Buddha in oils?
[This is the pre-edited version of my latest news story for Nature.]

Painters on the Silk Road may have been way ahead of the Europeans.

Artists working in Afghanistan were using a primitive form of oil paint hundreds of years before it became common practice in Europe, a team of scientists has claimed.

Yoko Taniguchi of the National Research Institute for Cultural Properties in Tokyo and her coworkers have analysed samples of Buddhist paintings in caves at Bamiyan in Afghanistan, made in the mid-seventh and early eighth centuries AD. They say that the paint layers contain pigments apparently bound within so-called drying oils, perhaps extracted from walnuts and poppy seeds.

But Jaap Boon, a specialist in the chemical analysis of art at the Institute for Atomic and Molecular Physics in Amsterdam, the Netherlands, cautions that this conclusion must be seen as tentative until more detailed studies have been done.

The Bamiyan caves sit behind the gigantic statues of Buddha that were destroyed by the Taliban in 2001. The paintings, showing robed Buddhas and mythical creatures, were also defaced but not obliterated. The Bamiyan caves are now a designated UNESCO World Heritage site.

The researchers removed tiny samples of the painted surface (typically less than 1 mm across) for analysis using state-of-the-art techniques. These can reveal the chemical identity of the pigments and the materials used to bind them to a layer of earthen plaster on the cave walls.

Taniguchi’s collaborators used X-ray beams produced by the European Synchrotron Radiation Facility in Grenoble, France, to figure out the composition and crystal structures of pigment particles, deposited in a series of microscopically thin layers. The synchrotron facility produces extremely bright X-ray beams, which are essential for getting enough data from such small samples.

Meanwhile, spectroscopic methods, which identify molecular structures from the way their vibrations cause light absorption, were used to identify the organic components of the paint layers. The findings are described in a paper in the Journal of Analytical Atomic Spectrometry [1].

The researchers found pigments familiar from the ancient world, such as vermilion (red mercury sulphide) and lead white (lead carbonate). These were mixed with a range of binders, including natural resins, gums, possibly animal-skin glue or egg – and oils.

Boon suggests that this variety in itself raises concerns about potential contamination – microogranisms on the rock surface, say, or the fingerprints of people touching the paintings (something encouraged in Buddhist tradition).

He says that other techniques that really pin down what the organic molecules are should be applied before jumping to conclusions. With spectroscopy alone, he says, it can be difficult to tell egg from oils, let alone animal from plant oils.

But Marine Cotte of the Centre of Research and Restoration of the French Museums in Paris, a coauthor of the study, is convinced of the conclusions. She says that oils have an unambiguous spectroscopic signature, and adds that their molecular components have been confirmed by the technique of chromatography.

Oil painting is commonly said to have been invented by the Flemish painter Jan van Eyck and his brother Hubert in the fifteenth century. But while the van Eycks seem to have refined this technique to create stunningly rich and durable colours, the practice of mixing pigments with drying oils is known to be considerably older.

It is first mentioned in the late fifth century by the Byzantine writer Aetius, and a recipe for an oil varnish (in which a drying oil is mixed with natural resins) is listed in an eighth-century Italian manuscript.

In the twelfth century, a German Benedictine monk named Theophilus describes how to make oil paints for painting doors. Oil paints are also known from this period on Norwegian churches.

Drying oils are relatively slow to dry compared with the common medieval binders of egg yolk and size from boiled animal hide, which initially led Western craftsmen to regard them as fit only for rather lowly uses.

So the use of oils in fine art as early as the seventh century is surprising – all the more so for painting on plaster-coated rock, where the translucency of oil paints would not be expected to recommend their use. ‘It doesn’t make a lot of sense to use oils’, says Boon. He says that it would be really difficult to keep the paint in good condition for a long time in an environment like this, exposed to damp, fungi and bacteria.

But Cotte says that the oils are found in deeper layers where contamination would not penetrate, while being laid over an opaque bottom or ‘ground’ layer.

It’s not clear who these artists were, the researchers say. They were probably travelling on the Silk Road between China and the Middle East, and may have been bringing with them specialist knowledge from China.

