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science teacher 2010

Featuring: Air Reducing drag in track cycling Storms and jet streams Clouds: Brown, Einstein and Perrin Bubbles in our food Weather impacts on health Wind engineering Modelling air flow Lifelong science learning Engaging students in science Why ‘absolute’ time? And more…

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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’s desk 3 Feature: Air Why clouds don’t fall down 4

Editorial Address: lyn.nikoloff@xtra.co.nz Editorial Board: Rosemary Hipkins, Chris Joyce, Suzanne Boniface, Beverley Cooper, Mavis Haigh, Barbara Benson Journal Staff: Editor: Lyn Nikoloff Sub editor: Teresa Connor Cover Design and Typesetting: Pip’s Pre-Press Services, Palmerston North Cover graphics: Antony Radley Printing: K&M Print, Palmerston North Distribution: NZ Association of Science Educators NZASE Subscriptions (2010) School description Roll numbers Subscription Secondary school > 500 $240.00 < 500 $185.00 Area School - to be determined TBA Intermediate, middle and > 600 $240.00 composite schools 150-599 $90.00 < 150 $65.00 Primary/contributing schools > 150 $90.00 < 150 $70.00 Tertiary Education Organisations $240.00 Libraries $110.00 Individuals $50.00 Student teachers $45.00 Special Interest Group (includes access to secure sites): BEANZ, NZIC, STANZ, SCIPED $10 per group Note: SIG fees are included all subscriptions except for individual members. Additional copies of the NZ Science Teacher Journal

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Subscription includes membership and one copy of NZST per issue (i.e. three copies a year). All prices are inclusive of GST. Please address all subscription enquiries to the NZASE, PO Box 1254 , Nelson 7040. Subscriptions: nzase@confer.co.nz Advertising: Advertising rates are available on request from nzst@nzase.org.nz Deadlines for articles and advertising: 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

Track cycling aerodynamics 6 Storms, jet streams, and climate change 9 Lightening our food using gasses 12 Weather and our health 17 Modelling air flow 20 Sailing in a wind tunnel 23 Atmospheric emissions and health 26 Aerophytic algae 29 Regular features Science education: Lifelong science learning 32 Engaging students in science 37 History Philosophy of Science: Why ‘absolute’ time? 41 Resources: National Library 43 Subject Associations: Chemistry 44 Physics 45 Primary Science 46 Science/PEB 47 Technicians 48

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.

Front cover: Track cycling research: wind tunnel tests of clothing and rider position sometimes use a mannequin secured in the riding position. Drag is measured with a force platform on which the bike is mounted. Photograph courtesy of Lindsey Underwood.

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communicating with integrity Good quality, honest, open communication might have saved Mary, Queen of Scots’ life, but sadly Elizabeth I eschewed a face to face meeting with her cousin, and relied instead on advisors and their skill with the language of political detente. So the intent of the cousins became, in part, constrained by poor communication. So have you ever stopped to think how your ideas about science might become confused in their delivery? Are you saying one thing and your students (or colleagues) hearing something quite different? Take, for example, the enlightening and slightly cringeworthy exchange between an observer (Ross Tasker) and a student (Keith) as relayed in Rosemary Hipkins’ ‘must read’ article (page 37). The student is conducting an experiment and in the final exchange the observer asks: ”Can you tell me the purpose of this activity?”“No ... not really,” replied Keith who had been simply following through the steps as required by the teacher/activity. How might this miscommunication between teacher and student impact on the student’s understanding of science? In view of such confusions, how do we ensure that our students retain a lifelong interest in science? (see Miles Barker’s article, page 32) While I have taken the above exchange out of context (and my apologies to Rose), it serves to illustrate that science communication, like all communication, is a dialogue, verbal and non-verbal, in context. Late last year I attended a conference for science communicators. Delegates consisted of media specialists, authors, film makers, scientists, publishers, science centre educators, academics and students. But there were no practising classroom teachers! While one or two delegates were communicating science to school-age students, most were engaged in science education via the popular media. Many of them had limited scientific acumen, and yet they have a profound impact in shaping society’s view of science. But it needn’t be like this − if teachers communicated to students a passion for lifelong learning about science then they would eschew the need for simplistic media sound bites. Most science teachers, in my experience, are excellent communicators, and most are passionate about what they are doing. And, as editor of the NZST, I feel passionate about bringing to their attention the endeavours of our research colleagues. In this issue, which has the theme of air, we begin by reflecting on why clouds don’t fall out of the sky. This is an engaging article that introduces basic physics’ concepts thanks to Robert Brown, Albert Einstein and Jean Perrin, and is written by Geoff Austin and Kim Dirks (page 4). Have you ever wondered why your tub of ice cream becomes firmer and has a less creamy texture if it melts before refreezing? Matt Golding enlightens readers on how

food gasses, including air, affects the textural properties of food − excellent science! (Page 12). The popular press seems to be fixated on sensationalising climate change, but it can be difficult to find credible scientific information that is written in an accessible way. In this issue, we have three great articles for you. First, James Renwick explains how storms and jet streams are affecting, and will continue to affect, NZ as result of climate change (page 9). Second, Kim Dirks explains that epidemiological studies are revealing a possible relationship between weather extremes and health (page 17). Third, Ian Longley explores the relationship between car usage and respiratory disease (page 26). Aerodynamics is a great physics’ context, and Mark Jermy explains how engineers are working to reduce drag on racing bicycles (page 6); Richard Flay describes how an understanding of wind flow is helping engineers to design better yacht sails (page 23); and John Cater explains how Large Eddy Simulation is helping engineers better understand air flows in and around buildings and wind turbines (page 20). And for the biologists, (and for those with an insatiable curiosity), there is an engaging article about Aerophytic algae, written by Phil Novis (page 29). I have just looked at the clock on my computer to see how long it has taken me to write this editorial. Have you ever wondered where the concept of absolute time came from? Philip Catton invites us to join him on a philosophical journey as he explores Newton’s search for absolute time (page 41). This issue also has a message from your President, Lindsey Conner and reports from the NZASE standing committees. Now where was I? Oh yes, communication. Many years ago, as a biology teacher, I was explaining courtship behaviour to my Year 13 students and discussed how humans might attract suitable partners. In the unit test I asked my students to describe benefits of courtship behaviour. One student wrote that wearing lipstick would ensure sexual intercourse! Wow, I had never said or intended to even intimate such a thing! So you see how poor communication could have dire consequences, just as Mary, Queen of Scots came to learn. What if we, as teachers, do not articulate science to our students in a meaningful way; does our society become prone to cronyism and soothsayers? And should we rely on the communication gurus, the ‘media experts’ to be gatekeepers of ‘good science’? The NZST is committed to communicating, with integrity, good science and education research. I wish you all a year that is, in a positive way, professionally challenging. Kind regards, Lyn Nikoloff, Editor

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Kia ora koutou, Welcome to this edition of the New Zealand Science Teacher. We hope you find it valuable as a reference and that the ideas contained here spark some new thinking and support the creative use of contexts in your teaching. This year, the focus for many of you will be aligning what you teach with the new curriculum, though I’m sure many of you are well underway with this. The New Zealand Curriculum requires science teachers to incorporate aspects of the nature of science (NoS) into teaching programmes. Although aspects of the NoS have been inherent in previous teaching resources, many teachers have already indicated that an explicit emphasis on NoS needs some careful thought and planning. At a national symposium on science education research held in Christchurch at the end of 2009, the participants identified some key ideas about raising teachers’ and students’ awareness and understanding of NoS and some processes that might help to support the explicit teaching and learning about NoS. The first thing that became apparent during discussions was that there are many interpretations of what NoS is exactly. Therefore, science teachers may need to discuss this more fully to come to a collective understanding. Secondly, a stronger emphasis on NoS is likely to enhance ideas about the culture of science and how scientists work. Explanations about NoS can drive this cultural brokering, but other dimensions of science can and should also be developed as well. We must not abandon the big ideas in science, the creative aspects of science and ways of embellishing awe and wonder about our world. To support you in assessing Level 1 NCEA, a sub-group of NZASE is developing new ‘highly scaffolded’ activities similar to those that were available for the Certificate in Science. These will be pre-moderated and available on the NZASE website very soon (www.nzase.org.nz). Although these will provide some examples of assessment of aspects of NoS, teachers need many examples embedded within resources. There is an opportunity here for you all to share what you create. The emphasis in school assessment and professional development on literacy and numeracy also provides opportunities for using science contexts to enhance these initiatives. The Ministry of Education has promoted the idea of integrating literacy and numeracy into science teaching through a series of articles in The Education Gazette in the latter part of 2009. There are also teaching and learning materials on the TKI website to support these approaches. It would be great if, as a science education community, we could create and share many examples of trialled activities. BEANZ, the biology standing group and the new chemistry

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education group are also providing resources for the new achievement standards. Teachers can disseminate their ideas through many avenues especially your regional associations. I would also like to encourage you to write articles for The Gazette, New Zealand Science Teacher, SET, New Zealand Education Review and to present at science teacher conferences. The SCICON organising committee warmly welcomes you to present your ideas and activities at the SCICON Conference in Nelson, 4–7 July, 2010. The theme of the Conference is ’Journey to Discovery’. This Conference will reflect the importance of understanding the nature of science as it is the overarching theme of the new curriculum. There will be keynote speakers who are scientists and science educators, as well as many opportunities to attend or present workshops, seminars and field trips to invigorate our teaching of science. The Royal Society of New Zealand plays a key role in promoting science education. Their recent promotions include the Prime Minister’s outstanding science teacher award and the teacher fellowships for primary teachers which are in addition to the science and technology fellowships for secondary teachers. Look out for the call for nominations for these later in the year and support your colleagues to apply for these. The Prime Minister’s Science Teacher Prize can be given to a primary or secondary teacher. There are amazing incentives for this award. The prize money is $50,000 for the winning teacher and $100,000 for the school in which they teach. To find out more information visit: http://www. pmscienceprizes.org.nz. Due to Government budget cuts, the Advisory Services nationally will not be centrally funded to provide professional development programmes in science, particularly for primary schools. As an association, we need to find ways to cater for your science teaching needs. NZASE and the standing committees provide vehicles for you to have a say about what your professional needs are and to find ways to make it happen. Your contributions and actions on these matters, whether within your own school, region or at a national level, make a difference. I look forward to working and networking with many of you in my new role as President, particularly those of you involved in regional associations and standing committees of NZASE. However, the promotion of science is the responsibility of all teachers of science, so we need to find ways to do this that are mutually beneficial. Kia kaha! Lindsey Conner President NZASE

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why clouds don’t fall down: Brown, Einstein and Perrin Robert Brown, Albert Einstein and Jean Perrin all played a significant role in the development of our understanding of physics and why clouds don’t fall down, as Professor Geoff Austin, Department of Physics, Faculty of Science and Dr Kim Dirks, School of Population Health, Faculty of Medical and Health Sciences, The University of Auckland, explain: We have all taken the time at some point in our lives to lie in the grass on our backs and watch the clouds as they pass by. Have you ever asked yourself how clouds are able to stay suspended in the air? After all, they are made up of water droplets that have a density of about a thousand times that of air, and on the scale of a typical large cloud (which is about 1km cube in size, or about 109 m3), the total mass of liquid water is about 106kg or 1000 tons! Of course, larger drops DO fall out of the sky sometimes (when it rains or pours!) but many of the clouds we observe don’t. This article looks at the role that Robert Brown, Albert Einstein and Jean Perrin played in the development of the physics that leads to the answer to this very question. Robert Brown and particle motion The solution to the mystery begins with Robert Brown who, in 1872, studied the behaviour of pollen and spores of mosses suspended in water. His observations revealed that these particles didn’t remain stationary or move in a systematic way, but rather jiggled about in a seemingly random way. What was the source of energy for this movement? When he tried suspending other small fragments of plants and inorganic particles he observed similar behaviour, ruling out the possibility that the movement arose due the substances being ‘alive’. From his observations, Brown concluded that the jiggling behaviour of small particles was apparently universal (not dependent on the type of material making up the particle). What Brown had actually discovered was evidence of the kinetic theory of gases and liquids which essentially states that gases and liquids are made up of a large number of small particles in constant random motion as a result of their temperature, and that the jiggling behaviour was caused by collisions between the particles (in this case pollen) and the (too small to be observable) water molecules making up the liquid in which the particles were suspended. At the time, however, there was still no direct evidence for the existence of atoms as such, so no sensible explanation could be provided for the cause of the seemingly random movement of particles in suspension. It was not until the 1880s that the kinetic theory of gases was developed. By the 1900s, Josiah Gibbs and Ludwig Boltzmann were well along the way in their development of statistical mechanics, but there was still no direct evidence for the existence of atoms. In fact, many distinguished scientists at the time (including Ernst Mach) did not accept the concept of atoms at all!

