Wednesday, July 01, 2015

Perkin's purple: a journey around London

I have just presented one of BBC Radio 4’s Science Stories, a new series looking at episodes in the history of science. This one tells the tale of William Perkin’s purple coal-tar dye and how it changed the course of chemistry. That, of course, is the kind of grand and often contentious claim these programmes inevitably end up making, but I do feel that there is a case to be made for it here.

The initial plan was for me to take a journey across London, visiting the key locations en route: from Shadwell in the East End to the Royal College of Chemistry in the West End and then the site of the Perkins’ factory in Greenford Green on the outskirts of west London. In the end it didn’t quite happen that way, but I got a few pictures of some of the relevant locations as we recorded, and so wanted to include these here with the original draft of the script – it changed considerably, and I’m sure very much for the better, but this at least tells and illustrates the story. For more details, see Simon Garfield's excellent book Mauve, Tony Travis's authoritative The Rainbow Makers, and my own Bright Earth.


“A reservoir of dirt, drunkenness and drabs” – that’s what Dickens called Shadwell, and I’m not sure that he wasn’t being affectionate. There’s not a lot of Dickens’ Shadwell left: whatever the bombs didn’t destroy during the war disappeared soon after in the slum clearances. But I can’t say that what took its place has added much to its appeal: all these ugly flats and traffic bollards.

But here’s the place I want. King David Lane. Just down here in the mid-nineteenth century there was a big old house at 1 King David Fort, but now it’s just a council block.

Visiting the site of William Perkin’s family home in Shadwell – on a very blustery spring day!

This was the home of the Perkin family, who were wealthy by the standards of Shadwell. George Perkin was a successful carpenter who could afford to indulge his son William’s passion for chemistry. William had a little home laboratory on the top floor of the house – just a simple place, with a table and bottles of chemicals, no running water, no gas. But when he was 18 years old and still a student, he discovered something here that for once justifies that awful cliché: it changed the world.

There’s a blue plaque here to back me up. “Sir William Henry Perkin, FRS, discovered the first aniline dyestuff, March 1856, while working in his home laboratory on this site, and went on to found science-based industry.”

The blue plaque marking the spot where Perkin discovered mauveine.

Listen to that again: “went on to found science-based industry”. In other words, what Perkin discovered led to the whole idea that industry might be based on science.

That’s an astonishing claim. What could this young lad have found that was so important?

Let’s start with a gin and tonic.

For the British army in India in the nineteenth century, this drink really was medicinal. The troops were issued with their bitter tonic water at daybreak, but the officers started taking this medicine on the verandah as the sun set, not just with a spoonful of sugar but with a splash of lime and a generous shot of gin.

You see, the bitter taste was due to quinine, the only effective anti-malarial drug then known. This stuff was extracted at great labour and expense from the bark of a Peruvian tree called the cinchona. The bark had been known since the seventeenth century to help treat and prevent malaria. No one really knew what was in it until two French chemists separated and purified quinine in 1820. With quinine to protect them, the Europeans were able to begin the colonization of Africa, the consequences of which are still reverberating today.

You really didn’t want to get malaria. Chills, convulsions, fever, vomiting, delirium, and quite possibly at the end of it all – death. But quinine cost a fortune. Peru was then just about the only place where the tree was found and the bark contained only tiny amounts of it. And the Peruvians kept a monopoly by outlawing the export of cinchona seeds or saplings. In the nineteenth century, the East India Company was spending about £100,000 every year to keep the officers and officials in the colonies healthy.

But what if, instead of extracting this stuff drip by drip from tree bark, you could make it from scratch?

What does that mean? Well, over the previous centuries, chemists had found how to take simple chemical ingredients and get them to combine to make entirely different chemicals: useful substances like soap, soda, bleach. Might they be able to make a complicated natural drug like quinine?

One man in particular had this dream of using chemistry to reproduce and even rival nature. He was a German chemist called August Wilhelm Hofmann, and many people, including Prince Albert, hoped that he’d be the savior of British chemistry. In 1845 Hofmann was appointed director of the Royal College of Chemistry in London, which had been set up at Albert’s request.

August Wilhelm Hofmann

So what do we know about Hofmann? Well, according to the sign that now marks the spot in Oxford Street where the Royal College of Chemistry used to stand [it’s next to Moss Bros, opposite John Lewis’s], he “inspired the young to do great things in chemistry, and relate them to both academic and everyday life.”

The plaque erected by the Royal Society of Chemistry to mark the former site of the Royal College of Chemistry in Oxford Street, London.

There were two aspects of everyday life that Perkin, walking down these streets in the mid-nineteenth century, couldn’t fail to have noticed. In the lanes and docks of Shadwell, Dickens said, everyone seemed to be wearing rough blue sailors’ jackets, oilskin hats and big canvas trousers. But up here in the fashionable West End, it wasn’t so different to the style emporiums of today: ladies wore the latest colours: yellow silks from France and fabrics printed in patterns of rich madder red and indigo. Those last two colours were plant extracts, and they faded after lots of washing and being out in the sun. But the yellow silk, which had graced the Great Exhibition in 1851, was coloured with a new dye that was made artificially – by chemistry.

And the stuff it was made of was a by-product of the other thing that distinguished the splendor of Oxford Street from the gloomy alleys of Shadwell: the street lights. They had brightened up the evenings since the start of the century, burning gas that was extracted from coal.

Left over from that process was a thick, smelly tar called, naturally enough, coal tar. At first it seemed to be just noxious waste, and was often just dumped into streams. But then folks figured out that coal tar might be useful. Charles Macintosh used it to make waterproof raincoats. And if you distilled it, then you could extract a whole range of chemicals, like coal itself primarily composed of carbon. They often had an acrid smell – aromatics, the chemists called them. One was carbolic acid, also known as phenol. You remember that stinky old coal-tar soap? That’s phenol you were smelling, and it was in there to act as a disinfectant, one of its main uses since the 1850s.

But phenol was also the starting ingredient for the yellow silk dye that rich ladies bought from Lyon. Yes, this coal tar had some valuable stuff within it.

No one knew that better than August Hofmann, who had become pretty much the world expert on coal-tar compounds. So when William Perkin enrolled at the Royal College of Chemistry in 1853, pretty soon he found himself working on coal tar.

And when Hofmann set Perkin the challenging task of trying to make synthetic quinine in 1856, the coal-tar compounds seemed like good materials to start from.

We need to do some chemistry now. But don’t worry. I’ve got a Scrabble set to help me. You see, molecules are like poems: you have to get the words in the right order. Each word is a cluster of letters, and we can think of each letter as an atom. Making molecules is like stringing together these letters in an order that has some meaning. Now, some molecules, like polythene or DNA, really are a lot like strings of atoms. But others have other shapes. Benzene, for example, which is at the heart of all the coal-tar aromatic compounds, is a ring of six carbon atoms, each with a hydrogen atom attached. I take all six C’s for carbon – and yes, this isn’t exactly a regular Scrabble set – and put them in a ring.

But the problem was that in Perkin’s day no one knew that molecules have shapes like this, with atoms in particular arrangements. All they knew was the relative amounts of each kind of element, like carbon and hydrogen, a substance contained. Benzene was equal parts of carbon and hydrogen, rather like a G&T is one part gin to three parts tonic water.

So then, what Hofmann and Perkin knew about the element cocktail that is quinine was that it is twenty parts carbon, to twenty four of hydrogen, two of nitrogen and two of oxygen.

What gives quinine its meaning – what lets it cure malaria – is its particular arrangement of these atoms. But Perkin knew nothing about that. His strategy – so crude that in retrospect it was obviously hopeless – was, roughly speaking, to take a compound that had half of these amounts – ten parts carbon and so on – and try and stick them together, as if mixing up these two piles of letters is going to miraculously give them the same meaning as quinine.

It’s not surprising he didn’t succeed. When he did the experiment at home one night, instead of colourless quinine he got a red sludge.

He could have been forgiven for just flushing it down the drain. But he was too good a student for that, which is why Hofmann had made Perkin his personal assistant.