Cotte says that these studies should aid efforts to preserve the paintings. “It helps you do that if you know what is there”, she explains – this would identify the most appropriate cleaning procedures, for example.

Reference
1. Cotte, M. et al., J. Analyt. Atomic Spectrosc. (in press, 2008)

Journeys in musical space
[This is one of the most stimulating things I’ve read for some time (not my article below, published on Nature’s online news site, but the paper it discusses). The paper itself is tough going, but once Dmitri Tymoczko explained to me where it was headed, the implications it opened up are dizzying – basically, that music is an exploration of complex geometries, giving us an intuitive feel for these spaces that we probably couldn’t get from any other kind of sensory input.]

Researchers map out the geometric structure of music.

To most of us, a Mozart piano sonata is an elegant succession of notes. To composer and music theorist Dmitri Tymoczko of Princeton University and his colleagues Clifton Callender and Ian Quinn, it is a journey in multidimensional space that can be described in the language of geometry and symmetry.

In a paper in Science, the trio offer nothing less than a way of mapping out all of pitched music (music which is not constructed from unpitched sounds like percussion), whether it is by Monteverdi or Mötörhead.

Commenting on the work, mathematician Rachel Wells Hall of Saint Joseph’s College in Philadelphia says that it opens up new directions in music theory, and could inspire composers to explore new kinds of music. It might even lead to the invention of new musical instruments, she says.

Although the work uses some fearsome maths, it is ultimately an exercise in simplification. Tymoczko and colleagues have looked for ways of representing geometrically all the equivalences that musicians recognize between different groups or sequences of notes, so that for example C-E-G and D-F#-A are both major triads, or C-E-G played in different octaves is considered basically the same chord.

By recognizing these equivalences, the immense number of possible ways of arranging notes into melodies and chord sequences can be collapsed from a multidimensional universe of permutations into much more compact spaces. The relationships between ‘musical objects’ made of small groupings of notes can then be understood in geometric terms by mapping them onto the shape of the space. Musical pieces may be seen as paths through this space.

It may sound abstract, but the idea brings together things that composers and musicologists have been trying to do in a fragmentary manner for centuries. The researchers say that all music interpretation involves throwing away some information so that particular musical structures can be grouped into classes. For example, playing ‘Somewhere Over the Rainbow’ in the key of G rather than, as originally written, the key of E flat, involves a different sequence of notes, but no one is going to say it is a different song on that account.

The Princeton researchers say there are five common kinds of transformation like this that are used in judging equivalence in music, including octave shifts, reordering of notes (for example, in inversions of chords, such as C-E-G and E-G-C), and duplications (adding a higher E to those chords, say). These equivalences can be applied individually or in combination, giving 32 different ways in which, say, two chords can be considered ‘the same’.

Such symmetries ‘fold up’ the vast space of note permutations in particular ways, Tymoczko explains. The geometric spaces that result may still be complex, but they can be analysed mathematically and are often intuitively comprehensible.

“When you’re sitting at a piano”, he says, “you’re interacting with a very complicated geometry.” In fact, composers in the early nineteenth century were already implicitly exploring such geometries through music that could not have been understood using the mathematics of the time.

In these folded-up spaces, classes of equivalent musical objects – three-note chords, say, or three-note melodies – can each be represented by a point. One point in the space that describes three-note chord types (which is cone-shaped) corresponds to major triads, such as C-E-G, another to augmented chords (in which some notes are sharpened by a semitone), and so on.

Where does this musical taxonomy get us? The researchers show that all kinds of musical problems can be described using their geometric language. For example, it provides a way of evaluating how related different sequences of notes or chords are, and thus whether or not they can be regarded as variations of a single musical idea.

“We can identify ways chord sequences can be related that music theorists haven’t noticed before”, says Tymoczko. For example, he says the approach reveals how a chord sequence used by Claude Debussy in 'L’Après-Midi d’un Faune' is related to one used slightly earlier by Richard Wagner in the prelude to 'Tristan und Isolde' – something that isn’t obvious from conventional ways of analysing the two sequences.