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Albert Einstein and the drunkard’s walk Albert Einstein was not one of the people willing to reject the idea, and was keen to develop experiments in support of the hypothesis of the existence of atoms. In 1905, Einstein proposed experiments that involved observing the movement of small particles suspended in water (because it made observations by microscope easier) to demonstrate that the multitude of invisible water molecules would fluctuate in their motion, and that in any short time period the momentum imparted to small particles placed therein would in turn fluctuate and cause them to jiggle about. In other words, they behave like ‘big molecules’ in thermal equilibrium with the water, consistent with Brown’s observations in the previous century in liquids consistent with Boltzmann’s theory of gases. Based on this hypothesis, Einstein derived a formula which gives the displacement of particles as a function of time − known as the ‘drunkard’s walk’ formula. The idea is that if a large number of drunks walk out of a bar and begin to walk randomly in all directions (and collide with each other in their drunken state) their average displacement from the bar over time will be zero, but the distribution of their distance from the bar at a particular point in time will be Gaussian. Figure 1 shows an

Figure 1: Example of movement of small particles in suspension in a liquid exhibiting Brownian motion as a result of collisions of particles with water molecules in their paths. Source: M Nott 2005.


Jean Perrin In 1916, Jean Perrin spent an enormous amount of time separating chemically-produced precipitates by repeated centrifuging in order to get a small quantity of particles of (roughly) the same size (mass in particular) in order to be able to carry out these experiments (Note: these days, all of this hard time-consuming work can be avoided simply by purchasing approximately equal-sized spheres made out of plastic!). By placing the particles in water and leaving them for a sufficient amount of time to reach equilibrium, Perrin found that the concentration of particles did indeed decrease exponentially from the surface (as shown in Figure 2) in much the same way as does the particle density (and pressure) in the atmosphere. In fact, by observing the distribution of particles at different heights, knowing the mass of the equal-sized particles and knowing the temperature of the solution, it is possible to estimate, with a reasonable degree of accuracy, Boltzmann’s constant, k. This distribution of particles would not be observed if they were not colliding with the water molecules (which of course we cannot see) and redistributing their energy in a random way consistent with the kinetic theory of gases. The fact that huge quantities of cloud liquid water do not (necessarily) fall out of the sky is direct evidence for the existence of molecules of air which collide with the small cloud droplets causing them to jiggle about. As an aside While Brownian motion and the evidence it provides for the existence of atoms is largely attributable to Robert

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example of painstaking work done tracking the position of individual particles over time undergoing the socalled Brownian motion. In contrast with drunkards (who are essentially selfpropelled; there are limitations associated with any analogy!) the energy of a gas associated with translation and rotation is governed by the temperature of the gas particles. Note that the energy is not evenly distributed amongst the molecules making up the gas, but that the average energy is determined by the temperature. This distribution of energy was demonstrated by Perrin, who in 1890, argued (along with Einstein) that the laws governing Brown’s jiggling pollen in liquids were the same as those in gas in the atmosphere. Einstein hypothesised that if this was indeed what was happening with particles in liquids, then such particles should produce a sedimentation equilibrium such that the number concentration, n, should decrease exponentially with height, h, given by n = noe – mgh/kT just as is observed with the pressure of gases in the Earth’s atmosphere decreasing exponentially with height. In this equation, the subscript ‘o’, refers to conditions at the surface, the symbol m represents the mass of the particle, g is the acceleration due to gravity, k is Boltzmann’s constant and T is the temperature.

Figure 2: A microphotograph of the height distribution of particles of resin suspended in water taken by Jean Perrin (© Palais de la Découverte, Paris). Source: Bigg (2008).

Brown, much earlier evidence of the observation of Brownian motion can be found in historical records. In particular, the Roman Lucretius’s scientific poem: On the Nature of Things (c. 60 BC) has a remarkable description of the Brownian motion of dust particles: “Observe what happens when sunbeams are admitted into a building and shed light on its shadowy places. You will see a multitude of tiny particles mingling in a multitude of ways... their dancing is an actual indication of underlying movements of matter that are hidden from our sight... It originates with the atoms which move of themselves [i.e. spontaneously]. Then those small compound bodies that are least removed from the impetus of the atoms are set in motion by the impact of their invisible blows and in turn cannon against slightly larger bodies. So the movement mounts up from the atoms and gradually emerges to the level of our senses, so that those bodies are in motion that we see in sunbeams, moved by blows that remain invisible.” While some of this movement can be explained by smallscale air turbulence, it also provides very early insight into Brownian dynamics and a belief in the existence of atoms.

In conclusion... The fact that particles are in sedimentation equilibrium is of major importance, not only in the understanding of clouds, but also in studies of air pollution and dust events. There are also significant consequences in biology (such as in the assembly of proteins). This shows that the behaviours of clouds in their environment provide excellent illustrations of basic physics’ concepts at work on a large scale. For further information contact: g.austin@auckland.ac.nz or k.dirks@auckland.ac.nz References Nott, M. (2005), Molecular reality: the contributions of Brown, Einstein and Perrin, SSR June, 39, 461. Perrin, J. (1909), Mouvement brownien et realité moléculaire, Annales de Chimie et de Physique, ser 8 (18), 1–114. Bigg, C. (2008), Evident atoms: visuality in Jean Perrin’s Brownian motion research, Stud Hist. Phil. Sci. 39, 312-322.

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track cycling aerodynamics Track cycling is a fast, indoor cycling sport at which New Zealand has been doing very well recently. Bike technology and drag reduction are areas where improvements are being made as Mark Jermy, Department of Mechanical Engineering, University of Canterbury, explains: Races take place in a steeply banked velodrome and the most prestigious disciplines are individual and team pursuit, although there are many other types of race including sprints. In individual pursuit, two riders start at opposite sides of the velodrome. They race from a standing start, until one catches the other, or covers 4000m (men) or 3000m (women). Team pursuit is similar, but two teams of three or four riders compete. The lead rider experiences the most aerodynamic drag, with his or her teammates riding in the slipstream. The leader fatigues quickly, and after a set number of laps, switches to the back, or middle, of the pack in a fast, precise and visually impressive manoeuvre on the steep track. Speeds in both events can reach over 60kph (Figure 1).

Figure 2: An early advert for the Rover Safety Bicycle. Source: www.bicycle-evolution.com.

Figure 1: The ILT velodrome in Invercargill. The upper rider, who has been leading, is moving into the gap between the lower riders. Photograph courtesy of Craig Palmer.

The Union Cycliste Internationale (UCI) sets rules for the sport which include strict specifications for the bicycle. The intent is to make sure the most important aspects are the fitness and skill of the rider, and to prevent the better funded teams gaining an unassailable advantage. Nevertheless, it is important to have good equipment, and every year brings innovations in the bicycle and clothing.

Track cycle frame design The UCI rules specify the traditional diamond-shaped frame (Figure 2), seen on conventional road and mountain bikes. This frame first appeared in 1885 on John Starleyâ&#x20AC;&#x2122;s Rover Safety Bicycle. At that time the penny-farthing was the most popular form of bike, but had an important safety flaw. The riderâ&#x20AC;&#x2122;s weight is just above the front hub. Applying the brakes sharply can lock the wheel, causing the rider to rotate with the wheel right over the handlebars and head first onto the road. Starleyâ&#x20AC;&#x2122;s design placed the rider between two wheels of approximately the same size, and much lower. Hard braking was much safer, and the bike was much easier to get on and off.  New Zealand Association of Science Educators

In the twentieth century the recumbent cycle emerged. Placing the rider so that they present a smaller frontal area, recumbents have lower drag so are more efficient. They have not been widely adopted. The recumbent is banned from the major cycling sports by the UCI. Also, the perceived danger from traffic to the low and less visible recumbent deters potential riders. The diamond frame of a track bicycle is built from carbon fibre for high stiffness and light weight. The rules specify a minimum weight of 6.8kg, and it is possible to build a bike lighter than this. The frame members are built up to stiffen the frame, until this minimum weight is reached. When pedalling hard, a flexible frame distorts and rebounds, losing energy each time the pedals complete a revolution. The dimensions of the frame are determined by the need to pedal efficiently in two modes. Races begin from a standing start and the rider stands up on the pedals to bring their full weight to bear. At the same time they pull down on the handlebars, usually gripping the bulbous ends of the bars. The bars have to be carefully designed for stiffness in this mode to withstand the extreme forces.

Evolution of riding position Riding position has evolved over the years. Scottish rider Graeme Obree developed new handlebars and riding positions in the 1990s, enabling him to break the world one-hour distance record for indoor cycling. The new positions were banned by the UCI for racing. The film The Flying Scotsman [1] charts this process. In the current position, once up to speed, the rider sits down on the saddle and moves their arms forward onto


Table 2: Power generated by humans and horses over different timescales [2, 3]. Elite Athlete Healthy adult Horse (1 horsepower)

Duration

Power output

Seconds 1min 1h 1h 1h

2500W 750W 500 W 200W 746W

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the aerobars (Figure 3). This makes for low aerodynamic drag, which must be balanced against biomechanical efficiency. This is the key to bike setup; finding the position for which the drag and the power available from the rider optimise the speed possible. This does not necessarily mean using the body position with the lowest drag; in some cases that position compromises the biomechanical efficiency.

Once training has maximised Prider, the bike designer, rider and coach can turn their attention to Cd and A, the parameters they have the best control of. Frontal area A can be reduced only so far, by adjusting the position of the athlete. This is typically done in a wind tunnel, with complementary measurements of rider power output on a stationary bike. Cd is a measure of how well-adapted the shape is for low drag, the lower the better.

Figure 3: Cyclist, Chad Adair in the typical riding position. Photograph courtesy of Lindsey Underwood.

With a few simplifications (constant speed in a straight line on a level track) this idea can be expressed in Equation 1: 1 Prider = Cd A — rV 3 + Ploss 2 Where Prider is the power the rider generates at the pedals, Cd the drag coefficient of the rider and the bicycle, A the frontal area of the same, r the density of the air and V the speed of the bike. Ploss are the other power losses, which also vary with speed, but which at race speeds are much less than the aerodynamic drag. They include rolling resistance (due to the deformation of the tyre where it contacts the track), frictional losses in the chain and gears, and the flexing of the frame. These power losses are typically proportional to velocity, but the power dissipated by aerodynamic drag (aerodynamic power loss) rises as the cube of velocity. Table 1 shows estimates of these losses for a typical rider; aerodynamic drag is by far the greatest at track speeds. Table 1: Aerodynamic and rolling resistance power losses for a 100kg rider with CdA = 0.2m2 and rolling resistance coefficient 0.001 in air of density 1.2kgm³. Speed/ Aerodynamic kph power loss/W

Rolling resistance power loss/W

15 30 60

8.2 16.4 32.7

Riding to work Road racing Track racing

8.7 69.4 555.6

For comparison, Table 2 shows the power generated by riders and how long it can be sustained. The human compares poorly to the horse – but horses cannot ride bicycles.