Instead, he thinks, well, what seems to be going on here? Let’s try the same reaction with another two identical piles of letters, rather like the ones before but a bit simpler. And so he goes through the same procedure with a different coal-tar extract, one of Hofmann’s own favourites: a compound called aniline.

Well, this time the result is even worse. Now the gunk is black. Even so, Perkin keeps going. He dries the stuff and swills it around in methylated spirits.

And now at last, something nice. It dissolves to turn the liquid a beautiful purple.

Here Perkin thinks of those fine ladies of Oxford Street in their bright silks. He knows that the textile industry is hungry for new dyes. And so takes a piece of white silk and dips it into the liquid, and when he pulls it out the colour has stuck fast to the fabric.

So what now? Perkin manages to get hold of the name of a dye works in Scotland and he sends them a piece of his purple-dyed silk. When the reply comes a few months later, it must make his heart beat faster:
“If your discovery does not make the goods too expensive it is decidedly one of the most valuable that has come out for a very long time. This colour is one which has been very much wanted in all classes of goods and could not be had fast on silk and only at great expense on cotton yarns… the best lilac we have… is done by only one house in the United Kingdom… and they get any price they wish for it, but… it does not stand the tests that yours does and fades by exposure to air.”

So there it was: Perkin had a potential new dye on his hands.

But remember what the man had said: “If your discovery does not make the goods too expensive”. Well, aniline was expensive. If this dye was going to succeed, Perkin had to find a way of making it cheaply – which meant, on an industrial scale.

He realized that he wasn’t going to be able to do that while he was still a chemistry student. So he told Hofmann that he was quitting. But Hofmann had made the young man his protégé, and as Perkin recalled many years later, “he appeared much annoyed”. What was his best student thinking of, abandoning a promising career in pure research to go into industry? As Perkin recalled,
“Hofmann perhaps anticipated that the undertaking would be a failure, and was very sorry to think that I should be so foolish as to leave my scientific work for such an object, especially as I was then but a lad of eighteen years of age.”

The funny thing is that purple was already fashionable even before Perkin discovered his aniline dye. From the 1830s a purple dye called murexide became popular, though probably its fans had little idea that it was made from Peruvian bird droppings. Another purple dye was made from an extract of lichen. In the year that Perkin made his discovery, the Pre-Raphaelite Arthur Hughes painted his picture April Love, showing a young woman in the kind of long flowing purple dress then in style. The French, who even at that time called the shots in fashion, had a word for these rather pale purples. It was what they called the purple-flowered mallow: mauve.

April Love (1856), by Arthur Hughes.

But he did leave, and when he couldn’t find a backer for the factory he proposed to build, his father George put up his life savings, even though he’d never wanted William to become a chemist in the first place. William’s older brother Thomas chipped in to help too.

Now they had to give aniline purple a catchy trade name. Perkin thought of the famous royal purple of Rome, originally made in the Phoenician city of Tyre from a substance extracted a drop at a time from shellfish. Why not call it Tyrian purple?

But it didn’t catch on. Soon enough the aniline dye he’d intended to call Tyrian purple had become synonymous instead with the colour mauve.

There was nowhere suitable in the East End for the coal-tar dyeworks of Perkin & Sons, and in the end they found a meadow right over in Greenford Green, near Harrow, northwest of London, conveniently close to the Grand Junction Canal. In less than six months, a factory was turning it into purple for the dyers of Great Britain.

Well, I can’t say that the industrial estate in Greenford Green is much of an improvement on the faceless modern development in Shadwell. But I guess it wasn’t any better in Perkin’s day. His dyeworks grew quickly, and it looks pretty grim in old engravings and photos, with its tall chimneys belching smoke and toxic nitrous fumes. He found a way to make aniline cheaply on the site from benzene, sulphuric and nitric acid, so goodness knows what the factory’s chemical vats spewed into the canal. The chemical process was dangerously explosive, and none of the Perkins had any experience with industrial-scale chemistry. It’s a wonder the whole place didn’t go up in smoke.

A photograph of the Perkins’ dyeworks in Greenford Green.

The last traces of the old factory were destroyed in 1976, but there’s a blue plaque here to mark its place… and here it is. “William Henry Perkin established on this site in 1857 the first synthetic dye factory in the world.”

The blue plaque at Greenford Green where the original coal-tar dye factory of Perkin and Sons once stood.

It became so much the rage in London that it even drew comment from Dickens in 1859:
“As I look out of my window, the apotheosis of Perkin’s purple seems at hand – purple hands wave from open carriages – purple hands shake each other at street doors – purple hands threaten each other from opposite sides of the street; purple-striped gowns cram barouches, jam up cabs, throng steamers, fill railway stations; all flying countryward, like so many migrating birds of purple Paradise.”

Perkin’s Greenford Green factory marks the end of the beginning – for aniline dyes and for the entire synthetic chemicals industry.

Perkin & Sons couldn’t get the French patent rights for their mauve, and within a year French and German companies started to make it too. Soon the coal-tar dyes were everywhere – not just purple but green, red, blue, black. The liberation of colour had arrived, and fashion became positively gaudy.

Bright colour – once the preserve of the rich – could be worn in all walks of life. Gone was the colour-coding of social hierarchies that had existed since the Middle Ages. Colour became a matter of individual expression.

What began as a stroke of serendipity in Shadwell was now becoming an exact science. Chemists came to understand that the particular arrangement of atoms in a molecule determines what it does – what, as I said earlier, the molecule means. And what it does might include which colours it absorbs and which it reflects, when light shines onto it.

So on the one hand, it became possible to make new colours to order. By carefully studying aniline dyes, chemists in the late nineteenth century could predict from the architecture of these compounds what colour they were likely to have. This is now the entire business of synthetic chemistry: constructing molecules with particular atomic arrangements and therefore particular properties.

On the other hand, if there was a substance found in nature that had useful properties – like quinine, say – then if you could figure out the shape of its atomic framework you had a chance of working out how to make it synthetically, perhaps more cheaply than harvesting it from plants.

But what became of the natural dyes, such as indigo and madder? They didn’t go out of fashion; instead, synthetic chemistry re-invented them. Getting these substances pure and in large amounts was costly and labour-intensive, and indigo plantations in India were the British Empire’s most lucrative business in all of Asia.

But as chemists came to understand that molecules were made of atoms linked together into particular architectures, they turned themselves into molecular architects who could even aspire to construct the molecules of nature. They figured out how, from simple ingredients like coal-tar substances, they could string together atoms to make the very molecules that gave indigo and madder their colours.

The molecular structures of indigo (top) and alizarin (bottom), which gives madder red its colour.

When two German chemists figured out how to make synthetic madder red in 1868 from the coal-tar compound anthracene, William Perkin quickly figured out how to do it more cheaply and on an industrial scale. By 1873 he’d got rich enough from this and other dyes to sell his company and return to pure research.

The blue plaque in Victory Place, near Elephant and Castle in southeast London, showing where the dyeworks of Simpson, Maule and Nicholson was situated. The company was established here in 1853, and in 1860 it began to manufacture aniline red dye, known also as magenta. Three years later they marketed an aniline violet, discovered by August Hofmann, that offered Perkin’s mauve some stiff competition. In 1873 William Perkin sold his dye company to the firm that Simpson, Maule and Nicholson had become, called Brooke, Simpson and Spiller. I was terribly excited when I discovered this plaque on my usual cycling route into London; I suspect I was the only person who could say that for a good many years.

Portrait of William Henry Perkin, painted in 1906 by Arthur S. Cope.

Perkin’s main competitor for synthetic madder was the German chemicals company BASF. If you’re like me, the name BASF will put you in mind of cassette tapes. But that’s just an example of how the dye companies diversified into other areas, because BASF stands for Badische Anilin und Soda Fabrik: the aniline and soda makers of Baden.

In 1877 one of their academic consultants, the German chemist Adolf Baeyer, worked out how to make indigo from the coal-tar extract toluene. BASF was soon producing it by the hundreds of tons. Within just a few years the price of indigo plummeted and the colonial plantations were put out of business, which the British government declared a national calamity.