Clearly, Debussy couldn’t have know of this mathematical relationship to Wagner’s work. But Tymoczko says that such connections are bound to emerge as composers explore the musical spaces. Just as a mountaineer will find that only a small number of all the possible routes between two points are actually negotiable, so musicians will have discovered empirically that their options are limited by the underlying shapes and structures of musical possibilities.

“Music theorists have tended to regard the nineteenth-century experiments in harmony as unmotivated whimsy”, says Tymoczko. But his geometric scheme suggests that they were much more rational than that, governed by rigorous rules that their new approach can now uncover.

For example, the scheme supplies a logic for analysing how so-called voice leading works in chord progressions. This describes the way in which a sequence of chords with the same numbers of notes can be broken apart into parallel melodic lines. For example, the progression C-E-G to C-F-A can be thought of as three melodic lines: the E moves to F, and the G to A, with a constant C root. Finding efficient and effective voice-leading patterns has been challenging for composers and music theorists. But in the geometric scheme, a particular step from one chord to another becomes a movement in musical space between two points separated by a well defined distance, and one can discover the best routes.

This is just one of the ways in which the new theory could not only illuminate existing musical works but could point to new ways of solving problems posed in musical composition, the researchers claim.

Reference
1. Callender, C. et al. Science 320, 346-348 (2008).

NASA loses its (science) head, Pfizer loses its case
[This is my Lab Report column for the May issue of Prospect.]

The resignation of NASA’s science chief Alan Stern in April is a symptom of all that’s wrong with the US space agency. Stern has given no official reason for his abrupt departure, which of course makes it seem all the more that the reason is one he’d rather not talk about. Many suspect his decision stems from a frustrating relationship with NASA’s leadership, specifically its head Mike Griffin, despite Stern’s assertion that Griffin is “the best administrator NASA has ever had”. Stern’s aim to keep projects on schedule and within budget – both persistent problems for NASA – is hard to fault, but it has sometimes caused a collision of priorities.

A highly respected planetary scientist, Stern has been seen as a true voice of science at NASA, favouring projects that actually teach us something about the universe. But increasingly, NASA seems compelled to support popular programmes that pander to the romanticised American vision of space exploration. Griffin has frozen the budget for fundamental science to fund a manned return mission to the moon – a political rather than scientific venture. Stern also tried to reduce the focus of planetary missions on Mars at the expense of the outer planets.

The crunch seems to have come over Stern’s decision in March to shut down Opportunity, one of the two Mars rovers currently exploring the planet’s surface. Griffin was not informed of that decision, and when he found out, he reversed it. Whatever the demands of etiquette, Stern’s decision made sense: the rovers have been an immensely successful testament to the power of robotic exploration, but they have long fulfilled their objectives. Opportunity and Spirit can still gather useful data, but the real problem was that the public loves them: the planned shutdown became headline news and provoked objections in Congress.

The rovers are now portrayed like pets: newspapers talked about Opportunity being ‘put to sleep’ rather than switched off. This pathetic fallacy is a projection of the longing to put humans on Mars. The irony is that a populist commitment to cripplingly expensive human spaceflight projects will ultimately give the taxpayer far less value for money than the kind of missions Stern supported. For now, that kind of absurd sentimentality has deprived NASA of a highly capable head of science.

*****

When scientists submit papers for publication, they usually enter into an unwritten contract of confidentiality with the journal: the paper will not be disseminated outside of the peer review process, but the reviewers will not be disclosed to the authors.

The pharmaceutical company Pfizer has decided that this arrangement should be subordinate to its own interests. During a lawsuit last year over alleged side effects of its painkillers Celebrex and Bextra, it subpoenaed the New England Journal of Medicine (NEJM) to release the reviews and reviewers’ identities for papers published on the drugs, along with details of the journals’ internal editorial deliberations. The NEJM’s refusal has now been upheld by a federal court in Massachusetts.

Pfizer’s lawyers say that the information could help to exonerate the company in deciding to put the drugs on sale. Bextra was withdrawn in 2005 after claims that it could cause heart attacks and strokes; Celebrex remains on the market.

