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Featuring: Light More to sunlight than meets the eye Myopia a light problem Ball lightning strike Water quality affects light Lasers sense Earth’s rotation Twinkle Twinkle little star Celebrating Darwin Biology education: complex or complicated change? Matauranga Maori refutes Pooper And more...

Number 122

ISSN 0110-7801


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Mailing Address: NZASE PO Box 1254 Nelson 7040 Tel: 03 546 6022 Fax: 03 546 6020 email:nzase@confer.co.nz

Editorial 2 From the president 3

contents

contents Celebrating Darwin Darwin’s dangerous ideas... 4

Editorial Address: lyn.nikoloff@xtra.co.nz Editorial Board: Barbara Benson, Suzanne Boniface, Beverley Cooper, Mavis Haigh, Rosemary Hipkins, Chris Joyce. Journal Staff: Editor: Lyn Nikoloff Sub editor: Teresa Connor Cover Design and Typesetting: Pip’s Pre-Press Services, Palmerston North Printing: K&M Print, Palmerston North Distribution: NZ Association of Science Educators NZASE Subscriptions (2010) The new subscription rates for 2010 will be available from October 2009. For further information contact: NZASE, PO Box 1254 , Nelson 7040 Email: nzase@confer.co.nz Advertising: Advertising rates are available on request from nzst@nzase.org.nz Deadlines for articles and advertising: Issue 123 - Air 20 December (publication date 1 March 2010) Issue 124 - Iron 20 April 2010 (publication date 1 June) Issue 125 - Nitrogen 20 August 2010 (publication date 1 October) NZST welcomes contributions for each journal but the Editor reserves the right to publish articles it receives. Please contact the Editor before submitting unsolicited articles: nzst@nzase. org.nz. Disclaimer: The New Zealand Science Teacher is the journal of the NZASE and aims to promote the teaching of science, and foster communication between teachers, scientists, consultants and other science educators. Opinions expressed in this publication are those of the various authors, and do not necessarily represent those of the Editor, Editorial Board or the NZASE. Websites referred to in this publication are not necessarily endorsed.

Feature: Light Impacts of light on myopia 7 Ball lightning – an easy explanation? 10 Light in waters 12 Light and UV radiation 17 Shining light on food 21 When is shorter better? 24 Rotation sensing with lasers 27 Twinkle twinkle little star 30 Regular features Education research: Complex or complicated change? 33 Human ethics guidelines for schools 35 History Philosophy of Science: Matauranga Maori refutes Popper 38 Resources: Just for starters... 23 National Library 42 Alignment update 41 Ask-a-scientist 26, 37, 42 Book review 45 Subject Associations: Biology 43 Chemistry 44 Physics 45 Primary Science 46 Science/PEB 47 Technicians 48

‘A new day is dawning’ – sunrise over Lake Wakatipu, Queenstown. In this image I like the contrast of the turquoise-blue water with the soft pale lemon horizon symbolising darkness giving way to light. Photograph courtesy of Lyn Nikoloff

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rainbows with pots of gold As a child I would chase after rainbows, hoping to find the illusive pot of gold buried by a leprechaun – alas, despite my frantic chasing there was no pot of gold or pesky leprechaun. Yet even now I still find rainbows a very wondrous thing as they define the boundary between stormy and fine weather. Science too is like a rainbow because it comes in a variety of hues, and this issue, which has the theme of light, contains a plethora of colour. Do you know what causes ball lightning? John Abrahamson’s (University of Canterbury) explains this and more (page 10). Emily Brunsden (University of Canterbury) has written an engaging article about how starlight is enabling us to better understand the Universe (page 30). And as we sit on the cusp of celebrating fifty years since the first demonstration of a working laser, Jon-Paul Wells, Robert Hurst and Geoffrey Stedman (University of Canterbury) explain how ring lasers are being used to sense the Earth’s rotation (page 27) and Cather Simpson shares with readers some exciting developments at the Photon Factory (page 24). Did you know that light transmission in water is affected by the water’s constituents? Research by Rob Davies-Colley (NIWA) is being used to better assess water quality (page 12). Richard McKenzie (NIWA) highlights the importance of better understanding the relationship between light and UV intensities because UV exposure provides both health benefits and risks (page 17). Light is also being used to assess food quality and as Steve Flint (Massey University) also notes in the analysis and treatment of food (page 21). Did you know that in some parts of Asia 70% of children need glasses? Research carried out by John Phillips, Simon Backhouse and Andrew Collins (University of Auckland) shows there is a strong link between lack of exposure to daylight and myopia (page 7). Also in this issue: Andy Pratt (University of Canterbury) reminds us that even after 150 years since Darwin published Origin of the Species his ideas are still transforming our lives (page 4); and we feature the final of the Matauranga Maori and Science series, written by Philip Catton (University of Canterbury - page 38). What might biology learn from disciplinary biology? Rosemary Hipkins (NZCER) answers this complex question in an uncomplicated way (page 33). And have you ever thought about human ethics when students are carrying out research? Rosemary de Luca and Bev Cooper (University of Waikato) describe the background to new human ethics guidelines (page 35). Along with our regular articles and standing committee reports, this issue of the NZST shines the light on some of the wonders of science.

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Thanks to... I would like acknowledge and thank all the people who work tirelessly to ensure that the NZST continues to bring science and education research to the attention of our readers. First, I would like to acknowledge the support, encouragement, passion and professionalism of the team who help to bring the NZST to print: Teresa Connor – proofreading; Philippa Proctor – typesetting; and Raymond Jones – K & M Print. Together they ensure that the NZST is produced to the highest standard possible. Thanks team. I would like to thank Conference and Events, especially Janet and Rose, who are a pleasure to work with. I would also like to acknowledge the ongoing support from our advertisers including Di Hartwell at the Biotechnology Learning Hub, the University of Auckland – careers in science posters, and in this issue: Cambridge University Press and G & A Sales. There are some regular contributors whom I would also like to acknowledge: Philip Catton who continues to write our regular History Philosophy of Science articles; Melva Jones – National Library; and all the Chairs of the NZASE Standing committees. I am indebted to the work and support of Rose Hipkins, a member of the Editorial Board, who is a vital part of the NZST team. I extend a big thank you and fond farewell, to Jenny Pollock – President of the NZASE (2007-09). Jenny is an enthusiastic supporter of the NZST, and I have appreciated her ongoing support during the past two years and I wish her well in her future endeavours. The NZST relies on the goodwill of all its contributors, and I would like to acknowledge the incredible support the publication receives from both the science and education research communities. This support reflects the high regard these communities have for science educators. We extend a very grateful thank you to all the contributors in this issue. Now back to chasing rainbows – here at the NZST we don’t make you, our reader, chase after rainbows, because we have already done the chasing for you. All you have to do is open these pages to find pots of gold . . . enjoy! And I wish you all an enjoyable sun-smart summer vacation.

Kind regards Lyn Nikoloff Editor


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comes to hand in an attempt to improve communication with all science educators. We have made the decision to only email the newsletter and to post it online. We are looking at its content and role to see what improvements could be made. If you are not receiving an emailed newsletter, or any of these email notices, then contact our administrators: nzase@confer.co.nz. The NZASE, and in particular Primary Science, continue to have a close relationship with the Royal Society. We also have a good working relationship with the Ministry of Education through the Alignment process, the writing of resources for the new standards and the development of the Teaching and Learning Guidelines. With personnel changes in the Ministry and NZQA we have found that it is often our members who have the institutional knowledge of science subjects and we are often the first port of call for suggestions for people to work on various projects. As part of secession planning, we have encouraged new people to work alongside our older, more experienced members so that knowledge is passed on. During the past two years we have come a long way, but there is still much more to do. We would now like to hear from you about how NZASE can best serve its members. And we need to decide how much we can realistically manage. By the time you read this, we will have debated this issue thoroughly at the AGM. Finally, I have many people to thank. Thanks to Carolyn Haslam for being such an effective treasurer working at times under very difficult circumstances; Bev Cooper for ably guiding us through the first few months without Peter; and Beverley Booker for doing much of our administration until retirement. Thanks to Jessie McKenzie of the Royal Society, who helped us during our transition phase when we moved our administration to Conference and Events, plus for being a listening ear and, at times, a shoulder to cry on when things got tough. Thanks also to Richard Meylan – I enjoyed our long and wide ranging conversations which have ensured that the NZASE still retains a strong relationship with the Royal Society. A big thanks to all the people at Conferences and Events – you are a great team to work with. And to Richard Meylan and Kerry Packer – thanks for stepping in to help with moving the Archives. Also to Lyn Nikoloff – keep up the good work with the NZST. Finally, a special thanks to Lindsey Connor, who has been a great junior Vice President to work with and will make a very effective president. The NZASE is in good hands. Jenny Pollock President NZASE

fromthepresident

Congratulations to the organisers of Physikos, ChemEd and Biolive Conferences which were all very successful conferences held during the July holidays. And good luck to Constanz who will hold their conference during the October holidays. Organisation is also well under way for SciCon 2010, which will run from the 4th to 7th July in Nelson and that many of you will be able to join us and that Nelson turns on its famously sunny winter weather for you all. This is the last time that I will be writing to you as President of the NZASE. After the AGM in September, Lindsey Connor became President and I will be the senior Vice President. Next year we will need a new junior vice president and a new treasurer. Some of you may like to consider these jobs. When I became President, I inevitably had an idea of what I would like to achieve and the size of the job. However, my presidency turned out to be much more difficult than I could ever have anticipated. The death of Peter Spratt, the first Executive Officer of the NZASE, was untimely and devastating. For most people Peter was NZASE, and I had certainly looked forward to working with and learning from him. His death led to the loss of much of our history and institutional knowledge plus a vast network of contacts and resources. It quickly became obvious to the NZASE executive, a small voluntary group of people with very busy professional lives, that we could neither manage all the roles that Peter had held, nor carry on with his numerous activities. Therefore, we had to decide what we could realistically cope with. The Royal Society, which had previously helped us, were no longer able to continue in that role, and so we contracted Conferences and Events as our administrators; and this relationship is working very well. Currently they are streamlining much of our work and can be contacted at nzase@confer.co.nz. Also our website has been updated (www.nzase.co.nz). Previously our archives were stored at the Royal Society, and for a short time (thanks to Kerry Packer) at the Correspondence School, and they are now, rather forlornly, in a lock up in Nelson where they are dry and safe and easily accessible. So after a lot of hard work, and with the day to day running of NZASE in good hands, we have finally been able to concentrate on our core business. We are now having teleconferences once a term with the regional associations and standing committees, and it’s great to be back in contact with them. We have a large database and are sending out emails with important information as it

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Darwin’s dangerous ideas and the evolution of their impact The bicentenary of Charles Darwin’s birth and the 150th anniversary of the publication of The Origin of Species are rightly celebrated this year because of the pre-eminence of Darwin’s Theory of natural selection in contemporary biology and beyond, writes Andy Pratt of the Department of Chemistry at the University of Canterbury. Darwin’s fame as the greatest scientist of his generation was such that he was buried in Westminster Abbey alongside the previous comparable giant of science, Sir Isaac Newton. What perhaps goes unrecognised is that in 1882, even amongst scientists, not only were many of Darwin’s ideas contentious, but there were few who believed in natural selection. Indeed, more than a further half a century would elapse before Darwin’s ideas emerged as the overarching theoretical framework of the biological sciences. Given the reticence to embrace natural selection at the time, why was Darwin lauded over other scientists, including preceding evolutionists? Why does Darwin’s fame extend beyond that of the co-discoverer of natural selection: Alfred Russel Wallace? Why has Darwinian natural selection become the founding core of biology? And why did it take nearly a century to assume this role? What are the ongoing challenges to Darwinian Theory? And why has evolutionary theory spread its tentacles to disciplines well beyond science? One way to address some of the many questions about Darwin’s ideas and their impact on science is to place them in an historical context. In so doing, this article follows on from a previous article in this journal (issue 115) by Peter Lineham (Massey University) that gave an historical overview of Darwin’s life. Here, we will touch on the steps that Darwin took in formulating his evolutionary theory and tackle both its key insights and limited impact in its early years. Finally, we will consider the factors affecting the widespread adoption of this theory in the twentieth century – in biology and beyond.

The evolution of Darwin’s thinking There are varied factors underlying the convoluted history of the adoption of evolutionary theory. Of course, the implications about the origins and nature of humankind have been problematic to many people, from Darwin’s wife, Emma, to many religious believers in the modern era. But what about scientists? Why did many of Darwin’s peers embrace evolution but not the theory of natural selection? A major factor was that The Origin of Species brings together several strands of thought – as we shall see. One way to appreciate the complexity of Darwin’s theorizing is to revisit the stepwise progress of his intellectual breakthroughs. The recent accessibility of Darwin’s notebooks has provided insights into the evolution of Darwin’s astonishing thought processes. Darwin’s conversion to belief in the veracity of evolution came suddenly in March 1837, in the year after his return from the voyage of the Beagle. The defining moment occurred when the ornithologist, John Gould, who was working on Darwin’s Galapagos bird collections, identified birds from different islands as different species with

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relatives on the South American mainland. Darwin suddenly saw everything in a new light; he could now understand why the existing fauna of South America bore a striking resemblance to fossils that he had found there. Having embraced evolution, Darwin worked intensively to accumulate evidence for evolution and to understand the mechanism by which it occurred. In July 1837, he started a clandestine transmutation notebook, ‘B’, headed ‘Zoonomia’ (in honour of a book of evolutionary speculations of his grandfather, Erasmus Darwin). Simple, insightful questions and possible responses abound in the text: ‘Why is life short and sexual reproduction so important?’ Because sex can produce variants, and quickly spread them through a population – to enable offspring to deal with changing environmental conditions. Darwin’s notebooks show him wrestling with the implications of transmutations. He agonises about contradictory evidence on the role of geographical isolation and the problems of transporting species to new habitats – what species could survive a sea crossing? This combination of profound questions of childlike simplicity, which he addressed with fastidious attention to detail, is at the heart of Darwin’s towering scientific achievements. Having grasped the significance of biological diversity arising by descent from common ancestors, Darwin develops his famous tree metaphor which provides the only illustration in The Origin of Species. Then begins the steady progress to build his second main idea – the mechanism by which evolution delivers its creative magic. By February 1838, Darwin was developing his ideas about diversifying traits by forging an analogy between domestic breeding and speciation. He actively discusses domestic breeding with a wide range of experts and makes notes about breeders’ ‘selecting traits’. Darwin surmounts the final major intellectual hurdle in September 1838, when he (re)reads Malthus’ essay on population. Darwin was struck by Malthus’ statistics: ‘The power of population is indefinitely greater than the power in the earth to produce subsistence for man. Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio.’ As Darwin wrote in his autobiography: ‘There is a war in nature, a struggle for existence … it at once struck me that under these circumstances favourable variations would tend to be preserved and unfavourable ones to be destroyed. Here then I had at last got a theory by which to work.’ The theory of natural selection was born. In June 1842 Darwin fleshed out a 35 page sketch of his evolutionary ideas which he redrafted into a 231 page essay in 1844. Fearing the backlash that would accompany publication, he then embarked on an intensive study of barnacles that occupied most of the next decade! It is only when Darwin’s hand is called by Wallace’s independent discovery of the theory of natural selection that his evolutionary ideas are finally put into print.

Breaking free of the shackles: Darwin’s theoretical breakthroughs Darwin understands the challenge of his ideas to anthropocentric visions of the world, especially religious


The impact of Darwinian Theory at the time of publication Contrary to Darwin’s own view, The Origin of Species was not ‘one long argument’ promulgating the theory of natural selection. Instead, it was a network of arguments weaving a web of evolutionary theory. It is possible to tease out (at least!) six elements: (i) evolution is a fact; (ii) evolution is a gradual process; (iii) evolution is based on descent from

common ancestors with modifications; (iv) evolution is the source of speciation; (v) the mechanism of evolution is natural selection; and (vi) natural selection operates through differential survival. Through time, scientists, and others, have accepted and challenged these different elements. For example, some scientists, saltationists, have challenged (ii) in favour of sudden changes from generation to generation; amongst these, the early geneticists, challenged (ii) and (v) – favouring discontinuous evolutionary change driven by mutation (as we shall see below). The fact that it was possible to accept some of Darwin’s tenets and not others led to a heterogeneous reception of Darwin’s ideas. Furthermore, individuals have taken it upon themselves to take selected bits of Darwinian evolutionary theory and use them to their own ends, whilst appropriating the Darwinian brand as their own. The introduction of Spencer’s term ‘Survival of the Fittest’ into later editions of The Origin has much to answer for in terms of the misappropriation of evolutionary ideas! As we saw earlier, Darwin developed his ideas about the ‘Tree of Life’, the theory of common descent, prior to uncovering the mechanism of evolution – the theory of natural selection. Many of Darwin’s scientific contemporaries were won over to the theory of common descent based on the wealth of detailed evidence that the ever-fastidious Darwin presents in its favour. It is this depth of evidence for evolution, presented in a popular and widely read text that was the primary reason for Darwin’s preeminence as a scientist in his own lifetime (and a reason for the differential reverence afforded Darwin over Wallace). Some areas of biology were transformed by the insights afforded by the theory of common descent. For example, the ability of this theory to explain the geographical distribution of species that cannot be understood from a creationist perspective makes The Origin of Species a founding document of biogeography. It also transforms morphology. Questions like “why is a whale’s fin like a bat’s wing?” become answerable on the basis that such structures are homologous remnants of a common ancestor (as opposed to ‘archetypes’ of idealistic morphology). For many scientists the study of morphology now shifts almost entirely to phylogeny. However, even here, Darwin’s victory is not complete. For example, in the preface to one of the most influential books on morphology, On Growth and Form, published in 1917 d’Arcy Thompson explicitly rejects Darwinian natural selection and ignores Darwinian explanations of adaptation. When we move from the theory of common descent to the theory of natural selection the situation gets worse. In contrast to the detailed direct evidence evinced for the former theory, Darwin’s reasoning for natural selection is primarily analogical; much is made of analogies with the domestic breeding of animals and nowhere does he ever directly address ‘the origin of species’! Consequently, many scientists, including many of Darwin’s main supporters, were not won over by the theory of natural selection. For much of the nineteenth century, large areas of biology were developing as experimental sciences, closer to the model of physical sciences. For these areas, especially, the insights that Darwin provided into the diversity of life in the wild were not appreciated, or even seen as relevant.

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beliefs, and relishes the new perspectives. As time progresses, his notebook views become more out-spoken on this issue. ‘What a magnificent view one can take of the world … The vast sweep of law controlled the climate, the landscape, the changes in animals and plants with everything synchronised by certain laws of harmony.’ He found the new perspective to be ‘far grander’ than the idea of ‘The Almighty – personally creating a long succession of vile Molluscous animals – How beneath the dignity of him.’ In this way, Darwin progresses to an out-and-out materialist view of the world and his theories reflect that quest. Darwin was a master of the complex interface between observation, theory and experiment and recognised the interdependent nature of these strands of scientific endeavour. In a letter to Wallace in 1857, that was shortly to come back to bite him, he encouraged Wallace to develop his theorizing about natural history for ‘without speculating there is no good and original observation.’ So what were the theoretical shackles that Darwin cast aside? Two types of pre-existing scientific theory acted as millstones to the development of a mature understanding of biology. First, the exemplary scientific theories were those of Newton – universal physical laws that predict precise outcomes in particular circumstances. Such universal, deterministic laws cannot form the basis of complex biological systems. As Darwin put it in Chapter 3 of The Origin of Species: ‘Throw up a handful of feathers, and all must fall to the ground according to definite laws; but how simple is this problem compared to the action and reaction of the innumerable plants and animals which have determined, in the course of centuries, the proportional numbers and kinds of trees now growing on the old Indian ruins!’ The theory of natural selection provided an alternative type of scientific theory that is appropriate for dealing with complex systems. This did not fit well with scientists, such as Sir John Hershel, who railed against Darwin’s “Law of the higgledy-piggledy”. Prior to Darwin, the prevailing view of biology derived from Aristotle, who saw the properties of living creatures in the context of a ‘Great Chain of Being’ of amoeba to man, a hierarchy of increasing perfection. The essential characteristics of species were designed according to their purposes. This hierarchy was accepted even by early evolutionists, such as Lamarck, who saw evolution in the context of scaling a ladder of life. It had long been realised that death can weed out errant individuals. However, such processes were seen as simply removing deviations from an archetype. Darwin supplanted these ideas by the insight that these features of apparent design are in reality the outcome of an historical process – evolution by natural selection. It is the creative capacity of natural selection acting on populations of related, but distinct, individuals that distinguishes the ideas of Darwin and Wallace from those of other biologists. Darwin and Wallace saw the power of selection to select and perpetuate modified organisms, better adapted to particular circumstances. Traditional vertical views of a graded ladder of life are discarded in favour of an understanding of biological diversity founded on population-based thinking.

Phoenix from the ashes: the rise and rise of natural selection It is the integrated theory of natural selection that is Darwin’s crowning glory in the eyes of contemporary biology; but it was a tortuous trail for it to assume its New Zealand Association of Science Educators




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science rightful status and for Darwin’s subtle insights to be fully teacher appreciated. One obvious limitation in Darwin’s writing is

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the absence of any mechanism of inheritance. The onset of the twentieth century saw the emergence of genetics, with the rediscovery of Mendel’s work. However, far from adopting Darwin’s ideas of natural selection, the geneticists set themselves up in opposition. They developed theories of mutation that they saw as countering Darwin’s gradualist evolutionary ideas. They saw mutational pressure, rather than natural selection, as the driving force for evolutionary change. This discord with Darwinian Theory is partly due to the disconnect between the reductionist nature of the mutationist’s laboratory science and the natural history world of wild populations that sparked Darwin’s original insights. Key to the eventual triumph of natural selection was a shift to population-based thinking. It was only when the statistical nature of natural selection was recognised and put on a sound footing in the first third of the twentieth century (with the development of HardyWeinberg equilibrium theory and of the working out of the statistics of population genetics by RA Fisher and others) that a rapprochement of genetics and natural selection was possible. The resulting overarching theory of natural selection, the so-called evolutionary synthesis, was fleshed out in the decade from 1937, inaugurated by the highly influential book, Genetics and the Origin of Species, written by Theodore Dobzhansky. With the universal adoption of the evolutionary synthesis, the post World War II era has seen the flowering of the theory of natural selection in all areas of biology; phylogenetics has become an ever-present backdrop. Not only are macroscopic features of organisms organised on an evolutionary basis, but this approach has now been extended to microstructures – first to cell structures and then, with an increased understanding of protein and DNA structures, to macromolecules. Sequences of proteins and now whole genomes have been produced that exquisitely mirror the phylogenetic trees drawn up from macrostructural homologies – these convergences, uncovered in the genomic world of the twenty-first century, are overwhelmingly compelling evidence of the veracity of Darwin’s Theory of natural selection. With the triumph of the core elements of the theory of natural selection, scientists have discovered rich veins of treasure in the subtle details of Darwin’s theorizing. For example, Darwin’s ideas about how mate choice can

influence evolution, the theory of sexual selection, that was introduced briefly in The Origin of Species, is now a major driving force in research on animal behaviour. Likewise, the emergence of ecology as a central biological discipline is rooted firmly in Darwinian insights. As scientists explore all the ramifications of the theory of natural selection, they now battle to resolve remaining conundrums. How much detail can we extract about the basis of variation in natural populations? And of the nature of the selection processes that mould evolution – not just of organisms, but of ecosystems? If, as Darwin surmised (and as seems clear from proliferating evidence) all life on Earth has descended from a common ancestor, then how did that ancestor arise? Was there evolution before cells? In short, what were the steps that led to the first cells and at what point does natural selection start to mould complex organisms?

Evolutionary theory in other sciences Darwin’s tree of life metaphor has spread its branches throughout the ecosystem of science and beyond. As Newton’s physical theories held sway in their scientific domain, Darwin’s population-based theory is an exemplar for the analysis of complex systems and for understanding the emergence of order. Some areas that have grasped the Darwinian nettle, such as the evolutionary analysis of language, would not have surprised him. It is the creative power of natural selection that also holds promise as a source of scientific and technological innovation. Darwin’s insights have permeated fields as diverse as computer programing, the generation of new pharmaceuticals, psychology, and economics. Darwin is not going away in a hurry. For further information contact: andy.pratt@canterbury.ac.nz Bibliography: reading Darwin and other treats. It is to our lasting benefit that Darwin wrote his ideas in accessible popular science books. It is marvellous that everyone can freely access Darwin’s great books on the Web. Janet Browne has written an historical overview of The Origin of Species (Darwin’s Origin of Species: a biography) that complements her extensive two-volume biography of (Darwin: Voyaging and Darwin: The Power of Place); together with the earlier biography by Desmond and Moore (Darwin) are key resources for understanding Darwin’s work, and have underpinned much of this article; as have the writings of Ernst Mayr (The Growth of Biological Thought), one of the founders of the evolutionary synthesis.

continued from page 9 References Gwiazda, J. (2009). Treatment options for Myopia. Optometry and Vision Science. Mandel, Y., Grotto, I., et al. (2008). Season of birth, natural light, and myopia. Ophthalmology, 115(4), 686-692. Phillips, J. R. (2005). Monovision slows juvenile myopia progression unilaterally. British Journal of Ophthalmology, 89(9):,1196-1200.

Rose, K. A., Morgan, I. G., et al. (2008). Outdoor activity reduces the prevalence of myopia in children. Ophthalmology, 115(8), 1279-85. Wildsoet, C. F. (1997). Active emmetropization – evidence for its existence and ramifications for clinical practice. Ophthalmic & Physiological Optics, 17(4), 279-290.