Impact of drag Aerodynamicists divide drag into three types: induced drag, skin friction and pressure drag (sometimes called form drag). Induced drag is a drag directly associated with lift forces, and while important for aircraft, birds and flying insects, is insignificant in cycling. Skin friction drag is essentially the friction between the air and a surface. Imagine the air next to the surface of a body divided into layers. The surface is stationary, and the air is flowing over it. The air molecules in the layer closest to the surface, losing their horizontal momentum (Figure 4a). They bounce back into the flow, where they collide with other air molecules, exchanging momentum. As more molecules collide with the surface and give up the horizontal component of momentum, this close lying layer slows to the speed of the surface. There is a corresponding force on the surface, dragging it in the direction of the wind. Molecules also leave this layer to penetrate into the next layer above, again colliding with other air molecules there and exchanging momentum. This slows the layer above, but molecules with fresh horizontal momentum from layers even further out also reach this layer. As a result, it slows, but not as much as the layer next to the surface. In this way, these intermolecular collisions establish a set of layers with speed gradually increasing as the layers lie further from the body. This set of layers, taken together is termed the ‘boundary layer’, first named so by Ludwig Prandtl in 1904. The process of momentum exchange by intermolecular collisions is the origin of viscosity. Skin friction is inescapable. It is lowest on smooth surfaces, and can be reduced by making the surface area smaller, but cannot be eliminated. For well streamlined objects, for example aeroplanes and albatrosses, most of the drag is skin friction. However, for any object which is (from an aerodynamic point of view) badly designed, the third kind of drag, pressure drag, is much greater. The human body did not evolve for low drag, unlike the albatross, and pressure drag is important. Pressure drag is caused when the boundary layer pulls away (separates) from the surface of the body. At the front or nose, the air impacting the body exerts a pressure well above atmospheric pressure. If the New Zealand Association of Science Educators




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Figure 4: (a) The formation of the boundary layer; (b) front-rear pressure imbalance in separated flow.

boundary layer remains attached, and the flow closes smoothly over the rear of the body, the pressure over the rear of the body is similar. The front and rear pressures are nearly balanced and there is little net pressure force. However, if the boundary layer separates, there is a region where the fast flowing freestream passes over the slow moving air in the separated region (Figure 4b). The frictional exchange of momentum between these layers of air dissipates energy, and as pressure is a form of internal energy, downstream of the point of separation the air has a pressure lower than atmospheric. The pressures over the front and rear of the body are now very different, resulting in a net backwards force (think of the body being sucked back by the low pressure in the separated region). Flow separation, and hence pressure drag, can be completely avoided on slowly tapering shapes like aeroplane wings and soaring birds. Pressure drag can be minimised over many parts of the bicycle frame, so each member is shaped like an aerofoil. It is lower on a disc wheel than a spoked wheel, where each spoke has a separated region. However, it cannot be avoided on the human body. Much effort goes into reducing the size of the separated region by finding the best body position.

Reducing drag There are several regions of flow separation on a cyclist’s body. The one behind the head is reduced by the slowly tapering tail of the helmet. The main region, responsible for much of the drag, is the one behind the back, and track cyclists reduce this by holding their backs as flat and close to the horizontal as possible. Good bike setup – proper design of the handlebars and the correct saddle height – helps here. There are other separated regions behind the upper arms and behind the legs, which are harder to reduce. Due to this flow separation, the rider generates more drag than the bicycle. Estimates in the 1950s [4] with  New Zealand Association of Science Educators

the tubular-steel frames of the road bikes of the time suggested the frame and wheels generated about one third of the drag and the rider the remaining two thirds. Measurements in the University of Canterbury wind tunnel with a modern carbon fibre time trial bike suggest that the drag of the frame has now shrunk to about one quarter of the total. The bicycle designer’s job is far from finished though. The bike may be the smaller source of drag, yet it is the one we have the most control over. The UCI regulations and the requirements of biomechanical efficiency mean there is less scope for changing the position of the rider to reduce drag. Nevertheless, it is important to pay attention to both, and each new rider entering the sport must refine their riding position. Also, a well-designed and correctly sized frame allows the rider to get into a good position comfortably, and still produce maximum power.

Other impacts Rolling resistance is much less important than drag, but every millisecond counts in a race. In a straight line, rolling resistance is caused by the deformation of the tyre in the contact patch, where it touches the track. When steering, the front tyre is at an angle to the direction of travel, and the contact patch is scrubbed sideways across the track, increasing rolling resistance significantly. Rolling resistance is minimised by using a narrow tyre (typically 19mm) at high pressure to reduce the deformation. Drivetrain losses and flexing of the frame accounts for only a few percent of the rider’s power output. Drivetrain losses are small on a track bike, with only a single gear so the chain (which can be kept clean and well lubricated in the indoor track environment) follows a straight path, unlike in a derailleur gear. In conclusion... Track cycling offers a lot of technical challenges, even after 135 years of development of the ‘safety’ bicycle, new materials and new understanding are allowing further improvements and raising interesting problems for physicists and engineers. For further information contact: mark.jermy@canterbury.ac.nz Acknowledgements I would like to thank SPARC, Bike NZ and Milton Bloomfield of Dynamic Composites for their ongoing support of our bicycle research. The hard work is done by graduate students past and present: Lindsey Underwood, Dan Barry and Jaclyn Moore, and wind tunnel manager Graeme Harris. I would also to like to thank all the athletes who have endured the cold blast of the wind tunnel. References [1] The Flying Scotsman, Dir. Douglas MacKinnon, Verve/MGM (2006) [2] Wilson DG, Papadopoulos J & Whitt FR, Bicycling Science, MIT Press (2004) [3] Padilla S, Mujika I, Angulo F. Scientific approach to the 1-hr cycling world record: case study. J Appl Physiol 2000; 89: 1522-7 [4] Nonweiler T., The air resistance of racing cyclists, Cranfield College of Aeronautics report No. 106 (1956)

Further reading Burke E R (Editor), High Tech Cycling in Human Kinetics (2003) Kyle C R & Weaver M D, Aerodynamics of Human Powered Vehicles, Proc. Instn. Mech. Engrs Vol. 218 Part A: J. Power and Energy 141-154 (2004)


New Zealand’s climate in the future will be determined, at least in part, by the future behaviour of the Southern Annular Mode (SAM), jet streams and storm tracks, as Dr James Renwick, Principal Scientist, Climate Variability and Change for NIWA explains: The Earth’s winds carry heat from the Tropics to the Poles in a vain attempt to equalise temperatures between the two regions. The reason we have most of our weather is because the Tropics are warm and the Poles are cold and the bigger the temperature difference, the stronger the winds, and the more weather we have. In simple terms, the winds should blow north-south, transporting heat directly between the Tropics and the Poles. Because the Earth rotates, we end up with westerly winds in the middle latitudes, flowing from west to east in the same direction as the Earth’s rotation, the air essentially being dragged along with the rotating Earth. Heat is still transported polewards though, because we have ‘weather’: storms, fronts and anticyclones, ripples on the westerly wind current that contain within them the crucial north/south wind flows that carry out much of the heat transport. Jet streams Westerly winds, induced by the Earth’s rotation, tend to be concentrated into bands known as jet streams, where wind speeds can be very strong, up to 250km/h or so at the top of the troposphere, i.e. about 10km above our heads. It is remarkable that only a few kilometres above us, winds in the jet streams can be more than 10 times stronger than what we are experiencing down at ground level. This is a ubiquitous feature of how the atmosphere works; changes in the vertical direction are much more rapid than those in the horizontal direction. Almost all of the mass of the atmosphere is within 20 kilometres of the Earth’s surface. The jet streams described above often lie over the top of the weather systems or storms we experience, in part because the storms act to mould and concentrate the jets. There’s an intricate and fascinating interplay between the tracks of the storms and weather systems, and the location and strength of the jet streams. Storms are encouraged to develop near the jet streams, as they can draw on the energy contained in the jets themselves. Yet, storms ultimately give up some of that energy as they decay, helping to keep the jet streams going, and helping to shape and define the jet streams. So, the storms tend to follow the jet streams, and vice versa. Tracking storms Figure 1 shows the location of all the storm centres over the Southern Hemisphere during January 2001 (a time period that was chosen at random). While it has quite a ‘scattergun’ look about it, we see that there are very few dots (low centres) south of 60°S (the innermost circle) and very few north of 35°S (the latitude of northern New Zealand), with most of them concentrated between about 40°S and 60°S. That latitude band is the usual range of the “storm track”, a term for the preferred path of

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Figure 1: The location of low pressure (storm) centres around the Southern Hemisphere during the first three weeks of January 2001. The concentric circles on the background map indicate 20°S (outermost), 40°S, and 60°S (innermost).

storms as they track around the hemisphere. The average track of storms and the location of the jet streams, tend to line up very closely. Moreover, the two tend to follow each other around from day-to-day, week-to-week, and month-to-month. All of this leads to some interesting behaviour, as the tracks of the storms can meander across a wide range of latitudes, sometimes heading north to lie across New Zealand, but more often tracking across the southern oceans and down towards the Antarctic coast. Because there’s a linkage, or feedback, between the storm tracks and the jet streams, those meanders tend to persist for weeks at a time. In fact, the most important way that the atmospheric circulation varies in the middle and higher latitudes is exactly that fluctuation between having the storm track near the Antarctic coast and having it across the latitudes of New Zealand. This form of variation is known as the Southern Annular Mode (SAM).

Southern Annular Mode The SAM varies from week-to-week, and from monthto-month, in a seemingly random way. A decent push in one direction can send the system careering towards one extreme, with the paths of storms either constrained to lie nearer Antarctica, or to travel through the lower latitudes, where New Zealand lies. Once in a given extreme, the linkage between the storms and the jets tends to keep things locked in for a few weeks, before another big enough disturbance sends everything off in a different direction. The SAM can be measured simply as the average strength of the westerly winds over the southern oceans at about 55°S, or as the average difference in mean sea level pressure between 45°S and 65°S. New Zealand Association of Science Educators




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When the storms tend to lie nearer Antarctica, the winds and the pressure differences are stronger than normal, and that’s labelled the ‘positive’ phase of the SAM. When the storm track lies nearer New Zealand latitudes, the southern ocean winds and the pressure differences are weaker than normal, and that’s labelled the ‘negative’ phase of the SAM.

Impact of SAM on our weather The phase of the SAM is very important for New Zealand’s weather and climate. For instance, in January 2008 the SAM was strongly positive and storms tended to track well south of New Zealand, while the country lay under the influence of intense high pressure systems. As a result, that January was unusually warm and dry, with drought conditions developing across much of the North Island and eastern South Island. Conversely, February 2004 saw the SAM strongly negative, and the country as a whole experienced a very cool and wet month. There was a string of significant storm and flooding events across New Zealand, including record floods in the Manawatu and parts of the Wairarapa around the middle of February. Figure 2 shows the rainfall and temperature

differences from normal for the months of January 2008 (right) and February 2004 (left). SAM was discovered about 30 years ago simultaneously by New Zealand and Australian researchers. For many years, it was considered to be an interesting but not particularly important or useful facet of the climate system, largely because its behaviour didn’t seem to be predictable. However, interest in the SAM (and its northern counterpart, the NAM) has skyrocketed over the last decade or so because it has been noted that since the 1960s, there has been a tendency for the winds and the storms to stay farther south, towards Antarctica, more often. So, there’s been a trend in the state of the SAM towards the positive phase, on top of all the natural varying in the paths of the storms and the jet streams described above. This has led to a gradual intensification of the westerly winds in the ‘furious fifties’, which looks set to continue in to the future.