Doesn’t this then make the chemist a kind of modern Prometheus? If you can control the shapes of molecules, what can you not create?

These colour manufacturers now pervade our language, our material world, our history. ICI, Hoescht, Agfa, Novartis – all began with dyes. In 1925 some of the major German dye companies merged to form the notorious cartel IG Farben, a force powerful enough to dictate its terms to Hitler. The diversification into pesticides left IG Farben with the patent for the poison gas Zyklon B, which it licensed for use in the concentration camps.

The diversification of the great dye companies into areas like pharmaceuticals had begun by the late nineteenth century. The coal-tar dyes themselves showed the way. In the 1870s the German physician Paul Ehrlich began to use the dyes for staining cells, which made them easier to see and distinguish under the microscope. He found that some dyes actually killed the microorganisms they stuck too.

That sounded useful. In 1909 Ehrlich discovered an arsenic-containing dye that would destroy the microorganism responsible for one of the most feared and deadly afflictions of the day: the disease that dare not speak its name, syphilis. Other coal-tar dyes worked as antibiotics.

Before this time, most drugs were, like quinine, extracts from natural sources, mostly from plants – like the extract of willow bark called salicylic acid that had long used as a painkiller. In 1897 a chemist at the German dye company Bayer turned phenol into a compound related to salicylic acid but which worked even better. The company started selling it under a trade name: aspirin.

To make sense of the science behind all this, chemicals companies couldn’t just any longer rely on hiring the services of academics. They started to employ their own chemists, who could design products like drugs based on a rational understanding of how the molecules needed to be shaped, and what they would do.

This, then, is what science-based industry is all about. It’s what the pharmaceuticals industry looks like today.

All the same, the revolution that Perkin began is in some ways still just getting started. We now know that there’s more to the way a drug works than just a good fit with the biological molecule that it aims to latch onto, like a lock and key. But we still can’t always fully understand or predict how a given drug will behave: you can’t be sure of designing it at the drawing board. Instead, most drug discovery still relies on trial and error, on shuffling molecular fragments into many different shapes and then seeing which ones work best.

What’s more, synthetic chemistry still has plenty of problems to solve: scientists struggle to put together some of the complicated molecules that nature produces. And even if they succeed, the route is often too long and too expensive to be useful in industry. This is why chemical synthesis is still as much an art as a science.

But Perkin is now regarded as one of its finest early stylists: a man who first gave us a glimpse of what might be possible if we can get clever enough at molecular architecture. And for that we have to thank the colour purple.

Saturday, June 27, 2015

Against big ideas

Sam Leith’s comment on the trend in non-fiction publishing is spot-on, and Toby Mundy’s analysis of it typically insightful. (And I’m not saying that just because you’re the new director of the Samuel Johnson prize, Toby – though, you know, congratulations and all.) Sam echoes my impression, though I suppose as someone published in the UK by Bodley Head (rightly exonerated here as a noble exception) and in the US by the University of Chicago Press, I would say this. It is good to have critical reviewers around, like Steven Poole and Bryan Appleyard, who will challenge this Gladwellization of non-fiction, but I fear they’re fighting against the tide. Sam’s complaint about the way the mainstream trade publishers seem mostly interested in books that offer a single “big idea” that explains everything about being human/history/the brain/the economy/the internet/the universe (until the next one comes along) is very well founded. Life is not just complex (in which case “complexity theory” would explain it all right?) but complicated. So are most areas of science. So are people. We need ideas and narratives that help us unravel the threads, not ones that pretend it is all just one big rope. This seems especially problematic in the US, where it feels ever harder – outside of the university presses – to publish a serious discussion of any topic rather than an airport book in which the subtitle tells you all you need to know. It’s very reassuring to hear that being published there by a university press there is increasingly a guarantor of substance.

Tuesday, June 16, 2015

The many truths of Tim Hunt

Blimey. That Tim Hunt then. It feels like any single point of view is not enough; I need a superposition of states here. I read Athene Donald explaining that, however much we can and should deplore his comments, he’s not a bad chap, and I think yes, that was very much my experience of Tim when I was on a judging panel with him: I liked him, found him not at all bigoted or oppressive or objectionable. Comparisons with Jim Watson are unfair – I think it is clear he is not that kind of person. Athene seems right to be saying, let’s not make it all about Tim, we need to focus on measures that will rid science of the blight of sexism that still evidently afflicts it.

Then I read responses and comments by Jenny Rohn, Margaret Harris and Deborah Blum, and I think yes, we mustn’t offer up feeble “he’s just a different generation” excuses and give a basically decent chap a break for making a stupid blunder. There is too much of this sort of low-level crap going on in science all the time, and when it comes from someone in a position of such authority and influence then we need to come down hard on it.

I can’t help feeling a bit sorry for Tim, seeing how genuinely distraught and despairing he seems. Christ, the man is human, and not a monster. And yet I can’t help feeling, you bloody fool, what really did you expect? And I don’t know quite what to believe anyway. Do we accept this as a bone-headed attempt at a joke, or do we believe that Tim passed up the chance to say later that of course he didn’t truly think these things? Do we believe rumours that Tim had form for this kind of thing, or accept the testimony of friends and colleagues that they’ve never seen him previously behave in a sexist manner?

The world can’t possibly need someone else saying “Here’s what we should do about Huntgate.” (I’m glad that’s not a word. Forget I wrote it.) But. Well, I’d simply like to offer a fee suggestions:
1. We stop name-calling and belitting of anyone who, while condemning the remarks, differs slightly from our own view of what is the appropriate way to deal with them. There’s no obvious right answer to that. What’s needed is discussion. (Obviously, this excludes London mayors who think Tim was merely pointing out some well known gender differences, and who in any event reckon it is OK to make off-the-cuff jokes about “piccaninnies”.)

2. We agree that denouncements of “politically correct witch hunts” are beside the point. People on Twitter will say horrid and unfair things about Tim Hunt because people on Twitter do that. Why cares (aside from the fact that it’s intrinsically nasty)? I see no reason to call the responses of, say, UCL, a witch hunt, let alone a “politically correct” one (unless your view is that it is trendy political correctness to show disapproval of sexism and want to distance yourself from it).

3. Tim’s situation has been worsened by the timing. People are frankly and rightly sick of the sexism that exists in science. When I think that my girls, were they to choose careers in science, might have their prospects damaged by bias, harassment, and exclusion, I want to take a hammer and smash up a lot of Pyrex. Actually I think I will encourage them to do it themselves (I suspect they’ll be quite good at it). I’m not saying that Tim got worse than he deserved for this reason, but just that it’s a part of the explanation for what happened.

4. We follow Athene’s action points, and use this sad affair positively to make change happen.

5. We stop making excuses. We can all make mistakes and say thoughtless things, for sure, but having an attitude that fundamentally opposes discrimination of all sorts and recognizes it when we see it in so obvious a manner as this is not bloody hard, whether you are 17 or 70. Science is, frankly, a bit crap at this. It tolerates obnoxious fools for too long, on the grounds that they once did some good science. (I’m not talking about Tim here.) It doesn’t just tolerate them, it excuses them. I don’t give a toss how good your science is, if you don’t behave decently and respectfully then you should expect to get no respect in return.

But here’s what gives me great hope and comfort: I’m not sure science is going to be this way much longer. It’s going to take time and effort, but it will change. I am buoyed by the fact that the ambassadors for science these days (and here I’m qualified only to talk about the UK) are people for who “jokes” about women scientists (no, “girls”) falling in love and crying and working in segregated labs aren’t just objectionable but utterly bloody weird. People to whom it would never occur to say or think such an outlandish thing no matter how “confused” or “nervous” or jet-lagged or drunk they were. People like Athene Donald, like Monica Grady, Alice Roberts, Maggie Aderin-Pocock, Brian Cox, Jim Al-Khalili, Mark Miodownik, Ed Yong, Andrea Sella. Certain older members of the science-communication fraternity (I use the word advisedly, and mention no names) might just purse their lips and mutter about witch hunts and the waste of scientific eminence. But their time is over.