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A worldwide epidemic of myopia is developing among children, but the cause is unknown? While the refractive development of the eye is controlled by an optically driven process within the eye, outdoor light exposure may provide some protection along with a better understanding of the influence that the season of birth (photoperiod at birth) has on refractive error in adulthood, as Drs John Phillips, Simon Backhouse, and Andrew Collins, Department of Optometry and Vision Science, The University of Auckland, explain: Many more children suffer from myopia (short-sight) than was the case 100 years ago; in parts of Asia, over 70% of children are now myopic and will require some form of vision correction for life. Although genetics plays a role in determining whether a child will develop a refractive error like myopia, the environment – and in particular the light falling on the retina – is equally important. Although myopia was identified more than 2000 years ago by Aristotle (384-321 BC), there is no cure, and its prevalence is increasing. The prevalence in New Zealand is estimated at about 20%. The symptoms of myopia include blurred distance vision, while near objects are seen clearly. What causes myopia? Why does it often get worse (progress) but never get better? Does wearing spectacles make it worse? Can myopia progression be inhibited? Providing evidencebased answers to such questions is difficult. A vast literature on myopia has built up over the years and distinguishing between myopia-myth and real evidence poses a significant challenge. An eye with myopia has grown abnormally large (long). Because the myopic eye is too long, the retina is located behind the focal plane of the optics (Figure 1b), with the result that distant objects are seen as blurred. In contrast, an eye with hyperopia (long-sight) is ‘too short’ (Figure 1c). It is only when the eye grows so that its length accurately matches the power of the optics that the eye has no refractive error and is said to be ‘emmetropic’. Most cases of myopia involve only a moderate enlargement of the eye, and good vision can be obtained by correcting the refractive error with spectacles or contact lenses. This ‘common’ or school myopia is an expensive inconvenience which can limit career and lifestyle choices. However, about 2% of the population suffer from ‘high’ myopia, in which the abnormal expansion of the eye is so great that the retina and its blood supply become stretched and can be damaged sufficiently to threaten vision (Figure 2). In fact, the abnormal eye enlargement in high myopia is a

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Figure 2: A fundus photograph (looking into the eye through the pupil) of the back of an eye with high myopia. The abnormal enlargement of the eye has resulted in stretching of the retinal layers and blood vessels which are thinner and straighter than normal. The resultant retinal atrophy, clearly visible to the left of the optic nerve head but also present elsewhere, leads to permanent reduction of vision. significant cause of registered blindness. An understanding of how normal eye growth is controlled makes an obvious starting point for understanding what goes wrong in eyes which develop myopia.

An optically driven process controls eye growth Although the eyes of humans and animals grow in size from birth to adulthood, they normally remain in focus as they grow. For this to happen, the increase in the size of the eye must perfectly match the position of the focal plane of the optical components. The focal plane moves progressively back because the surfaces of the cornea and crystalline lens become flatter as they grow in size and so their optical power decreases. One question is whether this match between the power of the optics and the size of the eye results from independent but co-ordinated growth of the different components, or whether an active growth control (feedback) system ensures that the retina is located in the focal plane of the optics to achieve emmetropia (Figure 1). Studies of the refractive development of animal eyes have provided a breakthrough in understanding the mechanisms controlling development of the human eye. These studies include raising young animals (e.g. chicks) wearing a small spectacle lens over one eye, so as to create optical defocus at the retina (Figure 3). Remarkably, within a few minutes, in the chick a compensatory response within the eye is initiated which, after several days, results in a change in size of the vitreous chamber of the eye, so as to compensate for the imposed retinal defocus.

Figure 1: In an emmetropic eye (a) the retina is located in the focal plane of the eye’s optics (cornea and lens) when accommodation is relaxed. Refractive error results from a mismatch between refractive power and axial length, where the eye is ‘too long’ in myopia (b) and is ‘too short’ in hyperopia (c).

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Figure 3: Inducing myopia with lens wear. A young chick is raised wearing a small spectacle lens over one eye (experimental eye) while the other eye (control eye) views the world normally. When the lens is initially worn (top left), the eye is out of focus with the lens in place. After a few days, both eyes have naturally grown larger. However, the lens-wearing eye has grown longer (a) than the control eye so as to compensate for the imposed defocus with the lens in place. If the lens is now removed the eye is too long and is myopic. The change in size of the vitreous chamber is brought about by a change in the growth rate of the sclera (the wall of the eye). In the chick, compensation is complete in a few days. This compensatory growth response is bidirectional. If a minus-powered (-ve) defocusing lens is worn (which causes the optical image to move behind the retina (as shown in Figure 3), then the vitreous chamber grows faster than normal to move the retina backwards by the amount necessary to bring the eye back into focus (i.e. achieve emmetropia with the lens in place). In contrast, wearing a positively powered (+ve) lens (which moves the image forwards in front of the retina – not shown), results in a slowing of the normal growth of the vitreous chamber. In this case compensation is achieved because the refractive surfaces of the cornea and lens become flatter (and consequently less optically powerful) as they grow, and the image they create naturally moves progressively back until the image is focussed on the retina. Then the vitreous growth commences again to maintain emmetropia. This optically driven ‘emmetropisation’ process has been demonstrated in several animal species, from fish to monkeys. Animals raised wearing either a +ve or a –ve powered lens thus develop either a smaller or larger eye than normal. Consequently, when the lens is removed, the treated eye is out of focus; animals which have worn a +ve lens are hyperopic and those raised with a –ve lens are myopic in the treated eye. If the animals are still developing when the lenses are removed, the animals recover from the induced refractive error by virtue of the emmetropisation process. Surprisingly, emmetropisation is a within-eye local process. Retinal defocus acts to locally influence expansion of the sclera by a retina-to-sclera signal and emmetropisation can still be demonstrated even after the eye has been isolated from the brain by section of the optic nerve (Wildsoet, 1997).

Nearwork and myopia The association between the development of myopia and the performance of near tasks has been recognised since the seventeenth century. Because the prevalence of myopia is now so high in some societies, there is increased interest in determining the environmental factors which trigger school myopia. The animal studies described above provide an explanation for why extended periods of nearwork may result in enlargement of the human eye and the development of myopia. Long periods of reading require long periods of accommodation (focussing of the eye onto a near  New Zealand Association of Science Educators

Figure 4: Lag of accommodation. (a) An eye fully accommodating for the target distance in order to bring a clear image of the near target onto the retina. The ciliary muscle (black triangles) has contracted and the lens has increased its optical power (the surfaces are more rounded). (b) An eye with lag of accommodation: the image of the near target is located behind the retina. The ciliary muscle is less contracted (grey triangles) and the lens has less optical power. target). Accommodation requires continued muscular effort (contraction of the ciliary muscle within the eye) to maintain the increased power of the crystalline lens necessary for reading. It has been suggested that long periods of close work, like reading, are associated with a ‘lag’ of accommodation in which the amount of accommodation exerted is insufficient to bring the image of the page clearly onto the retina (Figure 4). With a lag of accommodation, the image is located behind the retina. The animal studies outlined above would suggest that under these circumstances, when the image is focussed behind the retina in a developing eye, the eye will elongate and become myopic as shown in Figure 3.

Myopia Therapies There are currently no widely-used therapies for preventing the development of myopia or slowing its progression in children. While there is evidence for the control of myopia progression by optical means (Phillips 2005), attempts to reduce accommodative lag by prescribing bifocal or progressive-addition spectacles to children, or by undercorrecting their myopia, seem to be ineffective in most cases (Gwiazda 2009). Both animal and human studies have demonstrated that atropine eye-drops prevent abnormal eye elongation and the progression of myopia, but several factors have limited their use in practice. The well known pupil-dilating action of atropine (from the plant Atropa belladonna) is one of its undesirable side effects because of the extreme glare experienced when out of doors. Atropine also paralyses the ciliary muscle of the eye making changes in the eye’s focus, e.g. to view near objects, impossible. Atropine appears to inhibit myopia by some unknown action in the back of the eye, either on the retina, choroid or sclera. Because myopia typically develops over several years, atropine must be used for very long periods if it is to be effective and the long-term toxicity of atropine on the ocular tissues is unknown. Moreover, once atropine is discontinued the abnormal elongation of the eye recommences. These limitations have severely restricted the use of atropine eye-drops as a myopia therapy.

Protective effect of outdoor activity Recent research has found that outdoor activity, and by association light, may be protective against myopia development in children. The remainder of this article outlines the role that these factors may play in refractive development. The circadian rhythm, consisting of a cycling between periods of high and low activity, is a key feature of all living organisms. The retina not only contains classical photoreceptors but also intrinsically photo-responsive retinal ganglion cells (ipRGC) that are not involved in vision. The ipRGC send signals to the suprachiasmatic nuclei (SCN) in the brain which contain the mammalian internal clock. The main role of the SCN is the regulation of the production of melatonin by the pineal gland. Stimulation of the ipRGC


Figure 5: Light levels sampled every 10 seconds for one week. (a) Readings from a stationary sensor badge located outdoors. (b) Typical readings from another sensor badge worn by a University student during the same period. The amount of light experienced by this student was a small fraction of the potentially available amount. Katherine Rose and her colleagues conducting the Sydney Myopia Study (Rose, Morgan et al. ,2008) have shown that children who spend greater time outdoors, coupled with shorter time spent doing nearwork, have less myopia than children who spend longer time doing nearwork and less time outdoors. Surprisingly, time spent doing nearwork itself was found to be a poor predictor of myopia development. Children doing equal amounts of nearwork had differing risks of developing myopia depending on the time they spent outdoors. While this represents a correlation and not causation, it has been hypothesised that light received while outside may mediate lower levels of myopia development. Preliminary investigations from our laboratory show that university students do indeed receive very little of the total available light on a daily basis (Figure 5) and we are currently investigating light exposure levels in school-aged children. Combining the experimental studies

in animals with the human light exposure data suggests that low light exposure could result in higher melatonin levels and lower dopamine levels, which may increase susceptibility to the development of myopia.

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Season of birth and myopia A further recent finding is that season of birth appears to be correlated with refractive development, introducing the intriguing possibility that both maternal and immediate post-natal light exposure patterns may influence future refractive development (Mandel, Grotto et al. 2008). Children born in summer or autumn are more likely to develop myopia than those born in winter or spring. Again, light may be the key regulator here, as maternal melatonin is postulated to control the foetal circadian rhythm. It may be that our expected level of light exposure, based on season of birth, is programmed in utero during gestation or shortly after birth, and that if we do not receive that level of light exposure in later life, due to time spent indoors, then this results in a failure of the emmetropisation process. The question then is which aspects of light have most influence on refractive development? Two likely variables are the spectral composition (wavelength) of the light and its intensity (brightness). The spectral composition of light outdoors includes the visible part of the spectrum (380–760nm), but also contains large amounts of ultraviolet (UV) and infrared (IR). The UV and IR parts of the spectrum are largely absent from the light we experience indoors. Furthermore, dependant upon the light bulbs we are using, the visible spectrum indoors is shifted towards the blue (cool) or red (warm) end of the spectrum. Light intensity is also significantly different between indoors and outdoors. Outdoor light intensity is around 50,000 lux on a sunny, blue sky day, while indoors it is rarely more than 500 lux. The cumulative light exposure of someone who spends time outdoors is thus very much greater than someone who spends the same time indoors. Additionally, preliminary data show that it may be the change in light intensity (changing from dim light to bright light) that is most important for melatonin suppression/ dopamine stimulation and experimental myopia prevention. We are more likely to experience rapid changes in light intensity outdoors (e.g. walking from shade into full sun) than indoors, and this may be an important factor in preventing myopia from developing. The beneficial effect of light exposure on childhood myopia development may promise a simple and cost-effective option to help manage a disease of increasing prevalence. But such a proposal is not new and was suggested nearly a century ago by Fuchs: The following means are advised to put a stop to the extension of myopia in schools. First the excess of work which many scholars have at present to struggle with should be reduced to the proper standard. The way in which scholars are overtasked, both in school and at home, is prejudicial not only to the eyes, but also the child’s whole mental and physical development. Instruction ought not to begin too early (if possible not before the completion of the sixth year) and more time should be allotted to bodily exercise, especially in the open air, than has hitherto been the case. (Fuchs, Text-book of Ophthalmology, 1919). Are we finally assembling the evidence to back up Fuchs’ assertions? For further information contact John Phillips (j.phillips@auckland.ac.nz) or Simon Backhouse (s.backhouse@auckland.ac.nz)

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by light sends a signal to the SCN, blocking the SCN from signalling the pineal gland to produce melatonin. At night, there is no light-inhibition of the SCN, which signals the pineal gland to produce melatonin. Melatonin suppression is also dependant on light intensity, with brighter light leading to greater melatonin suppression. Melatonin may play a direct role in the control of eye growth: receptors for melatonin are found throughout the eye, and melatonin synthesis also occurs in some ocular tissues. Furthermore, melatonin has been shown to inhibit the release of dopamine. Dopamine, a neurotransmitter, has been shown to be decreased in eyes that are developing myopia, while introduction of a dopamine agonist to eyes with experimentally induced myopia stops the myopia from developing. Again, light exposure is a key factor, with dopamine production increasing in the light and decreasing in the dark. Melatonin and dopamine cycles are intrinsically linked by light exposure, and may play a role in the control of eye size and myopia development. Additionally, both melatonin and dopamine are produced within the eye, leading to the possibility of a local control loop which fits with the hypothesis that myopia development is controlled locally.

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ball lightning – an easy explanation? Networks of very small particles may make up ball lightning, as John Abrahamson, Chemical and Process Engineering, University of Canterbury, explains: Strange luminous objects There are luminous objects, that are occasionally seen with the naked eye, floating around in the air that are still very difficult to explain. Most of the difficulty comes from their long lifetime (seconds or even minutes). Some would lump these in with unidentified flying objects (UFOs) and further add that extraterrestrial intelligence was navigating them. Others have insisted that the objects are merely figments of the imagination, perhaps optical illusions. However, there is a hard core of objective reports with features repeating themselves – apparent properties in common – including not only visual but also sound, and even in some cases touch and smell when the observer has been close enough. Around 250 years ago, Benjamin Franklin used natural lightning to investigate what he considered to be ‘ball lightning’. He knew that ball lightning, an independently moving, long-lived radiant ball often of football size, could be made from a lightning strike, because a Russian contemporary was killed by such a ball, according to onlookers, after directing a lightning strike down to his laboratory. Franklin also tried (in vain) to reproduce the earlier (1757) creation of a small ball reported in England, when using a Van der Graaff high voltage generator. Arago, the French physicist well known for his work on light, stated in 1854 that this strange phenomenon of ball lightning was “one of the most inexplicable problems of physics today.”

A plethora of theories Have we made any progress in understanding ball lightning since? It has been especially difficult to explain the lifetime, the coherence of the ball (many have been seen bouncing against the ground and walls) and its method of release of energy. There have been many theories put forward over the last two centuries, from localised gaseous plasma with strangely stable properties, through focused electromagnetic waves by the Nobel prize winner Peter Kapitza, even to nuclear reactions and antimatter (Stenhoff, 1999). These theories have all been unsatisfactory in some respect. While they may have agreed with observation for one or even two properties (e.g. power radiated, stability), they either could not relate to, or were in conflict with other observed properties (especially the long lifetime and often a lack of apparent buoyancy). Of course, one of the theories has been that ball lightning does not exist, and is an optical illusion, perhaps from temporary blinding by normal lightning. This has become increasingly doubtful, since there are now careful compilations of sightings in all kinds of environments, numbering more than 5,000 in the scientific literature, including sightings by several people from different positions at the same time. Around twenty sightings have been made by practising scientists, some well known in scientific circles, and this number was doubled by sightings reported in a recent issue of the Phil. Trans. Royal Society (Abrahamson, 2002). This issue was solely devoted to ball lighting. In some of these reports there are graphic descriptions of rapidly moving or changing internal ball structure.

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Testing the existing theories in the lab Any valid theory of ball lightning must explain the natural phenomenon as reported by eyewitnesses. Also, the researcher has the capability to devise experiments in the lab to test out each theory. How does natural ball lightning compare with man-made luminous bodies? Plasma discharges exist for only for a few milliseconds after release of energy, and some of the most expensive physics projects have tried without success to extend this time. Also, hydrocarbon flames without a continuous feed of fuel do not last beyond a few milliseconds. Some ‘erosion discharges’ (pulsed electrical discharges that are forced through narrow channels, and remove some material of the channel wall) have produced small blobs luminous for about five seconds (Bychkov, 2002). Recently materials made up of very small particles (‘nanoparticles’ – otherwise called aerogels), thinly coated with iron metal have been made to glow by oxidation for many seconds. Such ‘pyrophoric’ materials are closely related to the stuff of fireworks.

Oxidising nanoparticles that glow The idea of oxidising metal particles was used in 2000 by myself and James Dinniss (2000) to model ball lightning made from silicon metal, using rates of oxidation documented for the process of making silicon transistors. The oxide layer that develops on the metal particles slows the rate by providing a barrier to the oxygen transport to the metal underneath. Otherwise the fine particles would burn so fast that an explosion would be experienced. Abrahamson and Dinniss postulated that the silicon was made by a lightning strike on soil, where at the high temperature the same process happened as is used to make the silicon of our electronic circuits. That is, the carbon chemically reduced the silicon oxides to silicon metal. The temperature was so high that the silicon was in vapour form, which then erupted out of the ground, cooled fast and condensed into nanoparticles. They found the suggested nanoparticles during laboratory attempts to copy lightning strikes on soil samples. Figure 1 shows a snapshot of the eruption from such a laboratory lightning strike (Abrahamson (2002)). In this paper, the metal oxidation

Figure 1: Plume rising from a 14 kV arc pulse onto soil. Ref: Philosophical Transactions of the Royal Society, London, volume A360, before page 36, 2002.


A huge luminous body Other particle theories also give indications of longer lifetimes. Vladimir Bychkov (2002) has also predicted lifetimes as long as those observed, from a theory of fractal tangles of polymer threads that charge electrically, and then discharge giving off light (as rubbed nylon can be seen to do at night). The charging process is unclear, and must equal the highest recorded charge density on a solid surface to achieve the required energies. It is interesting that Bychkov predicts much higher lifetimes for larger balls, which appears to agree with properties of a huge spherical stationary glow seen by two park rangers in outback Australia. The glow (one hesitates to call it a ball lightning!) had a diameter of around 100m, and a lifetime of around 5 minutes. They took a photograph, which is our Figure 2. It may well be made of the same stuff as the smaller mobile objects normally seen.

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idea was extended to other elements. Lightning also strikes metal structures, for example building fittings made of steel and aircraft made of aluminium alloy. The ball lightning is then expected to be of iron, or aluminium metal. Ball lightning has been seen many times within an aircraft cabin, moving down the aisle from front to back. Most observations of ball lightning appear to be in ‘thundery weather’, in accord with the above ideas of origin via lightning, but lightning is not the only electrical discharge occurring during a thunderstorm. Also corona discharges from sharply pointed objects is often seen (e.g. from power lines, even from leaves and branches of a tree). The metal particle oxidation model was found to predict correct luminosity, energy content, colour, and lifetime compared with average observed ball lightning, but still struggles to explain how it can penetrate through materials such as glass. The model relates the size of the ball to the size of the vortex ring (like a smoker’s puff ) that emerges from the discharge channel (lightning strikes on soil produce their own channel, which are called fulgurites by the geologists who dig them up). The vortex ring provides a low-turbulence region within it to enable the particles to form and assemble into a stable network. The estimated lifetime depends strongly on the initial temperature assumed for the vortex ring, which has been taken to be in the range 1200–1400K, but is difficult to estimate from first principles. As long as the particles are not heated too much, the ball will gradually burn out. If they are heated above the melting temperature of their oxide layer (around 2000K) one expects them to break up and suddenly react, causing an explosion. This is also in accord with the observed endings of ball lightning – ending by either fading away, or with a bang. Other experimenters have tested the above particle theory, with more success. Paiva et al. (2007) from Brazil used a welding arc power supply to heat discs of silicon, by creating an arc through simple separation of the previously contacting upper electrode. They observed bright balls 10 to 40mm diameter with many of the same properties as natural ball lightning, but were not free-floating (they fell gradually to the floor). Their lifetime was up to 8s. What was puzzling about the experiments was that the rate of movement of the upper electrode was critically important for producing the balls, and the upper electrode needed to be very hot.

Figure 2: Reflection of the light can be seen off the low clouds. 100m object seen at night in Queensland outback. Photograph courtesy of Brett Porter.

Videos, please! The more general acceptance of ball lightning as a known curiosity has led to more quality observations being reported. One recent observation included a video of ball lightning taken by security cameras and recorded over a couple of minutes (Abrahamson et al., 2009). Figure 3 gives one frame from the video. Detailed observations such as these will help to test our understanding of what this weird phenomenon is. Then maybe we can put it to some use!

Figure 3: Luminous sphere (see arrow) in front of a car park walkway. Photograph courtesy of Guillermo Escutia, Technicolor , Mexico

For further information contact: john.abrahamson@canterbury.ac.nz

References Abrahamson, J., & Dinniss J. (2000). Ball lightning caused by oxidation of nanoparticle networks from normal lightning strikes on soil. Nature, 403, 519-521. Abrahamson, J. (ed.) (2002). Ball Lightning. Phil.Trans. Roy. Soc. Lond., A360, 1-152. Abrahamson, J. (2002). Ball lightning from atmospheric discharges via metal nanosphere oxidation: From soils, wood or metals. Phil. Trans. Roy. Soc. Lond., A360, 61-88. Abrahamson, J., et al. (2009). Ball lightning captured by video camera – a natural nanoparticle phenomenon? Presented 4th AMN conference, Dunedin, NZ, February 2009. Bychkov, V.L. (2002). Polymer-composite ball lightning. Phil. Trans. Roy. Soc. Lond., A 360, 37-60 Paiva, G.S., et al. (2007). Production of ball-lightning-like luminous balls by electrical discharges in silicon. Phys. Rev. Lett., 98, 048501. Stenhoff, M. (1999). Ball Lightning, Kluwer Academic, chapters 11-13.

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light in waters The clarity and colour of natural waters is related to their composition (‘water quality’) via their optical properties as Rob Davies-Colley, principal scientist in aquatic pollution at NIWA, Hamilton, explains: Introduction Light behaviour in waters has long been a fascination for oceanographers and limnologists (freshwater scientists) (Kirk 1994). Light, of course, is fundamental to the photosynthesis of aquatic plants, just as it is to terrestrial plants, so the sunlight penetrating into waters powers aquatic ecosystems in the same way as it does terrestrial ecosystems. However sunlight penetration into even the clearest water is far more restricted than it is in air. As a result, plants can only grow to a certain depth in water bodies ((Kirk 1994; Davies-Colley et al. 2003). Below this depth, the ‘compensation depth’ (at which oxygen consumption by plant respiration just balances oxygen production in photosynthesis), the water is too dark to support plant growth and life only exists because of detritus sinking by gravity or otherwise arriving from the sunlit (‘euphotic’) zone or from (more distant) terrestrial ecosystems – or because of chemical sources of energy as with the strange communities associated with undersea volcanism. Phytoplankton, which move almost passively with water currents, can grow so long as the depth to which they are mixed in surface waters is not too much greater (as a rule of thumb, about 5 times greater; Talling 1971) than the compensation depth. Light in water is also fundamental to vision of aquatic animals or peri-aquatic animals like birds (Davies-Colley et al. 2003). Here we are concerned not so much with how much light reaches certain depths in water and illuminates submerged objects, but how well the image of those objects is transmitted through water. Image transmission requires that light travels in straight lines, and image attenuation over distance along the light path through water is brought about by two fundamental light-attenuating processes: absorption; and scattering (Davies-Colley et al. 2003). Although most animals can use senses other than sight to navigate, find prey, escape from predators, or find mates, a restricted visual range affects their behaviour, and ultimately their survival. Finally, light behaviour in waters greatly affects their use by people. We humans may be described as ‘peri-aquatic’ inasmuch as we favour recreation in or around water bodies, so vision through water is very important to recreational use of water. Furthermore, a minimal visual clarity of water is important for safety – so that we can see and recognise submerged hazards when bathing or wading. The colour of water also relates to light behaviour in water and also affects our aesthetic response to it. People seem instinctively to associate blue-green colours with ‘pure’ waters and yellow colours, particularly if also turbid with suspended sediment (giving a ‘muddy’ appearance) as degraded or ‘polluted’ (Davies-Colley et al. 2003). In this article, I will overview how aquatic plant photosynthesis, aquatic animal vision, and human use of waters depend on light behaviour in water – ‘aquatic optics’. The suitability of waters as habitat and for human use depend on their colour and clarity which, in turn, are related to the light-attenuating constituents of water – sometimes

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Water composition e.g., CDOM Phytoplankton Mineral suspensoids

Optical properties of water e.g., Absorption coefficient, a Scattering coefficient, b

Clarity and colour of water e.g., Euphotic depth Visual range (“visibility”) Hue, brightness

Figure 1: Conceptual relationships between water composition (optical water quality) and water colour and clarity via optical properties. (Modified after Davies-Colley et al. 2003: Fig 2.24, p 47).

referred to as ‘optical water quality’ (Figure 1). The linkage is established by the behaviour of light in water, so I begin with a very elementary (equation free!) introduction to light and to water as an optical medium.

Visible light and photosynthetically available radiation Light is one small wavelength band of electromagnetic radiation: between about 0.4 and 0.7 micrometres wavelength (Kirk 1994). This is the wavelength range that humans, and most animals including aquatic animals, can detect with their eyes. This band of the electromagnetic spectrum is also the photosynethetically available radiation (PAR) – the range of wavelengths that can be used by plants to power their conversion of solar energy to chemical energy (sugars). Despite the rather small (less than 2-fold) range of wavelengths in visible light (and PAR), there is a remarkably wide range of optical properties across this range. For example, light at the blue end of the spectrum near 0.4 micrometers, like the ‘ultraviolet’ radiation of even shorter wavelengths, can drive photochemical reactions of concern in water, whereas such photo-reactions (with a few notable exceptions) do not occur at the red end of the spectrum near 0.7 micrometers.