Why is SAM moving to a positive phase? Why are we seeing this movement towards SAMs positive phase?? Part of the story is actually the ozone hole, the loss of ozone in the stratosphere that occurs

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Figure 2: Rainfall (top) and mean temperature (bottom) difference from normal for February 2004 (left) and January 2008 (right). February 2004 was a month of strongly negative Southern Annular Mode (SAM), with storms frequently crossing New Zealand, while January 2008 was a month of strongly positive SAM, with the New Zealand climate dominated by high pressure systems (anticyclones). 10 New Zealand Association of Science Educators


over Antarctica every spring, as a result of the build-up of man made chlorine-containing compounds in the stratosphere. Ozone loss cools the Antarctic stratosphere, making the north-south temperature difference stronger, thereby causing intensification in the strength of the westerly winds in the lower stratosphere and down into the upper reaches of the troposphere, helping to encourage the storm track poleward. As the ozone hole recovers over the coming decades, that effect should weaken. But, the climate models all project that the SAM will continue to trend towards a more positive state through the twenty-first century. This means there will be stronger westerlies over the southern oceans and the storm tracks staying farther south more often. It seems that global warming/climate change, brought about by the increasing concentrations of greenhouse gases in the atmosphere, is also pushing the SAM to its positive phase. One way of thinking about why that should be is to note that global warming means that the world is getting a little more tropical, and in effect, the tropical regions are expanding out towards the Poles. In fact, there has already been a measurable increase in the width (latitudinal extent) of the Tropics. To make room, the middle latitude westerly winds and storm tracks have to contract a little towards the Poles. That’s at least part of the story shifting the average climate state a little poleward, but it doesn’t explain why the fluctuations in the locations of the jet streams and the storm tracks should tend to be in their poleward configuration more often. Recent research in New Zealand has suggested a subtle factor at play that might explain what’s going on. The story goes like this: as the atmosphere warms, through the presence of a higher concentration of heat-trapping greenhouse gases, the air tends to expand, making the troposphere deeper, and pushing the stratosphere upwards. A deeper troposphere means that storms expand vertically. At the same time, they tend to expand horizontally as well, so that storms and fluctuations in the atmospheric circulation generally, are becoming larger over time. The larger the extent of the storms, the better they are at sending energy polewards, so the

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around 50°C to near 0°C at about 50km altitude. Since temperatures increase with height in the stratosphere, it is a very stable (or stratified) layer of the atmosphere, resistant to vertical movements and generally lacking in moisture, clouds and weather. The stratosphere contains around 24% of the mass of the atmosphere, so the troposphere and stratosphere combined contain around 99% of the total mass of the atmosphere. Above the stratosphere are a number of tenuous layers, the mesosphere, thermosphere, and exosphere, extending several hundred kilometres before fading away into empty space. The temperature of the very thin gases in these layers range from around -100°C to +1,500°C.

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Atmospheric layers The atmosphere is divided into layers, mostly according to the temperature structure. The lowest layer, where we live and where the weather happens, is the troposphere. In the troposphere, temperatures decrease with height, from an average surface temperature of around 15°C to around -50°C at the top of the troposphere (the tropopause) at an altitude of around 10km. Since temperatures decrease with height in the troposphere, and the air is heated from the land and ocean surface below (much like a pot on a stove), it experiences a lot of vertical motion, as air bubbles up and overturns, creating clouds, rain, and weather. Around 75% of the mass of the atmosphere resides in the troposphere. Above the troposphere is the stratosphere, where the temperature increases with height, from

more likely the jet streams and the storm tracks (the most energetic parts of the atmospheric circulation) are to be polewards of where they usually sit. This picture fits with the trend towards bigger and more intense (but fewer) storms over the southern oceans, something that has been observed already, and which is expected to continue into the future. There are other competing theories in the scientific literature at present, and understanding the causes of trends in the SAM is a very active area of research. We’ll have to wait a few years to see whether the above ideas prove to be the fundamental ones.

What does this mean for NZ? So what does it all mean for New Zealand, going into the future? The trend towards poleward contraction of the storm track should leave New Zealand more under the influence of high pressure systems, implying a more settled and drier climate in future. This may be the case, at least, in the summer and autumn when the trend in the SAM is most pronounced and the storm track tends to be farthest south of New Zealand. In the winter, however, New Zealand looks set to remain under the influence of the westerlies and storm tracks, albeit with a warming trend thrown in. The overall picture, then, is perhaps one of more marked differences between the seasons: drier and more settled summers and relatively wet winters with storms tending to be a bit bigger and more vigorous than they are now. Even if overall annual rainfalls don’t change much, that shift in seasonality would still have significant impacts in many sectors. Drier summers but wetter winters (say) would mean more demand for water in the summer, while more may be available in the winter. So, both for urban water supplies and agricultural irrigation schemes, there may be a need to store more water than we presently do at the times of year when it is more plentiful to ensure that there is enough to distribute over the drier summer months. In any event, New Zealand’s climate in the future will be determined at least in part by the future behaviour of the SAM, the jet streams and the storm tracks, as well as by the overall rise in temperatures and other associated average changes in climate. For further information contact: j.renwick@niwa.co.nz New Zealand Association of Science Educators

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lightening our food using gasses Food gasses have a profound impact on the textural properties of our food and drinks, as Dr Matt Golding, Associate Professor of Food Formulation and Characterisation, Massey University explains: We wouldn’t get very far without air. As humans we can probably do without food for a few weeks, without water for a few days, but without air we wouldn’t last more than a few minutes. However, the importance of air to our lives extends beyond this most specific of benefits into other less obvious areas, and one area in particular is the contribution that air (and a few other gasses for that matter) makes to our eating experience. For many of our most familiar and favourite food products, such as cakes, bread, ice cream and beer, air has a crucial role in providing the desired sensory experience, and without which most of these foods would become quite unpalatable. Food gasses have a profound impact on the textural properties of our food and drinks. This is because the incorporation of air into the structure of a food product will have a significant effect on the subsequent material properties of that food. A question immediately arises of exactly how something as nebulous as air or gas can be structured in such a way so as to contribute to the material and textural properties of a food. The answer is through creation of a foam. Foams are a familiar concept in everyday life. From washing-up to fire extinguishers the principle of foam formation is essentially the same: air or any gas source is dispersed in a liquid medium in the form of bubbles. Whilst this relatively simple definition is generic across all foams, the actual properties and performance of a foam structure in any given application are dependent on a number of additional variables, particularly the ability to manipulate foam stability. Foams are a class of colloidal materials, in which two immutable phases are mixed together by dispersing one phase into the other (emulsions are another example of a colloid, in which oil can be mixed with water by dispersing in the form of small droplets, typically < 1µm in diameter). Colloidal states are generally kinetically stabilised, thermodynamically unstable systems – in other words over time they tend to revert into their separate states through various mechanisms of destabilisation. Foams are often particularly transient colloidal structures, and can be rapidly destabilised (consider for example, the lifetime of washing-up suds, or a bubble bath). However, the ability to control the relative lifetime of a foam is a crucial consideration to its application in any given system, and this is especially true for aerated foods. Foam lifetime is governed by several key variables, most notably: • bubble stability • bubble size • physical properties of the continuous phase. We will take a look at how foam lifetimes can be controlled through these different aspects, and how

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that in turn can be used in the design and production of some remarkably diverse gas-structured foods. Most foams are initially formed by the incorporation of air into a liquid medium, usually through some form of agitation, although sparging, injection and decompression can also be used to disperse air or other gas. Without any additional form of stabilisation, any bubbles formed in this way will be highly unstable and will tend to rapidly coalesce (through contact between neighbouring bubbles) or burst (upon reaching the surface of a container exposed to air). This is a relatively simple means of testing the purity of water, since pure water with no contaminants should be completely unable to provide bubble stability. Be a little concerned if you find that your drinking water is able to support a foam when you shake it! (See Figure 1)

Figure 1: Foam stability is not necessary in carbonated drinks, but addition of surface active components, such as proteins from ice cream, can result in increased foam stability and lifetime.

Bubbles from seconds to minutes For some aerated food applications lack of foam stability is a necessary and desirable state of affairs. Carbonated beverages rely on the fact that the bubbles of carbon dioxide that are released from the liquid on dispensing or consumption are not stabilised. The rapid formation of foam when pouring a fizzy drink into a glass is followed by an equally fast collapse of that foam, as the bubbles quickly coalesce and burst. Likewise, the rapid formation and collapse of bubbles in the mouth is responsible for the sensation of effervescence when drinking. Prolonging bubble lifetime by improving the stability of the foam would, in this case, have unwanted consequences. In-mouth, there would be no immediate bubble collapse, and consequently the sensation of effervescence would be replaced by more of a frothing


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Figure 2: Adsorption of surface active materials, such as detergents or proteins, is necessary to prevent immediate coalescence and collapse of bubbles and foams.

mouthfeel that would additionally make the drink more difficult to swallow. Even pouring the drink into a glass would become more difficult since excessive foaming and stability would make it difficult to get the contents of the drink into a glass, without it becoming full of foam. This is of course what happens when making a ‘Spider1’ – the ice cream serves to increase the stability of the bubbles when they form, and so the mixture tends to be a lot frothier in appearance and texture. When making one of these it helps to add the ice cream to the drink rather than the other way around in order to avoid too much foaming! However, controlled foaming for certain beverages is an essential aspect of quality. The most obvious example is beer, where the formation of a foamy ‘head’ on the top of the glass is a highly visual marker of quality. Ideally, the lifetime of this foam should last for the duration it takes to drink the beer – so, depending on relative thirst, anywhere from tens of seconds to tens of minutes. Most beer foam bubbles are formed in the same way as those of other carbonated beverages, with the release of carbon dioxide from solution. Pouring from a bottle or can into a glass encourages release of the carbon dioxide from the liquid due to nucleation of bubbles by the rough surface of the glass (consequently a dry glass will cause more initial foaming than a wet glass). Formation of beer foam requires additional stabilisation of these bubbles once they are formed in order to prevent immediate coalescence from taking place. This can be achieved by adsorption of specific molecules to the bubble surface as they are formed, forming a skin or film around the bubble which acts as a barrier to coalescence. Molecules that act in this way are termed surface active or ‘amphiphilic’. There are many surface active molecules capable of stabilising foams, such as sodium dodecyl sulphate (SDS), the main component in washing-up liquid and shampoo. Food grade systems include familiar proteins from milk and egg and gelatine, as well synthetic ingredients derived from oils and fats. The common feature of all these materials is that the molecules’ structure is divided into regions that either prefer to be in contact with 1

A combination of a scoop or two of ice cream with a carbonated drink, most commonly cola or lemonade. The terminology is peculiar to New Zealand and Australia. Commonly also called an ice cream soda elsewhere.