Christiaan Huygens - the first astrobiologist?

Necessarily cut from my piece in Nautilus on water and astrobiology was a paragraph of very early history, in which Christiaan Huygens anticipates this whole debate with eerie prescience. I hope it’s worth filling in that bit of the story here.

Galileo had looked at the moon and saw not the smooth, featureless sphere that Aristotelians believed in but mountains and valleys, their rugged topography picked out by the raking light of the Sun at the boundary where light meets darkness. Within just a couple of decades, writers and philosophers were starting to imagine journeying to this new world, much as Columbus had travelled to the Americas. The natural philosopher John Wilkins gave a factual account in his Discovery of a World in the Moone (1638), while the French soldier and writer Cyrano de Bergerac penned a satirical account of spaceflight in The States and Empires of the Moon, published posthumously in 1657. By the end of the century, scientists were starting to speculate about what the environments of these other worlds might be like.

In his posthumously published 1698 book Cosmotheoros, Huygens asserted that plants and animals on other planets must derive their “growth and nourishment” from “some liquid principle”. But he realized that water would freeze on Jupiter or Saturn, and so “Every planet therefore must have its waters of such a temper, as to be proportion’d to its heat”: Jupiter’s and Saturn’s “waters” must have a lower freezing point, and those of Venus and Mercury a higher boiling point. In other words, it isn’t too fanciful to say that Huygens was speculating that life on other planets might use non-aqueous solvents.

In my Nautilus article I veer towards the notion that there might be non-aqueous solvents for life. In my more technical article for the book Astrochemistry and Astrobiology (eds I. W. M. Smith, C. S. Cockell & S. Leach; Springer, Heidelberg, 2013), I equivocate rather more. It seems to me that this kind of Socratic dialogue (to be absurdly grandiose about it) is the best way of approaching the problem: one can make both cases, and it is hard to adduce any clear evidence at this point for which of them we should prefer. This is what I say in that latter piece:

“Attempts to enunciate the irreducible molecular-scale requirements for (as opposed to the emergent characteristics of) something we might recognize as life have been rather sporadic, and are often hampered by the difficulty of looking at the question through anything other than aqua-tinted spectacles. From the point of view of thinking about non-aqueous astrobiological solvents, a review of water’s roles in terrestrial biochemistry surely raises one key consideration straight away: it is not sufficient, in this context, to imagine a clear separation between the ‘molecular machinery’ and the solvent. There is a two-way exchange of behaviours between them, and this literally erases any dividing line between the biological components and their environment.

The key questions here are, then, necessarily vague. But the more we understand about the biochemical aspects of water, the less likely it seems that another solvent could mimic its versatility, sensitivity and responsiveness, for example to distinguish any old collapsed polypeptide chain from a fully functioning protein. It is perhaps this notion of responsiveness that emerges as the chief characteristic from a survey of water’s biological roles. It can be manipulated in three dimensions to augment the influence of biomolecules. It can receive and transmit their dynamical behaviours, and at the same time it can impose its own influence on solute dynamics so that some biomolecular behaviours become a kind of intimate conspiracy between solute and solvent. This adaptive sensitivity seems to facilitate the kind of compromise between structural integrity and reconfigurability that lies at the heart of many biomolecular processes, including molecular recognition, catalytic activity, conformational flexibility, long-range informational transfer and the ability to adapt to new environments. It is easy to imagine – but very hard to prove! – that such properties are likely to be needed in any molecular system with sufficient complexity to grow, replicate, metabolize and evolve – in other words, to qualify as living.

In these respects it does seem challenging to postulate any solvent that can hold a candle to water – not so much in terms of what it does, but in terms of the opportunities it offers for molecular evolution. This is by no means to endorse the dictum of NASA that astrobiologists need to ‘follow the water’. But hopefully it might sharpen the question of where else we might look.”

Friday, June 12, 2015

Set for chemistry: a longer view

It seems quite a lot of folk liked to hear about the old chemistry sets that I discussed in my article in Chemistry World. It was certainly a blast writing it. I didn’t mention, because she asked me not to quote yet, that Rebecca Onion has also been looking into this topic – I hope it’s OK to say now that she'll shortly be publishing something rather wonderful on it. In any event, I thought it would be worth putting up the full original article here. The images are, except where indicated, all courtesy of the Chemical Heritage Foundation, and I reckon that their exhibition in the autumn is going to be fabulous.


As you’re reading Chemistry World, I bet you had a chemistry set. Maybe you tinkered with a substantial rack of test-tubes containing compounds that would now be considered daring: potassium permanganate, sodium thiocyanate, perhaps supplemented with stronger stuff bought at the chemical supplier’s or “borrowed” from school: nitric acid, lumps of sodium under oil. Younger readers might have been denied such pleasures, having to be content with litmus paper for measuring soil pH. Today’s sets are likely to be more about “kitchen chemistry” or “colour chemistry”, using nothing more hazardous than bicarb and food dyes.

The content, appearance and aspirations of your chemistry set age you as much as your choice in music. When I recently got to look at the marvelous collection in the vaults of the Chemical Heritage Foundation in Philadelphia, I was struck by how these alluring boxes encode social narratives. They reflect changing perceptions of chemistry and science as a whole, shifts in the social strata of the target consumers, in attitudes to gender and in the objectives of science education. “Chemistry sets and science kits contained much more than vials of chemicals, test tubes, and microscopes”, says art historian and independent curator Jane E. Boyd, who is curating an exhibition of the CHF’s sets that opens in October. “Their colourful boxes and cases also held manufacturers’ ambitions for success and prestige, parents’ hopes and anxieties for the future lives of their sons and daughters, and children’s own desires for fun and excitement.”

What were these sets for? Are they toys? Were the meant to educate or to amuse? Why were they produced, and for who? And why do they seem – I’m sure it isn’t just me – to pack such a nostalgic punch?

The magic of chemistry

Chemical sets aimed at children started to appear from around the 1830s. One of the earliest was the “No. 1. Youth’s Laboratory, or Chemical Amusement Box”, produced in 1836-7 by the chemist Robert Best Ede. It contained “more than 40 Chemical preparations and appropriate apparatus, for enabling the enquiring youth… to perform above 100 Amusing and Interesting Experiments with perfect ease and free from danger.” These cabinets were luxury items: Ede’s was mahogany-cased and sold for the tidy sum of 16 shillings. Historian Melanie Keene of Cambridge University has shown, while the contents of the nineteenth-century cabinets were quite ambitious in their chemical scope, containing such compounds as potassium “superoxalate”, “prussiate” and “bi-chromate”, the emphasis of the booklets was on making chemistry “familiar”, with reference to household items such as soap or candles [1].

Robert Best Ede’s “Portable Laboratory”, c.1836. Wellcome Library, London.

It wasn’t until the second half of the nineteenth century that toy manufacturers began to make commercial sets as educational tools tailored for the affluent middle classes. The intended audience is clear from one of the CHF’s earliest items, a Chemcraft set sold around 1917 by the Porter Chemical Company in Hagerstown, Maryland, one of the major manufacturers of chemistry sets in the USA throughout most of the twentieth century. Like Ede’s set almost a century earlier, it is housed in a handsome wooden box with the ingredients kept in elegant little wooden bottles. The lid shows a well-bred young lad in suit and tie, hair neatly gelled, bending over his little burner under the watchful eye of his father.

Alongside but independent of the chemical cabinets, science popularizers of the nineteenth century produced how-to manuals describing experiments for children using household ingredients. Ede’s earliest cabinets were intended to accompany the popular 1823 book on chemical experimentation, Chemical Recreations by John Joseph Griffin – but Ede’s company later sold them independently with its own bespoke pamphlet. These two traditions of the cabinet and the booklet merged, so that when the cabinets became available to a wider “toy” market at a slightly cheaper price from the 1900s, the accompanying instruction manual became indispensible.