Optics of water Light transmission through water is affected by two main processes: absorption and scattering (Figure 2). If we could follow the trajectories and fate of individual photons of light traversing a clear-sided container of water we would find that some photons travel through the container unaffected by the water (Davies-Colley et al., 2003). These are the transmitted photons. Other photons suddenly disappear within the water. The energy of these photons has been converted to another form, ultimately heat, because of the process of absorption – which is quantified by an absorption coefficient (defined as the proportion of photons absorbed per unit small length of light path; units: metres-1). A third


Figure 2: Schematic diagram showing the trajectory of individual light photons in a collimated beam passing through a sample of water in a clear walled container. (Modified after Davies-Colley et al. 2003: Fig 1.1).

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If a submersible light (or PAR) sensor is lowered into water it is easily shown that light falls off almost exponentially with depth in water bodies (Figure 3). The depthattenuation in water depends strongly linearly on absorption because this optical process actually removes light from the water body. Scattering, in contrast, merely forces the photons to take a more tortuous path down through the water column so increasing their chance of being absorbed over a given depth interval(Kirk 1985). As a result depth-attenuation of light is less strongly dependent on scattering than absorption, and typically varies approximately as the square root of the scattering coefficient. A useful rule-of-thumb is that the plants can grow down to the depth at which PAR in sunlight declines to about 1% of the surface value. This depth (termed the ‘euphotic depth’) is, therefore similar in magnitude to the compensation depth mentioned earlier (Kirk 1994). The euphotic depth, a more conceptually ‘friendly’ index of light penetration than the depth attenuation coefficient, can be estimated by interpolation on a profile of PAR (Figure 3). Euphotic depths vary widely in natural waters, from less than a metre in extremely humic-stained or turbid waters to over 100 m in very clear seawater (Kirk 1994). Contraction of euphotic depth, related to a change in optical water quality, can have far-reaching ecological consequences in natural waters. For example, in New Zealand several shallow lakes (Ellesmere in Canterbury, and Waikare and Hakanoa in the northern Waikato) that originally had clear water and healthy growths of aquatic plants, are now extremely muddy, frequently suffer ‘blooms’ of blue-green ‘algae’ (actually bacteria), and support little by way of desirable aquatic life. In recent decades, sediment loading from catchment sources, or bed sediment disturbance by major wind-storms, has severely contracted the euphotic zone of these lakes, resulting in the aquatic plants being extinguished by light starvation (Davies-Colley et al. 2003). In some parts of the world, including Australia, seagrasses that are crucial to the ecology of estuaries have similarly suffered catastrophic decline because of reduced clarity of overlying waters.

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group of photons abruptly change direction within the water then move on a new path without change in energy (or wavelength). These photons have been subject to scattering – which is quantified by a scattering coefficient (the proportion of photons scattered per unit small length of light path; units: metres-1). Some of the scattered photons have been absorbed (by water molecules or solutes) and then almost immediately re-radiated in an arbitrary direction. This is molecular scattering. In all but the very clearest natural waters, molecular scattering is much less important than particle scattering – the interaction of light (by reflection, refraction, and diffraction) with solid particles suspended in the water such as clay micelles or bacterial or algal cells (Kirk 1994). The clarity of water is related to how efficiently light is transmitted – the greater the proportion of photons transmitted unabsorbed, and un-deviated by scattering, the greater the clarity. Colour of waters is more complicated, being related to how well photons of different energy (different wavelength, hence different spectral colours) are transmitted (Davies-Colley et al. 2003). Essentially all the important aspects of colour and clarity of natural waters can be explained in terms of their light-scattering, and light absorbing, properties – which, in turn, are a function of water composition (Figure 1).

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Figure 3: Light (PAR) profile in water, demonstrating the typical exponential attenuation with depth. The same data (for the Waihou River at Te Aroha on 14 December, 2005; Davies-Colley & Nagels 2008) is plotted on A. a linear scale of PAR and B. a logarithmic scale of PAR. The euphotic depth (at which PAR has fallen to 1% of its surface value) is indicated.

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In order for a coherent image to be received and interpreted by the eye-brain system light must travel in straight lines. Loss of light in waters by absorption or scattering (changing the direction of light) degrades the image conveyed by the light – ultimately to the point where it is no longer detectable. The point at which an image is extinguished in water is quite well-defined and depends mainly on the sum of the absorption and scattering coefficients – a quantity known as the beam attenuation coefficient (Davies-Colley et al. 2003). The visual extinction distance also depends on the threshold contrast (between the image and the background light in water) for detection by the eye – a quantity that is fairly near-constant for people (and aquatic animals) of normal vision. Traditionally, the visual extinction distance or ‘visibility’ has been indexed by lowering a white or black-and-white disc into water and recording the depth at which it is judged to disappear. This venerable device for assessing water clarity is called the Secchi disc after an Italian scientist, Dr A. Secchi, who first described its use in the early nineteenth century (Tyler 1968). The Secchi disc continues to be used as part of routine monitoring of lakes in New Zealand. Many valuable datasets on lakes include Secchi data – notably for Lake Taupo which seems to have suffered a decline in Secchi depth fairly recently, consistent with increased phytoplankton biomass in response to nitrogen loading. Contrary to common assumption, the Secchi depth is not an adequate indicator of light penetration into waters – which is far better measured by submersible light sensor (DaviesColley & Vant 1988; Davies-Colley & Smith 2001). The Secchi depth is flawed as an index of visual water clarity inasmuch as it is slightly dependent on the incident light field. A theoretically superior index is the visual range of a black target, viewed horizontally rather than vertically, termed the ‘hydrological range’ (Davies-Colley et al. 2003). This quantity is independent of incident lighting and provides an excellent and accurate (+/- 5%) estimate of the beam attenuation coefficient (Zanevald & Pegau 2003). A practical approach to measuring hydrological range – the black disc method (Davies-Colley 1988) – involves use of an underwater periscope for horizontal observations under the water surface without the need to don snorkel gear (Figure 4). This method is used routinely in water quality monitoring in New Zealand, notably in the National Rivers Water Quality Network (NRWQN) run by NIWA (Smith et al. 1997) (http://www.mfe.govt.nz/environmental-reporting/ freshwater/river/) (Figure 5). The (horizontal) black disc method has the major advantage of being suitable for shallow waters (including most rivers) in which the Secchi disc would be visible on the bottom (Figure 5). The method

Figure 4: Black disc method for measuring visual water clarity. An underwater periscope viewer is used to observe the black disc horizontally underwater, and a tape measure indicates the extinction distance. (Modified after Davies-Colley et al. 2003: Fig 3.12, p 74.)

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has been applied over a remarkably wide range from a few millimetres visibility (measured on diluted samples) in effluents and river floodwaters, to 63 m visibility in Waikoropupu Springs near Nelson which is a close approach to optically pure water (Davies-Colley & Smith 1995). The black disc visibility, as well as providing a direct index of visual clarity of water as it affects human recreational use, also indexes visual clarity for sighted animals like fish, for which visibility is limited by the same physical phenomena that limit human visibility. Empirically it is found that

Figure 5: Black disc visibility being measured in the Motueka River at the Gorge during a NRWQN sampling visit. Rob Merrilees, NIWA-Nelson, is on the left viewing the black disc through an underwater periscope, while measuring sighting distance with a tape measure attached to the stand on which the disc is fixed (white upright rod on the right of the photo). The visibility at this site, the clearest in the NRWQN, was 13m on this occasion. Photograph courtesy of Rob Davies-Colley.

Figure 6: The hue of water in the Blue Spring, discharging to the Waihou River near Putaruru, suggests optically pure water. Photograph courtesy of Rob Davies-Colley.


Light and water quality – optical water quality The composition of water affects light (and image) transmission through that water. Water constituents that absorb or scatter light therefore affect light behaviour in waters – shifting the overall optical character from that of pure water. Kirk (Kirk 1982) introduced the term ‘optical water quality’, defined as: the extent to which the suitability of water for its functional role in the biosphere or the human environment is determined by its optical properties. There are five main categories of light-attenuating water constituent that together determine optical water quality: water itself; coloured dissolved organic matter (CDOM); and the particulate constituents: mineral particles, phytoplankton, and detrital organic matter (Table 1). Water itself absorbs light selectively (mainly red light), which is why optically pure water appears blue-green in hue (Table 1). However, scattering by water (molecules) is very weak and can usually be neglected except in optically pure waters such as seawaters remote from land. New Zealand has several remarkably clear (optically pure) spring waters, such as Waikoropupu Springs near Takaka, Golden Bay (Davies-Colley & Smith 1995), Hamurana Springs near Rotorua, and the Blue Spring near Putaruru (Figure 6) – all of which display the blue-violet colour caused by (strongly blue-biased) molecular scattering.

Coloured dissolved organic matter (CDOM) (sometimes termed ‘aquatic humus’ or ‘yellow substance’ – Davies-Colley et al. 2003) is notable for strongly wavelength-selective absorption of light (Table 1). However, being dissolved, CDOM contributes minimally to light scattering. Like soil humus from which some fraction is derived, CDOM is not a well-defined chemical substance, but a random polymer of many different organic substances, characterised by acidic functional groups. CDOM is usually measured by organic carbon content (after suitable chemical cleanup and isolation), but when its optical character is the main concern, it is best indexed by absorption at blue or ultraviolet wavelengths. (The absorption coefficient of CDOM is approximately exponential in shape, rising systematically as wavelength declines through the UV-visible spectrum). In the NRWQN, CDOM is routinely indexed by g440, the absorption coefficient at 440 nm (= 0.44 micrometres)”measured on a membrane filtrate by laboratory spectrophotometer (Smith et al. 1997). Organic detritus has absorption properties similar to CDOM and may include aquatic humus chemically absorbed onto mineral particles or present in co-flocculated aggregates, as well as biochemically degraded cellular material. Organic detritus, being particulate material, scatters light as well as absorbing it, but it is difficult to generalise about the scattering of such poorly defined (and variable) material (Table 1). Phytoplankton are a particularly important lightattenuating constituent of water (Table 1). They are characterised as absorbing blue and red light strongly

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reactive distance of fish (to prey items, for example) is very similar in magnitude to black disc visibility. Accordingly, Newcombe (2003) introduced a model framework for protecting the ‘visual habitat’ of fish using black disc clarity.

Table 1: Light-attenuating constituents of waters Constituent

Absorbing properties

Scattering properties

Notes on optical water quality

Water itself

Absorbs red light strongly

Weakly scattering. (However blueweighted molecular scattering contributes to blue-violet colour of exceptionally clear waters.)

Optically pure waters (which may still contain salts or other solutes that do not attenuate light), are very clear, blue-violet coloured viewed from above, and greenishblue viewed when viewed in transmission (e.g., when diving).

Absorbs light in an exponentiallyincreasing pattern with declining wavelength. (Absorption of blue light is much stronger than red light.)

Negligible scattering.

The alternative name ‘yellow substance” refers to the tendency of CDOM to impart yellow colours to waters in which it occurs at high concentrations. CDOM is a potential inverse tracer of salinity in coastal waters.

Difficult to generalise given highly variable characteristics and associations with mineral suspensoids.

Contributes to ‘muddy’ appearance of rivers in flood and highly turbid shallow windexposed lakes and estuaries.

Dissolved constituents CDOM (aka ‘aquatic humus’ or ‘yellow substance’)

Particulate constituents (aka ‘suspensoid’)

Organic detritus (aka ‘tripton’)

Absorbs light in an exponentiallyincreasing pattern with declining wavelength (like CDOM).

Phytoplankton

Absorb blue light and red Strongly scattering. Scattering light strongly. Detailed coefficient is usually about 10-fold spectral absorption varies with higher than absorption. phytoplankton taxonomy (and thus accessory pigments).

Phytoplankton usually account for most of the light attenuation in lakes suffering ‘blooms’, and impart green or green-yellow hues to waters (or blue-green when cyano-bacteria dominate the phytoplankton).

Mineral suspensoids

Usually weakly absorbing (except Strongly scattering (owing to high iron-minerals, or when coated with refractive index relative to water). adsorbed coloured organic matter).

Usually dominate the light attenuation in turbid waters, with the exception of lakes with phytoplankton ‘blooms’.

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particularly important (generally undesirable, e.g. toxic) category of phytoplankton characterised by accessory pigments that induce blue-green hues. Light scattering by phytoplankton is approximately 10-fold higher than their absorption. Consequently phytoplankton strongly affect the visual clarity of waters which explains why lakes undergoing phytoplankton ‘blooms’ are very turbid, with visibility perhaps less than a metre. Mineral particles suspended in waters are of great variety, but layer silicate clays (e.g. kaolinite, smectite) are often particularly prominent in quiescent waters because their Stokes law settling velocity is much lower (perhaps by an order of magnitude) than that of equi-dimensional mineral particles of the same mass. Mineral particles, with the exception of some iron minerals, do not usually absorb visible light unless they have chemically absorbed coloured organic matter coating their surfaces. However, they scatter light intensely owing to their high refractive index, and often dominate the scattering (and therefore light attenuation) in natural waters. But visual clarity and suspended sediment concentration are only roughly (inversely) correlated because the particle size distribution and other properties of suspended sediment that affect its light attenuation can vary appreciably (Davies-Colley & Smith 2001).

Remote sensing Because light transmission is affected by water constituents, the light scattered back to space from within waters contains information about the water composition (Kirk 1994). Therefore, the (weak) optical signal backscattered from waters can be detected by sensors on satellites or aircraft, and the resulting images (in different wavelength bands) analysed in order to estimate concentrations of certain constituents. Fine particles of sediment increase the backscattering from waters so the ‘brightness’ of water colours correlates with suspended sediment concentrations – the higher the suspended sediment concentration, the brighter the water colour. Therefore, the brightness of pixels in images from satellite platforms can indicate spatial patterns of suspended sediment and even approximate concentrations. Usually a boat or ship must be sampling the water at the time of satellite imagery so as to provide ‘sea truth’ data for locally calibrating the imagery to suspended sediment concentrations. In shallow waters, the brightness of water in satellite imagery may be determined by the albedo of bed materials or modified by attenuation in the overlying water (which is usually darker than bed materials). Therefore imagery, again accompanied by suitable ‘sea truth’ data, can be interpreted to indicate spatial patterns of features such as seagrasses or other aquatic plant beds, or bathymetry. The colour (hue) of waters conveys information about the constituents that selectively absorb light, notably the phytoplankton due to their content of chlorophyll-a. As the chlorophyll-a content of water increases, the hue shifts from the blue-green of optically pure water towards green or even yellow-green, and satellite imagery can be interpreted

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to indicate spatial patterns of phytoplankton and even (with suitable ‘sea truth’ data) to estimate chlorophyll-a concentrations. CDOM also shifts water hue systematically, from blue-green through green, ultimately to (very dark) orange in very strongly humic ‘coloured’ waters. CDOM is usually appreciably higher in inland waters than the sea (mainly because of its photochemical oxidation in sunlit surface waters), so river plumes in coastal waters can sometimes be recognised in satellite imagery. CDOM may provide a useful (optically-detectable) inverse tracer of salinity in coastal waters.

Conclusion The behaviour of light in waters remains a subject of intense interest in aquatic sciences and related fields because of the fundamental significance of light to photosynthesis, the crucial role of vision in aquatic animal behaviour, and the importance of water appearance to human use of water. Furthermore, remote sensing of optical imagery from water continues to advance, providing a means for spatial mapping of water composition and other features. For further information contact: r.davies-colley@niwa.co.nz Further reading: An introduction to the optics of water is given by Kirk (1994) as a lead-in to a very comprehensive survey of photosynthesis in waters. A more elementary introduction to aquatic optics is given by Davies-Colley et al. (2003) as a lead-in to a discussion of optical water quality. A review of the relationship between turbidity, suspended sediment and water clarity in water resources science and management is given by Davies-Colley & Smith (2001).

References Davies-Colley, R.J. (1988). Measuring water clarity with a black disc. Limnology and Oceanography, 33, 616-623. Davies-Colley, R.J., & Nagels, J.W. (2008). Predicting light penetration into river waters. Journal of Geophysical Research-Biogeosciences, 113, doi10.1029/2008JG000722 Davies-Colley, R.J., & Smith, D.G. (1995). Optically-pure waters in Waikoropupu (‘Pupu’) Springs, Nelson, New Zealand. New Zealand Journal of Marine and Freshwater Research, 29, 251-256. Davies-Colley, R.J., & Smith, D.G. (2001). Turbidity, suspended sediment, and water clarity: A review. Journal of the American Water Resources Association, 37(5), 1085-1101. Davies-Colley, R.J., & Vant, W.N. (1988). Estimation of optical properties of water from Secchi disc depths. Water resources bulletin, 24, 1329-1335. Davies-Colley, R.J., Vant, W.N., & Smith, D.G. (2003). Colour and clarity of natural waters. Science and management of optical water quality. Caldwell, New Jersey, 310 p. Kirk, J.T.O. (1982). Prediction of optical water quality. In E. M. O’Loughlin & P. Cullen, (Eds.), Prediction in water quality (pp. 26-30). Proceedings of a symposium sponsored by the Australian Academy of Science and the Institution of Engineers, Australia, held in Canberra 30 November to 2 December 1982. Kirk, J.T.O. (1985). Effects of suspensoids (turbidity) on penetration of solar radiation in aquatic ecosystems. Hydrobiologia, 125, 195-208. Kirk, J.T.O. (1994). Light and photosynthesis in aquatic ecosystems. 2nd ed. New York, Cambridge University Press. 509 p. Newcombe, C.P. (2003). Impact assessment model for clear water fishes exposed to excessively cloudy water. Journal of the American Water Resources Association, 39(3), 529-544. Smith, D.G., Davies-Colley, R.J., Knoeff, J., & Slot, G.W.J. (1997). Optical characteristics of New Zealand rivers in relation to flow. Journal of the American Water Resources Association, 33, 301-312. Talling, J.F. (1971). The underwater light climate as a controlling factor in the production ecology of freshwater phytoplankton. Mitteilungen der internationalen vereinigung fur theoretische and angewandte Limnologie, 19, 214-243. Tyler, J.E. (1968). The Secchi disc. Limnology and Oceanography, 13, 1-6. Zanevald, J.R.V., & Pegau, W.S. (2003). Robust underwater visibility parameter. Optics express, 11, 2997-3009.


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Although the UV Index (UVI) was developed to represent damage to human skin, it may be applied to other processes as many biological UV effects have similar action spectra. Since the UVI is based on the erythemal action spectrum, its sensitivity to ozone change is the same as for erythema. For a 1% reduction in ozone, the UVI increases by approximately 1.1%. The UVI is an open-ended scale. In the British Isles, from where many New Zealanders are descended, its peak is ~6, and at northern mid-latitudes, its peak is ~10. Peak values are greater in the southern hemisphere because of our lower ozone amounts, closer summertime SunEarth separation, and generally cleaner air. For example, the peak UVI in NZ is approximately 40% greater than at corresponding northern latitudes, and it often exceeds 12 (McKenzie et al., 2006]. In the tropics it is higher again, with the highest values on Earth occurring in the Peruvian Andes where the UVI can reach 25 (Liley and McKenzie, 2006). Outside the protection of the Earth’s atmosphere the UVI is ~300. The relatively high UV intensities in New Zealand are a contributing factor to our high rates of skin cancer (an unwelcome world record that we share with Australia). But that’s not the only factor. For those of European extraction, skin types are better adapted to the lower UV intensities in the British Isles. Our outdoor lifestyle is also important.

The spectrum of sunlight extends over a much broader range of wavelengths than detected by the human eye, which responds only from 400nm (violet light) through to 650nm (red light), with a peak response near 550nm (green light). A substantial component of sunlight falls outside that range as infrared (IR) or ultraviolet (UV) radiation.

Risks and benefits of UV radiation The risks from UV radiation include health effects in humans, such as damage to skin and eyes; damage to aquatic and terrestrial plants and ecosystems; deterioration in air quality; and damage to materials. Since UV radiation is not detected by the human eye, or by usual light meters, a different standard is needed to quantify how much of it is present at any time. The ‘brightness’ of UV radiation is generally reported to the public in terms of the so-called UV Index (see Box 1). Instead of referring to the response of the human eye (photopic response) for light, it refers to the response of human skin to sunburn (erythemal response), which has no contribution from visible radiation, but increases rapidly towards shorter wavelengths within the UV range.

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There’s more to sunlight than meets the eye. Although unseen, UV radiation can cause both adverse and beneficial health effects as Richard McKenzie, from NIWA Lauder explains:

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Box 1 - UV Index Box 1 - UV Index UV-B

(a)

1

0.1

0.1 SZA Ozone 22.5 300 67.5 300

0.01

0.001

0.0001 280

0.01

0.001

300

320 340 360 Wavelength (nm)

380

0.0001 400

Erythemally Weighted UV (W m-2 nm-1)

0.02 panel shows the spectral UV irradiance for The upper (b) SZA(note Ozonethe UVlog Irradscale two sun angles, with ozone 300 DU DU Wm-2 UVI for the y-axis). The erythemal (i.e. the ‘skin-reddening’ 22.5 300 0.25 10.0 or 300 on 0.03the 1.2right ‘sunburning’) weighting function is67.5 shown 0.015 axis. The lower panel shows the corresponding spectra of erythemally weighted UV irradiance (UVEry). The internationally-agreed UV Index (UVI) is defined 0.01 in terms of UVEry. The weighting function involves an arbitrary normalization to unity at wavelengths shorter than 298nm, so UVEry is not strictly an SI unit. Furthermore, when UV information was first provided to 0.005 the public another normalization was applied to give a maximum UVI of ~10 in Canada, where it was first used.

0 280

Erythemal Weighting

Irradiance (W m-2 nm-1)

1

UV-A

300

320 340 360 Wavelength (nm)

380

400

The UVI is therefore a unitless number corresponding to the integral under the curves in the lower panels, multiplied by 40 m2/W. UVI = 40Ú I(l) w(l) dl, where l is the wavelength in nm, I(l) is the irradiance in W m-2nm-1, and w(l) is the erythemal weighting function, defined as: for 250 < l < 298 nm w(l) = 1.0 for 298 < l < 328 nm w(l) = 100.094(298- l) for 328 < l < 400 nm w(l) = 100.015(139- l) for l > 400 nm w(l) = 0.0

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l shows the spectral UV irradiance for two sun angles, with ozone 300 DU

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Figure 1: Approximate exposure times as a function of UVI leading to erythema and for maintaining adequate vitamin D. Exposure times corresponding to the red shaded area represent too much UV, leading to erythema (skin reddening, and sunburn). Exposures within the dark blue region represents too little UV to maintain an intake of 1000 IU for full-body exposure. The unshaded area represents the range of times for optimal exposure assuming only the hands and face are exposed. The other blue curves give the lower exposure limits for adequate vitamin D for different areas of skin exposed. All times shown are for fair skin (skin type II). For brown skin or black skin (skin types IV and VI) all exposure times should be multiplied by 2 and 5 respectively. With our temperate climate, it is quite comfortable to spend long periods of time in the direct sunlight. The folly of that behaviour manifests itself only later – when we experience the discomfort of sunburn. But, in addition to the well-publicized risks of damage from UV radiation, there are also possible benefits through the production of vitamin D. And again the news is bad for New Zealanders. During the winter months, our UV intensities are lower than at corresponding northern latitudes, so our seasonal swings in UV are much larger than in the northern hemisphere. This wide seasonal variation is also a health risk. In winter the UV intensities may not be high enough to maintain adequate vitamin D. The problem is exacerbated because our skin becomes tanned to protect ourselves from further damage in summer, and this tan persists into the winter, so inhibiting our ability to absorb further UV radiation. Those with darker skins, such as many Maori, Pacific Islanders, and Asians, are at greater risk. The weighting function for vitamin D production is similar to that for erythema, but does not extend as far into the UV-A region. Consequently it is a stronger function of ozone amount and sun angle. Nevertheless, the minimum exposure time for sufficient vitamin D production can still be estimated in terms of the UV Index. It also depends on the skin type, the SPF of any sunscreen applied, and the area of skin that is exposed to sunlight. The estimated exposure times for sufficient vitamin D production are compared with the exposure times for erythema in Figure 1 (McKenzie et al., 2009). In summer when the UVI can exceed 10, skin damage occurs in about 15 minutes for fair-skinned people, while for full-body exposure sufficient vitamin D can be produced in less than 1 minute. In winter, when the maximum UVI is ~1, skin damage occurs in 150 minutes, and even with full-

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Figure 2: Upper panel: The spectrum of solar radiation incident at the top of the atmosphere, and transmitted to the Earth’s surface. Middle panel: Detail of the UV, visible, and mid infrared portions of the spectrum as transmitted by glass. Lower panel: Detail of the UV region, including the cut off for transmission by glass. The red curve shows the action spectrum for damage to human skin. body exposure (unlikely in winter), it would take at least 20 minutes to produce sufficient vitamin D. If only the hands and face are exposed, there is only a small margin between receiving too little or too much UV; and in winter it would be impossible to receive sufficient vitamin D without skin damage. For darker skins, or if sunscreens are applied, these exposure times must be increased.