Figure 3: Guinness Foam – nitrogen gas, being less soluble than carbon dioxide, is used to generate extremely small bubbles resulting in a creamier appearance and texture.

water (hydrophilic – ‘water loving’), or would rather be excluded from exposure to the aqueous environment (hydrophobic – ‘water fearing’). Subsequently when a bubble is formed (thereby presenting an interface between the water phase and the hydrophobic air phase), the surface active material will adsorb to this interface and will partition itself such that hydrophilic regions are preferentially exposed to the water phase, and that hydrophobic regions are more closely associated to the air phase, thus creating a stabilising layer. Just as houses of brick are stronger than those of sticks or straw, the relative stability of a foam is very much dependent on the type of surface active material adsorbed to the surface of the bubble. (See Figure 2) In the case of our beer foam, the bubbles are stabilised by a number of surface active molecules including proteins from barley and bitter acids from hops. These molecules are able to quickly adsorb to bubble surfaces when carbon dioxide is released from the beer during pouring, providing initial, rapid foam stability that allows a ‘head’ to be formed and generally be maintained during the drinking experience. However, for these systems the surface stabilisation is not all that robust compared to some other food foams, and bubble stability in beer can be easily compromised. Fats and oils, in particular, are particularly effective at collapsing foams as they interfere and compete with the mechanism of stabilisation by the surface active components in beer. Dirty beer glasses and the consumption of crisps, peanuts and other fatty snacks are often the main culprits for the premature collapse of a beer foam. Whilst the formation of a foamy beer head might be considered a purely visual cue, there can also be a New Zealand Association of Science Educators

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Figure 4: Changes in milk protein structure on heating greatly improve the stability of a capuccino foam.

significant textural contribution. The most obvious example is Guinness. Guinness is one of the most recognised beers anywhere in the world, characterised by the intense dark colour of the beer which contrasts with the shiny whiteness of the head that forms on top. (See Figure 3). In this case, the bubbles in the foam are much smaller in size than those of most other beers resulting in a smoother, finer, whiter appearance of the foam in which the bubbles are almost undetectable to the naked eye. The small size of the bubbles also imparts a particularly creamy, smooth mouthfeel to the foam when it is consumed, which is also an important and recognisable characteristic of the product. The formation of smaller bubbles has less to do with stabilisation of the bubble surface and more to do with the choice of gas. In this case, nitrogen is used rather than carbon dioxide. It is a less soluble gas than CO2, and consequently is less prone to diffusion. Consequently on dispensing, smaller bubbles are formed which are more resistant to bubble growth through coarsening/ripening. Beer foams stabilised with nitrogen tend to have better stability and longer bubble lifetime compared to those formed with CO2. Another beverage for which a creamy foam is an important sensory marker is capuccino. As with beer, a capuccino foam only needs to be stabilised for the duration that it takes to consume the drink. The incorporation of gas takes place through the process of injection of steam and air into the milk, which also serves to heat the milk up. The steam and air rapidly create bubbles within the milk which are initially stabilised by the adsorption of milk proteins (casein and whey) to the bubble surface. The stability of these bubbles is further improved as the high temperature steam acts on the milk proteins at the bubble surface causing them to interact and bind closely with each other. This has the effect of increasing the mechanical strength of the protein layer, making it more effective as a barrier to coalescence and additionally helping to slow down the rate of bubble coarsening as the foam ages. The strength of the bubble surface stabilised by the heat-treated milk proteins is even sufficiently robust to survive the sprinkling of cocoa powder on the top of the foam – which would normally tend to act as an antifoam. (See Figure 4). 14 New Zealand Association of Science Educators

Figure 5: The aggregation of fat droplets helps to support the structure of whipping cream. Bubbles in this foam are typically about 0.05 – 0.2mm and are no longer visible to the naked eye.

Bubbles from hours to days One common characteristic of the beverage-based foams discussed above is the partitioning of the aerated foam into a separate layer at the top of the drink. This maximises the visual appeal of the foam, and provides a textural contribution as the consumption of the beverage allows the foam to be swept along with the liquid as it is drunk, creating a unique sensory experience. For these liquid-based products, it’s perhaps not surprising that this should be the case. There is a considerable density difference between water (which has a density of ~1000kg/m3) and air (which has a density of only ~1.2kg/m3). Consequently, even the relatively small bubbles produced on pouring a glass of Guinness will rapidly rise due to buoyancy effects, resulting in the ‘creaming’ of bubbles under gravity to form a separate layer at the top of a container2. In the case of many other foam-based foods, the specific textural contribution of the foam requires that the bubbles are uniformly dispersed throughout the food structure. In such cases the visual impact of these foamed structures is less obvious. How then, to stop the foam from separating as it does for beverage systems? The answer is to change the rheological (material) properties of the liquid phase as a means of trapping the internal gas structure, so that bubbles become immobilised. This can not only improve the stability of individual bubbles to coalescence and/or coarsening, but can help to stabilise the structure of the foam against creaming or drainage. This effect can thus be used to extend the lifetime of the foam beyond just a few minutes. A nice example of this is whipped cream. The air content of a whipped cream (containing 30% or more of fat) is usually about 50% by volume of the product, and imparts a light, fluffy texture to the cream that melts in the mouth. To achieve this particular texture, the foam needs to be evenly distributed throughout the cream and remain stable for up to a few days (under refrigerated conditions). This is particularly true of foams with a relatively low air phase volume. Separation of foams with higher volumes of air is more typically characterised by a process termed “drainage”, in which free liquid is released at the bottom of the foam.

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In a whipping cream, air is incorporated by thorough vigorous whisking of the cream, generating relatively coarse air bubbles. In the early stages of whipping, protein in the cream helps to initially stabilise the bubbles. During this stage of the whipping process there is little change in the thickness, or viscosity of the cream, and if left to stand the bubbles would rapidly settle out at the top of the mixing bowl. (See Figure 5). As whipping progresses, however, there is a noticeable thickening of the cream to the point where the foam becomes self-supporting allowing it retain its shape on standing. As anyone who has whipped cream knows, once you reach this point in the whisking process you should stop, since over-whipping of cream causes the foam to collapse. These changes in the structure of the cream are due to changes in the behaviour of the fat globules during the whipping process. As more air is incorporated into the cream, fat globules are driven onto the surface of bubbles, creating a shell of droplets around each bubble. This helps to reduce bubble size and acts as a very effective barrier to coalescence. In addition, the high-speed shearing of the cream causes fat droplets to stick together forming aggregated chains of fat. These structures greatly increase the thickness and rigidity of the cream to the point where the air bubbles are effectively trapped within a network of fat droplets, and the foam becomes self-supporting (and can remain so for several days if stored under the right conditions). Over-whipping leads to over-aggregation of the fat globules into granules, which causes the foam to collapse. The structure of the whipped cream cannot be recovered at this point, although alternatively you are well on the way to making butter. Effective cream whipping also relies on the fact that the fat globules in the cream are solid. As a consequence, cream should be chilled prior to whipping. If allowed to warm up, the butterfat melts to oil which acts as an antifoam, and the cream can no longer be whipped. This behaviour is also responsible for the delightful melting sensation in the mouth when whipped cream is consumed. At in-mouth temperatures the fat begins to melt and consequently fat droplets lose their effectiveness to stabilise bubbles and the foam rapidly collapses. It is a fortunate coincidence that butterfat melts in this temperature range. A higher melting point would potentially result in a whipped cream which remained stable in the mouth, resulting in a texture more like shaving foam! A slightly different example of an aerated food that most of us consume everyday is bread. The foam structure formed in bread is absolutely essential to provide the soft eating, spongy texture that is so characteristic of the product. Un-aerated or unleavened bread, in comparison, has a much firmer and chewier texture, and as a consequence tends to be served as thin sheets since thick slices would be almost impossible to eat. The aerated structure of bread comes from a complex leavening process. The addition of yeast during dough processing results in fermentation of carbohydrates in the flour releasing carbon dioxide which is trapped by the elastic properties of the dough as a foam, or solubilised into the dough itself. This process continues during the proofing stage of breadmaking, during which the volume of the loaf can increase by 20–30%. (See Figure 6).

Figure 6: The open, porous nature of bread foam helps to prevent the structure of the bread from collapsing after baking. Pore size can be controlled through formulation of the bread in order to provide softer crumb structures.

During the baking process, heat from the oven causes further release of carbon dioxide from the dough as well as forming steam. The bubbles produced from these gasses expand with increasing temperature, but are initially stable as the wheat proteins in the thick, elastic dough prevent bubbles from immediately coalescing. However, as baking progresses and the dough starts to solidify, the bubbles begin to destabilise and rupture, forming channels and pockets of air within the bread. This change in structure actually helps to prevent the bread foam from collapsing, as the bubbles in a highly stable foam would tend to shrink on cooling (as happens with a soufflé). The solidified dough also acts as a robust framework to maintain the integrity of this porous structure once the bread has fully cooled down. The final volume of air in a typical loaf is around 70%, and as said provides a significant contribution to the softness of the product. In this particular example, once baked, the physical properties of the aerated structure do not change, and product lifetime is determined rather by spoilage factors such as mould growth and/or staling of the bread over time.

Bubbles from weeks to years For other aerated products, the ability to stabilise and trap a foam structure for extended periods of time is an essential aspect of maintaining quality and prolonging shelf life. Take ice cream for example – a product consumed more by New Zealanders than just about anyone else (around 26 litres a year on a per capita basis). Ice cream is a bit like whipped cream in that as a foam it also tends to contain about 50% air by volume. However, unlike whipped cream, this foam is frozen, which allows ice cream to be stored in a stable state for longer periods of time. The bubbles in ice cream are generally in the range of 0.05 to 0.1mm, and as with whipped cream are spread uniformly through the product. These bubbles have an important role in providing the requisite sensory properties of the ice cream. Without any air present ice cream would be extremely hard , icy and excessively cold. The dispersion of bubbles throughout the structure makes for a softer, warmer eating product as well as contributing to the creamy texture so characteristic of ice cream. The foam in an ice cream is created in a freezer operating at about -20°C. The ice cream mix is sheared at high speeds and at the same time air is introduced under New Zealand Association of Science Educators

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pressure. This creates both a fine bubble structure and a fine ice crystal structure, which ensures that the ice cream is soft in texture. The bubbles that are formed during the freezing process are generally stabilised by milk proteins or by fat globules (in a similar manner to that observed for whipped cream). The bubbles formed in the ice cream mixer are smaller than those in the final product. This is mainly due to the fact ice cream is initially extruded from a freezer comes out at a temperature between about -5°C to -10 °C. On extrusion the air bubbles in the foam are immediately prone to expansion due to the pressure drop from within the freezer barrel back to atmospheric pressure. Bubble coarsening also starts to take place due to gas diffusion from small bubbles to big bubbles, and the longer the ice cream remains at these temperatures, the larger the bubbles will grow, leading to a decrease in quality. To ensure that high quality is maintained it is necessary to inhibit bubble ripening as quickly as possible, and this is achieved by lowering the temperature of the ice cream by transferring to a blast freezer. The reduction in temperature reduces the internal pressure within the bubbles which slows the rate of gas diffusion. Reducing the temperature also has the effect of increasing the ice content of the ice cream, and concentrates the remaining liquid phase into a highly concentrated syrup. This provides a highly effective means of trapping the foam structure and prevents further bubble coarsening from taking place. For most ice creams, storage at typical home freezer temperatures (minus 18 °C) is sufficient to prevent any change in bubble size over time. Of course, this only applies while the ice cream stays at these temperatures. As soon as the ice cream starts to warm up, the product may become more prone to bubble growth and coalescence. This can lead to a pronounced loss of quality and shrinkage of the ice cream if allowed to progress too far. If you watch ice cream melting you can actually start to see bubbles appearing as the foam destabilises. It may sound obvious, but to ensure the best possible quality make sure that ice cream is the last item that you pick up from the supermarket, and don’t leave the tub out for too long when serving – that way you’ll minimise any changes to the structure of the foam. (See Figure 7). The ability to trap a foam structure to prevent any changes in bubble size is a feature of a number of other aerated food systems, such as meringue (egg white protein stabilises the bubbles and solidifies the foam on cooking), and marshmallows (bubbles are stabilised by gelatine, which also forms a gel on cooling, trapping

Figure 7: Electron microscopy is used to show the foam structure in ice cream showing both bubbles and ice crystals which are trapped in a concentrated sugar syrup.

the foam). Under these circumstances the lifetime of the foam can be extended almost indefinitely allowing the textural impact of the incorporated air to be maintained across the shelf life of the product.