Both the early chemistry sets and the experimental booklets had a strong link to the tradition of “performative chemistry” that developed during the nineteenth century. Dramatic chemical demonstrations were a hallmark of the public talks at the Royal Institution given by Humphry Davy and Michael Faraday in the early part of the century. “These performances were intended to make chemistry ‘familiar’, as enticements to active practical investigations that could be carried out in the home”, says historian of science Salim Al-Gailani of the University of Cambridge, who has made one of the few detailed studies of chemistry sets [2]. He says there is a clear link between publications such as Faraday's book of his RI lectures, Chemical History of a Candle (1861), the penny-pamphlet handbooks, and later chemistry-set manuals.

Chemistry displays, lodged somewhere between music-hall spectacle and public education, were refined at institutions such as the Royal Polytechnic Institute in London, where lecturers like John Henry Pepper wowed audiences with chemical magic. Pepper, best known for devising the illusion of “Pepper’s ghost” used in performances of Hamlet and A Christmas Carol, went on to set up his own Theatre of Popular Science and Entertainment at the Egyptian Hall in London, the home of Victorian stage magic, and took his show on tour in the USA and Australia. Some stage magicians were even contracted to write popular treatises on chemistry.

A chemical manual from c.1894, in which the link to stage magic is clear. (Harry Price Library, UCL)

This link between stage magic and the early chemistry sets is personified in Albert Gilbert, the founder of the A. C. Gilbert Company of New Haven, Connecticut, which was the main US rival to Porter’s Chemcraft and became one of the biggest toy firms in the world. Gilbert was a stage magician, and he founded his company in 1909 to supply materials for magic shows, marketed under the brand Mysto Magic.

The early Chemcraft sets reflect this association too, promising “Mysterious experiments in chemical magic.” There were hints of a connection with alchemy, for example in the suggestion that the deposition of copper onto iron was a kind of transmutation. The manuals offered tips on how to stage a magical demonstration, combining practical instruction with the misdirection and sleight-of-hand methods of the magician. This dabbling with the old imagery of alchemy was sometimes filtered through racial stereotyping that seems shocking now. One Chemcraft manual suggested that the performer dress as some sort of Oriental fellow, like a “Hindu prince or Rajah.” And he would need an assistant “made up as an Ethiopian slave”, with “his face and arms blackened with burned cork”. He should be given “a fantastic name such as Allah, Kola, Rota or any foreign-sounding word.”

“The influence of ‘natural magic’ continued to shape the iconography and pedagogical function of chemistry sets well into the twentieth century”, says Al-Gailani. Even one of the CHF’s most recent sets, from around 1994, was marketed under the “Mr Wizard” brand, harking back to the American television show Watch Mr Wizard produced and presented by Don Herbert from 1951 to 1965. Herbert aimed to demonstrate the science behind the everyday, and he revived the show (and the brand) from 1983 to 1990 as Mr Wizard’s World for the children’s channel Nickelodeon.

Still revealing the magical secrets of nature in the 1990s?

While children might delight in the prospect of mysterious thrills, the parents who forked out for these sets were more likely to be persuaded by the idea that they would be educational and improving. Chemistry experimentation was often presented in the late nineteenth century as morally virtuous: as Griffin put it, “Chemistry is a subject qualified to train both the mind and the hands of young people to habits of industry, regularity, and order”. Such manuals stressed cleanliness, dexterity and common sense – a stark contrast to the “diabolical sorcery” that one might find promised in magic-themed chemistry. The early twentieth-century makers of chemistry sets sometimes tried to reconcile the contradictions by suggesting that they were demystifying the stunts still then being pulled off by mediums and spiritualists. As one Gilbert manual put it in 1920, “We explain how they are performed by purely natural means.”

This tension, says Boyd, is just one of the “many contradictions inside these eye-catching boxes: between dreams and reality, structured learning and free exploration, mysterious magic and rational science, safety and danger.” The boxes in which the kits were housed sent out contrasting messages about what home chemistry was all about. Many show the experimenter as a young scientist, in the time-honoured chemist’s pose of holding up a test-tube or flask of coloured liquid. Some offer a futuristic, utopian vision of science as saviour, perhaps with the tubes of a chemicals plant hovering in the background. “Experimenter today, scientist tomorrow”, promises a Chemcraft manual from 1934.

A brave new world promised by Chemcraft.

“Experimenter today, scientist tomorrow”

Toys for the boys

The imagery throughout is decidedly male. “Manufacturers’ expectations and assumptions about masculinity are particularly apparent in chemistry set marketing copy in the United States in the twentieth century”, says Al-Gailani. He points out that, after the Second World War, chemical experiments that might earlier have been presented as “magic”, such as invisible ink, would instead be likened to the crime-sleuthing associated with the FBI, “an institution that was immensely influential in defining and popularising the predominant ‘all-American, square-jawed’ masculinity of the post-war era”. Chemistry was not just a male but a manly affair. The disheveled “mad scientist”, while beginning to feature in movies, is nowhere to be found here – instead, the young experimenter is smartly dressed and well disciplined, accustomed to following instruction (manuals). If he obeyed the rules, a chemistry set wasn’t just a recreational pursuit but a preparation for a career in science.

Did girls get a look in? A British Lott’s set from around 1915 claims that it is for both boys and girls, and reassuringly places the home chemistry lab in what looks rather like a domestic kitchen, albeit with (highly questionable) periodic tables on the walls. But if girls did chemistry, it was with a view to preparing them for their obligations in “mother’s kitchen”, not the laboratory. As a Chemcraft manual put it in 1933 “in the home, the housewife who knows nothing of the chemistry of the foods she prepares or the materials which she uses daily is handicapped”. The man who knows no chemistry is handicapped too, the manual adds – but strictly in the professional, not domestic, domain. It was the father’s duty to inculcate such knowledge in his son in preparation for a life of work, just as the mother should educate her daughter in the chemistry of cooking and domestic chores.

A Lott’s chemistry set made in England, c.1915

For boy’s only?

When Gilbert finally produced a set specifically for girls in the late 1950s, fetchingly decorated in pastel pink, it is not exactly a “chemist’s set” at all. Instead it reminds the girl who squints into a microscope, while her big sister looks on encouragingly, that all she can aspire to is to use her natural domestic skills to become a “lab technician”.

…or for girls too (if they don’t aspire too high)?

Keeping safe

By the 1970s things seem to have improved a little. Both girls and boys, as golden-haired and wide-collared as David Soul, feature on the lid of Johnny Horizon’s chemical set, although the girl seems to be reduced to looking on adoringly as her brother (boyfriend?) does the measuring and pouring. Yet this is no longer marketed as a chemistry set: in the post-Silent Spring era it is now an “Environmental Testing Kit”. “Is the air around you polluted?” it asks. You can examine river waters for contamination too, and the set promises that you and your family “will be able to do more about our environmental problems.”

A chemistry set post-Silent Spring.

How times change. What would those who bought the Johnny Horizon kit have made of Chemcraft’s offering from the late 1940s, which includes “safe experiments in atomic energy”, including – probably my favourite element (literally) of the entire CHF collection – uranium ore and a “radio active screen”? The latter is incorporated into a “spinthariscope”, a device first invented by the chemist and entrepreneur William Crookes in 1903, which uses a zinc sulfide phosphor screen to reveal the scintillations of alpha particles.

Home experiments in atomic energy, c. 1948.

Compare this with the Tree of Knowledge Chem-Science set from around 2000-2005, which – despite offering standard experiments such as the bicarb-vinegar volcano and litmus testing – assures the buyer that the “35 fun activities” contain “no chemicals”.

The Tree of Knowledge Chem-Science set (c.2000-2005) takes no risks.

If you’re inclined to bewail this apparent taming of home chemistry for kids, bear in mind that social anxieties about safety are nothing new. A concerned parent wrote to the Times in 1903 warning that “the placing in the hands of young boys of such ingredients as chlorate of potash, sulphur, &c., must always be deprecated as a temptingly dangerous proceeding”. (If only we could have responded by saying “Yes, that’s the point.”)