Understanding sunlight The Sun’s output is well approximated by the Planck black-body curve for a temperature of 6000K (Houghton, 1977), which has its peak in the green part of the spectrum. Approximately 50% of the solar output is emitted at infrared (IR) wavelengths longer than 750nm. These IR wavelengths are an important component of our energy budget. A much smaller fraction of the solar output is emitted in the ultraviolet (UV) region. This UV light is nevertheless important because, as the wavelength of light decreases, the amount of energy carried per photon increases and can be large enough to break chemical bonds in molecules such as DNA – which is the building block of life. Superimposed on the smooth Planck function for sunlight are absorption lines from gases in the Sun’s atmosphere (Fraunhofer lines), or in the Earth’s atmosphere (see Figure 2). In the visible region, absorptions by terrestrial gases are small – which is why the region is called an atmospheric window. The relative transparency of that spectral region is


How does UV differ from visible light? If our eyes were sensitive to UV radiation rather than visible radiation, our perception of the world would be very different. The sky appears blue because air molecules scatter blue light more strongly than red light. This dependence on the wavelength (l) of light is very strong. It varies as l-4, so at 300nm, the strength of this scattering is about 32 times greater than at 600nm. That’s why photographers choose to use blue-blocking filters if they want to obtain dramatic images of clouds. The filter can greatly enhance the contrast between the bright cloud and dark background. Because of this wavelength-dependence in scattering from air molecules, the UV radiation field is much more diffuse than for visible radiation (light). An eye sensitive 1

Some authors use 320nm as the boundary between UV-A and UV-B radiation.

to UV radiation would therefore perceive a much smaller contrast between clouds and sky, and a smaller contrast between sky and sun. Under clear skies, the diffuse UV component would normally dominate over the direct beam component, whereas in the visible, the diffuse component is typically only 5–10% of the direct. When the sun is low in the sky, these losses become so large that the solar disc in the UV region would not even be detectable from the surrounding skylight. Our sphere of consciousness would be greatly reduced because objects more distant than even a few kilometres would be completely lost in the gloom of diffuse light. It would be like living in a fog. Shadows would be less distinct. Have you ever noticed that when the sky is overcast, places normally in the shade receive more light than they would under clear skies? One practical implication of this more diffuse field is that any reduction in UV radiation in a shaded area is smaller than the reduction in visible light, as perceived with the eye. So the protection from shade may be less complete that anticipated. The brightness of objects would appear very different too. Most natural surfaces reflect a significant fraction of the incoming visible radiation. But in the UV region, very few surfaces are strongly reflecting. Most natural surfaces would appear quite dark because they reflect less than 5% of the incoming UV-B radiation. Snow and clouds are two of the few exceptions to this rule. UV intensities can therefore be significantly enhanced over snow-covered surfaces, particularly at high altitudes where scattering by air molecules is less important. Under unpolluted conditions, the UVI increases by about 5% per kilometre increase in altitude. On NZ ski fields, the combined effect of these two factors is that the UVI is approximately 25% more than at corresponding locations near sea level (Allen, 2005 #8381). The absorption by clouds is similar in the UV and visible regions, but any enhancements in radiation due to reflections from clouds are more muted in the UV. The stronger dependence of UV radiation on atmospheric path-length (and hence sun elevation angle) leads to a much more marked contrast between summer and winter. Typically, in southern NZ, UV intensities on a winter’s day are less than 10% compared to those in summer, in contrast to the situation for visible radiation where the intensities in winter are more than 50% of those in summer. Finally, in this modern age, the transmission of glass has to be considered. Looking through the glass windows in your house or car, the outside view would appear quite dark even in the middle of the day because most glasses do not transmit UV-B radiation. The damaging effect of UV radiation is therefore greatly reduced behind glass windows. For example, most glass transmits less than 10% of sun burning radiation – so the SPF of most window

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why plants use it to photosynthesize, and why the human eye evolved to sense it. In the infrared region, absorptions become ubiquitous. In some regions, virtually all sunlight is absorbed by water vapour and other trace gases such as CO2. In other regions, these gases only partially block the spectrum. Therefore, any changes in concentrations of these gases in this region will affect the transmission of the atmosphere, and so contribute to the energy balance of the planet, and global warming. Absorptions by terrestrial gases are even more important in the UV region, which is arbitrarily subdivided into three wavelength bands: UV-A (315–400nm)1 radiation, UV-B (280–315nm) radiation, and UV-C (100–280nm) radiation. UV-A radiation is largely unaffected by gases in the atmosphere. Only a small amount of UV-B radiation penetrates to the Earth’s surface because it is strongly absorbed by atmospheric ozone whose absorption cross section increases rapidly towards shorter wavelengths in this spectral region. UV-C comprises less than 0.6% of the incident solar spectrum at the top of the atmosphere, but none of it reaches the Earth’s surface. Radiation below 240nm is absorbed by molecular oxygen (O2, which comprises 20% of the atmosphere). This radiation is capable of photo-dissociating molecules to form two oxygen atoms. The atoms so formed then recombine with another oxygen molecule to form ozone (O3). Ozone is crucial to life because it absorbs much of the harmful UV-B radiation which would otherwise reach the Earth’s surface. In fact, ozone blocks virtually all radiation less than 290nm. The amount of longer-wavelength UV-B present depends most critically on the amount of ozone, and the path length of sunlight through the ozone layer (see Table 1).

Table 1: Approximate UV-A and UV-B contributions (W m-2) to solar energy for two solar zenith angles (sza = 90 – solar elevation angle) and for three column ozone amounts measured in Dobson Units (1 DU = 2.69 x 1016 molecule cm-2). All for a Sun-Earth separation of 1 A.U. (mid-March or mid-September), cloudless skies, and no aerosols. The solar constant is 1370 W m-2. Conditions Extraterrestrial Earth surface, sza:00, ozone: 300 DU Earth surface, sza:60, ozone: 300 DU Earth surface, sza:60, ozone: 450 DU Earth surface, sza:60, ozone: 100 DU

UV-B (280–315nm)

UV-B * (280–320nm)

UV-A (315–400nm)

17.3 2.07 0.38 0.20 1.13

20.8 3.82 0.90 0.60 1.89

85.1 65.1 26.7 26.3 27.2 New Zealand Association of Science Educators

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Table 2: Relationships between various weightings for the solarium compared with natural sunlight (noon sun in summer and winter at Lauder New Zealand) and a powerful 1000W quartz halogen lamp at a distance of 0.5m are given in the table below. UV_Ery and UV_VitD are erythemally-weighted and vitamin D-weighted UV radiation respectively. * It takes approximately 2 to 3 SED (1 SED= 100 Jm-2 of erythemally-weighted UV) to burn skin type II). UV-A (µWcm-2) UV-B (µWcm-2) UV_Ery (µWcm-2) UV_VitD (µWcm-2) UVI T(2SED*) (min) VitD/Ery UV-B / UV-A

UVA solarium Sun 17514.8 156.9 30.0 34.8 12 11.1 1.16 0.009

Winter Sun 1797.0 17.9 2.6 3.2 1.0 128.2 1.2 0.010

Summer 0.5m 6161.5 206.6 28.2 56.7 11.3 11.8 2.0 0.034

1000 W FEL lamp at 0.5m 106.2 6.6 7.0 3.8 2.8 47.4 0.5 0.062

materials is more than 10 (Figure 2, bottom panel). Any benefits are also greatly reduced. In sunlight transmitted by glass, the capacity to photosynthesize vitamin D is reduced by an even greater amount than its capacity to cause sunburn.

Comparing artificial light sources with sunlight When considering artificial light sources compared with sunlight, our perceptions in the visible region don’t necessarily translate to realities in the UV region. In Figure 3 we compare irradiances from overhead sun (blue curve) with the irradiance from a powerful 1000W quartz halogen calibration lamp at a distance of 0.5m (black curve), and a solarium (red curve). The quartz halogen lamp approximates a Planck function at 3000K (compared with sunlight at 6000K). In the visible region, its output is at least an order of magnitude less than sunlight. But because of the strong absorption by ozone in sunlight, the output from the lamp exceeds that for sunlight at wavelengths shorter than about 300nm. Consequently, although it is far less damaging to the eye than sunlight, skin damage can still occur after a few minutes’ exposure. The solarium output peaks in the UV-A region, as is typical for many commercial sun beds. In this case, the peak is a factor of 5 greater than natural sunlight. The output in the UV-B region also greatly exceeds that of natural sunlight. Consequently, while these solaria may be effective in tanning, or in the production of vitamin D, they also pose unknown risks. It has already been shown that their regular use greatly increases the risk of developing skin cancer in later life.

Conclusion A small but significant part of the spectrum of sunlight falls in the ultraviolet range of wavelengths. Our bodies have no means of perceiving this because it falls outside the range of sensitivity of our eyes, and any direct heating effect is undetectable because the amount of energy involved is too small. Nevertheless, this UV radiation is vitally important to human health and to the wider world. Its negative effects have been well documented, but its positive effects are now receiving greater recognition. There is no place on Earth where UV intensities from sunlight are optimal all year round. The exposure times from sunlight to optimise health have been quantified in terms of the UV Index. The exposure times also depend on skin type, application of any sunscreens, and the area of skin exposed. There is a huge

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Figure 3: Comparing the UV and visible spectra of sunlight for overhead sun conditions, a 1000W quartz halogen lamp at 0.5m, and inside a solarium. variation between the optimal exposure times in summer and winter at mid latitude sites such as New Zealand. There is no simple relationship between the intensity of UV radiation and visible radiation. In the case of sunlight it is true that as light levels increase, UV radiation also tends to increase, but the relationship is complex and non-linear. For artificial light sources, the relationships between visible and UV components can be completely unexpected. For example, a quartz halogen lamp is extremely bright to the eye, but contains relatively small amounts of UV radiation. On the other hand, solaria may not appear particularly bright to the eye, but they can contain dangerous amounts of UV radiation. Some light sources, such as mercury vapour lamps, or lasers may be invisible to the eye, yet capable of causing permanent damage to the skin or eyes in a matter of seconds. For further information contact: r.mckenzie@niwa.co.nz

References Houghton, J. T. (1977). The Physics of Atmospheres. Cambridge University Press, Cambridge, UK. Liley, J.B., & McKenzie, R. L. Where on Earth has the highest UV?, in UV Radiation and its Effects: an update, http://www.niwa.co.nz/__data/assets/pdf_ file/0014/41252/Liley_2.pdf McKenzie, R.L., Bodeker, G.E., Scott, G., & Slusser, J. (2006). Geographical differences in erythemally-weighted UV measured at mid-latitude USDA sites. Photochemical & Photobiological Sciences, 5(3), 343-352. McKenzie, R.L., Liley, J.B., & Björn, L.O. (2009). UV Radiation: Balancing risks and benefits. Photochemistry and Photobiology, 85, 88-98.

UV 2010 Workshop: UV Radiation and its Effects. Queenstown. Date: 7-9 April 2010. For more information visit: http://www.niwa.co.nz/our-services/online-services/ uv-and-ozone/workshops/2010


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shining light on food Most people would not instantly see many relationships between light (infrared, visible and ultraviolet light) and food, yet light is an essential ‘ingredient’ in the food chain. The obvious fact is that sunlight is needed for photosynthesis, with light providing the energy for plant growth that directly provides the raw material for many of our foods, or provides a food source for animals that in turn provide us with food. Light, however, has many other ‘hidden’ influences on what we eat.

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Light affects how we appreciate foods Light provides us with colour, assisting in our sensory appreciation of food. This can have such an influence on our appreciation of a food that taste panels often taste food under red light to disguise the actual colour of the food so they can focus on the true taste and avoid interpretations based on the appearance of the food. Another sensory effect of light relates to the oxidation of fat, destruction of vitamins and production of undesirable flavours in some food products, such as beer and milk. The result of ‘light strike’ (as it is often called), results in undesirable flavours. Light degrades iso-alpha acids from the hops that combine with sulphur compounds in the beer to produce what is described as a ‘skunk’ odour. This can be prevented in beer, for example, by storage in brown bottles. When milk was commonly distributed in clear glass bottles, it was important to keep the bottles in the shade,

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Light is not only important for food quality, it is also being used by food technologists in the analysis and treatment of the food, as Associate Professor Steve Flint, Institute of Food Nutrition and Human Health, Massey University, Palmerston North, explains:

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Figure 1: Butter showing fat (red) and water (black). Photograph courtesy of Liz Nickless, Fonterra Research Centre.

Figure 3: Cheese sauce showing protein (green), starch (blue) and fat (red/brown). Photograph courtesy of Liz Nickless, Fonterra Research Centre.

Figure 4: DNA strand before exposure to UV light.

Figure 2: Cheese showing protein (green) and fat (red). Photograph courtesy of Liz Nickless, Fonterra Research Centre.

Figure 5: DNA strand after exposure to UV light. New Zealand Association of Science Educators

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science partly to prevent milk warming to temperatures that teacher would encourage microbial spoilage, but also to prevent

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fat oxidation and vitamin deterioration associated with ‘light strike’. Vitamin A is one such vitamin in milk that is destroyed by light. Vitamin A plays a role in a variety of functions in the body, with vision being the most often quoted. Light-induced milk flavour is a serious problem for the dairy industry because of the strong taste and the speed with which this develops. Packaging materials are essential for avoiding this particular deterioration of milk.

Testing food using light Light has become an essential tool to food technologists as a basis for rapid and accurate analytical techniques for testing food during and after manufacture. One of the simplest devices using light is a refractometer. This is a laboratory or handheld device that measures the index of refraction and can be used to estimate sugar concentrations based on light refraction. Light of specific wavelengths provides us with processes and analytical techniques that are used extensively in the manufacture of food. Near infrared (NIR) analysis of foods enables rapid estimates of fat, protein, moisture, starch, sugars and fibre. This requires light in the wavelength range 780–2500nm of the electromagnetic spectrum. NIR analytical techniques are based on absorption of radiation. NIR is now used routinely for the compositional analysis of food and food ingredients. Both quantitative and qualitative assays are possible. There are applications for almost every kind of food including cereals, milk and dairy products, meat, fish, fruit and vegetables, confectionery and beverages. Many large bakeries use NIR to monitor the quality of flour and other raw ingredients in terms of protein and moisture content in particular. Monitoring changes in the moisture content of dough allows optimal baking. The success of NIR as an analytical tool is that, usually, no sample preparation is required, analysis is rapid (within seconds) and it can be done in-line in a food manufacturing plant. NIR is so good that it is often superior to the reference wet chemistry methods in terms of precision. In the dairy industry, NIR allows rapid and accurate analysis of protein, moisture, fat and lactose in liquid milk, dried dairy products, and cheese. Instantaneous and continuous measurements enable tight control of dairy manufacturing and ensure consistency of the final product. The fat content of meat carcasses measured by NIR spectroscopy enables carcasses to be sorted on the basis of fat content. Special instruments are used to measure the protein, fat and moisture of minced meat and processed meat products. NIR fibre-optic probes are used to measure the protein, moisture and oil content of whole fish. Automated fruit sorting machines use NIR to determine the sugar content of fruit without damage to the fruits. This provides an objective assessment of the ripeness of a variety of fruits including peaches, mandarins, melons, mangoes and pineapples. For confectionary, NIR is used to measure moisture in sugar and chocolate crumb, protein and oil in cocoa powder and fat in whole chocolate. NIR data can be used for the sensory analysis of chocolate. In the brewing industry, NIR is used to monitor the alcohol in beer and wine, as well as monitoring the quality of ingredients (barley and grapes) for both of these products. The moisture content of tea and coffee, and the sugar content of fruit juices are measured by NIR. Even the sensory quality of tea and coffee can be determined through NIR analysis. 22 New Zealand Association of Science Educators

One of the concerns of food manufacturers is the compositional purity of the ingredients they purchase. The purity of coffee, fruit pulps, milk powders, orange juice, pig carcasses, rice, sausages, sugars, vegetable oils, wheat grain and wheat flour can be successfully determined by NIR. This is based on comparing the spectrum of the test sample with that of a reference sample. Another example of the use of infrared light for the analysis of food appeared in a recent article written by scientists at the University of Manchester describing how micro-organisms that cause spoilage of food can be detected within seconds. They have developed an infrared spectroscopy technique that picks up infrared light reflected from the surface of meat and produces biochemical fingerprints of any micro-organisms on the surface, rapidly estimating their number. Conventional laboratory techniques for growing and identifying spoilage bacteria can take hours or days. The technique has been used on chicken and beef. The authors hope that this technique can be incorporated into production lines to monitor the quality of product as it is produced. Laser light detection of micro-organisms using flow cytometry is another extremely rapid method of analyzing the quality of food. As long as micro-organisms can be stained with a fluorescent dye, they can be counted using a laser light flow cytometer. Many of these instruments count total bacterial cells – dead or alive – using stains that bind to the DNA of cells. Results are obtained within minutes in fully automated machines. An example is the Bactofoss, used routinely in many countries, including New Zealand, for counting micro-organisms and grading milk collected from farms. In fact, New Zealand leads the way in using this technology for grading milk. Other systems have been developed that count living bacteria in food samples by mixing the sample to be tested with a compound that is digested by enzymes in micro-organisms, resulting in a product within the cells that fluoresces when exposed to ultraviolet (UV) light at 488nm. The fluorescing micro-organisms are pumped past a laser light and each individual cell is counted. Using this laser-based counting method a manufacturer does not have to wait days for results to ensure that the food he is producing is safe – the results are ready within minutes. Another use of laser light is in observing food structure. Confocal laser microscopes allow us to see the microstructure of food in three dimensions. This is a very powerful tool in understanding and developing foods. A confocal microscope creates sharp images with better contrast than does a conventional microscope. The main advantage of the confocal microscope is in building three dimensional images of specimens through a computer assemblage of images taken at different depths through the specimen. Some examples of confocal images in foods can be seen in Figures 1 to 3.

Using light to improve food safety and prevent spoilage Ultraviolet light is a powerful antimicrobial agent used to treat packaging and reduce the microbial load in foods. Water has been treated with UV light for many years, but it is also possible to treat any food that can be pumped. This includes a variety of drinks and food ingredients such as whey (the by-product of cheese manufacture used as a protein source in many foods). Ultraviolet light is the most common ‘cold’ processing technology used as an alternative to standard heat treatment; heat is costly and can damage some of the nutrients in foods. Ultraviolet light does not produce chemical residues and is low-cost.


used to store food. This all helps to prevent spoilage and ensures that food is safe and has a long shelf life. The effectiveness of UV light can be enhanced by applying it in high intensity pulses. With 200 pulses of high-UV light, microbial populations are reduced by 5 to 6 log10 orders, whereas a 1 to 2 log10-order reduction in cell numbers is achieved with standard UV treatment. In summary, UV light is an emerging cold processing technology that has been used for many years for the treatment of water, but currently is being considered for treating foods by replacing or enhancing thermal processes. Next time you enjoy a meal, think about the role light plays in food quality and how food technologists make use of light in the analysis and treatment of the food. For further information contact: S.H.Flint@massey.ac.nz; and for information about food science and careers visit: www.nzifst.org.nz

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Further reading Bintsis, T., Litopoulou-Tzanetaki, E., & Robinson, R. K. (2000) Existing and potential applications of ultraviolet light in the food industry – a critical review. Journal of the Science of Food and Agriculture, 80, 637-645. Flint, S., Walker, K., Waters, B., & Crawford, R. (2006) Description and validation of a rapid (1h) flow cytometry test for enumerating thermophilic bacteria in milk powders. Journal of Applied Microbiology, 102, 909-915. Guerrero-Beltran, J. A., & Barbosa-Canovas, G. V. (2004) Review: Advantages and limitations on processing foods by UV light. Food Science and Technology International, 10, 137-147. Osborne, B. G. (2009) Near-infrared spectroscopy in food analysis. In Encyclopedia of Analytical Chemistry, Wiley and Sons Inc. ISBN 0471 97670 9. deMan, J. M. (1980) Light-induced destruction of Vitamin A in milk. Journal of Dairy Science, 64, 2031-2032.

Teachers at the recent Biolive conference, held at the University of Otago, were invited to attend a workshop run by members of the New Zealand Institute of Food Science and Technology (NZIFST) and staff from the Department of Food Science, University of Otago. The goals of the workshop were first, to introduce the teachers to a series of biology and chemistry based experiments that NZIFST members had developed in

conjunction with Food Science Department staff and which are available on the NZIFST web site (see below) and second, to facilitate interactions between the teachers and the university. The six experiments featured on the website were developed with the goal of promoting a career in the food industry to secondary school science students. Topics covered include: catalase activity; peroxide value (titration); extraction of fats from foods (gravimetric analysis); presence of protein in foods (qualitative analysis); monitoring changes in lactic acid concentration and pH during the production of sour cream; and isolating bacteria from sour cream (www.nzifst.org.nz/careers/secondaryresources.asp). The website also contains a teacher’s guide and background information relevant to the experiments. All the experiments are designed to be carried out during either one or a series of one hour classroom sessions. They were developed to fit within the science curriculum and school guidelines, and aim to expose students to key skills such as how to carry out titrations and colorimetric assays. The experiments highlight the fact that Food Science / Food Technology degrees are based upon science disciplines such as chemistry, biology, microbiology, physics, and mathematics and that a career in the food industry is a fantastic way to apply fundamental science skills to realworld problems associated with production of safe, tasty, and stable foods. For further information contact: phil.bremer@otago.ac.nz New Zealand Association of Science Educators

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Food science experiments online

Figure 1: Derrith Bartley (St Hilda’s Collegiate School, Dunedin) and Miriam Denney (Unlimited, Christchurch) share a smile of success.

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Ultraviolet light of a specific wavelength (200–280nm), also known as UVC (ultraviolet subtype C), is the most effective at inactivating micro-organisms. At this wavelength, DNA bonds are split by cross-linking between thymine and cytosine. This results in the cell being unable to function and eventually dying. However, when these cells are exposed to light at wavelengths of 330nm or higher, this injury to the DNA can be repaired. This is known as photoreactivation and is a result of DNA repair genes in the microorganisms. To avoid this problem, foods treated with UV light should be stored in the dark. (See Figures 4 and 5) The actual UV treatment process is simple: passing liquid food through glass tube surrounding a UV light source. Factors affecting the success of UV treatment include the amount of energy produced by the light source, the time the product is exposed to the UV light and the clarity of the liquid. UV light does not penetrate well into opaque liquids such as milk, therefore the liquid needs to be exposed to the UV light as a thin film. Even with fruit juices, the penetration of UV light is only about 1mm with light absorption at 90%. Some manufacturers of UV treatment systems have developed turbulent flow applicators that ensure products such as milk are evenly exposed to the UV light source. UV treatment of solid foods, such as fruits and vegetables, reduces the initial count of micro-organisms on the surface of the product, and increases the resistance of fruits and vegetables to further microbial colonization through the formation of phenolic compounds. Ultraviolet light is also used to sterilize in-process food contact surfaces and the internal surfaces of packaging

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When is shorter better? When is shorter better? When you are talking about laser pulses of course, as Cather Simpson and Charles Rohde, The Photon Factory, Departments of Chemistry and Physics, University of Auckland explain: The laser1 is one of a few remarkable inventions that has transformed civilization within a single lifetime2. Lasers are everywhere. We use them to listen to music and watch movies, to purchase items at the store, and in our high-speed communications and computer networking. Lasers are increasingly useful in medicine, where they can repair tissues in the eye, remove birthmarks, and promise new ways forward in the war on cancer. And, of course, lasers in research labs around the world have enabled groundbreaking discoveries in chemistry, physics, biology and engineering. Next year marks the fiftieth anniversary of the laser. On

16 May 1960, Theodore Maiman at Hughes Research Laboratories in the United States, won the heated race to be first. He made a ruby crystal go into a ‘negative temperature’ state, and thereby generated laser light at 6943 Å and 6929 Å3. What most people don’t realize is that Theodore Maiman’s first laser was pulsed. Unlike laser pointers used in lectures and scanners at the supermarket, Maiman’s laser emitted coherent light in short, microsecond (ms) to millisecond (ms) bursts. 4 Immediately, researchers like Nobel Prize winner Charles Townes began using laser pulses to forge new branches of experimental physics and chemistry5. Two years later, ‘giant’ laser pulses of ~120 nanoseconds (ns) long were created by Q-switching6. Q-switching turns the laser cavity ‘on’ or ‘off’ using the electric field-sensitive birefringence of a material such as nitrobenzene or lithium niobate. If the dependence is linear in the electric field, it is a Pockels cell; if the dependence is quadratic then it is a Kerr cell. This approach

Figure 1: Interesting things happen on short time scales. (a) the age of the Universe is about 13 billion years; (b) evolution of humans (Homo erectus) begins about 2 million years ago; (c) Neanderthal man (Homo neanderthalensis) goes extinct about 30,000 years ago; (d) ½ life of plutonium-238 (238Pu) is 87 years; (e) the human heart beats about 1-2 times per second; (f) – (j) bacterial photosynthesis: sunlight is absorbed by the Light Harvesting Complex and the (j) energy is transferred to the special pair of bacteriochlorophylls in the reaction centre in 10s of fs, (i) the first electron transfer step occurs in ~3 ps while subsequent ones (h, g) are a bit slower, and (f) the generation of ATP takes ms; (k) the period of a single CH breathing vibration in benzene; (l) the first step in vision, the photoisomerization of retinal, takes ~700 fs; (m) thermal energy transfers from the heme to the surrounding protein on the 20-100 ps timescale; (n) intramolecular vibrational energy redistribution in the heme occurs on 2-20 ps timescales; (o) heme nonradiative electronic relaxation is a sub-ps process; (p) nuclear fission processes span ns to ms; (q) electron-phonon collisions in semiconductors occur in ps; (r) electron-hole recombination happens in ns to ms; (s) – (u) CPU clock cycles over the last 40 years. Protein structures downloaded from the Cambridge Protein Data Bank (www.rcsb.org) : Reaction Center (R. viridis) structure ID 1PRC, Light harvesting complex (R. acidophila) structure ID 1NKZ, human deoxyhemoglobin structure ID 1A3N. 24 New Zealand Association of Science Educators


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Figure 2: Comparison of ns and fs laser ablation of a substance with a pre-deposited surface feature (yellow bar). (left) Ns ablation relies primarily on heat transfer from the laser to the material.This can result in unwanted long-range damage, including shock-wave induced micro-fracturing and surface damage, surface shadowing from re-solidified slag, and damage to nearby features. These effects are absent in fs laser ablation (right), due to the rapid ionization of the substrate material that precludes heating of the bulk substrate. is still used routinely today to produce laser pulses as short as a few nanoseconds. The march to shorter and shorter pulses continued rapidly with the development of mode-locking just a few years later in the mid-1960s7. In mode-locking, the axial modes in the cavity are forced into phase with one another. Interference leads to the generation of a train of very short pulses separated temporally by the cavity round trip time. Mode-locked lasers output pulses from 10s of picoseconds (ps) to sub-30 femtoseconds (fs)8. Such short pulses are limited by Heisenberg’s Uncertainty Principle. For example, a 120 fs laser pulse with a centre wavelength of 800nm has a width of about 10nm, due to the conjugate relationship between energy and time. The discovery that Ti:sapphire could self-mode-lock in a robust laser cavity led directly to femtosecond lasers being ‘off the shelf’ technology today. Now, the frontier of laser pulses is in attoseconds (as)9 – pulses that last less than one cycle of visible light! Attosecond lasers use a very nonlinear process called high harmonic generation and induce coherent electron rescattering from atoms and molecules10. An electron is driven away from its parent ion by a high-field laser pulse. Each time it passes back by the parent, it can recombine to release an attosecond flash of X-ray laser light. So in only 50 years, the state-of-the-art in laser pulse duration has improved by about a trillion fold.