Conclusion These few examples have hopefully shown the impact that air and other gasses have on the eating properties of many of our favourite foods and drinks. A lot of these foamed foods have originated from traditional recipes and can be traced back many years , and their popularity has seen them subsequently adapted by food manufacturers for mass production and widespread general consumption. The food industry enjoys working with air, since it is essentially a free ingredient, and consumers enjoy air, since it contains no calories and, as said, creates some wonderful textural experiences. Consistently creating and mass-producing the requisite foam properties is not, however, a trivial exercise, as has hopefully been demonstrated. To ensure that the most appropriate foam structures are formed, stabilised and preserved requires good scientific understanding in a number of key disciplines including surface chemistry, processing and material science and how these can be applied into the design, development and manufacture of aerated food products. Such disciplines are a few examples of the elements that comprise a modern Food Technology Degree, such as currently taught at Massey University’s Institute of Food, Nutrition and Human Health. Worth thinking about the next time you eat one of these. For further information contact: M.Golding@massey.ac.nz

continued from page 31 Further reading Armstrong, R. (2004). Lichens, lichenometry, and global warming. Microbiologist, Sept (www.sfam.org.uk). Broady, P.A., & Ingerfeld, M. (1999). Ammatoidea normanii (Cyanobacteria, Homoeotrichaceae) from La Gorce Mountains, Antarctica. Algological Studies, 130, 1-13. Broady, P.A. (2007). Ecology of terrestrial algae. Algae of Australia: introduction. Canberra, CSIRO Publishing, 486-510. Graham, L.E., et al. (2009). Algae (2nd edition). San Francisco, Benjamin Cummings. López-Bautista, J.M., et al. (2003). Phragmoplastin, green algae, and the evolution of cytokinesis. International Journal of Systematic and Evolutionary Microbiology, 53, 1715-1718.

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Lücking, R., et al. (2009). Do lichens domesticate photobionts the way farmers domesticate crops? Evidence from a previously unrecognised lineage of filamentous cyanobacteria. American Journal of Botany, 96, 1409-1418. Martin, W., et al. (2002). Evolutionary analysis of Arabidopsis, cyanobacterial, and chloroplast genomes reveals plastid phylogeny and thousands of cyanobacterial genes in the nucleus. Proceedings of the National Academy of Sciences USA, 99, 12246-12251. Rindi, F., et al. (2008). Distribution, morphology, and phylogeny of Klebsormidium (Klebsormidiales, Charophyceae) in urban environments in Europe. Journal of Phycology, 44, 1529-1540. Sun, H.J., & Friedman, E.I. (2005). Communities adjust their temperature optima by shifting producer-to-consumer ratio, shown in lichens as models, II. Experimental verification. Microbial Ecology, 49, 528-535. Wilcox, M .(Ed). Natural history of Rangitoto Island. Auckland Botanical Society.


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Everyone’s health is affected by the weather, both directly and indirectly, as Dr Kim Dirks, Senior Lecturer in the School of Population Health, Faculty of Medical and Health Sciences, the University of Auckland explains: Introduction If you had any doubt about there being a relationship between the seasons and people’s health, then Figure 1 should help. Across the main centres of NZ there are sharp peaks in respiratory mortality during the winter months, similar trends can also be seen for mortality from circulatory conditions, though the seasonality is somewhat reduced in comparison. Given the differences in population sizes (which, to a large extent, explain the differences in peaks between the main centres), the excess winter mortality (a measure consisting of the mortality rate in winter relative to the yearly average) is perhaps a better measure of seasonality. Excess winter mortality over the same period for the main centres is shown in Figure 2. We all know that people tend to suffer more ill-health in the winter months than in the summer due to colds and influenza, but the daily weather and seasonal climate patterns also affect us in much more subtle ways as well. Of course, the notion of a link between the weather and health is not new. Indeed, as early as 400BC, Hippocrates wrote: “Whoever would study medicine aright must learn of the following subjects. First he must consider the effect of each of the seasons of the year and the differences between them. Secondly he must study the warm and the cold winds, both those which are common to every country and those peculiar to a particular locality.” Hippocrates was clearly well ahead of his time! Heatwaves Despite the clear wintertime peaks in mortality, the most reported upon direct impact of weather on human health is the occurrence of heatwaves during the summer months. In some cases, heatwaves are just an inconvenience, requiring us to avoid physical exertion and staying in the shade during the peak of the day. The effects are worse if the humidity is high, as cooling by the evaporation of perspiration is less effective. During heatwaves, many people will also complain of a poor night of sleep if there is little reprieve from the high

temperatures during the night. In such hot conditions, the blood vessels responsible for carrying blood to the skin expand, resulting in reduced blood pressure and lower levels of oxygen. The effects are particularly noticeable in those who already suffer from low blood pressure and both this, and a lack of sleep, can bring on fatigue. The effects can be alleviated by drinking plenty of fluids and making use of air conditioned environments and this is certainly the advice given to people when heatwaves are expected. While these effects are relatively minor in some instances, there can be much more significant health consequences as a result of heatwaves when the temperatures are extreme and widespread. A very dramatic example was the 2003 heatwave in Europe which reportedly killed over 50,000 people. Italy and France were the worst affected in response to temperatures exceeding 40°C, with many of the people who suffered most being elderly or those with existing respiratory or circulatory conditions (Hemon and Joula, 2004). The very high death toll is attributed primarily to the high night time temperatures. In a more recent episode, temperatures in Melbourne in January 2009 soared up to 46°C, triggering bush fires that resulted in over 200 deaths as a direct consequence of the fires, and a roughly equivalent number of people who died of heat stress (Pers. Comm. Prof. Glen McGregor, The University of Auckland, 2009). While these are extreme cases, even temperatures as low as 30°C have been found to be associated with adverse health effects, especially when people are not acclimatised to such conditions. Within New Zealand, apart from perhaps Gisborne, the temperatures in the North Island rarely exceed 30°C so there are unlikely to be any significant health impacts associated with heat stress. Exceptions to this are isolated cases of people involved in sporting events during the peak of the day, or those carrying out work that involves a significant amount of physical activity in hot environments. In the South Island, temperatures above 30°C are more common, especially in central Otago and in the Canterbury region. The Canterbury Nor’wester, in particular, is renown for its strong winds and high temperatures, and has long been associated with unusual human behaviour. A recent study carried out

Figure 1: Respiratory mortality in the main centres across New Zealand from 1991 to 2004.

Figure 2: Excess winter mortality for the main centres across New Zealand from 1991 to 2004. New Zealand Association of Science Educators

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by James Horrocks (The University of Canterbury) in 2009 found significant correlations between weather conditions and crime rates: the higher the temperature the greater the level of crime (Copeland, 2009). Hot conditions therefore, not only affect our health, but also affect our behaviour.

Winter conditions Unlike heatwaves which are in some sense ‘sporadic’ events, the impact of cold winter conditions on human health is observed consistently year after year (as shown in Figures 1 and 2). While the immune systems of most people are able to cope with cold and ‘flu viruses that prevail at this time of the year, for the elderly in particular, the winter months can have much more serious consequences, leading to significantly increased hospital admissions and increases in mortality. Fatal coronary heart disease, stroke and respiratory disease together account for a large proportion of deaths in this age group, and much of the seasonality in the mortality statistics are attributed to these conditions (Wilkinson et al., 2001, Ballister et al., 2003, Curriero et al., 2002). The fact that there does not seem to be any significant increase in the wintertime peaks moving down the country to colder regions (as one would expect if cold winters were the main culprit) suggests that there is more to it than just the wintertime temperature. Also, while on an international scale, one might expect that the effect would be more pronounced in countries that experience very cold climates, observations suggest that in fact the reverse is true: The Scandinavian countries fare much better than those with temperate climates (Wilkinson et al., 2004, The Eurowinter Group, 1997). A difference in socioeconomic status has been suggested as a possible explanation, and differences in the quality of housing appears to a major player. In countries that experience very cold winters, houses are generally well-insulated and warm, and people are acclimatised to such conditions. In more temperate climates (such as in New Zealand), houses are generally poorly insulated and therefore damp and cold in the winter. Air quality In addition to temperature effects, there are other factors that are significantly influenced by the weather that are also known to affect human health. Air pollution is one of these. In large urban centres such as Auckland, much of the air pollution originates from vehicles and industry. While the emission rates themselves do not vary significantly with meteorological conditions when home heating using wood burners is a small player, the rate at which the pollutants disperse once emitted is heavily influenced by the meteorology in particular. Conditions of persistent temperature inversions sometimes occur in Auckland, particularly during the winter months. A dramatic event occurred in Auckland during June 2009 (as shown in Figure 3). The stagnant air and resulting build-up of fog and pollutants is evident across the city. In such conditions one would expect the cases of respiratory and circulatory admissions to hospital, and also mortality, to increase as the air pollution concentrations increase. Figure 4 shows a time series of mortality in Auckland along with corresponding time series of atmospheric particulate matter (Total Suspended Particulate)

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Figure 3: Temperature inversion in Auckland as seen from the top of Mt Wellington. Photograph courtesy of Kim Dirks.

as well as oxides of nitrogen, a gaseous pollutant associated with transport. Note that there are some clear associations between respiratory mortality and air pollution concentrations, but that there are some significant periods where there is a mismatch in the records. During the winter of 1997, for example, there was a high level of mortality in the absence of any significant amount of air pollution, and during the winter of 1992, there was a significant air pollution event with a modest increase in mortality. People living in regions of New Zealand that experience cold winters, such as in much of the South island , have a significant reliance on wood burners for home heating, so the concentration of pollutants is affected not only by the meteorology but also by the amount produced. In Christchurch , especially before the introduction of legislation restricting the use of open fires and wood burners, a sharp increase in air pollution levels (for particles) could be observed when the temperature dropped to below about 10°C. Note: during calm temperature inversion conditions, the nights in particular tend to be cold. For this reason it is difficult to establish causality (is it the air pollution or the temperature or a combination of both?). Some mechanisms have been proposed linking temperature to health effects, likewise for air pollution. It is also worth bearing in mind that high air pollution levels in urban centres are a direct consequence of meteorological conditions conducive to high air pollution levels (and of course the use of vehicles to produce the air pollution in the first place), but not the other way around. Without the right meteorology, air pollution levels would remain low, so even air pollution effects are essentially local meteorlogical effects superimposed on urbanisation. Interestingly, during the winter of 1996 Mt Ruapehu erupted and for a brief period of time the resulting ash plume passed over Auckland; there was also a very high respiratory mortality rate in Auckland in the month or so following this event. An extensive investigation was carried out to see if there was any link between the two, but the study was largely inconclusive (Newnham et al., 2010). Also, it turns out that during the winter of 1996 there was a new strain of influenza that resulted in 98 more respiratory deaths than usual which complicates matters (Jennings et al., 2001).


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Figure 4: Time series of monthly respiratory morality, TSP (total suspended particulate) and NOx for the Auckland Region.

Behaviour While much of the work carried out looking at the influence of climate on health deals with quantitative measures (such as meteorology and air pollution), it is important not to underestimate the impact of behavioural changes that occur with changes in weather. On miserable winter days we are inclined to stay indoors and read a book on the couch (an inherently safe activity both from a respiratory and cardiovascular point of view!). And is it not the beautiful cold and crisp winter days that draw people outside, perhaps to go for a run for the first time in a while, or engage in other invigorating outdoor exercise? The weather (and our state of health!) can also outdoor influence our choice of transport, affecting the pollution emission rates. Likewise, our state of health can impact on our choice of transport which affects air pollution levels and impacts on health. Clearly, human behaviour and the influence of meteorology is something that needs to be taken into account when trying to assess the impact of climate on human health. Conclusions In the case of heatwaves, the mechanisms underlying the physiological response to heat are relatively well understood and causality is well established. Future climate predictions suggest that the frequency, intensity and duration of heatwaves will increase. If this is the case, then the health impacts of heatwaves will become more serious in the future. In the case of increases in mortality and admissions to hospital as results of the winter season, while the associations are strong the causality is much less clear, as are the physiological mechanisms leading to poorer health. The pattern is complicated, as many of the factors that are believed to impact on human health are highly

correlated. Also, between cities and across cities there can be differences in demographics, housing, lifestyles and transport options which ultimately need to be considered [See Ian Longley’s article in this issue – Ed]. Some good progress has been made towards addressing some of these problems from an interdisciplinary point of view. However, many interesting questions remain unanswered. For further information contact: k.dirks@auckland.ac.nz

Acknowledgements The mortality data for the study were provided by the New Zealand Health Information Service. Air pollution data were provided by the Auckland Regional Council while the meteorological data were provided by NIWA (National Institute of Water and Atmospheric Research). References Ballester, F., Michelozzi, P., Iniguez, C. (2003). Weather, climate and public health. Journal of Epidemiology and Community Health, 57(10), 759-760. Copeland, J. (2009, September 2). Warmer weather linked to increase in crime - research. Retrieved September 3, 2009 from www.3news.co.nz Curriero, F.C., Heiner, K., Samet, J., Zeger, S., Strug, L., Patz, J. (2002). Temperature and mortality in 11 cities of the Eastern United States. American Journal of Epidemiology, 155(1), 80-87. Hemon, D., Joula, E. (2004). La canicule de mois d’aout 2003 en France. Rev Epidemiol Sante Publique, 52, 3-5. Jennings, L., Huang, Q.S., Baker, M., Bonne, M., Galloway, Y., Baker, S. (2001). Influenza surveillance and immunisation in New Zealand, 1990-1999. New Zealand Public Health Report, 8, 9-16. Newnham, R. Dirks, K., Samaranayake, D. (In press). An investigation into longdistance health impacts of the 1996 eruption of Mt Ruapehu, New Zealand, Atmospheric Environment. The Eurowinter Group. (1997). Cold exposure and winter mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe. The Lancet, 349, 1341-1346. Wilkinson, P., Pattenden, S., Armstrong, B., Fletcher, A., Sai Kovats, R., Matani, P, McMichael, A.J. (2004). Vulnerability to winter mortality in elderly people in Britain: population based study. British Medical Journal. Wilkinson, P., Landon, M., Armstrong, B., Stevenson, S., Mckee, M. (2001). Cold comfort: the social and environmental determinants of excess winter deaths in England, 1986-96. Joseph Rowntree Foundation: York.