“The idea that the sets used to have terribly dangerous materials in them, and then these gradually got nanny-stated out, isn’t fully supported by the sets themselves”, cautions CHF curatorial assistant Elisabeth Berry Drago. “Even the earliest sets contained fairly innocuous stuff: things that were corrosive, or shouldn’t be inhaled, but not intrinsically deadly or dangerous.”

Compare, for example, the contents of the Lott’s chemistry set from around 1915 with those of a 1965 Skil Craft set (see Box): there was rather little change over five decades. “The ads and print material demonstrate that a concern for safety and toxicity was not a late development, but something that was very much a part of the context from early on”, says Drago. “Even in 1917 the onus is on safety.” The Porter Chemcraft set from that era insists that it is “Perfectly safe” and “Contains no poisonous or otherwise harmful substances”. Yet there was probably more concern about the sources of heating than about the chemical ingredients. Early chemistry sets contained Bunsen burners, Drago says, while later even “alcohol lamps with open flames are not considered child-safe any more.”

This wasn’t simply a matter of changing perceptions of what was hazardous, but also of who was to blame: as medical historian John Burnham of Ohio State university has argued3, there was an increasing tendency over the course of the twentieth century to switch the responsibility for child safety from parents (particularly mothers) to manufacturers and the “engineering” of the childhood environment. If manufacturers were to be held responsible for accidents, they weren’t going to take any risks.

“There is no doubt that contents of today's chemistry sets are far tamer than they were a few generations ago”, says Al-Gailani. But he is not convinced that this is the only or even main reason behind the much lamented “decline in popularity of the chemistry set.” To understand that, he says, “we need a much better understanding of wider shifts in the toy industry, especially the perceived profitability of scientific toys, and the place of chemistry in popular culture.” He thinks that the perception that the chemistry set should play a role in drawing children into science “has a lot to do with the iconic status of the chemistry set in writing about scientific careers and nostalgia for a less risk-averse era” – that it’s a story we tell, but not necessarily the right or complete one.

Smells and stinks

The chemistry set today is rarely marketed with the sobriety of the past. It emphasizes science as fun – smelly, disgusting, tactile and visual. We will surely one day be judged for this, for better or worse. There are certainly dangers in suggesting that chemistry is going to be relentlessly fun and entertaining, selling itself on stinks and bangs, as UCL chemist Andrea Sella argued when accepting the Royal Society Faraday Prize for communicating science this year.

But those sensual delights are harder to procure anyway when the range of chemicals permitted in a chemistry set is constrained. One alternative – some will see as a poor one, lacking the true tactile and aromatic sensations of chemistry – is the CHF’s Chemcrafter app, tellingly displayed in a 1950s visual style.

The chemistry set of the future? The Chemcrafter app from the Chemical Heritage Foundation.

Yet the questions confronting manufacturers now are in some ways not so different than ever they were. Should chemistry be made to feel exotic or familiar? Are chemistry sets about fun or sober instruction, and how far can the two be combined? Should they be marketed at the children (and which children?), or their parents? Whatever answers we find will say a lot about us.

Totally gross: chemistry sets today.


Box: What’s in the Box?

In circa 1915, the British Lott’s Bricks Chemistry Set No. 5 contained the following:
“Alum powder, ammonium carbonate, ammonium chloride, borax, calcium carbonate, charcoal (powdered), Congo red, copper sulfate, iron filings, iron sulfate, lime, manganese dioxide, potassium bichromate, potassium permanganate, potassium iodate, potassium iodide, potassium nitrate, “Sky blue”, sodium bicarbonate, sodium bisulfate, sodium carbonate, sodium nitrite, sodium thiosulfate, strontium nitrate, sulfur and zinc.”

In 1965 the Skil Craft Chemistry Set contained these ingredients:
“Ammonium chloride, gum arabic, cobalt chloride, sulfur, calcium chloride, sodium silicate solution, phenolphthalein solution, tannic acid, sodium ferrocyanide, manganous sulfate, sodium thiosulfate, ferric ammonium sulfate, sodium salicylate, borax, sodium bisulfate, and aluminum sulfate.”


1. M. Keene, Ambix 60, 54 (2013).
2. S. Al-Gailani, Stud. Hist. Phil. Sci. 40, 372 (2009).
3. J. C. Burnham, J. Soc. Hist. 29, 817 (1996).

The Chemical Heritage Foundation’s exhibition Science at Play: 100 Years of Chemistry Sets and Science Kits runs from October 2015 to September 2016 in Philadelphia.

BB's blues

My tribute to the late, great B. B. King for my “music cognition” column in the next issue of Sapere.

B. B. King, who died aged 89 on 14th May, was one of the first guitarists to evolve a style of playing that instantly identified him. His sweet, plaintive sound was so closely associated with the Gibson guitars he used to call Lucille that the Gibson Corporation launched a “Lucille” model in 1980. But it was the way he played them that mattered: bending notes that strayed far from the standard diatonic scale of Western music, especially on the fifth of the scale and the famous “blue” notes of blues and jazz: the third and the flattened seventh, which in the key of C correspond to E and B flat. The “blues third” lies in an ambiguous space between the minor third (E flat in C) and the major third (E natural), so that in the convention that makes major keys “happy” and minor keys “sad”, the blues – and especially B. B.’s blues – take on a bittersweet character, the sound of loves recalled and lost.

All this from simply playing “out of tune”? Well yes, because it’s precisely this quality that animates folk music in many traditions, giving it a soul that dies whenever classically trained musicians attempt to “go popular” and bring their perfect intonation to a musical form that demands rough edges. When musicologists and anthropologists first started to study folk music seriously in the early twentieth century, at first they often took the “imperfect” tunings to reflect poor technique – until they realised that the performers (usually singers) would replicate these off-key notes precisely from one rendition to the next. They knew what they were doing.

And what they were doing was what all music so often does when it pulls the emotions: it introduces uncertainty and ambiguity, creating a tension in the listener that turns into passion.

This is an easy principle to grasp, but fiendishly hard to get right. When other guitarists sought to emulate B. B., or singers to copy Billie Holliday doing the same thing with her vocal blue notes, they risked cliché or straining for effect. It takes exquisite judgement to keep the detuning emotive rather than kitsch. You’ve got to know how far to push it, perhaps quite literally. Will B. B. bend that note from a minor right up to a major third, “resolving” the discord and telling us that the story came good in the end? No, not quite – his hopes, like his intonation, are thwarted: joy withheld at the last moment. The thrill is gone.

Thursday, April 23, 2015

The moral challenge of invisibility

Here is an extended version of my latest piece for Nature News. There are of course more details about lots of the things discussed here in my book Invisible.


Experiments that give subjects the illusion of having an invisible body might reveal how we respond to the ensuing temptations.

We’ve all had those moments of social embarrassment: you’ve just said or done the dumbest thing, everyone is looking at you, and you wish you could just – well, vanish. But what if you really could? Would that help?

Apparently it would. Using a virtual-reality headset and a calculated confusion of the senses, neuroscientists at the Karolinska Institute in Stockholm, Sweden, have been able to give people the illusion that their body is invisible [1]. The subjects feel someone stroking their body with a brush, but when they look down all they see is the brush moving through thin air. This is enough, they testify, to give them the sensation that their entire body cannot be seen. It feels, many say, not only invisible but hollow – a weird dematerialization of their physical person.

And according to both the testaments of the subjects and objective measurement of their physiological response to stress as revealed by their heartbeat rate, this sensation of invisibility reduces their anxiety in social settings, for example if they can see an audience of “serious-looking strangers” seated and watching them.

Why would you want to know what it’s like to have an invisible body? One potential reason is that the technique could be used to treat social anxiety disorder, in which people are acutely susceptible to stress in situations such as having to deliver a presentation or perform before an audience. This is a very common disorder, affecting an estimated one in ten people at some point during their life. They sweat, shake, blush and hear their heart thumping away. Aside from prescribing anti-anxiety medication, this condition is generally treated with cognitive behavioural therapy, which attempts to condition the subjects by degrees to stay calm in a socially stressful setting.

