Mine is I suppose a little similar, although it went considerably beyond that. What really perplexes me is the triple repeat, with episodes of clear and even lucid waking in between. I have, once or twice, awoken only to slip back into something like the same dream – one can never be sure how “similar” it really is, given the way dreams leave odd imprints on the memory. But I’ve never known anything even remotely like this.

It’s why I like the fact that Clarke remains open-minded in his book and doesn’t try to explain everything away, even though he reports the known hoaxes, the possible role of ultrasound, and so forth. I think he probably believes in ghosts, in a way that I can’t – for one thing, each manifestation seems too attuned to the preconceptions and ethos of its times. But something very strange happened to me all those years ago, and I simply don’t know what it was.

Bleary-eyed in Madrid: on Catholicism, curiosity, and ghosts

There is probably some unwritten rule somewhere that you should never blog at 5 in the morning, but I see no real prospect that the Atletico Madrid fans celebrating their victory over Barcelona in the square outside are going to stop singing before dawn. Ah well, it is just one of those things you have to love about Spain. Also, I doubtless drunk too much coffee in this interview with El Pais during what is now yesterday. The headline (and ensuing comment) reminds me, as did a nice dinner with the folks at the Fundacion Telefonica discussing Franco and Catholicism, that some things are going to be perceived differently down here in the south.

Needless to say, I’m not sure that I will exactly be retiring from football in order to spend more time with the Internet… And it seems that there is no way now that I’m going to prevent people forever suggesting that I am/was the “editor of Nature”. But Javier was a very nice chap, and I’m not complaining. Anyway, this is all an excuse to mention the lovely quote that I found yesterday in Roger Clarke’s wonderful A Natural History of Ghosts. He says that the shade of the dead brother of Robert Boyle, Lord Orrery, once appeared to Boyle’s sister Lady Ranelagh. Boyle, one of the key figures in my book Curiosity, responded to this news in typical fashion by asking his sister to pose a series of metaphysical questions to the ghost when it next appeared. She duly did so, whereupon the ghost replied “I know these questions come from my brother. He is too curious.”

I was delighted to find that Roger Clarke, like me, grew up on the Isle of Wight, and so knows all about the local ghosts there. I have another one for him, of which more later.

Ballard - always head of his time

My enjoyment of eulogies for J. G. Ballard, like this one in the Guardian on the 5th anniversary of his death, is always tempered by a sense of bitterness. For I can’t help feeling some resentment at the way the literary world now embraces this writer who was considered infra dig when I devoured everything he wrote 40 years ago. Even as a callow and barely literate teenager, I had a sense – which I could never then have articulated – that his works were far more relevant a window on the modern (by then almost postmodern, I suppose) age than the majority of works celebrated by what I now imagine was a literary community of a largely Leavisite mindset. Deborah Levy has it quite right in this article that the classification of Ballard as “science fiction” was really an attempt to tame and marginalize a writer who was too edgy, strange and visionary for that kind of sensibility. I think young Ballardians like me could intuit that writers like Michael Moorcock, Philip K. Dick, Kurt Vonnegut and most of all Ballard were working in a different kind of genre from Asimov and Clarke, and that the superficial sci-fi traits that some of them used from time to time were merely tools that suited their ulterior purpose. I surely read books like The Atrocity Exhibition with as threadbare a set of cultural references as I brought to my uncomprehending forays on Dostoevsky, having no real notion of who this Ralph Nader and Ronald Reagan were (that was the 1970s) and little idea of why Jackie Kennedy represented much more than a dead president’s wife (specifically, the harbinger of the modern age of celebrity). In short, a lot of it went right over my head. But I read on, feeling I suppose that this stuff was going to matter, that it was worth more than the values of the day seemed to allow.

What has changed, I suppose, is that the literary community is now populated by folks from a similar time and attitude as mine – Self, Kunzru, Mieville – for whom that kind of “speculative fiction” was as valid as the old, approved canon. I think this is progress. But it would be foolish to imagine that they too, we too, are not now overlooking and snobbishly dismissing writers who will turn out, in retrospect, to be the true prophets of our times.