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modelling air flow Modelling turbulence presents a great challenge when finding solutions to flow in and around complex geometries like wind turbines or buildings, but Large Eddy Simulation could be the answer as Dr John Cater, Auckland University explains: In engineering applications the behaviour of air can usually be modelled as a continuum, this entails neglecting the effects of individual molecules and how they interact with each other, instead treating a volume of air as one smoothly connected space. The movement of air is governed by a conservation of momentum relation, known as the Navier-Stokes equation. This equation is relatively simple, but exhibits non-linear behaviour which gives rise to the phenomenon of turbulence. Modelling turbulence presents a great challenge when finding solutions to flow in and around complex geometries like wind turbines or buildings. Air is also compressible so that it has the ability to support travelling pressure waves, which we experience as sound or noise; this adds a further complication to the analysis. There are only a few known solutions to the NavierStokes equations, for a small number of special, simple geometries. A method of finding a general solution for these equations has also not been demonstrated, in fact the Clay Mathematics Institute in America has offered US$1 million for a proof of the solvability of the NavierStokes equations as one of the Millennium Prizes (the prize has not yet been claimed). A brief overview of models Computational Fluid Dynamics: Because we donâ&#x20AC;&#x2122;t know how to construct solutions for most air flow problems, numerical solutions are formulated in a field known as Computational Fluid Dynamics (CFD). CFD was initially developed for applications in the aerospace industry such as designing aircraft wings or modelling the reentry of spacecraft, but has now spread to cover the behaviour of most fluids and gases for many different geometries. Computer-based modelling is attractive because it does not require the physical resources of building wind tunnel models and making flow measurements directly. In typical CFD a spatial domain is divided into small cells to form a volume mesh or grid, and then a suitable algorithm is applied to solve the equations of motion. The results of the computation can be used to predict the density, velocity and pressure of the airflow at any point in space. Direct Numerical Simulation: If the Navier-Stokes

Figure 2: Mean air flow velocity calculated for complex terrain. Source: Oâ&#x20AC;&#x2122;Sullivan et al. (2010).

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equations are discretised directly in time and space, the solution process is called Direct Numerical Simulation (DNS). This is a reliable way to get solutions for the flow speed and direction, but can take excessive amounts of computer processing time and memory. DNS solves the entire range of fluctuations present in the airflow, from the vortices shed from buildings to the smallest eddies that dissipate energy as heat; from hundreds of metres in size to micro-metres. A large range of sizes necessitates a large number of mesh points and a corresponding increase in the time taken to produce a solution. The largest simulation of flow in the world used 40963 mesh points and was carried out in the Japanese Earth Simulator supercomputer; however, this still represented a relatively small flow problem. Reynolds Averaged Navier-Stokes: A computationally cheaper alternative algorithm that is often used in industrial contexts is known as Reynolds Averaged Navier-Stokes (RANS) modelling. In this case different equations are solved which include an expression known as a turbulence model. Impressive looking solutions for the flow can be generated in relatively short periods of time, but these models only produce time-averaged solutions and smooth out most of the turbulent fluctuations. RANS models are often used for computer graphics and as part of the manufacturing design process. They are no good for understanding the details of turbulent flow.

Figure 1: Eddy simulation of flow through a wind turbine. Source: Š Copyright 2009 ACUSIM Software, Inc.


Modelling the wind for power Energy in the wind can be captured and turned into electricity using a range of wind turbine devices, but designing the most efficient and effective wind turbine calls for modelling tools that provide accurate, reliable numerical predictions of turbine rotor performance over a machineâ&#x20AC;&#x2122;s full range of operating conditions. The demands of the wind power industry have driven particular developments in simulation of air flows and stimulation of a wide range of research projects (Ayotte, 2008). Power generation companies want to model a turbineâ&#x20AC;&#x2122;s power output versus wind velocity, and then the power output for a wind farm with air flow direction data. In addition, detailed information on wake turbulence and velocity deficits in large arrays of wind turbines may help to avoid the under-prediction of power outputs that plagued previous methods. LES is appropriate for wind engineering applications because its computational power and memory requirements are reasonable, yet a wide range of flow behaviours can be predicted. This is especially important because many innovative designs being considered cannot be reliably modelled using conventional tools (Hartwanger & Horvat, 2008).

Figure 3: LES of flow over a vegetated 3-dimensional hill. Source: Tamura et al. (2007).

The power available from the air to a wind turbine is directly proportional to the cube of the velocity of the oncoming air, so doubling the flow speed generates eight times as much power. This means that small changes to the wind speed have a big effect on the cost of generation, so that accurate prediction of the local flow conditions is extremely important when considering where to put turbines. This process is called site selection and it is of primary importance in windenergy projects. Power companies would like to identify locations with the strongest, most sustained overall wind patterns while avoiding wind shadows and highly turbulent areas. Site selection is directly influenced, not just by prevailing wind patterns such as speed, direction and regularity, but by factors such as turbulence and altitude, which impact air density. Changes in air density come from temperature differences that occur because of heating by the sun, cooling from rain, or variations in the terrain, such as rocky areas adjacent to areas covered by vegetation. An example showing these variations using an eddy model is shown in Figure 1. The power generated by a turbine is also directly proportional to the swept area of the blades. For a horizontal axis turbine the cross-sectional area is proportional to the square of the blade length, so doubling the blade length gives an increase of four times as much power. Advances in the manufacture of composites have led to increases in blade length, so that horizontal wind turbines can have diameters in excess of 60m. As turbines get larger the spacing between them is often decreased. This may be a problem, as shorter distances between successive installations can reduce the production from downstream turbines, and result in a significant decrease to service life due to the increased load levels created by turbulence. The largest turbines now in use are particularly vulnerable to variations in the air flow created by the wakes of the turbines in front. As manufacturers design larger turbines, they are finding variations to the wind in the area swept by the rotor. This affects the loading on the blades. The amount of turbulence at the top of a blade versus at the bottom of the rotation can lead to vibration and fatigue failure. Long blades may bend more on larger turbines so there may be a risk of blade tips hitting the tower. Therefore, a comprehensive vibration analysis also requires high fidelity simulation of air flow disturbances. LES can be used in smaller scale studies to maximise the predicted power output from

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Large Eddy Simulation: A recent innovative blend of direct simulation and turbulence modelling is Large Eddy Simulation (LES). In LES the largest energy containing turbulent eddies are simulated directly, while small scales are modelled using a simple RANS-type turbulence model (Cater & Williams, 2009). The turbulent eddies are usually smoothed in regions close to surfaces. In this way the computational demands are reduced; this means that for the same computing power, larger problems can be tackled. LES also produces transient solutions, which allow time varying features in the flow to be visualised and to be compared with experimental data. LES is particularly applicable to wind resistant design of very large buildings and structures including wind turbines, the determination of wind velocity affected complex terrain or vegetation, noise generation, and the atmospheric dispersion of pollutants and heat in urban areas (Tamura, 2008). Development of new algorithms and the widespread advent of parallel computing have allowed the prediction of wind flows around buildings and structures at the resolutions required to understand physical reality. This is something which has only recently become possible.

Figure 4: Dispersion of a chemical pollutant in an urban area calculated with LES. Source: Tamura et al. (2006).

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a turbine or farm of turbines and therefore significantly reduce the costs of wind power.

Airflow over complex terrain There has been progress towards using LES for real world atmospheric conditions over non-idealised terrain. In particular, this work has focused on the creation and downwind transport of eddies shed in the lee of topographic features. This work is particularly relevant in countries like New Zealand where the changes in landforms can be sudden and dramatic. In situations where there are sudden changes in steepness of a surface the performance of a RANS model is significantly degraded. Wind tunnel measurements and anecdotal evidence from the wind industry suggest that the presence of bumps in a landscape lead to local regions of recirculation that cannot be ignored. These regions are also associated with high turbulent activity and with the transport of sediment such as sand. Understanding these effects and their origins is therefore a valuable objective. An example of a recent CFD analysis of flow over a complicated landscape is RANS modelling done at the University of Otago, where sand dune formation was studied using a digital map of Mason Bay, Stuart Island (Wakes et al., 2010). This work successfully showed the utility of computational methods for predicting wind flow over dunes and compared the results to wind measurements. Current research in the Department of Engineering Science at the University of Auckland is using LES to study the unsteady air flow of gusts over complex terrain for the placement of wind turbines. An example of an averaged flow field is shown in Figure 2. Airflow through vegetation The geometry of the surrounding surfaces for a flow is not the only factor in reaching an accurate solution. Rarely are the surfaces smooth, and small variations can change the behaviour of the bulk flow, which requires different solution techniques. An area where progress is being made is in modelling vegetative canopy flows i.e. flow through trees (Ross and Vosper, 2005). Wood (2000) concluded that this could be an easier problem for eddy simulation techniques to resolve as over a rougher surface the inner layer of the flow becomes deeper and therefore more of the flow is modelled and less is directly simulated (Figure 4). An example of using LES for modelling flow over grasses and trees on the ground surface based on the actual surface condition of a terrain has been computed for flow over a three-dimensional hill as shown in Figure 3. In this model, the equation of motion for trees or grasses is coupled with the Navier–Stokes equation, so turbulence in the vegetation canopy can be expressed numerically. The computed results over the hill both with and without vegetation are in good agreement with the previous experimental data. The effects of vegetation on turbulence statistics, including the coherent structures above the vegetation, are also visible and the turbulence statistics inside the vegetation canopy can be found. Urban airflow modelling LES has also been used to estimate the vertical profiles of wind velocity in urban areas and cities (Okuno et al.,

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2005). This is a challenging task, as urban areas have very rough surfaces and therefore relatively thin boundary layers compared to building heights, due to presence of tall buildings. Nevertheless, LES of wind flow models over various actual urban areas have been computed and the results once again are consistent with data obtained by experiment and field measurements. Matching of these results indicates that LES can accurately predict wind loadings on claddings of high-rise buildings of various shapes (Li et al., 2005). As well as building design, transient flow simulations can be used to model the dispersion of pollutants such as smoke or gas through an urban environment. This field has become particularly active in the last decade with new research now focused on the literally thousands of chemical compounds released into the atmosphere and their subsequent chemical reactions. (Figure 4)