Virtual reality has already shown its value in such treatment. But what if, say the Stockholm team, led by Henrik Ehrsson, you could “give” a patient an invisible body and then gradually make them more visible in stages? The illusion that they create is, after all, a matter of degree: subjects said that they experienced varying depths of visibility, depending on the conditions.

The illusion is also related to studies of how a sense of “body ownership” is triggered by visual and tactile stimuli. In 1998, psychologists Matthew Botvinick and Jonathan Cohen showed that when people see a rubber hand being brushed at the same time as their own hand, out of sight, experiences the same sensation, they feel that the rubber hand is part of their body [2]. Ehrsson and colleagues recently showed that this “rubber hand” illusion can even be invoked for an “invisible hand”, when subjects see the sensation that they feel applied to empty space [3]. That’s what inspired them to carry out the present study, and the results could also cast light on the “phantom body” illusion experienced by some people with paralysis due to spinal-cord injuries, in which they feel they have a body that is out of alignment with their real one.

So, plenty of potential clinical applications. But the research touches on something far deeper, for notions of personal invisibility feature in many of our myths, legends and stories, from Plato’s telling of the myth of Gyges in his Republic to H. G. Wells’ Invisible Man, J. R. R. Tolkien’s The Lord of the Rings and Harry Potter. Invisibility there has other connotations. Gyges is a shepherd of Lydia who discovers a ring of invisibility by chance, and uses it to seduce the queen, kill the king, and make himself ruler. The moral, says Plato’s narrator Glaucon, is that
“No man can be imagined to be of such an iron nature that he would stand fast in justice. No man would keep his hands off what was not his own when he could safely take what he liked out of the market, or go into houses and lie with anyone at his pleasure, or kill or release from prison whom he would, and in all respects be like a God among men.”

Wells seems to have intended his novel to be an updating of the Gyges story, demonstrating the corrupting temptations of invisibility and its severance of personal responsibility. He took great pains to make his invisibility scientifically plausible by the standards of the time, and interestingly he anticipated that an inability to see one’s limbs would confuse the coordination: his invisible man initially can barely walk. Ehrsson’s coauthor Arvid Guterstam says this is something they can now test, but he doesn’t anticipate such an effect. “We are already very used to moving our limbs without directly looking at them, when they are occluded or in the dark”, he says, “so guiding our limbs through space without direct visual feedback shouldn’t be a major issue.” We wouldn’t, it seems, become like David McCallum’s Invisible Man in the 1970s television serial of that name, forever blundering into potted plants – an exigency forced on him, the series producer Robert O’Neill admitted, by the challenge of convincing an audience that an invisible person was actually there.

But would invisibility also confuse our morals? This is where the new work could get really interesting, because the researchers want to examine this “Gyges effect”. “We are planning to expose participants to a number of moral dilemmas under the illusion that they are invisible”, says Guterstam, “and compare their responses to a context in which they perceive having a normal physical body.” I anticipate the worst here, not least because the Gyges effect seems already to operate in internet trolling [4].

One thing is for sure: we should take with a big pinch of salt the authors’ suggestion that there is “the emerging prospect of invisibility cloaking of an entire human body being made possible by modern materials science”. This alludes to recent work on so-called metamaterial invisibility cloaks [5,6]. But not only is that work very far from achieving full cloaking in the visible spectrum (let alone in a wearable suit), but there is good reason to suspect that it will stay that way for the foreseeable future. The hiding of a cat and fish that Ehrsson and colleagues mention [7] sounds impressive but is in the end a kind of high-tech version of the Victorian stage magician’s trick of using mirrors (and probably smoke) to make half a woman’s body vanish.

There are other technologies afoot for making “invisibility cloaks” for humans, generally involving a kind of adaptive camouflage in which the background is either projected onto highly reflective clothing [8] or captured with “onboard” cameras and displayed on wearable LED screens [9]. The first offers a compromised and static illusion – if you want to appear transparent while you give your presentation, you’d do just as well to stand in front of the projector. The second is another speculative and remote (albeit fun) idea that is in any event undermined by the laws of optics [10]. So fear not – no one is going to become a real-life Gyges any time soon.

1. Guterstam, A., Abdulkarim, Z. & Ehrsson, H. H., Sci. Rep. 5, 9831 (2015). (here)
2. Botvinick, M. & Cohen, J., Nature 391, 756 
(1998). (here)
3. Guterstam, A., Gentile, G. & Ehrsson, H. H. J. Cogn. Neurosci. 25, 1078–1099 (2013).
4. Hardaker, C. Guardian 3 August 2013. (here)
5. Schurig, D., Mock, J. J., Justice, B. J., Cummer, S. A., Pendry, J. B., Starr, A. F. & Smith, D. R., Science 314, 977-980 (2006).
6. Leonhardt U.&. Philbin, T. G., Geometry and Light: The Science of Invisibility. Dover, Mineola, 2010.
7. Chen, H. et al., preprint (2013).
8. Tachi, S. Proc. 5th Virtual Reality Int. Conf. (VRIC2003), 69/1-69/9 (Laval Virtual, France, 2003). (here)
9. Zambonelli, F. & Mamei, M. Pervasive Computing 1(4), 62-70 (2002) (here).
10. See comments by M. Hebert in ref. 8.

Monday, April 20, 2015

Goebbels: the gift that keeps on giving?

The story about demands (on my publisher) for royalties for quoting Goebbels raises fascinating issues. It is all the more complex because of the fact that the claim on behalf of Goebbels’ estate is being pursued by the daughter of Hjalmar Schacht, Hitler’s Economic Minister, who is a lawyer.

I considered Schacht’s story briefly in my book Serving the Reich; a more detailed account is given in Eric Kurlander’s excellent Living With Hitler. Schacht offers an interesting case study of the complexities of anti-Semitism during the Nazi regime. He was in many respects a liberal, and although he became a supporter of the Nazis and President of the Reichsbank, he lost his influence after a disagreement with Hitler in 1937 (“You simply do not conform to the general National Socialist framework”, Hitler told him two years later) and eventually became a member of the German Resistance. He was imprisoned after the failed assassination plot of June 1944 and sent to Dachau, but survived.

Schacht seems to have been instinctively averse to racial hatred, and was frequently reprimanded by Party officials for speaking out against attacks on Jews and their property. He argued against some anti-Semitic measures on the grounds that they would weaken Germany domestically and isolate it abroad. Put on trial at Nuremberg, Schacht claimed that he had served in the government “to prevent the worst excesses of Hitler’s policies”, although some historians argue that he aided the Holocaust by expropriating Jewish property. He was acquitted at the trials, and later became an adviser to developing countries on economic development.

Schacht’s trajectory shows how unwise it is to attempt to label individuals as Nazi or not, or as pro-/anti-Semite. As I pointed out in my book, few scientists actually served, as Schacht did, in the Nazi administration; but few, too, spoke out publicly against the regime and actively opposed it, as Schacht did. Does this make them better or worse than him?

Either way, the fact that Schacht’s daughter and Goebbels’ family apparently think it is right that the family should get royalties for quoting him – in preference, indeed, to donating such proceeds to a Holocaust charity – should not shock us as much as it might. It’s a reminder that the legacy of the Nazi regime did not vanish either with Hitler’s death or with the fading of his generation. It is of a part with the widespread sense in Germany after the war that the case was now closed and that only the ardent Nazis had questions to answer.

Remember that the postwar trials were notoriously ineffectual, not just because it was extremely difficult and time-consuming thoroughly to investigate any allegation (let alone to prove it) but because many who supported the regime had little difficulty in obtaining the so-called Persilscheine or whitewash certificates of clearance. The most vociferous Nazis in the universities were dismissed without compensation, while others who had doubtless helped the regime were eased into early retirement. Hardly any of the scientists were incriminated. Pascual Jordan, for example, a Party member whose enthusiasm for National Socialism was such that its ideology even seeped into his physics, was issued a whitewash certificate by Werner Heisenberg, who attested that he had “never reckoned with the possibility that [Jordan] could be a [true] National Socialist” (rather inviting the question of what it would take to convince Heisenberg of that). Niels Bohr was less obliging: he replied to Jordan’s request for a letter of exoneration by sending the physicist a list of Bohr’s friends and relatives who had died in the camps.