What is so interesting about such short time scales? Science and technology are often driven by the desire to push back the boundaries of the unknown; this is just as true for pulsed lasers. However, each successively shorter laser pulse has also underpinned tremendous advances in biology, chemistry, physics and medicine. For example, the inherently large fields in ultrashort pulses have probed fundamental physical processes that depend nonlinearly upon the electric field. That same nonlinear dependence has also fostered rapid advances in medical imaging. Many critically important processes occur on sub-microsecond time scales (Figure 1). The power of lasers is that they can be used as very fast stopwatches – one pulse can stimulate a process, and a second then interrogates the sample some

time later. This approach was used by Professor Ahmed Zewail on his route to the Nobel Prize in Chemistry in 1999 for “ his studies of the transition states of chemical reactions using femtosecond spectroscopy11.” Haemoglobin is just one of many systems whose inner workings have been revealed by time-resolved laser studies. Human haemoglobin has four subunits, each with one heme (one O2 binding site). Binding is cooperative; when one oxygen binds a heme, the affinity of the other three sites increases12. In the 1980s, ns and ps laser pulses probed the vibrational (Raman) spectrum of the heme active site after photoinduced dissociation of the diatomic ligand from the heme iron. The findings explained how Fe-ligand bond breaking/forming is communicated to the protein, and accounted for the differences in binding rates in the ligatedand unligated hemes13. Later, even shorter pulses probed a functional adaptation hemes share with DNA bases – they are very hardy in intense light14. Absorption of a UV-Vis photon is followed by sub-ps, non-radiative decay to the ground state, and efficient dissipation of excess vibrational energy to the surroundings. Research into the mechanism of this extraordinary behaviour is ongoing in the Photon Factory at the University of Auckland.

Ultrashort laser pulses in the Photon Factory The University of Auckland established the Photon Factory at the end of 2008 with an investment of over $1.5M (NZD). The goal to bring short (ns, ps, and fs) laser pulses to New Zealand scientists, engineers, and educators in a flexible multi-user facility is well in hand. The Photon Factory is moving in two complementary directions. The first is construction of capabilities to watch chemical and physical processes in ‘real-time’ with femtosecond UV-Visible absorption, fluorescence, and vibrational spectroscopies. The second exploits laser pulses for micro- and nanomachining and fabrication of devices. In 1959, just as the laser was being invented, Professor Richard Fenyman famously exhorted scientists to explore the “room at the bottom15.” Ultrashort laser pulses are now making this truly possible. Researchers increasingly take advantage of the powerful, and often unique, capabilities of ultrashort pulses to machine tiny features. For example, New Zealand Association of Science Educators

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science ultrashort laser pulses can machine 3-dimensional stents teacher from soft, flexible, biocompatible materials16. The Photon

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Factory provides a prototyping facility for NZ researchers. It offers ns and fs laser machining capabilities because the interaction between the pulse and the material depends on pulsewidth (Figure 2). While ns pulses give fast, efficient processing, they deposit significant energy in the material and generate heat-induced effects. Fs pulses, on the other hand, lead to very fine, clean features down to 10s of nanometers in size and repeatability. The Photon Factory hosts a wide array of ongoing projects, in addition to our own research in the photochemistry and photophysics of molecules in solution. Examples include probing the photochemistry and photophysics of solar energy harvesting materials, exploring new ways to generate nanosecond white light pulses with optical fibres, creating microchannels for lab-on-a-chip devices, and constructing micron-scale actuators for marine microrobots. We also teach classes, hold workshops and host school visits, on request. There’s always something exciting going on at the Photon Factory.

What does the future hold?

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From their discovery in 1960 to the present, laser pulses have enabled extraordinary advances with huge societal impacts, and the evidence suggests it’s not over yet! From 1990 to 2003, over 350,000 papers studying or applying lasers were published in the peer reviewed literature, and these numbers continue to increase: 46,000 papers were published in this area in 2007 alone17. Lasers continue to transform the way we think about light and its interaction with matter. As physicists push into the attosecond domain, other basic and applied researchers follow closely behind, probing the fundamental behaviour of the Universe. Five or ten years from now will we be talking about the marvels of zeptoseconds? We certainly hope so. For further information contact: c.simpson@auckland.ac.nz

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LASER stands for Light Amplification by Stimulated Emission of Radiation, an acronym widely attributed to Gordon Gould in a paper he presented at a conference in 1959 (Gould, R. Gordon, (1959) “The LASER, Light Amplification by Stimulated Emission of Radiation” in The Ann Arbor Conference on Optical Pumping, U. Michigan 15 June – 18 June 1959, editors Franken, P.A. & Sands, P.H) The laser was invented within the lifetimes of nearly one-third of New Zealand’s population (http://www.stats.govt.nz/infoshare/ Last Accessed August 26, 2009) Maiman, T.H. (1960). Stimulated Optical Radiation in Ruby. Nature, 187, 493-494. ms = millisecond = 1 x 10-3 s; ms = microsecond = 1 x 10-6 s; ns = nanosecond = 1 x 10-9 s; ps = picosecond = 1 x 10-12 s; fs = femtosecond = 1 x 10-15 s; as = attosecond = 1 x 10-18 s. Townes, C.H. (2003). “The First Laser“ excerpted from A Century of Nature: Twenty-One Discoveries that Changed Science and the World (eds. Garwin, L. & Lincoln, T.), p. 107-112, University of Chicago Press, The University of Chicago, USA. McClung, F.J., & Hellwarth, R.W. (1962). Giant Optical Pulsations from Ruby. J. Appl. Phys., 33(3), 828-829. Haus, H.A. (2000). “Mode-Locking of Lasers” IEEE J. Selected Topics in Quantum Electronics, 6(6), 1173-1185. This article discusses the history of mode-locking, as well as the principles and examples. For a sense of scale, light travels the distance of about the width of a human hair (30 mm) in 100 femtoseconds; It travels about the length of a car or elephant (3 m) in 10 nanoseconds. Both of these pulsewidths are routinely commercially available today. Science (2008). 317, 765-778. Science Magazine (AAAS) published a special section in 2008 on Attosecond Spectroscopy. The three reviews in this section cover the generation of attosecond pulses, their use in lightwave electronics, and the attosecond spectroscopy. Kapteyn, H., Cohen, O., Christov, I., & Murnane, M. (2008). Harnessing Attosecond Science in the Quest for Coherent X-Rays. Science, 317, 775-778. http://nobelprize.org/nobel_prizes/chemistry/laureates/1999/ (Last Accessed 31 August, 2009). For a basic review of haemoglobin and cooperativity, see Stryer, L. (1995), Biochemistry 4th Ed. W.H. Freeman and Co., New York, pp. 147-177. Findsen, E.W., Friedman, J.M., Ondrias, M.R., & Simon, S.R. (1985). Picosecond Time-Resolved Resonance Raman Studies of Hemoglobin: Implications for Reactivity. Science, 229, 661-665. Challa, R., Gunaratne, T.C., & Simpson, M.C. (2006). State Preparation and Excited Electronic and Vibrational Behavior in Hemes. J. Phys. Chem. B., 110, 19956-19965. This paper has a fairly comprehensive review of the literature in this area, for the interested reader. For more information about fast behaviour in DNA see Crespo-Hernandez, C.E., Cohen, B., Hare, P.M., & Kohler, B. (2004), Ultrafast Dynamics of DNA, Chem. Rev., 104, 1977-2020. For the full text of his comments, delivered in 1959 before Maiman’s demonstration of the laser, see http://www.zyvex.com/nanotech/feynman. html Nolte, S. (2003). Micromachining. In Ultrafast Lasers: Technology and Applications. Marcel Dekker, Inc. Golnabi, H., & Mahdieh, M. H. (2006).Trend of laser research developments in global level.” Optics & Laser Technology, 38, 122-131. Rohde, Charles, SciFinder Scholar Search, October 10, 2008.

ask-a-scientistcreatedbyDr.JohnCampbell Why do mountains appear to be blue when seen in the distance? Emma Jukes, Palmerston North. Henning Klank, a physicist at Massey University, responded: Scattering of light is basically what makes the mountains appear blue in the distance. Scattering is the reason why we are able to see the light beam of a movie while sitting in the movie theatre. The same is true for the blue sky. How do we perceive the colour of an object? Light from a light source (e.g. the Sun) is scattered/reflected from the object and passes through the air to our eye which responds to a small range from red to violet. So the colour we see depends on what the source emits, the molecules in the object that cause the scattering/reflection, how light interacts with air, and how our eye responds to light. Think about how the Sun shines on a cloud-free day. The atmosphere consists of air, which consists of very small molecules. Air seems to be very transparent over shorter distances. The light from the Sun passes through our

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atmosphere. If we look at the Sun directly (or almost directly, which would be better for our eyes) when it is high we see what appears to be white light. If we look away from the Sun we see the blue sky which shows us that blue light is scattered. The molecules of air scatter light, with the shorter wavelengths (violet) scattered much more than the longer wavelengths (red). We should therefore see a violet sky, but our eyes are more receptive to blue in comparison to violet and blue is scattered almost as much as violet. When we look at mountains in the distance then the mountains are often dark and we see blue light scattered by the air between. The more distant the mountain, the longer the air path and the bluer it appears. If we looked directly at the Sun we would see the Sun in yellow light, because some blue light is scattered away on the path between the Sun and our eyes. This is most dramatic at sunset, when the Sun appears red, because the path through the atmosphere is rather long. For further information: questions@ask-a-scientist.net


While lasers are found in many areas of modern life, few people are aware of their use as rotation sensors with extreme sensitivity as Jon-Paul R. Wells, Robert B. Hurst and Geoffrey E. Stedman, Department of Physics and Astronomy, University of Canterbury explain: Introduction Next year, 2010, is the fiftieth anniversary of the first demonstration of a working laser by Theodore Maiman at Hughes Research Labs which formally occurred on the 16th of May, 1960. For his experiment, Maiman chose ruby (Al2O3 –sapphire – doped with trivalent chromium ions), a pulsed laser system. The laser (or optical maser) was born out of the microwave devices developed by Charles Townes and Arthur Schawlow in the 1950s, and it was they who wrote the seminal work outlining the prospects for an optical maser which culminated with Maiman’s experimental realization of that concept.1 Upon its development, the laser was famously viewed as ‘a solution without a problem’. Despite this, it didn’t take more than a few months before applications were found and of course, we all know that the laser has become ubiquitous in modern life. As early as 1963, the first laser gyroscope was developed by Macek and Davis2. So what is a laser gyroscope? A typical laser is constructed from a so-called ‘gain medium’ that provides optical amplification (such as helium and neon gas) within a minimum of two mirrors which form an optical cavity. In a helium-neon (He-Ne) laser, the gas is electrically excited within a discharge tube. Light emission from the neon atoms is captured within the cavity by the mirrors and coherently amplified by repeated passes through the gaseous gain medium. Thus a laser is essentially an oscillator with optical feedback. What we see as a laser beam is the small fraction of light that is allowed to ‘leak’ out of one of the cavity mirrors. In an He-Ne laser the laser output has a wavelength of 632.8 nanometres, the characteristic red light one sees at the supermarket barcode scanner. By contrast, a ring laser has the mirrors arranged in a triangle, square or rectangle forming a closed path or ‘ring’. This allows two essentially independent laser beams to travel around the ring, one in the clockwise direction, the other counterclockwise. Suppose the whole apparatus is rotated clockwise at some rotational velocity,W. Imagine a beam of light beginning at one mirror. Since light travels at the same speed in both directions it will take longer for the clockwise travelling beam to reach its starting position compared to the counterclockwise beam since the starting position has moved since the beam departed. This effect alone causes a phase shift between the two beams and was discovered by French physicist Georges Sagnac who first demonstrated the principle in 1913, before the laser era. Nowadays it is precisely this phase shift that is measured in a passive Sagnac interferometer such as a fibre-optic gyroscope. Coherent amplification in a resonant laser cavity demands that there must be an integer number of wavelengths of the laser light around the closed loop (the electric field of the associated electromagnetic wave must have a node at the cavity mirrors). As a result, the wavelength must either stretch (a red shift) or shrink (a blue shift) in response to an input rotation. This causes a subtle change in the frequency of each beam depending on the rotation speed. By optically combining these two beams we can make a very accurate

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measurement of the beat note or Sagnac frequency. Since this beat frequency is proportional to the input rotation, we are able to accurately infer the magnitude of the rotation in question. One of the problems to be overcome in constructing ring lasers capable of measuring rotation is the phenomenon of ‘lock-in’. The ring laser, as discussed above, is viewed as two essentially independent oscillators, i.e. the laser beams propagating in either direction are not considered to be coupled in any fashion. However, this is not strictly the case, since even the most perfect mirrors (our laser mirrors have a reflectance of 99.9995%) will generate a finite amount of scattering of either beam, some of which will remain trapped in the cavity. Thus light from the counter-propagating beam can be ‘injected’ into the co-propagating beam (and vice versa) thereby coupling the beams. This coupling tries to make the optical frequency of the two beams degenerate (they are ‘frequency pulled’ together). To overcome this either the ring laser must be subject to large rotational velocities, or the scatter from the mirrors must be very small such that one may maintain a rotation sensing ability. The range of rotational velocities for which the ring laser has frequency degenerate beams is known as the ‘lock-in’ region.

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University of Canterbury Ring Laser Project By the early 1980s an astonishing number of techniques had become available for interfering waves in a ring to measure rotation, each involving some remarkable fundamental physics. Many of these were sufficiently sensitive to show the effects of Earth rotation in the laboratory. One was the interference of waves formed by electron pairs travelling in both directions in a superconducting ring. Another was the interference of neutron matter waves from a nuclear reactor in a quartz crystal interferometer. The most sensitive and accessible for us, however, appeared to be those formed with interfering laser light waves in a ring of mirrors as described above. What made this exciting was evidenced by two major engineering advances. First, these optical gyros had become standard equipment in the inertial navigation of aeroplanes, rockets and all kinds of missiles. Second, these applications had stimulated an immense amount of work into making

Figure 1: Schematic layout of a ring laser gyroscope. New Zealand Association of Science Educators

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Figure 2: World War II plan of the Cashmere Caverns. better mirrors having reflectances approaching the value mentioned above. While these were engineering advances, the benefits of such tools for scientific research had been ignored and that was where our interest and expertise could help. We did not want to be involved in military goals as, in many ways, it would only be a case of ‘beating swords into ploughshares’ using military grade mirrors; an old military cavern for a laboratory and, eventually, with German collaborators. So our ring laser experiment began as a collaboration between the University of Canterbury and Oklahoma State University in the USA. For various technical reasons, the common wisdom in the ring laser field at that time, held that the upper practical limit on the laser perimeter was around 60cm. In 1988 we started with a laser which we called C-I built on a glass plate made of a low expansion ceramic (Zerodur) in a similar fashion to an oven top. This device was slightly less than one metre square with a general layout as in Figure 1. The technological leap forward afforded by C-I was that it was the first ring laser to un-lock on the bias provided by Earth rotation alone. At first we had no where to put it, except the eight storey Physics building on the Ilam campus, but every time there was a north-west wind, the building rocked. This had the effect of cancelling out the Earth rotation and killed the interferometric (Sagnac) signal. After some time, we heard of the old wartime cavern that had been built in Cashmere, under the Port hills, which were intended to be a command post should the Japanese invade New Zealand but were never used during the War (Figure 2). The cavern environment was ideal because of its small temperature changes and relatively little mechanical noise. With the permission of the owners (and later of the Christchurch City Council) we set up a series of rings. One was built in Germany by colleagues who were interested in measuring changes in the rotation of the Earth to extremely high precision. The machine, which we called C-II, represents a total expenditure of around NZ$2 million and was a major acquisition for New Zealand science. It easily reveals the tilting of Banks Peninsula when there are high tides on the local beaches, as the extra-tidal water pushes the Earth down. It also revealed (to our surprise) another effect from the Moon. The Earth is a bit like an outof-balance car tyre, it has bulges near the equator, and the Moon’s gravity can move the axis of rotation of the Earth by tugging on these, moving the north-south axis of the Earth through a rotation each day amounting to a motion of about 60cm at the poles. A series of large ring lasers followed. The largest ring laser constructed so far (UG-2) has an area of 834m2 (it is a 28 New Zealand Association of Science Educators

Figure 3: Inside the Cashmere Cavern showing one arm of the 834m2 UG-2 ring laser. rectangle of approximately 40 by 20 metres – see Figure 3). These very large ring lasers are the most sensitive man-made rotation sensors ever built. The reason for their sensitivity is that the rotational signal increases in proportion to the area, and that other things being equal the sharpness, and so the measurement precision of the optical resonance also improves with size. The accuracy is such that over one second they can measure a change in angle roughly equivalent to the angle seen between the two sides of a human hair as viewed from a distance of 550km. As such they totally eclipse the capabilities of the old pre-laser Sagnac interferometers. Albert Michelson, one of the legendary experimenters of science, built a Sagnac device to measure Earth rotation in 1925. This had a perimeter of 1904 metres, far bigger than our caverns. It would be a fascinating experiment to reproduce his experiment in our laser era, and of course one can expect many complications whose clear separation from the Earth signal would be amongst the scientific problems to be solved.

Rotational dynamics 1. Microseismic Activity Almost at any time, small oscillatory rotations with a period around 5-6s are detectable with the large ring lasers. They are indeed small, typically of order 1 nano-radian in amplitude. They are caused by ocean waves, but not by the obvious mechanism of waves breaking on the shore. They

Figure 4: Double-frequency microseismic rotations (6 May 2004) as observed by UG-2.


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occur at twice the frequency of the larges waves, and they originate from pressure fluctuations on the seafloor when trains of waves cross each other. (They are officially termed double-frequency microseisms.) Not surprisingly the amplitude varies somewhat with meteorological conditions around New Zealand. A typical graph of this rotation is shown in Figure 4.

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2. The Movement of the Earth’s Poles Planet Earth as it rotates in space behaves like a rather nonideal gyroscope, in that the orientation of the rotation axis wanders around. Part of this is well known to astronomers as precession of the equinoxes: Because the Earth is an oblate spheroid, and the Sun and Moon spend most of their time outside of the equatorial plane, they exert gravitational torques, which cause the rotation axis to precess. Figure 5 shows the predicted movement of the rotation axis during the first half of 2002. The large arc of about 8m radius is in fact not gravitationally induced but a ‘free-body’ Eulerian wobble known (for its discoverer) as the Chandler wobble. The small cycles getting periodically larger and smaller are the gravitational effects. These occur with a periodic time of a day.

Figure 6: Top: Prof Ulli Schreiber and Dr Athol Carr setting up a fibre gyroscope on level 54 of the Sky Tower. Bottom: Deflection of the Sky Tower in moderate winds.

Figure 5: Theoretical prediction of the movement of the Earth rotation axis and its observation in early 2002.

3. Displacements of static structures The discussion above centres on the measurement of very small rotational effects. Larger events do not require the extreme sensitivity afforded by large ring lasers. Small (handheld) fibre-optic gyroscopes (FOG) are a good example of laser based Sagnac interferometers which, although in principle are capable of detecting Earth rotation (5.3x10-5 radians per second), are generally

better suited to the measurement of larger rotation rates. An illustration of this point is made by measurements performed by our team on the Sky Tower in Auckland. A FOG was attached to the window supports and oriented to be sensitive to the rocking motion of the structure in the north-south direction. The excursion of the building is then evaluated from the measured rotation rate in wind speeds between 24 and 36km/hr. As can be seen in Figure 6, this corresponds to a 2cm amplitude rocking motion of the building over a period of seven seconds. The overall envelope of these excursions shows the response of the Sky Tower to wind gusts. The particular interest of structural engineers arises here because in an earthquake nothing remains static. The laser gyroscope becomes invaluable in this context because it does not require an external reference frame to measure absolute rotations. This greatly contributes to our understanding of the structural response of buildings during earthquakes, which in turn will enable engineers to design buildings better resistant to structural failure during them. Good rotational sensors like these are in fact quite uncommon and little engineering data on building rotation exists despite its proven importance in earthquakes for buildings with a structure based on several vertical concrete columns. So this work at Canterbury and by partners in Germany has helped to trigger a new direction both in seismology and in civil engineering research. For further information contact: jon-paul.wells@canterbury.ac.nz

References Schawlow, A. L., & Townes, C. H. (1958). Phys. Rev., 112, 1940. Macek, W. M., & Davis, D.T.M. Jr. (1963). Appl. Phys. Lett., 2, 67.

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twinkle twinkle little star “Twinkle, twinkle, little star, how I wonder what you are…” The reality of the children’s rhyme is that astronomers can use the light from stars to discover an incredible amount of information about the workings of the universe as Emily Brunsden, PhD student, Department of Physics and Astronomy, University of Canterbury explains: A star’s temperature, composition, distance from the Earth, relative speed to us, size, and even its internal structure can be determined just by gathering the light. From analysing the twinkling light of a myriad of astronomical objects (such as planets, stars, nebulae, galaxies and galaxy clusters) we gain insight into what is around us, how it works, and we strive towards understanding our place in the universe.

What is light to astronomers? Light is everything. From when people first looked at the stars, until today, light has been the single most significant way we learn about the greater universe. Light is an electromagnetic wave but it is quantized into packets of energy called photons, each with a precise wavelength. Photons with shorter wavelengths have more energy and form the ‘blue’ end of the spectrum (although this goes far beyond what humans see as the colour blue). Similarly, low-energy photons have a longer wavelength and can be found towards the ‘red’ end of the spectrum. The energy, E, of a photon is related to its frequency, f, or wavelength, l, by: E = hf = hc/l where h = 6.626 x 10-34 J.s is the Planck constant and c is the speed of light.

Astronomers today collect light across the electromagnetic spectrum from a variety of objects in the universe (Figure 1). Because light is all we have to analyse, many clever techniques and technologies are used to extract as much data as we can from simple starlight.

How do we collect light? Astronomy begins with the naked eye. On a dark night we can see up to 3000 stars in the sky, along with other galaxies, gas clouds, planets and satellites. To analyse these objects and more, astronomers use a range of telescopes that can see beyond the naked eye in two ways: in the first instance, light we see from the stars comes from only a small segment of the electromagnetic spectrum, from around 400–700nm. To see outside of this range, different telescopes are used to detect light from highenergy gamma rays to low-energy radio waves. The second function of a telescope is to see fainter objects. This is achieved by increasing the light-collecting area of the telescope. This means that more photons are collected in the same amount of time – much like how a bucket with a larger diameter will collect more raindrops in a storm than a narrow one. Telescopes are designed and built to look at certain parts of the spectrum. Most ground-based telescopes look at the optical or radio parts of the light spectrum as photons from other regions are absorbed by the Earth’s atmosphere (Figure 2). For most other areas of the spectrum, satellites orbiting above Earth’s atmosphere are gathering light, such as from the infrared and microwave regions. Optical telescopes are generally classed by the diameter of the primary light-collecting area – traditionally a lens, but more commonly in modern times, a curved mirror. Telescopes work on the principle of gathering more photons to see further, rather than higher magnification. New Zealand has several optical research telescopes such as the 1.8m MOA telescope and the 1.0m McLellan telescope at Mt John University Observatory in Tekapo (Figure 3). These telescopes can see objects thousands of time fainter than the naked eye and into parts of the infrared and ultraviolet spectrum beyond human vision. Radio telescopes collect photons with wavelengths in the order of several metres. As such, they do not require a smooth mirror, but can use a dish with a surface like chicken wire to collect radio ‘light’. Radio telescopes also benefit by

Figure 1: The electromagnetic spectrum.

Figure 2: Absorption by the Earth’s atmosphere.

Source: http://en.wikipedia.org/wiki/File:Electromagnetic-Spectrum. png

Source: http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_transmittance_or_opacity.jpg

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Figure 5: The Hubble Space Telescope. Source: http://en.wikipedia.org/wiki/Hubble_Space_Telescope

Figure 3: The 1.0m McLellan telescope at Mt John University Observatory. Photograph courtesy of Department of Physics and Astronomy, University of Canterbury.

not having to wait until a clear night to observe. Since radio waves pass through clouds and are unaffected by daylight, radio astronomers can observe 24 hours a day to collect their data. Radio telescopes can also be linked in such a way that two telescopes far apart can act like a huge telescope as large as the distance between them. This technique, called interferometry, is the science behind telescope arrays such as the Square Kilometre Array (SKA), which is a giant radio telescope, proposed to be built in the Australian western desert (Figure 4). It would comprise of many dishes in a core

Figure 4: An artist’s impression of the SKA main site in Western Australia. Source: http://en.wikipedia.org/wiki/File:SKA_Artists_Impression_of_ Dishes.jpg

area of Western Australia with a handful located in other states and in New Zealand. The Earth’s atmosphere shields us from photons across most of the other areas of the spectrum. This is good news for us as we are protected from potentially dangerous radiation, but bad news if the radiation is coming from an astronomical object we wish to observe. To overcome this, satellites are launched to orbit the Earth and observe objects at gamma-ray, X-ray, ultraviolet, infrared and microwave wavelengths. The most famous space telescope, the Hubble Space Telescope, is essentially an optical telescope with extended observing power in the infrared and ultraviolet. The reason Hubble can take such breathtaking pictures of the universe is because it is unimpaired by distortions in Earth’s atmosphere. Although we receive light from the visible spectrum at ground level, small-scale motion of air particles at different altitudes causes the stars to ‘dance around’ and ‘twinkle’. Orbiting above the atmosphere allows Hubble to take long exposure photographs where there is no such distortion in the image (Figure 5).