“The public has no interest in protecting the editorial process of a scientific journal”, the lawyers have say. But the public has every interest in knowing that scientific claims will be checked out by independent experts who not only are guaranteed anonymity but do not expose themselves to the danger of litigation. The best reviewers might otherwise decline the task rather than take that risk. A counter-argument is that information relevant to public health should not be kept confidential – but drug companies are after all under no obligation to disclose their own tests and trials.

Besides, Pfizer has not specified what it hoped to find in the documents. One interpretation is that the company is simply fishing for anything that might help its case, rather than acting on a belief that the NEJM holds some pivotal evidence. The court’s decision is the right one, but will it persuade drug companies that they cannot rewrite the rules by which science is conducted?

*****

The new head of the Human Fertilisation and Embryology Authority (HFEA), Renaissance historian Lisa Jardine, has certainly begun her role during ‘interesting times’. The impending vote on the Human Fertilisation and Embryology Bill crystallizes several moral dilemmas about today’s research and practice in these areas, and threatens to heighten the polarization they induce. Whatever positions Jardine takes are sure to upset some vocal group or other.

Perhaps this is why the appointment of someone used to taking the long view, and accustomed also to the hard knocks of public life, makes sense. Certainly, Jardine’s popularizing instincts seem right for the HFEA just now: she considers public education about fertility issues (“something people need to know about”) as important as the regulatory responsibilities. The HFEA, while not exactly an opaque bureaucracy, has seldom previously shown an explicit commitment to inform.

And now is the time to do it. So far, it seems that the kind of misinformation about the bill spread by Catholic officials and other religious groups – talk of animal-human ‘cybrid’ embryos in research as ‘of Frankenstein proportion’ – has not significantly dented a public appreciation of the benefits such research could bring. (The ‘animal’ component here is a mere shell for human genes.) But it’s never a good idea to underestimate the determination of zealots.

On their way to a bookshop near you

Well look, you don't seriously think I'm going to go to all this effort if I do not allow myself a bit of advertising now and again. These two books - Universe of Stone (Bodley Head), a study of the twelfth-century renaissance through the prism of Gothic architecture, and The Sun and Moon Corrupted (Portobello), a novel - are on their way to the warehouses as I write. I have gleaming new copies of both books beside me now, and believe me, you should judge these ones by their covers. Oh, you don't need me to put an Amazon link here, do you?

You can hear me talking about the book on Gothic (and a mixed grill of other things, including creationism) on the latest Guardian science podcast (one "l" please).

And there is now a reissue of my book Bright Earth: The Invention of Colour available from Vintage, with a bright and bubbly new cover.

Radio sweat gland - 90 GHz

[Given that part of the point of this blog is to add a bit of value to stuff I publish elsewhere, I thought it was worth putting up this piece that appears this week in a necessarily abbreviated form in Nature's news pages. In particular, it's a shame not to hear from Merla, who is close to this topic, and more from the famous Paul Ekman.]


Sweating – a sign of recent physical activity and, often, of mental stress – can be detected from a distance by a beam of millimetre-wavelength radiation, a team in Israel claims[1].

They have shown that sweat ducts in human skin acts like an array of tiny antennas that pick up radiation at frequencies of about 100 gigahertz – the so-called extremely high frequency or EHF range, lying between microwaves and terahertz radiation. The antenna behaviour is all down to the ducts’ curious shape: they thread through the epidermis as regular helices. Filled with electrically conductive sweat, these channels act a little like coils of wire that absorb radiation across the millimetre and sub-millimetre wavelength band

Yuri Feldman of the Hebrew University of Jerusalem and his colleagues measured the reflection of EHF radiation from skin on the palms of subjects after 20 minutes of jogging, and found that there was a strong band of absorption compared to people who had not exercised. The absorption gradually disappeared as the jogging group rested. They also found that the reflection signals were proportional to blood pressure and pulse rate, known to be indicators of physiological stress.

And when the researchers suppressed sweating with a synthetic compound that mimics the localized paralysis of snake venom, inactivating the sweat glands, they found that the EHF absorption was lower.