The ‘denazification’ of German science was actively obstructed even by those who had had no sympathy with the National Socialists. The prevailing attitude was one of resentment at the intrusiveness of the occupying Allied authorities, which led to a closing of ranks and a feeling of solidarity between the most unlikely of bedfellows. Even relatively blameless individuals refused to condemn those who had been clearly implicated in the Nazi regime. Others drew an invidious parallel between the rooting out of Nazis after the war and the persecution of ‘non-Aryans’ before it. For Otto Hahn, denazification involved “attacks against the science of our nation”.

These prevarications and evasions during ‘denazification’ meant that it quickly became impossible to construct a clear picture of how the nazification of German society had proceeded. And it’s German historians who say this. Klaus Hentschel, for instance, has said that “It was one of the most depressing experiences I ever had as a historian to see reflected in the documents how very soon after 1945 the chance of coming to grips with the National Socialist regime was allowed to slip away, thus missing the opportunity to make a frank assessment of the facilitating conditions the regime had set.”

The prevailing attitude was not guilt or remorse, but self-pity and resentment at the indignities suffered in a defeated nation. Visiting Germany in 1947, Richard Courant, the mathematician who had been forced out of Göttingen in 1933, despairingly described its residents as “absolutely bitter, negative, accusing, discouraged and aggressive.” Hartmut Paul Kallmann, the postwar director of the former Kaiser Wilhelm Institute for Physical Chemistry in Berlin, who as a ‘non-Aryan’ had been dismissed under Fritz Haber’s directorship in 1933 and had worked for IG Farben during the war, wrote to the emigré Michael Polányi in 1946 saying that “the tough momentary situation [here] is deplored much more than the evil of the past 10 years… The masses still don’t know what a salvation the destruction of the Nazis was to the whole world and to Germany as well.” “It is a difficult problem with the Germans”, Margrethe Bohr told Lise Meitner two years later, “very difficult to come to a deep understanding with them, as they are always first of all sorry for themselves.” In 1947 the president of the polytechnic at Darmstadt complained that for some student “it seemed that the only thing the Nazis had done wrong was to lose the war.”

I think such sentiments still prevail in some quarters. From a certain generation of Germans, I have heard comments in response to my book even from evident anti-Nazis to the effect that “well of course you have no idea how hard it was for us.” In fact I have no doubts how hard it was for them. But such comments are offered as a shield against deeper reflection about the moral fallout. Sometimes it’s worse than that. Even for raising the question that folks like Heisenberg and Debye might have had questions to answer, I was called by one party a “cockroach” – and I can’t imagine for a moment that the similarity with the language used by the Nazis to dehumanize Easter Europeans and Jews could have been lost on that person. (This is not, let me stress, a specifically German response – I’m pretty sure that, as Ian Kershaw has intimated, what we saw in Germany before and after the war could have happened anywhere, mutatis mutandis. We are certainly not free from such language in Britain today, as we have sadly discovered recently.)

So no, there is really nothing so strange or surprising about the Schacht/Goebbels response. I am proud that Bodley Head is standing up to it.

Tuesday, April 14, 2015

Condensed-matter physics gets its hands dirty

Here is the original version of my leader for Nature Materials, which I want to put up here to acknowledge the insightful input from Bob Cava and Bertram Batlogg - N Mat's leader style doesn't permit direct quotes, so I had to paraphrase their words.


Is condensed-matter physics becoming more materials-oriented? Or is this just a new wrinkle in an old tradition?

Condensed-matter physics is becoming increasingly oriented towards materials science and engineering. That’s the conclusion reached by two Harvard physicists, Michael Shulman and Marc Warner, after analyzing the statistics of abstracts for the main annual (March) meeting of the American Physical Society since 2007. They enumerated key words used in abstracts to identify trends over the past eight years, and say that during this time the words that are increasing in popularity are often ones associated with specific types of material system, such as “layer”, “thin”, “organic”, “oxide” and indeed “material”. In contrast, words or (word fragments) with generally declining popularity include “superconduct” and “flux” (as well as, oddly, “science”).

What should we make of this? Probably not too much. As the authors are the first to point out, the analysis is preliminary and its timespan limited. It would be good to see it extended over a longer period and expanded to include, say, words in the abstracts of publications in Physical Review Letters, not to mention paying more attention to soft matter rather than primarily solid-state. The present results also paint a slightly confusing picture, taken at face value: condensed-matter physics (CMP) as a whole has been expanding if one judges from the gradual rise in the total number of abstracts submitted to CMP sessions of the March meeting, yet the “condensed matter” section of the preprint server arxiv has made up a shrinking proportion of the total during that time. There are various possible explanations for the discrepancy.

All the same, if it is qualitatively true that CMP has become more materials-focused, it’s worth asking why. Are established researchers in the field are altering the direction of their work away from abstract theoretical questions – what is the origin of high-temperature superconductivity, to take one obvious former preoccupation of theorists – and towards applications of particular materials systems? Or does that reflect a change in the interests of young researchers entering the field? Robert Cava of Princeton University doubts that it’s merely the latter, since old hands enjoy fresh challenges: “For old-timers like me, new areas are a way to use your stored knowledge to have insights that the youngsters miss.”

It is tempting to infer that researchers are just following the money: in this increasingly goal-oriented scientific climate, there may be better funding prospects for a project that can promise concrete applications at the end of the line. But might not the trend instead reflect the internal dynamics of the research community, so that funding follows areas deemed “hot” for other reasons? It’s almost sure to be a bit of both, as the example of graphene shows: there are high hopes for applications in electronics and composites, but much of the interest has come from the fundamental physics that this one-dimensional system seems to offer. More data on the dynamics and trends of funding priorities might help to separate cause and effect.

In any event, Bertram Batlogg at ETH in Zurich says that practical applications of the materials it studies has always been “in the best tradition of CMP”. Given the enormous contributions that the field has made to society – underpinning the technologies of smart phones and solar energy, say – it’s only natural that researchers should have an eye on ensuring that this tradition continues.

Shulman and Warner found that, in comparison to subjects such as atomic, molecular and optical physics, CMP changes fast: the statistics of key words are more volatile. Cava agrees that this is a feature of the field. “Occasionally, say once every 5-10 years, a subject comes up that is so new that many people work on it, because physicists are intrinsically enthusiastic and interested in new science.” He cites the case of pnictide superconductivity, which enjoyed its greatest popularity just before the period of this analysis. Superconductivity is now seeing another little surge of interest owing to topological superconductors.

“I believe that all fields have a natural life cycle”, says Cava. “They naturally go up in activity and then back down as people have had a chance to see what they can contribute and then move on to other new areas.” Shulman and Warner wonder if this cycle is shorter in CMP than elsewhere, perhaps because it can be stimulated by the discovery of a new material system (carbon nanotubes, say, or magnetic multilayers) but also because it can be hard to get at the high-lying fruits for many of these systems owing to the complexities of the many-body interactions they present – that, at least, seems to be what has kept a general theory of high-temperature superconductivity out of reach. What’s more, high-temperature superconductivity showed that there is a very low entry barrier for studying exciting new materials if they are relatively easy to synthesize: any lab well equipped with instrumentation can quickly and easily switch direction and still hope to make a useful contribution.

Might there also be a life cycle for CMP as a whole? The APS division was created only in 1978, from what was formerly the Division of Solid State Physics. Yet Shulman and Warner wonder if it still presents the kind of exciting challenges of 20-30 years ago. No one would claim, however, that the most demanding questions are all answered: perhaps some of them will need to await new techniques or new theoretical methods better able to accommodate complexity. And like chemistry, to some extent CMP creates its own subject: our inventiveness (or serendipity) with new materials systems prompts new questions. As Cava says, “to explore the complexity of the physics people have to think about and perform experiments on real materials. Each material has a different balance of the competing forces that give rise to the complexity of condensed matter physics, so each new material is an opportunity to learn new physics.”