How do we interpret light? Telescopes can help us to see more detail about the universe, but this data has to also be recorded and interpreted. Unlike most areas of science, astronomers can not travel to measure their objects of interest, and so rely on many sophisticated techniques to extract as much information as possible from just the light we see. One such technique is spectroscopy. Spectroscopy is a broad term for the measurements made of the electromagnetic spectrum, generally in high detail. In the visible wavelengths, the spectrum looks like a continuous rainbow. A perfect rainbow would come from an object thermally emitting white light. Although this is what is produced in the core of a star, the starlight must pass though the outer layers of the star’s own atmosphere. Elements in this atmosphere absorb photons at very specific wavelengths causing gaps to appear. These gaps are called absorption lines and they tell us information about the elements present, temperatures, magnetic fields and pressures, whether the star is moving towards or away from us and even if the surface of the star is pulsating. A similar effect is caused by glowing gas, or ‘nebulae’, in the universe. This produces the opposite effect – emission lines of colour against a black background. These lines match up to absorption lines and tell us specific information about the elements that are excited in the clouds (Figure 6). High-resolution spectroscopy can be used to calculate the New Zealand Association of Science Educators

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Figure 6: The absorption spectrum of the Sun. The dark lines, known as Fraunhofer lines, are caused by elements such as sodium, calcium and iron in the Sun’s atmosphere which absorb photons at specific wavelengths. Source: http://en.wikipedia.org/wiki/File:Fraunhofer_lines.svg

velocities of objects using Doppler shifts of the spectral lines. Measurements of spectral lines in laboratories on Earth tell us the location of each line when it is at rest. When a photon is emitted from an object moving towards us the wave is slightly compressed and thus shortened, making it appear slightly bluer. The same thing happens with objects moving away from us, like most galaxies, where the lines become red-shifted (Figure 7). The shift in the wavelength, Dl, is directly related to the speed of recession, v, by: Dl/lrest = v/c where Dl = (lmeasured – lrest) and c is the speed of light. The instruments that collect these kinds of spectra are termed spectrographs and can use either a prism or a finely ruled diffraction grating to split the light. One such instrument is the HERCULES spectrograph on the McLellan telescope, which can measure surface movements and velocities of stars to a precision of 15m/s.

What will the future of astronomy be like? Telescopes, instruments and observing techniques are constantly evolving and improving alongside technological developments. Computing processing power and storage developments have allowed for more detailed and comprehensive observations, while satellite and electronic advancements allow us to build better space telescopes. One example is the James Webb Space Telescope due to be launched in 2014. This giant eye in space will see further than Hubble to the farthest reaches, and thus oldest objects in the universe. Fibre-optic cables and robots are beginning to appear in observatories and technologies are being developed so astronomers will not even have to leave their offices to use the world’s largest telescopes. The final, most exciting advancement is the research that astronomers are constantly producing that contributes to, and challenges our thinking of the nature, origins and future of our universe.

Figure 7: Doppler shifting of absorption lines. An object moving away from us will have photons with slightly longer wavelengths. We can measure the velocity of the object from the red-shift in the spectrum.

Daytime astronomy

Source: http://en.wikipedia.org/wiki/File:Redshift.png

The Sun is the most obvious place to start when observing during the day. Sunspots are dark patches on the surface of the Sun caused by strong interactions in the surface magnetic fields. Observing sunspots requires a small telescope or binoculars and a bit of care, but it can be very exciting to see daily changes in the spots and observe the rotation of the Sun. For more information on how to see sunspots refer to http://spaceweather.com/sunspots/ doityourself.html. The daily solar surface can be viewed at http://spaceweather.com. Olbers’ Paradox can spur an interesting discussion about light and infinity in the universe. In the nineteenth century Olbers postulated that if the universe is infinitely big and contains an infinite number of stars then the sky should be as bright as the Sun in all directions. We all observe this is not the case! We can understand why using three principles of cosmology. First of all, light is limited to

travelling at 300,000km/s. This means as we look at objects farther away we are looking back in time due to the significant delay in the light reaching Earth. Secondly, the Big Bang theory tells us the universe is not infinitely old. The universe has only been in existence for a finite period of time (some 14 billion years) so only light from objects closer than 14 billion light years (100 000 billion billion kilometres) can reach us. This is called the ‘observable universe’ and is a subset of the universe as a whole. Finally, the Big Bang theory also states that space is expanding. Light that was emitted in the early universe has been ‘stretched’ with the expansion of the universe, so that now instead of visible light we detect longer-wavelength microwaves, the ‘afterglow’ of the very hot Big Bang that was the beginning of our universe. For further information contact: emily.brunsden@gmail.com

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What might biology education learn from disciplinary biology? Asks Rosemary Hipkins, NZCER, and keynote speaker at Biolive 2009. At the 2009 Biolive Conference in Dunedin I suggested that biology educators could look to the cutting edge of biology when searching for ways to manage the complex changes in teaching and learning signalled by the phrase ‘a 21st century education’. This article sets out my argument for those biology teachers who were not able to be there, but I believe the deeper message is relevant to all teachers, given the curriculum challenges that confront us as we work out how best to implement the New Zealand Curriculum in our various schools. I began my talk by comparing challenges facing biologists and biology teachers. Researchers in any area of science can’t afford to be left behind, especially where their research field is fast-moving and changing. Neither can teachers! Education is changing, but it’s not easy to see that when you are immersed in it day-to-day, and when the job requires a certain ‘presentism’ that demands instant decision-making and little time for reflection (Hargreaves and Shirley, 2009). Complexity theory has been a key theoretical influence in biological research, and its influence on the ways we think about the challenges of educating students for an uncertain future is growing. In this article, I take one tiny slice of the curriculum – the part that relates to teaching key ideas about genetics – to consider how ideas about complexity, drawn from current research in cell biology, might change not just the genetics we teach, but also some of our deepest metaphors about life and learning. This in turn might change the way we think about ‘the curriculum’ and how to implement it.

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What’s all this got to do with genetics? Quite a lot actually. Some years ago the science philosopher Evelyn Fox Keller wrote a slim but powerfully argued book called Refiguring Life: Metaphors of Twentieth-Century Biology (Fox-Keller, 1995). In this book she argued that we are teaching outdated metaphors of life while we continue to teach the simple mechanical genetics of the middle of last century. As the sometime author of a widely-used genetics textbook (Hipkins, 1990), one that purported to represent what was ‘new’ in genetics at the time, this argument struck me with some force! I knew I had unwittingly contributed to perpetuating a worldview that was now being questioned. Back then I wrote with such confidence that genetic control of bacterial activity is much simpler than in humans because their genomes are much smaller than ours. This was the prelude to describing the well-known Lac operon, which is still taught and examined in the senior biology curriculum. (I hope this will change with the shift of the gene expression achievement standard from Level Three to Level Two, along with signals that it will be refocused on gene-environment interactions.) For those of you who don’t teach genetics, here’s a typical diagram.

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Complexity thinking in the context of genetics The American physicist Fritjof Capra, has been writing about complex systems for more than thirty years now. In the preface to The Hidden Connections he comments: At the beginning of the 1980s, when I wrote The Turning Point, the new vision of reality that would eventually replace the mechanistic Cartesian worldview in the various disciplines was by no means well articulated. I called its scientific formulation “the systems view of life”, referring to the intellectual tradition of systems thinking, and I also argued that the philosophical school of deep ecology, which does not separate humans from nature and recognizes the intrinsic values of all living beings, could provide an ideal philosophical, and even spiritual, context for the new scientific paradigm. Today, twenty years later, I still hold this view (Capra, 2002, p. xvii). Systems thinking is not a minor adjustment to the way we see the world. It is nothing less than a new view of reality, a change of worldview. It goes to the very heart of our deepest assumptions about what ‘is’ and can ‘be’. The turning point that Capra refers to here is indeed a paradigm shift – a move from seeing the world in terms of a linear, and hence predictable, mechanics of cause and effect, to non-linear dynamics of complex systems where the outcomes of interactions cannot be predicted in advance, but rather emerge as the system evolves and learns. Systems can be socially constructed as well as formed in the natural world. For example, we’ve all had a sharp and nasty lesson about what this can look like with the recent crisis in the world’s financial system and it is by no means clear how this will continue to play out.

Figure 1: The diagram shows the Lac Operon when Lactose is present in the cell. Ref: Hipkins (1990), pg 28.

Systems theorists contrast complex and complicated models. The latter are understood as being the sum of their many parts – to know the bits is to know the whole. Complex systems, by contrast, are more than the sum of their parts so they can surprise us by doing unexpected things in response to change; sometimes doing seemingly nothing at all until they reach a ‘tipping point’ when many things change dramatically. You can see that the Lac operon belongs in the complicated worldview. Via a linear, predictable series of mechanical events it regulates lactose metabolism in bacterial cells. So far, so good. I’m not for one moment suggesting this doesn’t happen. Operons are apparently found in some eukaryotes with a relatively simple body structure, but are most common in prokaryotic cells. If we give the impression that all parts of any genome, including our own, could be understood in this way – if only we could unravel the complications – then we are doing our students a great disservice. With the clear foresight borne of deep thought, Fox Keller lamented the neglect of the older, less dramatic, field developmental biology and embryology once physicists had brought exciting new techniques of analysis to DNA sequencing. There was, she said, more to an organism than could be predicted by its DNA alone. This is a criticism of New Zealand Association of Science Educators

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science ‘reductionism’, which is a way of thinking that belongs with teacher a complicated worldview.

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Reductionist thinking assumes: the parts are the whole; the individual rather than the group should be the focus of attention; there is an obvious separation between an entity and its environment; and this in turn leads to the false dichotomy between nature and nurture. At this point you might be getting a hint of where I’m taking this argument with respect to education in general, but let me stick with genetics just a bit longer. Peter Dearden opened the 2009 Biolive Conference with an enthralling and memorable overview of his research team’s work. He leads a University of Otago team of scientists who study developmental genetics, thus bringing together the techniques of molecular genetics and the previously neglected field of developmental biology. He couldn’t have illustrated more vividly the perils of the reductionist viewpoint that we are simply what our DNA dictates we will be. For example, he discussed a cluster of ancient developmental genes called ‘Pax6’ that control eye formation. Pax6 genes have been found in every animal whose genome has been sequenced, including the human genome. In the fruit fly, Drosophila, this cluster of developmental genes controls the formation of an insect eye. In mice, the very same cluster of genes controls the development of a vertebrate eye. Put the mouse Pax6 complex into a fly and what will develop is fly eyes, not mouse eyes. So these genes do not operate independently of the environment in which they are located. They are part of a system, and the overall interactions of the systems’ many parts determine what gets made and what happens next. Gene and cellular environment interact as a whole. The reductionist view that our DNA makes us who we are is very pervasive in the media. For example, during the week I was putting my Biolive talk together our local newspaper ran an article that declared our genes make us ‘hard-wired’ to get fat. Such an argument takes no cognisance of the ways we have altered our food environment, as discussed in popular books such as The Ominvore’s Dilemma (Pollan, 2006), to name just one. Another article that same week proclaimed that scientists had extracted DNA from ancient feathers to ‘rebuild’ moa in the laboratory, allowing them to tell us more about what individual species looked like. Reading between the lines (for example picking up on the cue that the feathers had faded) I correctly guessed that what they had actually done was to match feathers to bones, thereby determining which moa species had shed the feathers while alive. That’s a far cry from ‘rebuilding’ a whole moa, but that’s how the science was portrayed. There are two immediate educational implications here. The first and most obvious one is that we need to update our approaches to teaching gene expression. The second is that we also need to help students read reductionist accounts of our DNA ‘destiny’ more critically. The curriculum certainly provides the necessary flexibility. Indeed, lining up its various components sends strong signals that this could be a really productive context for senior students to explore. So, for example, helping students to become ‘lifelong learners’ is one of four aspects of the vision statement; subsumed under that heading we find becoming an informed decision-maker (p. 8). This aligns with critical thinking as a key competency (p.12) and, arguably, integrity (being honest, responsible, accountable and acting ethically) as a value (p.10). One can’t argue here “my genes made me do it!” In the science learning area at Level Seven we find DNA/ environment interactions in gene expression as one of the

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achievement objectives, and at that same level the Nature of Science communication achievement objective points to the need to study the implications of representations of science ideas. I read this as including the deep metaphors coded in the language we use to describe phenomena, and this is where the DNA example gets really interesting. There is more at stake here than just how we understand DNA itself.

Why systems thinking matters for education more generally In a series of radio talks in the early 1990s, well known geneticist Richard Lewontin picked up similar themes to Evelyn Fox Keller, for similar reasons. Here in a nutshell is his argument about the very deep roots of reductionist thinking, and its soulmate biological determinism: It is usually said that genes make proteins and that genes are self-replicating. But genes can make nothing. A protein is made by a complex system of chemical production involving other proteins, using the particular sequence of nucleotides in a gene to determine the exact formula for the protein being manufactured. Sometimes the gene is said to be the “blueprint’ for a protein or the source of “information” for determining a protein. As such it is seen as more important than the mere manufacturing machinery. Yet proteins cannot be manufactured without both the gene and the rest of the machinery. Neither is more important. Isolating the gene as the “master molecule” is another unconscious ideological commitment, one that places brains above brawn, mental work as superior to mere physical work, information as higher than action. (Lewontin, 1993, p.48, emphasis in the original). Lewotin’s book is called Biology as Ideology: The Doctrine of DNA. The ideological position he has in his sights is often called biological determinism. He says this ideology rests on three key ideas: • We differ in our fundamental abilities because of innate differences • Those differences are biologically inherited • Human nature guarantees the formation of a hierarchical society. Taken together these three ideas lead to very familiar metaphors of a meritocracy – for example ‘survival of the fittest’. This is an ideological commitment that runs very deep. To take just one example from the history of science, the story of why the discoverers of the so-called ‘Piltdown man’ fossil were so readily duped hinges on their expectation that intelligence (and hence large brain size) would be a necessary enabler of other aspects of human evolution such as walking upright (Barker, 2006). Many other similar stories from the history of science could be told. The three linked ideas of this ideology lie at the very heart of the way modern societies have structured schooling and the high stakes assessment of learning (see for example Gilbert, 2005). But, Lewontin says, this idea ignores the impact of learning and culture on how our biological potential is expressed. It’s the same argument against reductionist thinking as the gene/environment one – but this time at the level of the whole person in their societal context. He is specifically critical of determinist assumptions that some students are better able to learn than others, and his argument has interesting resonances with the way sociocultural theories explain the nature of learning. Sociocultural theories say that all learning is situated: it takes place in contexts that can be manipulated to maximize learning benefits. It is mediated: the extent and efficacy of our learning depend at least partly on the supports that are provided – both by people and other

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The human ethics guidelines for schools: Ethical Practice When Doing Research: Guidelines for Students and their Supervising Teachers (2009) are for students and teachers in classrooms in New Zealand who are engaged in school research and other projects that involve people, such as other students, family, and members of the community, as Rosemary De Luca and Bev Cooper, both from University of Waikato, explain: This article describes the background to the development of these guidelines, the process of development, the composition of the guidelines, and some particular features.

Background to the development Formal ethics review of school-initiated research that involves animals preceded formal acknowledgement of the need to review research that involves persons. With the introduction of the Animal Welfare Act 1999, advocacy from the Royal Society of New Zealand (RSNZ) and the New Zealand Association of Science Educators (NZASE) resulted in acceptance by the Ministry of Education of the need for a unified Code of Ethical Conduct and an ethics approvals process for all schools using animals for research and teaching. Initially, schools used a range of committees managed by individual schools, local science teachers’ associations or science advisors, or used the ethics committee of other organisations such as a tertiary institutions to gain ethics approval. To ensure consistency and accountability under the Act, RSNZ was contracted in 2003 to develop the Code of Ethical Conduct approved by the National Animal Advisory

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Committee of the Ministry of Agriculture and Fisheries (MAF); establish protocols and implement an Approvals Committee; manage compliance on behalf of all schools, teachers and students in New Zealand; and provide them with advice. Partway through the contract, MAF noted that the RSNZ was not the appropriate organisation to hold such a Code on behalf of schools. The RSNZ continued to administer and support the approvals committee to implement the Code, and NZASE became the Code holder. The development of the Code of Ethical Conduct was completed and approved in December 2004, and is now being successfully promulgated and monitored by the Animal Ethics Committee (AEC), a committee of NZASE funded by the Ministry of Education (MOE). Schools need to follow a formal approvals process for projects and research involving animals. Entries are not permitted into science fairs unless there is proof that an approval had been given by the AEC. An assumption was made, understandably by teachers in schools, that science fair entries that involved human participants also required ethics approval and this became de facto policy and practice. Because the AEC is not accredited or entitled to deal with ethics approvals relating to humans, the approvals application process for science fair entries involving humans was initially dealt with on a case-by-case basis by one or more of the Ministry of Health’s regional Health and Disability Ethics Committees. While these committees are accredited by the Health Research Council Ethics Committee (HRCEC) to give ethics approval for human research, the nature of their role is particular to health research as defined by the Health

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continued from page 34 resources in the learning environment. It is distributed across the whole learning network of people and things (think for example about how much easier it is to read an instruction manual when you have the machine to which it refers ready to hand). It is participatory: new learning emerges in the interactions that unfold. The links to systems thinking should be evident here, and indeed there is a growing body of literature that discusses classrooms and schools as complex systems, and how best to manage them so that all students can learn. One very easy to read example is Engaging Minds: Changing Teaching in Complex Times (Davis, Sumara, and Luce-Kapler, 2008). It is my view that the New Zealand Curriculum should be read in this sociocultural, systems framing if we really do want it to be a curriculum for the twenty-first century. Earlier in this article I gave just one example of how the various parts of the curriculum should be read together, in interaction with teach other. If we read key competencies in a more determinist frame, it is easy to see them as personality traits – something the student brings to school, or not. Then it can’t be our fault if they don’t learn – can it? But if we read the key competencies in a sociocultural frame, and in interaction with the vision, values, principles and advice about pedagogy sections of the new curriculum, then it’s really important to think about the ways in which we provide opportunities for students to learn and grow (Hipkins, 2006). We can’t change their genetic inheritance, but we can change the environment in which each

individual expresses their potential! Working through these ideas takes a lot of reflection. One challenge of the metaphors on which our language, and hence our thinking, rest is that we use them without knowing we are doing so. We can’t all be philosophers, but we do need to keep abreast of contemporary thought if we truly believe our school system needs to be transformed so our students are ready for the uncertain times ahead. For further information contact rosemary.hipkins@nzcer.org.nz

References Barker, M. (2006). Ripping yarns: A pedagogy for learning about the nature of science. New Zealand Science Teacher, 113, 27-37. Capra, F. (2002). The hidden connections: Integrating the biological, cognitive, and social dimensions of life into a science of sustainability. New York: Random House. Davis, B., Sumara, D., & Luce-Kapler, R. (2008). Engaging minds: Changing Teaching in Complex Times. Second Edition. New York and London: Routledge. Fox-Keller, E. (1995). Refiguring life: Metaphors of twentieth-century biology. New York: Columbia University Press. . Gilbert, J. (2005). Catching the Knowledge Wave? The Knowledge Society and the future of education. Wellington: NZCER Press. Hargreaves, A., & Shirley, D. (2009). The persistence of presentism. Teachers College Record, 111 (11). www.tcrecrod.org ID Number 15438 Hipkins, R. (1990). The New Genetics. Auckland: Longman Paul Ltd. Hipkins, R. (2006). The nature of the key competencies. A background paper. New Zealand Council for Educational Research. http://nzcurriculum.tki.org. nz/references [August 22 2008]. Lewontin, R. (1993). Biology as ideology: The doctrine of DNA. London, New York, Ringwood, Toronto, Auckland: Penguin Books. Pollan, M. (2006). The Omnivore’s Dilemma: The search for a perfect meal in a fastfood world. London: Bloomsbury Publishing.

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science Research Council Act (1990) not education research. Apart teacher from the various ethics committees operating within each

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of New Zealand’s tertiary education organisations, there are no accredited committees set up to approve human ethics-related research undertaken by school students in an education setting or any legislation that requires this. Therefore, unlike the requirements set down by the Animal Welfare Act, students’ school-based research and projects involving human participants are not legally required to follow any formalised approvals process. However, in 2008 the MOE determined that there was a need to provide schools with Human Ethics Guidelines, suitable for guiding school-based student research that involves human beings as participants in the research. They also recognised that the development of working tools to help student and teacher researchers to plan their investigations with foresight and to alert school management to their responsibilities – and possible issues and risks – was necessary. NZASE was contracted to develop these. It was stressed that these were to be guidelines to schools and not intended to be mandatory requirements.

Development of the guidelines NZASE contracted a group to develop the guidelines including: an experienced teacher who also was a member of the AEC; a university senior lecturer who had experience in both the health sector ethics arena and chairing human research ethics committees in university settings, and an experienced science educator who had been involved with the AEC, and was an executive member of NZASE. The group met to set the parameters for the development and it was decided that the guidelines should be readable and accessible to students as well as teachers and provide examples of scenarios that highlighted appropriate ethical practice. Templates would then be developed to assist students and teachers. For expediency it was resolved that the experienced ethicist would draft the guidelines and the science educator would provide appropriate scenarios based on common school practices. At each stage the experienced teacher would be asked for feedback. It was also decided to involve at the initial stages of drafting, two other people who had a background in regional or national ethics work as a reference group. Before being sent to the MOE, the guidelines would also be critiqued by several experienced heads of school science departments who were also asked to get feedback from students. It was also resolved that once the guidelines were made available to schools they would be reviewed periodically and feedback would be sought from schools to inform the review. The draft guidelines were critiqued by the MOE and posted on the NZASE website in May 2009.

Composition of the guidelines The guidelines have four sections: section one explains the scope and purpose, some special terms, ethical practice criteria, and the responsibilities of both students and teachers; section two includes examples of research scenarios; section three has templates for informing and getting permission from people who are going to be involved in the research/project; and section four includes the titles of two Ministry of Education publications about research involving people and also animals. These guidelines recommend that: teachers explain these guidelines to students and monitor students as they design and engage in research and other projects; students follow these guidelines and liaise regularly with their teachers.

Particular features 1. Using scenarios within a guidelines document A feature of these ethical practice guidelines is the

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inclusion of classroom-initiated research scenarios that illustrate ethical practice in a narrative and applied way. These scenarios situate the guidelines pedagogically within a teaching and learning context familiar to students. An example of how each scenario is presented in the guidelines, and how ethical issues are highlighted to teachers and their students is shown below. Scenario Three. This experiment is about effectiveness of short-term memory. The question is whether there are differences in recall based on short-term memory across different age groups. Sky and Nick are Year 9 students. They are interested in finding out how many items 7–9 year olds, 13–16 year olds, 35–50 year olds and 60+ year olds (ten in each group) can recall after the same time period has elapsed. They put twenty items on a tray and give each person one minute to memorise them. They then give them one minute to recall as many items as possible. They record and date results in their log books. The 7–9 year olds are from a primary school class in another school, the teenagers are from their own school, and the adults are from their families and friends. Sky and Nick prepare and use written information and written consent forms for all three groups. They keep these in a file. A number of ethical issues arise from this scenario. A major point to consider is how Sky and Nick will get informed consent from those they wish to involve in their project. They need to focus on two things in particular at this point. First, they need to understand that people they involve in their project should participate voluntarily and on the basis of knowing what their involvement will mean. Second, they need to understand that there is more to ‘getting informed consent’ than applying a standard process. They will have to devise a process that both meets the requirements spelled out in the guidelines and also fits with the individuals they wish to involve. They have four categories of participant: 7–9 year olds, 13–16 year olds, 35–50 year olds and 60+ year olds. Age is a factor to be considered. Also, their relationship with participants varies, so degree of formality is a factor. The youngest participants are pupils at a primary school, the next group are students at Sky and Nick’s own school and mostly older than them, and the third and fourth groups are people they know outside of school, some of whom may be family members. They will have to devise an approach and develop a way to explain information about their project to suit each group. They also need to be aware that there will be individual variation within each category of people. Culture is a factor they will have to consider, both in terms of ethnicity of potential participants and the culture of each setting. For example, within a school the practice is to approach school authorities and the classroom teacher. Within families and with family friends there are also established and expected ways of doing things. Sky and Nick will need to be clear about their roles and the responsibilities associated with these. For the project they are student researchers conducting an experiment. They need to take the task seriously, complete the task properly following all instructions with care, and take full notes, keep a formal record and report honestly. Outside of their own school they will need to conduct themselves as ambassadors of their school. As well, they will need to manage their classmate and family/friend roles within the exercise of the more serious student researcher role. As students they are obliged to liaise with their teacher, keep him or her fully informed of progress, and follow instructions and advice. Privacy is an important aspect of this project. Participants may be sensitive about their capacity to remember, so particularly in this experiment an individual’s results should


commence their project; they need to negotiate a time frame for reporting to their teacher at regular intervals; in preparing written information for their research participants they must use the templates provided in section three of the guidelines; they are required to seek guidance from their teacher if they are unsure about whether to get consent from the parents/caregivers of older school aged participants as well as from the students themselves; they must consult with their teacher before they make a change to their project; and they must advise their teacher immediately if a problem arises. How to report verbatim what a participant has said needs to be talked through with the teacher, as does any proposed use of photographic images. As well as being available for the day-to-day planning, execution and reporting associated with student research in a pedagogical sense, teachers have wider responsibilities to their discipline and to the research enterprise generally, and also professionally through compliance with Ministry of Education requirements, for example, those outlined in Safety and science: A guidance manual for New Zealand schools (2000). Teachers also need to make sure students are aware of any implications of the Privacy Act 1993 for what they are proposing to do.