Feldman and colleagues say that the helical antenna array makes skin a kind of biological metamaterial, in which the material’s response to electromagnetic radiation is determined by structure rather than composition. Metamaterials made from arrays of tiny electrical circuits are being explored for applications ranging from super-lenses to invisibility shields. “Nature has done what is being attempted extensively today in nanophotonics”, say the researchers.

Arcangelo Merla, who works on biomedical imaging of arousal states at the University ‘G. D’Annunzio’ in Chieti, Italy, calls the work “quite fascinating” and agrees that “it may open an alternative way for remote sensing of this important physiological phenomenon”.

They speculate that their technique could be used to gauge people’s mental state from a distance, perhaps even without their knowing. “This effect might be used for biomedical applications and homeland security applications”, the Israeli team say. Detection of sweating hands has previously been used as in lie detection, although the use of such physiological parameters in ‘polygraph’ lie detectors has become controversial after being strongly criticized in a 2002 report by the US National Academy of Sciences.

“Perspiration is related to increases in emotional arousal”, agrees Paul Ekman, a psychologist in Oakland, California, and one of the authors of that report. “But as with other measures of arousal, such as heart rate, it can be the consequence of many different mental processes. In terms of lying, arousal measures only tell you the person is aroused. Suppose you did not kill your spouse but the police are interrogating you: wouldn't you be aroused? The fear of being caught looks just like the fear of being disbelieved.”

Merla also points out that emotional sweating is driven and controlled in a different way from thermoregulatory sweating caused by exercise. He adds that “understanding a mental state from measures of peripheral activity is a very complex task”. He says that it would be inappropriate to apply the technique to lie detection and monitoring of stress and anxiety unless one combines it with other indicators of arousal. He is developing infrared thermal imaging of skin to determine several such measures simultaneously.

So far, however, Feldman and his colleagues are cautious about whether the idea will work at all, let alone how it might be applied. “We must first to evaluate the limits of performance – for example, what is the range at which we can detect a meaningful signal, how fast changes in the various biometrical parameters we want to monitor are manifested in our signal, and so on”, they say. “We are just starting our journey in these uncharted waters.”

Reference
1. Feldman, Y. et al. Phys. Rev. Lett. 100, 128102 (2008).

Astrology’s myopia
[Do I make rods for my own back? I suspect astrologers will respond to this piece, just published as a Muse column for Nature news, by saying that I clearly haven’t understood what astrology is really about or how it is meant to work. That’s because they have no idea about it themselves – the maze of different theories and traditions is a nightmare. But I think I do know what astrology used to be about, back in the days when it was arm in arm with astronomy.]

Seasonal effects on birth physiology inevitably raises spectres of astrology. But that’s just ahistorical nonsense.

Near-sightedness, or myopia, may be more common in babies born in the summer than the winter, a team of scientists in Israel have claimed [1].

This is just the latest in a string of suggestions that the season of our birth may affect our physical make-up. Among recent findings of this kind are reports of seasonal effects in fingerprint patterns [2] and in animal gestation length and birth weight [3][4].

Like these earlier claims, the seasonality of myopia seems an entirely reasonable thing to suppose, since there is already evidence that exposure to strong light both before and shortly after birth affects the ability of the eye to focus properly. The effect, identified by Yossi Mandel of the Israel Defence Force Medical Corps and colleagues, is small, and seems to kick in only for moderate to severe cases of myopia, which are probably preconditioned by a genetic susceptibility.

So far, so plausible. But you know what I’m thinking? How long before this result is touted as ‘further’ evidence that there is something to astrology after all – that the celestial configuration can imprint itself on our bodies and minds?

We can surely expect this finding to be added to the growing list of scientific findings, so far including sunspot cycles, animal navigation, solar-terrestrial climate correlations and even Gaia theory, that some astrologers have presented as evidence not only that science supports astrology but that it is trying to appropriate its key ideas.

This isn’t the kind of thing one can nip in the bud, and I don’t delude myself otherwise. Let me say simply that all these Cancerians whose poor vision has no doubt made them introverted, bespectacled bookish types are presumably born in the Northern Hemisphere, since one must anticipate that the myopia effect appears in January in the antipodes.

No, I think it is perhaps more edifying to consider why astrologers wants to draw solace from science at all. Most notoriously, they cite the statistical studies of French psychologist Michel Gauquelin, who claimed to show in the 1950s that more successful sportspeople and athletes were born when Mars was “rising or culminating” – just as you might expect for the ‘warrior’ zodiacal sign, after all.

This ‘Mars effect’ can be found echoed in a recent claim that English football league players are almost twice as likely to be born between September and November. (Sceptics might wonder whether the fact that those birth dates make British boys older and thus often bigger than their school peers has anything to do with it.)

Actually, Gauquelin himself called horoscopes an “exploitation of public credulity”. But his research was extolled by the British astronomer Percy Seymour, who has argued in several books (most recently The Scientific Proof of Astrology (2004)) that the configurations of the planets, moon and sun can leave an imprint on us via their magnetic fields. “The whole solar system is playing a symphony on the Earth’s magnetic field”, he says; the ‘interference’ of these fields somehow affects the development of babies’ brains in the womb.

Oh, I know. It is only the thought of countless astrologers saying “He had no arguments against it” that rouses me to point out that a fridge generates stronger magnetic field in the average household than Jupiter does, or that there is not the slightest reason to believe that exposure to magnetic fields can alter infants’ personality in consistent, or indeed any, ways. But I’m not going to preach to the choir.

No, I happen to think that the truth about astrology is more interesting than this kind of silliness. I’d argue that one cannot simultaneously afford astrology its proper place in the history of thought and still believe in it today.

To say (as many scientists might) that astrology has always been nonsense is to say something more or less without meaning. No one can reasonably say that Aristotelian science was nonsense; it was a best guess that proved to be wrong. The same is true of astrology.

It relied on two principles: a correspondence between the macrocosm and the microcosm (“As above, so below”), and on the action of ‘hidden’ (occult) forces. The latter was a perfectly valid assumption: there was nothing to ‘see’, no bodies in contact, that explained magnetism or gravitation. The former – in part, the idea that events in the heavens governed those on Earth, perhaps by some form of astral ‘emanation’ – was part of a long tradition, dating back at least as far as Babylonia, for which the tides and the seasons supplied corroboration.

Yes, the tradition was mistaken, but not unmotivated. Certainly, it is a whole lot less arbitrary than the modern astrologers who have allowed the whims of an astronomical nomenclature committee to determine the astrological virtues of the Centaur planetoid Chiron, discovered in 1977 – named after a mythical centaur renowned for skill at healing, this captured outer asteroid is therefore now associated with astrological healing powers.

In any event, one foregoes the right to claim any justification for these ancient beliefs in modern science if one does not accept what those scientific explanations rule out too. When astrologers say (as one did apropos of Seymour’s work) that the moon affects the oceans and so why not our predominantly watery bodies, they are in effect disqualifying themselves from using gravity as an explanatory mechanism. (Just do the sums.)

More seriously, astrologers who might want to seize on the latest scientific findings, whether of summer-induced myopia or seasonality of sporting prowess, as proof of their beliefs are like theologians hunting for God in dark energy, or indeed scientists seeking to rationalize biblical miracles: they misunderstand the function of those beliefs in the history of ideas. Astrology ‘worked’ when embedded in ancient and medieval cosmologies, which were not scientific but metaphysical. The only meaningful point of scientific continuity between historical and contemporary astrology is not about finding new physical mechanisms for how it ‘works’ but about asking whether the psychological motivations for such convictions – most probably, a need to find meaning in and control of one’s life – remain the same.

But there’s probably more too. Astrology endures, according to social critic Theodore Roszak, because of the inspirational appeal of its rich, venerable imagery. “It has poetry and philosophy built into it”, he says. He’s right about that. All it lacks is veracity.

References

1. Mandel, Y. et al., Ophthalmology doi:10.1016/j.ophtha.2007.04.040 (2008).
2. Kahn, H. S. et al., Am. J. Hum. Biol. 20, 59-65 (2008).
3. Davis, G. H. et al. Anim. Reprod. Sci. 46, 297-303 (1997).
4. Jenkinson, C. M. C. et al. New Zeal. J. Agric. Res. 38, 337-345 (1995).