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Where to from here? Working tools and templates within these guidelines have been developed to assist teachers and their students to explore and describe ethical issues associated with their projects. The guidelines have been made available on the NZASE website: (http://www.nzase.org.nz/ethics-human. html). As a normal part of document design practice, review of the guidelines will be carried out after they have been tested by teachers and students. Feedback will be sought from schools at the end of 2009 through the NZASE website, local science teacher associations and science fair committees. Students’ views will be an important component of this process. The guidelines will be informed by this feedback and reviewed and modified where necessary. For further information contact: deluca@waikato.ac.nz or bcooper@waikato.ac.nz

References Ministry of Education. (2009). Ethical practice when doing research: Guidelines for students and their supervising teachers. Retrieved 23 June 2009 from: http:// www.nzase.org.nz/ethics-human.html. RSNZ (Royal Society of New Zealand). (2004). Code of Ethical Conduct. Retrieved 23 June 2009 from: http://www.nzase.org.nz/ethics.html. New Zealand Association for Research in Education Ethical Guidelines. Retrieved 24 November 2008 from: http://www.nzase.org.nz/pdf/NZARE_ethical_ guidelines. Ministry of Education. (2000). Safety and science: A guidance manual for New Zealand schools. Wellington, New Zealand: Learning Media. Tolich, M. (2008). Guidelines for community-based ethics review of children’s science fair projects. Journal of Bioethical Inquiry, 5(4), 303-310.

collisions increases as the fast electrons and protons get to lower and lower altitudes where the gas molecules are closer and closer together. Eventually, at about 100km altitude, the electrons and protons are ‘spent’—they have lost all their energy from hitting atoms so they can’t go any further. The atoms hit by the fast electrons and protons ring like bells. Atoms are too small to ring at sound frequencies, so they ‘ring’ at light frequencies and emit red and green light characteristic of nitrogen and oxygen atoms and molecules. (In much the same way as neon atoms emit their characteristic red light when excited by the electrical discharge in a red neon advertising sign.) For further information: questions@ask-a-scientist.net New Zealand Association of Science Educators

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ask-a-scientistcreatedbyDr.JohnCampbell What causes the Northern/Southern Lights? Natasha James, St Peter’s College, Palmerston North. Dick Dowden, an upper atmospheric physicist retired from Otago University, responded: This bright but diffuse glow in the night sky, seen when looking towards the Earth’s poles on dark nights, is also called aurora. The Sun, as well as pouring out a vast amount of light, ejects enormous numbers of nuclear particles such as electrons and protons. These take about four days to reach Earth. As they approach the outer reaches of the Earth’s atmosphere, at an altitude of about 200km, these very fast electrons and protons start hitting atoms of nitrogen and oxygen in the rarefied air. Naturally the rate of these

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not be disclosed to others. Results will be reported in aggregated form so concealing identity of individuals will be straightforward, but it would be easy for Sky and Nick to openly tease a family member about a memory lapse, for example, and they need to know that this would be unethical behaviour. Telling individuals their results and the outcome of the project overall and saying thank you are both important aspects of demonstrating respect for people. There are five scenarios in the guidelines. Topics include choosing healthy foods; change in chemical properties; effectiveness of short-term memory; effectiveness of energy drinks; and conservation. The scenarios illustrate a range of research methods: experimentation in a controlled situation and experimentation in the field involving ‘human subjects’; observation; face-to-face interview; survey and questionnaire. Although the scenarios appear simple, in each case generic ethical research practice applies including: valid design of the project; safety of the participants; participant privacy; systematic recruitment and selection of participants; informed consent; accurate recording and filing of results; complete and honest reporting on the project; and reporting back to and thanking participants. There is an overall good inherent in the educational value of the projects, but no specific benefit is attributable to individual participants, so any potential risk to participants should be very low and preferably nonexistent. There should be no known risk (see Tolich, 2008, for discussion about no benefit/no risk). Each scenario also has specific ethical issues. Two scenarios emphasise safety aspects. In scenario one, for example, Year 9 student Che experiments with food colouring and food appeal so he checks with his parents that his four-year-old brother is not allergic to food colouring. Another scenario involves testing saliva, and safety and hygiene issues are highlighted. Ethical implications of gathering data through the use of email are explored in scenario five. This scenario also introduces caution in making approaches to persons unknown to the students; being honest about results when survey returns are low in number; and placing thank-you notes in the mail boxes where questionnaires had been left earlier. 2. Specifying teacher and student responsibilities Another feature of these guidelines that makes them particularly school-focused is the specification of teacher responsibilities and student responsibilities. There is a strong sense of duty in the articulation of student responsibilities. The teacher is there to supervise and guide so is responsible, but the student also has a defined role as researcher with associated tasks to carry out. Students are to get teacher approval before they

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matauranga maori refutes Popper Was NZ’s most famous philosopher, Karl Popper, correct to compare ‘tribal’ consciousness so invidiously with his vaunted ‘open society’? Philip Catton, co-ordinator for History and Philosophy of Science, University of Canterbury, explains that Popper’s invidious comparison was surely excessive: In significant respects the mnemonic arts of Maori were developed within a few centuries, to provide powers of survival and flourishing within a landscape enormously different from those of places that were home to ancestors only a few generations back. There is a four-thousand year story, which issues from a time when ancestors of present-day Polynesian peoples perfected the art of tacking upwind, perfected the technologies of sailing craft, and created for themselves an opportunity to become an amazing ocean-going, navigating people, who over many generations would make their way eastward upwind across the Pacific populating island after remote island, able to explore outwards against prevailing winds across a vast ocean, with the navigational capacity to move out and then come back to points of origin, and thus to be explorers, safe from the prospect of catastrophe, saved by extraordinary, arcane understandings of navigation, of the perfection of sailing craft, of commitment of people to waka and the sea. Contrast the situation of these people from 4000 years ago onwards, with the situation of European explorers (‘discoverers’?), working out from Europe 250, 200, 150 years ago, in their big lumbering barks, slow moving, fragile, utterly at risk. When Captain Cook’s vessel ran aground in an inlet and holed itself, that event was potentially curtains for all. The ship’s men were ever so far from home, and their ability to return seemed to be entirely forfeited. Contrast that with taking a waka, fitted with inverted sails, urged by refinements over scores of generations into optimal forms for achieving speed at sea very close to the limits of theoretical possibility. Consider these vessels getting about. They are perfectly safe. They hit a rock, they bounce. They go many times faster. Thus, without inducing sickness or fatigue upon the persons aboard, they can cover vast distances in the ocean. With their proven powers of navigation, the people aboard could sail out against prevailing winds to great distances and the near exhaustion of their food supplies, and if no new island was found, could turn about at that point, whipping home downwind in no time to return to food and safety. No wonder these people travelled ultimately all the way to South America, acquired connections there, commandeered resources there such as the sweet potato, spread these resources back in a westward direction into the Pacific islands, and had very evidently come to these lands now called Aotearoa New Zealand not once but also on very much earlier occasions. When I was in secondary school in this country, I was told the patronising story of Maori who were hapless, starving, weakened by an interminable voyage, blown desperately off an intended course, and who cheated death only by accidental one-time-forever arrival to these shores. This story is completely incompatible with the scientific evidence, especially that concerning mitochondrial DNA in the Polynesian rat which shows that long before Maori voyages of settlement, ancestors had arrived and returned again homeward, possibly many times, having a look, taking

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information about the locations and qualities of these lands back to distant islands; giving opportunity for people to wait until they needed to take the huge step of coming across vast distances to settle these lands…lands which were extraordinarily different from, and in many ways more and certainly differently challenging, than former homes.

Popper and Enlightenment Karl Popper is sometimes claimed by New Zealand since he did teach at the then Canterbury College of the University of New Zealand during the 1940s. It was in Christchurch that he wrote The Open Society and its Enemies, a justly famous book which with clarion voice calls for the defence of Enlightenment values against totalitarianism. Partly for that reason, and for other contextual reasons, Popper was very down on what he called ‘tribalism’ of thought and culture. Popper lauded the ideal of an open society, where tradition doesn’t matter, where people are free to criticise anything, where an idea has only as much going for it as can be marshalled for it by reasons given in its defence, where the idea of its having worth by virtue simply of a role it plays in tradition, or by its being the voice of the ancestors, is utterly proscribed. Popper was a passionate defender of a way of dealing with intellectual culture which was shaped by the Enlightenment and by (Popper’s distinctive interpretation of ) Enlightenment values. In the context of his Open Society book, Popper says some desperately critical things about the kind of oral cultural form that I am trying to offer some understanding of. Popper says some critical things; he also says some false things. Popper suggests that, in tribal cultures, ideas can stabilise, whereas in an open society, he reckons that ideas are constantly at risk of being changed, of being found under the force of criticism to be rationally wanting, whence they are rejected, and replaced by new ideas. Popper emphasises continuity in tribal cultures, and insists that too much continuity can be a bad thing. We should be open to discontinuity, he believes. The idea of an open society that he lauds is the idea of a society whose further development does not take a predictable form; it is open not only in the sense that everyone’s ideas are open to criticism, but it is also a society whose future cannot be predicted. Popper reckons that if a society allows its knowledge to develop properly, in an environment of criticism, then you don’t know how its knowledge will change, so you don’t know how the society will change. He insists that this is how we should be, this is the ideal; we should want to be open to that kind of uncertainty. If we hanker after certainty, if we hanker to know how our future will be, if we want things staid and constant through the generations, then we are enemies of the open society, and that is a very bad thing in his view. I think that Popper’s point of view is understandable in its context, and salutary even in some select respects, but I think it is seriously flawed in many ways, even for understanding the character and possibility of science. Popper’s position is quite clearly mistaken in its implications about Maori. Traditional societies have knowledge forms that do change, and Matauranga Maori as an intellectual accomplishment is a sure sign that that is so. Look how profoundly different the circumstances of life were for Polynesian people as they moved across the


Whakapapa is a vehicle for knowledge Something is going on in the pattern of intellectual accomplishment of Maori that Popper hasn’t laid hold of. It’s true that the way in which ideas are carried in this oral culture make the voice of tradition important. Your survival depends upon powers of knowing things which you would never possess unless you were made party to a tradition of mnemonic forms. Your people have to work on you to become receptacle to a vast amount of information, carried by oral memory arts, and if you resist that then you’re not a player in a way that your society needs you to be for the sake of its very survival. So there will be powerful calls to be receptive to the voice of the ancestors; there will be powerful calls for you to be respectful of tradition, because of what it represents, namely your wherewithal, everyone’s wherewithal, to continue to survive and flourish. And all this is different from Popper’s ideal in ways that need to be acknowledged and thought about. But the idea that these differences cause closed mindedness, or thus unsusceptibility to intellectual change, cannot be right. One of the significant facts about the oral arts of memory of Maori is how ancestry is used as template for the mnemonic forms. Whakapapa is the vehicle for vast amounts of knowledge about the world generally. By knowing your ancestry, you know the protagonists within the stories that maintain in memory all the information that you need to keep accessible to you in order to survive and flourish. Knowing your ancestry means knowing your way about in all sorts of vital practical respects. Typically (and Maori seem no exception), societies with an oral culture of which ancestry is the vehicle remember out to roughly 25 generations back. This is prodigious. Can you remember your ancestry, having ideas about the personalities, deeds, accomplishments and failings of ancestors back 25 generations from your own? I know nothing about my great grandparents, 3 generations back from me. I can guess, knowing where they lived, and knowing what the overall ambient cultural characteristics were at the time, what their characteristics would have been in some very general respects. In all those characteristics they would have been very different from me, so that if somehow I were able to meet them then I would find that I had virtually nothing in common with them. I don’t know what their jobs were; and what their jobs were would condition what small part of the ambient culture of their time they knew, a part of culture that would scarcely overlap at all with the part I know in performing my kind of job. Thus, my sense of connection with them is

nil. I have no sense of connection to 3 generations back, so I marvel at a people that possesses the strongest sense of connection all the way back for 25 generations. I am not party to anything like that sense of connection. Twenty-five generations is a lot to remember, and that provides the number and range of protagonists and of timescapes for all sorts of stories, enough to fill out the mnemonic arts. It is no coincidence that the number of generations typically remembered by peoples whose culture is oral is 25. More, and the increment of burden on memory by virtue of the extra protagonists that must be remembered is insufficiently compensated for by gains in the richness of memory-art stories that can be told. The taxing of memory is increased without sufficient recompense in further extension of the memory arts. What you want in memory is the number of generations that help the memory arts to work their best, and you can go too far by having too many generations. That roughly 25 generations is optimal for the memory arts is illustrated by the similarity cross-culturally of mnemonic forms settling upon that number. (Usually looking back 20, 21, 22 etc. generations, it becomes difficult to distinguish between ancestor and deity. This also seems to reflect something basic about how the memory arts work.) Consider now that I am remembering 25 generations back and I’ve got children. How many generations must they remember? And now they have children, who must remember how many generations back from them? We seem to have a problem here, if 25 is the optimal number. It’s clear that as the generations tick by, we’re liable to get memory forms that are configured no longer as optimally as earlier forms had been. It is a problem faced by all oral cultures. What is its solution? It is solved by creativity. The elders have powerful ways to be sensible about the memory arts, to adjust them towards continued optimality, and thus pass them along in ever revised forms. Within the forms of discussion, performance play etc. through which people are again and again made aware of the things that they have to remember if they and their fellows are to survive and flourish, creative elisions are made, of protagonists. Suddenly instead of there being a protagonist who did this and a protagonist who did that, a single protagonist does both of those things in the stories. Instead of there being a difference of generations between when this was done and when that was done, the deeds in question suddenly merge into one generation. By such creative means, the elders keep alive just the kinds of memory art structures that can best serve their people; they conserve optimality rather than all the stories. Now, any adept at oral culture, anyone who can assume those special responsibilities of an elder, knows what is going on here. And that conditions what people are about when they tell stories. It’s part of the ideal that Popper had in mind to think that the difference between what is a well functioning thing to say or to think, and an ill functioning thing to say or to think has only to do with the impersonal standard of whether what I am saying or thinking squares with what I would still be saying or thinking if I were somehow to consider everything and have it all rationally systematised. Science and philosophy have a weddedness to an ideal of all-things-considered, rationally-best-systematised thinking. It is an impersonal ideal. It has connection with what we call objectivity in science. But to claim that unless we are wedded to this ideal, we will intellectually stagnate, so that neither our knowledge nor practical capabilities in the world will grow, is surely false, as the outstanding example of Matauranga Maori

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Pacific. Each new land had its own utterly distinct resources, and yet the people managed. Imagine the challenges that there would be, when all the wherewithal that people had, for finding resources, for utilising them in familiar ways, for going about life, and all the oral structures in the mind for remembering these things, were always found to be fitted well to circumstances that had been left behind, rather than those found in new island contexts. And never was there a more profound change in material conditions of life than happened when people moved from far north in the Pacific to Aotearoa New Zealand. In its flora and fauna and other resources, in its climate, topography, coastal and inland challenges, this place was extraordinarily different. And yet within a very short time these people were flourishing. That is adaptability. That is intellectual change. It’s intellectual change unfolding within an oral culture, rapidly and well. It gives the lie to the idea that oral cultures are static. It gives the lie to Popper’s conviction that oral cultures must compare very invidiously to his preferred kind of society in terms of openness to intellectual change.

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science clearly shows. It is remarkable how much was being dealt teacher with by Maori, given the exigencies of holding all facets

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of culture within the largely oral mnemonic forms. And it is remarkable how quickly across the generations the knowledge by Maori of Aotearoa could grow. Among peoples with an oral culture, Maori are stand-outs in the extent of technological sophistication attained, and also, and relatedly, in their development, within their social forms, of defining roles for knowledge-enhancing specialists. To give just one instance which shows the scale of this, I have seen a drawing by an early European in New Zealand of a fourteen-storey building built by Maori, altogether without nails. (It testifies among other things to Maori ingenuity in creating and using extraordinarily strong cording.) In this structure there was standing room on every level. It was for food storage only, but the impressive thing was its height. We do not think much today of Maori creating such structures, for building patterns changed very quickly after nails, sawn timber, and different design concepts arrived with arriving Europeans. The earlier designs were replaced, the older buildings came down in the end, and much of the change happened before the reports took forms that would be propagated all the way down to us. Suffice it to say that the many accomplishments of which this is but one example imply prodigious ingenuity by Maori in doing things to make life good, and consequently imply a prodigious extent of knowledge. There were kaumatua whose special role it was to be researchers, indeed to conduct much research by experimental means, and thereby develop arcane knowledge. Their role included work to propagate that special knowledge not to all, but to some carefully selected protégé who would become the next generation’s special knowledge-adept. And there were also, as a truly impressive kind of social accomplishment, ways that iwi had for commanding the special knowledge of these people and making it relevant for public decision-making. How you make the decision-making of a people as a whole sensitive to the right extent and in the right ways to the special knowledge of experts is a great problem for political arrangements, and it is impressive how Maori solved it; they had well considered ways for how to accomplish that, a massive social accomplishment.

Literal-minded understanding of the world Even though there was, from the evidence that I am aware of, an experimental quality to the work of these specialist inquirers – even though they do learn vast amounts about the living and physical environment of these islands, some aspects of which are still not discovered to ‘modern science’ (and there needs to be more dialogue, precisely because that would be a help in both directions I think, to understandings of the world) – even though there was, already many hundreds of years ago, in the experimental quality to these researches, one feature that help explain why science ignited at all 350 years ago in Europe, still, those inquiries were nonetheless being done in ways that reflect the exigencies of oral culture, and they are imbued with the mytho-poetic forms of the overall consciousness. So, in my story about science I want to say still that science comes about only when a very strangely literal-minded orientation is coupled with an experimental approach among specialists. I see the practical, experimental aspect roundly, and to some extent the openness to specialism, in Maori intellectual accomplishment. But I don’t see the literalminded aspect. I see instead a way of thinking that deeply reflects, as you would expect, how oral arts of memory function, and thus that is deeply mytho-poetic in form. 40 New Zealand Association of Science Educators

This way of thinking is one we are bound to misunderstand if we bluntly compare it to science. You just can’t do justice to the kind of intellectual accomplishment that mythmaking represents (a mnemonic accomplishment) by considering the myths as forms of literal-minded theorising. Mytho-poetic thought structures simply are not attempts at literal-minded understanding of the world. Fair recognition of the excellences of what is brought together intellectually in Matauranga Maori is befuddled not helped by the gross comparison with science. We have seen by now that in mytho-poetic thought structures you are often not trying to explain, or identify causes, so much as to make memorable a range of facts that it will be useful to recall at will for use. To look into these myths from the outside and see in them attempts at explanation is to miss the point entirely of the mythmaking. It draws into complete obscurity what the myths were for. So I say the better to avoid all that, by recognising in the question whether Matauranga Maori is science a mistaken first step. Maori and Pakeha are not going to form themselves into a mutual self-understanding by posing and pursuing that question. In traditional Maori society, you connect with your ancestors. Whereas I have almost nothing in common with even my great grandparents, in the context of an oral culture you share with your great grandparents a mighty edifice of thought, which has propagated in the memory arts down the generations to you. There is much in your mind that makes you resemble your great grandparents. Just as their survival and flourishing depended on those knowledge structures, so yours does as well. You sense your connection to those ancestors of yours, and indeed you relate almost all your wherewithal to survive and flourish with what they have gifted to you and your mind. You owe great respect to what has propagated to you from them. So you owe great respect to them, and to what they would think. But the idea that the difference between your doing well and your not doing well, chiefly concerns whether what you do will be received as right by your fellows, your elders, your ancestors – that way of thinking about good or bad, right or wrong is alien to Enlightenment culture. Popper was simply horrified by the respect for tradition implied within oral cultural forms. Consider Enlightenment culture by contrast. By the ramification of social roles, by the compounding of culture into a condition where each person is inheritor to just a tiny, relatively individualised, portion of total culture, everyone is out on their own. It’s not as though whatever your cultural bearings are is going to be adequate to all the tasks that you will face in life. Here you are alienated from your fellows. You have to find your own way. Common understandings are no longer adequate to all the challenges that you face. Since that is your circumstance, your society is going to work on you to consider things quite differently. It’s not the mark of doing well to do what your fellows count as right. The question rather is the impersonal one, of what you and your fellows ought to count as right. Instead of making out that what it would be right for you to do is what is conformable to the general understandings, what will be taught instead is that what is right for you is something independent from what your fellows will expect. You can do something which your fellows think bad and be right to do so, you can do something which your fellows think good and be wrong to do so. You’re out on your own, you’ve got to figure things out yourself, and this is a large task, for the idea ultimately is that what


we have a lot of evidence that it won’t. So I am not for a minute saying it’s a superior thing to go literal-minded, and give up the traditional ways. I am saying it’s really different, and that has to be taken into account when we look at whether Popper is correct in his claims. Over against Popper I have urged that many qualities of culture that he abhors are necessary when peoples employ not writing but rather oral arts of memory to hold onto their culture, to use it to survive and flourish, and to create the means for culture to propagate down the generations. I have also argued that oral arts-of-memory-based culture can be dynamic, not static, quite able to adjust itself to change, and to compound the knowledge and practical wherewithal of the people that possesses it. Popper held a view of science (which I have criticised in some longago articles in NZST) according to which Matauranga Maori compares utterly invidiously with it. But he is surely mistaken (if not about science) about a tradition of knowledge such as Matauranga Maori. This tradition is far more flexible and subject to continuous fine-tuning than Popper can explain. In its way, this point again underlines why more harm than help follows if we look to Matauranga Maori with the question whether it is science. For further information philip.catton@canterbury.ac.nz

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The alignment process has caused a lot of anxiety over the last few months. Standards have been written for Science, Biology, Chemistry and Physics at Level One and matrices for Levels Two and Three, so that there is now a sense of direction in these subjects. However, there are still unanswered questions about certain standards and I’ll attempt to answer some of these.

What is happening to the 189xx series of Unit Standards? At the moment, we are not sure. The writing group has presented many submissions asking that they be kept, but have not had any definite answers yet. At the moment NZQA and MoE are consulting on a proposal that 20 credits towards Level One NCEA can come from standards at below curriculum Level Six (just as 20 credits towards Levels Two and Three NCEA can come from Level One and Two respectively). There will be literacy and numeracy standards developed for this purpose, but these may not include the 189xx standards. We are worried that these will be removed so we are planning for this eventuality. We will be facilitating the development of Achievement level tasks for the new internal standards that, if passed, can count towards NCEA Level One as well as the NZASE Certificate of Science.

What is happening to the Human Biology standards? We are not sure of this either. The biologists and the writing group have been working very hard to retain Human Biology standards at Level One and to ask that they be developed at Levels Two and Three. Again we haven’t had much success from our numerous submissions.

However, all matrices can now have up to 30 credits so the biologists have developed a suite of standards at Level One, many of which can be assessed in a Human Biology context. Schools can still run both Biology and Human Biology courses concurrently if they wish.

What is happening to Science standards at Levels Two and Three?

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would be right for you to do, is what you would still be thinking that you should have done, if you had managed to consider everything, and had managed to make it all out in the rationally most beautiful way. A large task – God, so to speak, is looking at you, and knows whether you are erring or not. I have emphasised that there is a huge cost for people from abandonment of the bearings of an oral culture and the replacement by the orientation ultimately to the Enlightenment ideal. The evidence for this, I repeat, is that peoples undergoing the cultural transition in question report an enormous sense of loss, that the transition is resisted mightily, for millennia, and that many pathologies of the human condition seem to have arisen because societies eventually did make the change. Whether it is an experiment that will work, no one knows. Peoples have survived and flourished on this planet for hundreds of thousands of years, through the use of oral memory arts. That’s a lot of success. By comparison, we’ve got 12,000 years of agriculture, 5,000 years of literacy, 2,500 years of literal-mindedness, and a bare 350 years of burgeoning science. That’s not a lot of experience of a cultural form. It might be a very unstable experiment. We don’t know that it will work out, and indeed,

Sciences were given a special dispensation from the strict ‘no duplication’ requirement at Level One only. Most of Science Level Two and Three standards overlap with standards from Physics, Chemistry and Biology and are also not at the correct curriculum level, except for Planet Earth and Beyond ones. Because of this, the writing group was asked to develop standards for the Planet Earth and Beyond strand with the same credit value as standards for the other Sciences. This means that Planet Earth and Beyond standards now have plenty of substance in them. It has been proposed that they form the basis of a new subject called Earth and Space Science. However, there is a call for Science to be kept as a subject at Levels Two and Three so more standards have been added so that this can happen. It is important that teachers give feedback when the Level Two standards are put out for consultation if they wish for Science to be kept as a subject. The matrices at Levels Two and Three for Physics, Chemistry and Biology will also contain standards that will be accessible for Science students.