Medieval instrument suggests astronomical knowledge was widespread
[Here’s a story I picked up on a recent visit to the wonderful Museum of the History of Science in Oxford. It is published in Nature today. To my great embarrassment and dismay, while I was at Merton College many years ago, I knew of neither the museum nor of Merton’s ‘Chaucerian’ astrolabe mentioned below. But I was just a nipper then.]

UK museum seeks cash to keep a rare miniature astrolabe in public hands.

The fate of a fourteenth-century pocket calculator is hanging in the balance, while the British Museum in London attempts to raise the £350,000 needed to acquire this extremely rare archaeological finding before the deferral of an export licence expires, releasing it to private sale.

The device, a brass astrolabe quadrant that can tell the time from the position of the sun, calculate the heights of tall objects, and work out the date of Easter, opens a new window on the mathematical and astronomical literacy of the Middle Ages, experts say.

Most surviving astrolabes are larger and more elaborate, and include other functions such as astrological calculations. Their use tended to be highly specialized, confined mostly to academic settings.

But the new quadrant is a simple, everyday item – the kind of thing a cleric or a merchant would have carried with them for convenient time-keeping. All the same, says Jim Bennett, director of the Museum of the History of Science in Oxford, “you had to know some astronomy to work one of these devices.” Bennett was an expert witness in the hearings that deferred a private sale. He says the device suggests that, at least within some parts of fourteenth-century society, “people had a closer astronomical awareness than we do now.”

Most intriguingly of all, the quadrant was found at Canterbury, and has been dated quite narrowly to about 1388, just before Geoffrey Chaucer began to write his Canterbury Tales. Chaucer was highly informed about astronomy and astrology, and in 1391 he wrote a treatise on the astrolabe that became the standard reference text for several centuries.

The Canterbury quadrant was found in 2005, when excavations revealed it beneath a series of clay floors on the site of an old inn called the House of Agnes, just outside the city walls on the main road to London. It had lain there for over 600 years. Conceivably it was lost at the inn by a merchant travelling to or from Canterbury, rather like Chaucer’s pilgrims.

The quadrant was initially put up for sale in 2007 by the auctioneers Bonhams, where it was expected to fetch £60,000-100,000. But subsequent dealings led to an agreed sale at a price of about £350,000 (neither dealer nor buyer has been publicly disclosed).

Because of the perceived cultural importance of the object, however, it was considered by the UK’s Reviewing Committee on the Export of Works of Art and Objects of Cultural Interest, which recommended to the government’s Culture Minister Margaret Hodge that granting of an export licence should be delayed until June 2008, giving time for the British Museum to try to buy the instrument for its forthcoming Medieval Gallery. Such decisions are usually applied to works of fine art, not to scientific items, Bennett says.

The quadrant was clearly made for use in England – it works only within a certain range of latitudes. It has design features that would appeal to medieval gadget freaks, Bennett says, such as a moveable eagle that indicates the date of Easter. “Relatively everyday pieces like this don’t usually survive”, he adds. A quadrant astrolabes kept in the library of Merton College in Oxford, one of the few other such instruments known, is considerably more elaborate and geared for academic use.

The existence of this simple, practical device sheds new light on Chaucer’s treatise. He dedicated it to his son – a gesture that has left scholars wondering whether this was just a literary affectation, since it seemed a little hard to believe that Chaucer could have expected a young person to appreciate an astrolabe’s uses. But the Canterbury quadrant “supports the idea that Chaucer could write such a treatise at a popular level”, says Bennett. “It suggests that this kind of knowledge wasn’t too arcane or academic.”

Science made simple

Starting, I think, on 14 April, the UK's Independent newspaper is issuing a series of booklets called 'Science Made Simple', based on extracts from the Very Short Introductions series published by Oxford University Press. As you might guess, I am offering this little advert for them because some are written by me. They've chosen extracts from my volumes on molecules and the elements (originally published as Stories of the Invisible (2001) and The Ingredients (2002)) for three of the booklets, on 15, 16 and 20 April. Of course, the others will be splendid too, ranging from Earth sciences to cosmology to the brain.