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by Melva Jones A number of good science series held in the National Library’s Schools’ collection contain titles on Light. The following would all be useful for intermediate, junior secondary students and as an introduction/overview for older students. Voyage of a Light Beam: Light Energy by Andrew Solway follows the ‘voyage’ of a light beam from a star in our galaxy to the human eye. The easy to read format makes this series appealing from senior primary up. There is a glossary on each page, repeated in total at the end, and diagrams are clear and easy to follow. For more titles from the Raintree Fusion: Physical Science series visit: http://www.raintreelibrary.com/index.asp Physics Projects With A Light Box You Can Build by Robert Gardner. In this title instructions are given for the building of a lightbox, which can then be used to carry out a range of interesting experiments. For more titles in the Build-a-Lab! Science Experiments series, by Enslow Publishers, visit: http://www.enslow. com/catalog.asp?Exact=true&Seri esID=225

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Seeing Things: Light by Ann Fullick. How we see, how light moves, how light is shaped, and how it is used, are themes covered in this title. The part light plays in our lives now and how it may be used in the future, is also explored. Photographs and fact boxes are integrated with the main text and a detailed glossary is provided. Everyday Science titles can be viewed at: http://www.heinemannlibrary. com/product/9781403448194

Easy Genius Science Projects with Light by Robert Gardner. There are more experiments and ideas and all clearly explained using everyday equipment. The books are basic in their presentation with limited colour, but very practical. For more titles in the Easy Genius Science Projects visit: http://www.enslow.com/catalog. asp?Exact=true&SeriesID=253 From Newton’s Rainbow to Frozen Light: Discovering Light by John Farndon. The Chain Reactions series explains how discoveries and inventions start off a chain reaction that changes thinking and understanding throughout the world. In this title the initial spark comes from Newton’s particle theory of light. The final chapter summarises current theory and looks at future possibilities. Details on more Chain Reactions titles at http://www. heinemannlibrary.com/product/9781403495587 Exploring Sound, Light, and Radiation by Andrew Solway. Solway provides explanations about sound waves, light waves and electromagnetic waves and how to measure frequency and wavelength in this title. Chapters include: Sight and light; Bouncing and bending; Adding colour; and Beyond light – radiation. Find this series and more science titles at: http://www.waylandbooks.co.uk/Science_ Books.htm

Online resource Learning Materials on EPICs Britannica Online (http:// www.tki.org.nz – school password needed) provides student activities and audiovisual lessons on colour, eyes and sight, and the photoelectric effect. Select the PreK12 edition and go to Learning materials. Follow the trail from ‘Learning materials’ to locate the section on Science: Physics.

ask-a-scientistcreatedbyDr.JohnCampbell Is it realistic that cars will eventually be replaced with solar powered cars? Lizzie Hayes, Nayland College, Nelson. Richard Duke, an electrical engineer at the University of Canterbury, responded: At sea level on the Earth the total incident solar power is about 120,000,000,000,000 kilowatts.The present population of the Earth is just under 6 billion people, and so about 20 million watts of solar power is available to each person. Thus it seems that there should be plenty of solar power for everyone. However, we must remind ourselves that this 120,000 billion kilowatts is spread over the entire surface of the Earth. So on a bright sunny day the Earth receives at best about 1 kilowatt for every square metre of area. An average small car’s bonnet, roof and boot area typically totals less than six square metres and the efficiency with

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which incident solar energy can be converted into electric energy by a solar cell is only around 15%. Thus, if these areas were covered in solar cells the obtainable electric power is only about 0.9kW (1kW per square metre x 6 square metres x 0.15). Compared to an average small car which has a petrol engine capable of delivering 60 to 200kW, the solar powered car appears to be an unlikely alternative. Of course, electric energy can be stored in batteries to be used at some later time, and most experimental solar cars around the world use various types of batteries for this purpose. Batteries are however, heavy, expensive and take a long time to charge from solar cells. Thus the totally solar powered production car is unlikely to be built. We are more likely to find solar cells used to power accessories, such as ventilation fans. For further information: questions@ask-a-scientist.net


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By Bill MacIntyre, Massey University College of Education (and edited by Lyn Nikoloff) At the BEANZ forum, held at Biolive, I spoke about how Biology educators are different from other science educators because their undergraduate training often included a combination of ecology, zoology, botany, physiology, and anatomy. All of these share common elements of systems, models and complexity, and it is these common elements that uniquely enable biology educators to align themselves with teaching twenty-first century thinking and The New Zealand Curriculum. Recently there has been a progression in biology from linear-thinking to complexity, or systems thinking, which is in contrast to the linear thinking content of chemistry and physics (see Rose Hipkins’ article in this issue). Biology (and other science) educators can draw upon an understanding of ecology and the interrelationships of living and nonliving to bring a systems thinking approach into the new curriculum. To study change in an ecosystem ‘it depends’ on taking account of all the possibilities in the ecosystem, because if one factor is changed then so too is another, and so on. For example, Figure 1 is a complex system that requires

1. Pillars of biology taught separately

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complexity thinking yet it is not complicated. And biology educators are well equipped to think in this way and to cater for diverse needs in their programmes.

Figure 1: System ecology – web of life. So what turns on learners? Being intrinsically motivated, passionate when their learning is relevant, meaningful and manageable for them (not for the teacher!). How can we do this? The Biolive ‘09 theme was transformation and change and so I proposed some changes that could help transform biology (and science) education. My proposals are captured in Figure 2, and as biology educators we will never know if we are addressing the needs of the twenty-first century learners, who are diverse, unless we use the ‘pillars of biology’ differently.

4. Some connections established between standards

2. Pillars are linked during the teaching and learning

5. Links identified and connections made during teaching and learning of each. 3. Subject disciplines and their standards 6. Blurred boundaries as science today is no longer based on solitary disciplines Figure 2: Pillars of biology that can transform biology (and science) education.

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chemistry update bySuzanneBoniface Chemistry Olympiad team wins medals

New Zealand Chemistry Olympiad Team celebrate their success at King’s College Cambridge. From left: Jared Lewis, Sunnii Roh, Joel Lawson, and Kevin Jan. The 2009 New Zealand Chemistry Olympiad team returned from the International Olympiad held in Cambridge, England on 18-27 July with 4 medals. A silver medal was won by Joel Lawson (Macleans College, Auckland) and bronze medals were won by Kevin Jan (Burnside High School, Christchurch), Jared Lewis (Dunstan High School, Alexandra) and Sunnii Roh (St Cuthbert’s College, Auckland). The team had been preparing for the Olympiad for months, studying topics such as organic, inorganic, physical and analytical chemistry as well as biochemistry and spectroscopy, at Year 13, scholarship and university level. At the competition they sat two five-hour exams in theoretical and practical chemistry, competing against 253 of the top high school chemistry students from 65 different countries. Gold, silver and bronze medals were awarded to individuals with marks in the top 10, 20 and 30%. The New Zealand team’s medal count put them in 21st place, the same as more populous counties like Canada, Indonesia and Mexico. The top country was Taiwan with four gold medals and the top student was from China.

Element 112 is named In the last issue of NZST we commented on the fact that many of the periodic tables used in text books or even seen on the walls of chemistry laboratories have not kept up to date with the latest ‘discoveries’ of elements. In particular elements 110 and 111, darmstadtium and roentgenium were discussed. Since then element 112, discovered 13 years ago has officially been added to the periodic table and given the name copernicium with the symbol Cp. The team of scientists who discovered the element chose to name it after the man whom they consider to have “changed our view of the world”. Copernicus was born in 1473 in Torun, Poland. His discovery that the planets circle the Sun refuted the then accepted belief that the Earth was the centre of the Universe. This discovery underpins much of modern science and was pivotal for the discovery of gravity, which is responsible for the motion of the planets. It also led to the conclusion that the stars are incredibly

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far away and the Universe very large, since the size and position of the stars does not change even though the Earth is moving. Copernicus did not receive any accolades in his lifetime. Element 112 was not actually ‘discovered’. It was made in a laboratory in Darmstadt in Germany by a nuclear fusion reaction brought about by bombarding zinc ions onto a lead target. The element decays after a split second of its existence. It has the heaviest nucleus of all the elements created in the laboratory with 112 protons and 165 neutrons. Twenty-one scientists from Germany, Finland, Russia and Slovakia were involved in the discovery. Under the rules of the International Union of Pure and Applied Chemistry (IUPAC) this team, lead by Professor Sigurd Hofman was allowed to suggest the name for the element, although it was not permissible for them to name it after a living person. The name will be officially endorsed in six months’ time in order to give the scientific community time to discuss the suggestion.

ChemEd ‘09 resources This year’s highly successful ChemEd Conference had 160 delegates – congratulations to the hard working committee. The diverse nature of the keynote presentations provided plenty of food for thought. These included Donald Petit, a NASA astronaut; Mary Kirchoff, director of the American Chemical Society Education Division; Peter Hollamby from the University of Wales; and Peter Atkins, a prolific writer of chemistry text books and popular science books. The local committee had decided that their emphasis would be on practical activities and ran a total of seven practical workshops which were very well received. These have now been made available, along with some of the other Conference presentations. It is well worth taking a look through these resources. There are over 60 different activities and they have been conveniently packaged for Years 9 to 11 science, and the different aspects of Year 12 and Year 13 chemistry. See: http://www.chemteach.ac.nz/chemedresources. shtml (or ref: http://tinyurl.com/ndjzll).

Central ideas in chemistry The following is taken from Peter Atkins’ address at ChemEd ‘09. Currently we have the opportunity to take stock of what we are teaching due to the alignment process and the new curriculum, and the following view of chemistry provides an interesting starting point for discussion: 1. matter consists of atoms 2. elements form families 3. bonds form by sharing electron pairs 4. shape is of paramount importance 5. there are residual forces between molecules 6. energy is conserved – the 1st Law of Thermodynamics 7. matter and energy tend to disperse – 2nd Law of Thermodynamics 8. there are barriers to reaction 9. there are only four types of reaction: radical reactions; Lewis acid-base reactions; proton transfer reaction; and electron transfer reactions.


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by Paul King Those of you who couldn’t make it to this year’s Physikos in Christchurch missed seeing a brilliant series of practical teaching demonstrations delivered by Associate Professor Gorazd Planins˘ic˘ from the University of Ljubljana, Slovenia. In his talk entitled ‘Multilevel simple experiments: an approach with increasing cognitive demands’, Dr Planins˘ic˘ insisted that: “Simple experiments are [an] indispensible part of [a] physics teachers’ repertoire. Simple experiments are met in various activities ranging from demonstrations to home experiments, as a base for active learning methods, for student projects or even as a base for competitions... Carefully selected simple experiments offer also a great opportunity to be presented as sequences of structured problems that all together form complete stories.” You can download his talk and resources at: http://www. phys.canterbury.ac.nz/Conferences/NZIP2009/ Resources/index.shtml, select: Gorazd Planins˘ic˘ : Multilevel simple experiments; Invisible visible ppt; and Project Labs. Also check out some of his resources at: http://www.fmf. uni-lj.si/~planinsic/PEMbG.htm Most physics teachers will find his paper on ‘Multilevel simple experiments’ illuminating but pay heed to his warning not to work through his presentation all at once with students: “All in due course of time. Don’t pour on students all the repertoire at once!” Also take time to browse the Physikos Conference page (as listed above) and check out some of the other material, which will inspire both you and your students. One of Dr Planins˘ic˘’s demo’s, not listed in these resources, is a must for any lesson involving electrostatics: the effect of an electric field on the flow of oobleck.

Effect of an electric field on the flow of oobleck. 1. Make up a small pot of oobleck from about 2 parts cornstarch (or custard powder) mixed with 1 part oil (NB: I used Canola oil, it worked fine). Use enough oil to allow the oobleck to flow smoothly from a spoon. 2. Bring up a charged rod (I used a plastic comb, rubbed on a woollen sock; but you will have a Van de Graaff ) and hold it close to the flowing stream. This will cease to flow!

It’s as if a pair of shears has chopped the stream, with the ‘fluid’ just hanging there and a little pointy bit on the end questing after the charged rod. Why? The electric field has altered the viscosity of the oobleck by forcing an alignment of the starch grains across the direction of the flow. It’s a fabulous effect. The usual recipe for oobleck calls for a water and cornflour mixture which responds to the electric field in a similar, but more pronounced fashion, to that of a water stream. Students might have fun investigating and reporting on the differing responses of the two ooblecks. Let me know (via Dave) if any effect is observed with other liquid streams. A small point occurred to me while I was trying out this demo: the deviation of a water stream by an electric field is a standard part of our repertoire, yet do we always remember to do the control demonstrations? Don’t forget to show that an uncharged rod has no effect on the stream, and a rod discharged by having the water flow over it, also no longer deviates the stream. For further information contact: dhousden@xtra.co.nz

as how and what to set up in advance. There is a matrix that can be used to plan your teaching programme – a great idea for long-term relieving teachers. And there are plenty of homework activities. And that’s not all…the Year 11 CD has interactive NCEA papers with revision links catering for a wide range of academic ability – our students enjoy using these. And we continue to find new uses for the various sections of the books and CDs. These are not just homework books, they are well thought out and meticulously developed teaching tools for junior science, written by people who really know how we do things in New Zealand. I highly recommend them. New Zealand Association of Science Educators

bookreview

Science 9 and 10Workbooks, and New Directions in Science Workbook NCEA Level 1 Reviewed by Elizabeth Hill (HOD Science) St Catherine’s College. By Anne Wignall, Terry Wales, Wendy Robinson (and Janet Dixon – Year 9 and 10 only) Published by Pearson, RRP $16.99 (incl GST). The Science Workbooks and CDs, for Years 9 to 11 contain material that is up to date, relevant to the New Zealand curriculum, and attractively presented. There is good supporting material that makes these books even more useful for busy teachers. The lesson starter quizzes are useful in helping students to refocus on the previous lesson’s work. The practical laboratory activities come complete with technician notes, such

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thinking about the nature of science? Written byWarren Bruce and Chris Astall, University of Canterbury By now most schools would have read through the essence pages for Science as a learning area (NZC, 2007 p 28-29) and will be considering the importance of the statement “The core strand, Nature of Science, is required learning for all students up to year 10. The other strands provide contexts for learning”. But what does this mean for the classroom teacher? How often are the four aspects of the Nature of Science (NOS) taught explicitly in schools? Often the classroom teacher, knowingly or otherwise, may well be teaching elements of the NOS during their science lesson but is it being made explicit to the children? How aware is the teacher of what NOS is? There is now a need to teach children how scientists work, how they investigate, how they share their ideas and make connections with their wider world. Does the implementation of the NOS mean teachers should now focus their attention more on teaching children the processes involved with doing science, as scientists might actually do, rather than focusing mainly on knowledge? It is the need for explicitness that we feel is so important in developing both teacher and learner understanding of what the NOS is all about. The Science exemplar matrices featured in the New Zealand Curriculum Exemplars (2004) fit very closely to the four aspects within the NOS . Aspects of NOS can be seen in the Science exemplar matrices under the ‘Key Aspects of Learning’ and indicate what some of

these learning experiences could be and how they could progress across levels. Below, we have given a number of examples of what the Nature of Science could look like (This could be) in each of the four aspects. This material allows teachers to identify those areas of NOS that they could focus on when planning and developing lesson or units of work. The Postcards in Science Project provides good examples of those types of activities that could be used to make the Nature of Science (NOS) more explicit to both teachers and learners. Detailed teacher planning that includes specific examples of NOS, pupil notes, links to curriculum material and children’s literature can be downloaded from www. sciencepostcards.com. One example, the science postcard ‘No to Noise’ uses the book ‘Ruby Sings the Blues’ by Niki Daly to explore the Nature of Science aspect ‘Participation and Contribution’. Here students explore the problem of exposing their hearing to loud noises in their everyday lives. Sound (physical world) is the context used for teaching this aspect of NOS. Maybe it is time to get thinking about how you will include the Nature of Science in your teaching… For further information contact warren.bruce@canterbury.ac.nz or chris.astall@canterbury.ac.nz

Understanding about Science

Communicating in Science

Exemplar Matrices Links: Thinking in Scientific Ways (Matrix C) Achievement Aims: Learn about science as a knowledge system: the features of scientific knowledge and the processes by which it is developed; and learn about the ways in which the work of scientists interacts with society.

Exemplar Matrices Links: Developing and Communicating Scientific Understanding (Matrix D) Achievement Aims: Develop knowledge of the vocabulary, numeric and symbol systems, and conventions of science and use this knowledge to communicate about their own and others’ ideas

This could be: Being open-minded, Asking questions, Making observations, Discussing their ideas with others, Knowing science ideas / knowledge may change over time, Using creative insight to aid explanation, Being aware of other cultures, Understanding science knowledge is one way of explaining their world, Working together and needing to provide evidence to support their ideas, and Being prepared to re-evaluate their own ideas.

Investigating in Science Exemplar Matrices Links: Investigating in Science (Matrix B) Achievement Aims: Carry out science investigations using a variety of approaches: classifying and identifying, pattern seeking, exploring, investigating models, fair testing, making things, or developing systems. This could be: Use a variety of investigative approaches (exploring, classifying, identifying and pattern seeking, fair testing and investigating models), Developing explanations based on evidence, Being curious, Asking questions, Discussing their ideas with others, Being openminded, Thinking critically about their own and others ideas, Use evidence to support their ideas, Looking for trends and patterns in data, and Being creative.

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This could be: Using scientific language, Building their scientific vocabulary, Making predictions based upon their existing science knowledge, Realising science explanations must withstand peer review before being accepted, Sharing explanations of experiences and observations, Using scientific language, including symbols, graphs and diagrams when explaining an idea, Being able to question the accuracy of texts they are using, Having experience of a range of text types, including web resources, and Being able to argue a point of view.

Participating and contributing Exemplar Matrices Links: Developing Interest and relating Scientific Learning to the Wider World (Matrix A) Achievement Aims: Bring a scientific perspective to decisions and actions as appropriate This could be: Discussing issues of concern to them, Understanding that science investigations could be influenced by their communities, Exploring ways of taking informed action, Knowing science interacts with other cultures, globally, Being aware of the needs of others, Using their science knowledge when considering issues of concern to them, Being openminded when exploring aspects of an issue, Making decisions based upon evidence, and Being aware of science in their world.


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the carbon cycle byJennyPollock

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As we know, carbon is the fourth most abundant element in the Universe, after hydrogen, helium and oxygen, and is the building block of life. It’s the element that forms the skeleton of all organic substances, from fossil fuels to DNA. Carbon cycles through the land, ocean, atmosphere, and the Earth’s interior in a major biogeochemical cycle (the circulation of chemical components through the biosphere from or to the lithosphere, atmosphere, and hydrosphere). The global carbon cycle can be divided into two categories: the biological, which operates at shorter time scales (days to thousands of years); and the geological, which operates over very large time scales (millions of years). http:// earthobservatory.nasa.gov/Features/CarbonCycle/

Biological carbon cycle Carbon, used by all living organisms, continuously circulates in the Earth’s ecosystem. In the atmosphere, it exists as colourless, odourless carbon dioxide gas (and some methane). Plants take in carbon dioxide during photosynthesis and give out carbon dioxide during respiration. When herbivores eat the plants, they acquire the carbon stored in plant tissues. Much of the food (carbon compounds) eaten is used up for the herbivore’s life processes and given off as carbon dioxide in respiration, but some is stored in animal tissues. If that herbivore is then eaten by a carnivore (or omnivore) the carbon (stored in the animal tissues) will be passed on. Dead plants and animals decay and carbon dioxide is released into the atmosphere to be used by plants again. The carbon cycle repeats itself endlessly. Some carbon from dead plants is temporarily removed from the carbon cycle as fossil fuels such as coal, oil and natural gas. Fossil fuels give out carbon dioxide when burned. Industries, coalfired power plants and exhausts from motor vehicles have contributed additional carbon dioxide to the environment.

Geological carbon cycle This is not as well known as the biological cycle although it has a much larger role. In the geological carbon cycle, carbon moves between rocks and minerals, seawater, and the atmosphere. Carbonic acid (a weak acid derived from atmospheric carbon dioxide and water) slowly but continuously combines with calcium and magnesium in the Earth’s crust to form insoluble carbonates through weathering. The carbonates are washed into the ocean and eventually settle to the seafloor as layers of sediment. The calcium carbonate shells of plankton also form part of the sediments. Subduction carries these sediments deep underground where, under the great heat and pressure far below the Earth’s surface, they melt and react with other minerals when lava is formed. When volcanoes erupt carbon dioxide is released into the atmosphere, completing the cycle. The balance between weathering, subduction, and volcanism controls atmospheric carbon dioxide concentrations over time periods of hundreds of millions of years.

The role of the ocean In the oceans, carbon dioxide exchange is largely controlled by sea surface temperatures, circulating currents, and by photosynthesis and respiration. Carbon dioxide can dissolve easily into the ocean and the amount held depends on ocean temperature and the amount of carbon dioxide already present. Cold ocean temperatures favour the uptake of carbon dioxide from the atmosphere, whereas warm temperatures can cause the ocean surface to release carbon

(Ref: http://www.vtaide.com/png/carbonCycle.htm) dioxide. Cold, downward moving currents such as those that occur near Antarctica absorb carbon dioxide and transfer it to the deep ocean. Upward moving currents such as those in the tropics bring carbon dioxide up from depth and release it to the atmosphere. Life in the ocean consumes and releases huge quantities of carbon dioxide. But there is virtually no storage of carbon as there is on land (i.e. tree trunks and soil). Photosynthetic microscopic phytoplankton are consumed by respiring zooplankton (microscopic marine animals) within a matter of days to weeks. Only small amounts of residual carbon from plankton settle out to the ocean bottom and over long periods of time represent a significant removal of carbon from the atmosphere.

Teaching of the carbon cycle The carbon cycle can sometimes seem very dry and some imagination needs to be used to make it interesting. Here are some ideas: 1. The web link ref: http://tinyurl.com/2zwgre takes you to a very effective interactive game and is a good starting point. 2. The web link ref: http://tinyurl.com/masxg7 is a much larger resource with a similar game. 3. This interactive game incorporates energy and carbon: ref: http://tinyurl.com/lrjsjy 4. Use your local area to illustrate aspects of the carbon cycle. For example, coal fields, limestone formations, dairying, a cold stormy ocean, forests, industrial smoke and the use of fossil fuels in cars all illustrate key aspects of the carbon cycle. 5. Practical exercises can also illustrate key aspects. Combustion experiments, the uptake of carbon dioxide by water as shown by a change in pH, the bubbling of carbon dioxide from respiration through limewater and the effect of acid on rocks and shells can all be easily done. Fieldtrips to features such as limestone outcrops and road cuttings showing strata; visits to dairy farms; and the modelling of subduction with 3D models or computer animations also increase understanding. 6. The Science Hub also has information on the carbon cycle. This link introduces the topic, ref: http://tinyurl. com/ksojny. This page has a link to this good interactive site, ref: http://tinyurl.com/22rtef For further information contact: jenny.pollock@ncg.school.nz

New Zealand Association of Science Educators

47


NZ

science teacher

technicians

122

a day in the life of a science technician What’s in the diary today? Oh good... just food testing for Period 4. I might be able to get on with sorting out the Chem store, writes Annette Hobby, Science Technician, Shirley Boys’ High School. Oh, dear...Geoff has come off his bike on the way to work and will need relief for his classes. Yes, I will find an Earth Science video and worksheet and get it to F7 for Period 1. You need a class set of Level 3 and 4 Motion Test for next period but the printer is down? Alright, I’ll use my printer and then run it off. Food Testing Kit: there is no Benedict’s solution or iodine, why didn’t anyone tell me! Fortunately, I know how to make up iodine solution in a hurry; you know how long that stuff takes to dissolve. Here’s my trick: dissolve the 12g KI in about 50ml water then add the 3g iodine and shake – works a treat, only takes a few minutes – then top up with water. Make up test solutions for the food test hoping they can’t tell the difference between the beakers of milk, starch and glucose. You want to do rat dissections tomorrow? Okay, I will take them out of the freezer; must check if we have enough rats for the other classes. Check the gloves, trays, and scissors. Wonder if they will be doing hearts next week? I have changed the supplier and it takes longer to get them. Have we got any paramecia for my classes to look at under the microscopes? Oh yes, I will just pop down to the shop and get some!! Ha ha! Just as well I have still got a culture going; and must re-culture it too. Favourite culture recipe: one cat biscuit, a piece of dried lettuce about the size of a milk bottle top, 500ml of water, and leave it for 24 hours to brew. Then add some of the old culture and it will be thick in about a week. Need more magnesium ribbon? Cut up pieces from Electroflash, makes it much simpler than having pupils cut it up and they all have the same size. Can’t find the iron filings and there is none in the chem store? Well, that would be because they are in sprinkle containers on the shelf with the magnets. Must be time for a bit of lunch; will I stay here or go to the staffroom? Just as well I stayed here, some Year 13 boys needed the books that we took on the Bio trip as they are now doing their write up. Check the emails; isn’t SciTech-talk wonderful? We are such a diverse and knowledgeable group that if you put any question out there someone will have ‘invented the wheel’ before you have to; and we are happy to share. Set up the seed growing kit for tomorrow; have a great idea that I brought back from Labcon in Melbourne. Use

clear plastic disposable cups, and a piece of paper towel with some photocopy paper to hold it up, wrapped inside. In the middle put a ¼ teaspoon of crystal rain and add enough water to swell the crystals (¼ teaspoon will swell to about a third of the cup, and it stops the seeds drying out and gives stability). Slide several corn or pea seeds half way down the slot between the paper towel and the side of the cup. Cover with lid or glad wrap, watch the seeds sprout. Help! I want to use the Electricity Kit but only half of them are here! Find the power packs; which are in the last lab I look in – the fourth block, Lab 9. And need more 12 volt bulbs. Yes, they will be in the bulb drawer, and there’s plenty of spare ones. Can’t find any copper sulphate for crystals? Go to Chem store and take off shelf – staff hadn’t looked hard enough. I need a video for relief tomorrow; we are doing plants. What about this one on The Brazil Nut Tree? It’s a great video as it shows what a Brazil nut needs to grow. Did you know that a rat-like agouti gnaws open the outside covering on a Brazil nut cluster; The nuts are the size of coconuts; and they are a great source of selenium (a mineral NZ soils are deficient in)? That reminds me, I had better check supplies of Brazil nuts as we use them for our nut burning practical. We got rid of peanuts as some boys are allergic to them and it took some experimenting to find a suitable nut replacement. Funny how some nuts just won’t boil the water. I cut the Brazil nuts into about 6 pieces; otherwise we would have bonfires on our hands. Talking about allergic reactions, need to see the Executive Officer about updating my First Aid certificate, it runs out in about 6 weeks and we need to have someone on our field trips who has a current certificate to comply with regulations. Make up the 2 mol acids for 1.1. Remember the old adage, “Do what you oughta, add the acid to the water.” Must order a copy of the updated Bio Lab Sourcebook from http://www.biologyresources.co.nz; it has all the information techies (or teachers) need for practicals. Phone call from another techie... wants some cockroaches for Wednesday. OK, I understand that not everyone wants the little beasties around but mine thrive on a cat biscuit diet. What’s the time? Oh, it’s time to go home and I didn’t even have time to check out the Chem Store, maybe tomorrow... For further information contact: mgarnett@christscollege.com

NZASE flagship biennial conference

Journey to Discovery 4-7 July 201&šD[bied9ebb[][\eh=_hbi"D[bied"DP

;cW_b0iY_Yed(&'&6Yed\[h$Ye$dpšM[Xi_j[0mmm$Yed\[h$Ye$dp%iY_Yed(&'& 48 New Zealand Association of Science Educators


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NZASE #122  

New Zealand Science Teacher #122

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