Summary Examples of air flows over a range of scales have been shown in order to understand the current state and the future possible practical use of computational fluid dynamics. Large Eddy Simulation is capable of providing accurate predictive values that are comparable to wind tunnel experimental data and provide rigorous and reliable modelling. LES can also result in significant time and cost savings by reducing the need for scale models, wind tunnel tests, and field testing. This has led to a recent explosion in the variety of applications of LES technology in recent years. Continuation of this trend will require more computational power and perhaps a new view of how computations of airflow are used. Given recent advances in multi-core computer chip technology and other possible future advances, it seems likely that some type of eddy simulation will eventually make its way into the mainstream analysis of all turbulent air flows. For further information contact: j.cater@auckland.ac.nz References Ayotte, K.W. (2008). Computational Modelling for Wind Energy Assessment, J. Wind Eng. Ind. Aerodyn, 96, 1571-1590. Cater, J.E., Williams, J.J.R. (2008). Large eddy simulation of a long asymmetric compound open channel, J. Hydr. Res., 46, 445-453. Hartwanger, D., Horvat, A. (2008). 3D Modelling of A Wind Turbine Using CFD, NAFEMS UK Conference 2008 “Engineering Simulation: Effective Use and Best Practice”, Cheltenham, UK, June 10-11, Proceedings. Li, X-X., Liu, C-H., Leung, D Y.C., Lam, K.M. (2006). Recent Progress in CFD modeling of wind field and pollutant transport in street canyons, Atmospheric Environment, 40, 5640-5658. Okuno, A., Tamura, T., Okuda, Y., Kikitsu, H. (2005). LES estimation of wind velocity profiles over various roughened surfaces in cities, In: Proceedings of APCWE6, 437-445. O’Sullivan, J. P., Archer, R. A., Flay, R. G. J. (2010, submitted for publication). Consistent boundary conditions for atmospheric boundary layer flows, J. Wind Eng. Ind. Aerodyn. Ross, A.N., Vosper, S.B. (2005). Neutral turbulent flow over forested hills, Q. J. R. Meteorol. Soc., 131, 1841-1862. Tamura, T. (2008). Towards practical use of LES in wind engineering, J. Wind Eng. Ind. Aerodyn., 96, 1451-1471. Tamura, T., Nagayama, J., Okuda, Y. (2006). LES estimation analysis on atmospheric dispersion in spatially developing turbulent boundary layer in actual urban area, J. Eviron. Eng. Trans. AIJ, 604, 31-38. Tamura, T., Okuno, A., Sugio, Y. (2007). LES analysis of turbulent boundary layer over 3D steep hill covered with vegetation, J. Wind Eng. Ind. Aerodyn., 95, 1463-1475. Wakes, S.J., Maegli, T., Dickinson, K.J., Hilton, M.J. (2010). Numerical modelling of wind flow over a complex topography, Environmental Modelling & Software, 25, 237-247. Wood, N. (2000). Wind flow over complex terrain: a historical perspective and the prospect for large-eddy modelling, Boundary-Layer Meteorol., 96, 11-32.


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Building on their strengths in wind engineering, engineers at the University of Auckland developed the world’s first Twisted Flow Wind Tunnel for sailing yachts, as Professor Richard G J Flay, Director of the Yacht Research Unit, and Deputy Head of Department of Mechanical Engineering at the University of Auckland explains: Introduction Wind is simply air in motion, and is driven by the largescale pressure systems. In this article, I will describe the main causes of atmospheric motion that are interesting from an engineer’s point of view, i.e. they produce strong winds, and the modelling that is needed to achieve a design result that satisfies the relevant design criteria. The study of the wind and how it affects buildings is called wind engineering. There are many similarities between design and testing buildings for wind effects, as well as testing sailing yachts. For example, Boundary Layer Wind Tunnels (BLWT) are used for testing buildings, and the World’s first Twisted Flow Wind Tunnel (a development of a BLWT), designed and built at the University of Auckland, was used to help New Zealand win the 1995 America’s Cup in San Diego. Today the twisted flow wind tunnel is in high demand, although it is no longer unique as its design has been copied by several other groups. Understanding wind The wind loading chain Wind engineering is a multi-disciplinary topic which includes aspects of engineering, mathematics, climatology etc. from a host of related areas. The wind loading process can be regarded as a chain of interconnected components as shown, and each component must be studied. The strength of the chain is determined by the adequacy of the weakest link (see Figure 1). While wind climate is important regionally, local effects such as hills and surface roughness (trees, houses etc.) affect the local air speed (the wind) and how gusty it is. A building responds to the wind depending on its shape (round, square, flat like a sail) and its stiffness (is it made of stone, or is it a flexible light pole), and the designer must take this into account in order to achieve a suitable result. A building shouldn’t move, a light pole shouldn’t break, and windows shouldn’t deflect too much. Large-scale air movement The uneven heating of the Earth by the Sun causes temperature gradients on the Earth’s surface, and in the air itself. The heating effect at the equator tends to make the air less dense than the surrounding air, and so it rises and is replaced by cooler air from the north and south. Conversely, the low temperature at the Poles causes the air in these regions to sink. Thus air from the Poles tends to flow towards the equator. This N-S motion of the air is

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deflected by the Coriolis force such that in the Northern Hemisphere, air is deflected to the right, and in the Southern Hemisphere the air is deflected to the left. The Coriolis force arises because the Earth is rotating, and we measure wind speed and direction with respect to the Earth’s surface. It makes anticyclones around high pressure systems rotate anticlockwise, and to rotate clockwise around low pressure systems (in the Southern Hemisphere). The Coriolis force makes the wind in the upper atmosphere generally flow along the isobars (lines of constant pressure) whereas we might intuitively think that it should flow directly from high to low pressure. Meteorological events that produce strong winds The major storm types that cause strong winds are tropical cyclones (hurricanes or typhoons), extra-tropical cyclones and thunderstorms. Tornadoes are even stronger, but usually not considered for design − if one hits your house, it is likely that your house will get damaged. Tropical cyclones are storms that derive all their energy from the latent heat released by the condensation of water vapour, and originate generally between the 5 and 20 degree latitude circles. Their diameters are usually of the order of several hundred kilometres. The depth of the atmosphere involved is of the order of 10km. In the mid-latitudes from about 40 to 60 degrees, the strongest winds are gales generated by large and deep depressions or extra-tropical cyclones, of synoptic scale. They can also be significant contributors to winds in lower latitudes. Navigators, particularly in sailing ships, were familiar with the strong westerly winds of the ‘Roaring Forties’, of which those of the North Atlantic, and at Cape Horn are perhaps the most notorious. Whereas tropical cyclones form over the sea and take their energy from the condensation of warm moist air, extra-tropical cyclones form in frontal zones and take their energy from the temperature gradient in the frontal region. These systems are usually large in horizontal dimension − they can extend for more than 1000km, so can influence large areas of land during their passage − several countries in the case of Europe. Thunderstorms require the formation of tall convective clouds produced by the upward motion of warm, moist air. The motion may be started by thermal instability or by the presence of mountain slopes or of a front. If condensation of the water vapour contained in the ascending air produces heavy rain, viscous drag forces exerted by the rain on the air through which it falls contribute to the initiation of a strong downdraft. The cold downdraft spreads out over the ground like a wall jet, and produces squally winds for 5–30 minutes. As the energy supplied by the updraft is depleted, dissipation of the thunderstorm occurs.

AERODYNAMIC RESPONSE

MECHANICAL RESPONSE

CRITERIA - strength - deflections - comfort

Figure 1: The wind loading chain.

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Tornadoes contain the most powerful of all winds, and consist of a vortex of air, typically of the order of 300m diameter, which develop within a severe thunderstorm and move with respect to the ground with speeds of 30–100km/h, but they may in fact be considerably higher. Tornadoes are observed as funnel shaped clouds. The tangential speeds are probably highest at the funnel edge, and drop off towards the centre, and with increasing distance outside the funnel. The pressure in a tornado decreases towards its centre. The difference between the pressure at the centre and a few tens of metres from the centre of the vortex may be as high as 0.1 atmospheres − extremely high. The high speeds and large pressure differences is why they are so destructive. Planetary Boundary Layer Engineers are mainly interested in the lowest part of the Planetary Boundary Layer − the layer of wind which is slowed down by friction on the Earth’s surface. It is quite thick for large storms such as extra-tropical depressions − 500m to say 2000m, but for thunderstorms it is much thinner, perhaps 100m. In particular it is the lowest 300m or so which is of interest, as engineering artefacts live in this layer. Figure 2 illustrates the velocity profile in the atmosphere for strong wind conditions, and shows that the velocity varies with time about a mean value. This velocity variation is what we experience as gustiness, and it is largest near the ground over terrain covered in large obstacles like big buildings.

Figure 2: Velocity profile above the ground Note: The aerodynamic response of a structure or building depends on its shape, and the resulting motion depends on its strength and damping properties. These aspects are outside the scope of this article, so are not discussed further.

Wind tunnel tests − Buildings There are generally three reasons to undertake wind tunnel tests on buildings; these are: to ascertain the pedestrian level winds to ensure that the area is suitable for its intended use; to determine the pressures on cladding so that the appropriate glass thickness can be selected; to determine the overall loads to ensure that the building does not deflect more than a suitable amount. Such data are also used to determine the acceleration to make sure that it meets internationally acceptable limits so that occupants are not uncomfortable. These different types of tests require different models and test procedures. The wind tunnel flow has a velocity and turbulence profile with lower speeds and increased gustiness near the ground (see Figure 3) which is developed by the blocks and barriers on the floor upwind of the model. 24 New Zealand Association of Science Educators

Figure 3: Looking upstream in the boundary layer wind tunnel at a 1:400 scale model of Auckland. This wind tunnel produces sheared turbulent onset flow. Photograph courtesy of

An erosion technique can be used to ascertain how windy it is. The wind tunnel speed is gradually increased and the increasing areas of erosion are photographed. The recorded data enable the speed ratio between a particular location near the ground, and a reference location to be determined. These velocity ratios can then be combined with the long-term wind climate data to ascertain how many hours per year specific wind speeds are exceeded which are then used to put the areas into wind comfort categories. We have computer programs that automatically colour code these areas (Figure 4) and these diagrams are given to the architect.

Figure 4: Pedestrian wind comfort map for Queen Elizabeth II Square, Auckland (before it became a bus station). The white area indicates very calm locations, green is less calm, then red, and blue. A yellow area is unsafe, and therefore unacceptable.

Many laboratories also use special sensors to measure the wind speed at a point by attaching a sensor to a traversing rig (like a robot arm) that can be programmed to move the sensor to any desired point. Pressure measurements for cladding and overall loads and accelerations require the use of hundreds of small pressure transducers, which are connected to holes on the surface of the model by small tubes. The pressures are recorded at high speed to enable the statistics of the fluctuations to be found. Then the pressure data can be combined with the peak design wind speed to ascertain the maximum pressure at each point, and these data are given to the cladding designer. Nowadays such pressures are also used to obtain the overall loads by basically adding up the contributions from all the pressures acting on the entire surface at any time instant. This has replaced the method that uses a complicated force balance that is built like a


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Figure 5: Vertical wind speed gradient and wind twist. The wind speed and direction of the wind changes with height up the mast and in this example the wind (red) is blowing at right angles to the boat’s heading. The blue arrows (vectors) illustrate the ‘twisted’ velocity profile that must be produced in the wind tunnel to provide a realistic simulation.

sophisticated set of kitchen scales − measuring six forces simultaneously.

Twisted flow wind tunnel − Sails You can see from Figure 3 that a boundary layer wind tunnel is a duct with a rough floor, down which air is blown with a fan. The blocks etc. on the floor are carefully placed to generate turbulence to simulate the natural wind. (Finding the right combinations of blocks usually takes students a fair bit of time.) However, this type of wind tunnel is not suitable for sails because the wind blowing onto sails comes from over the sea. Although the sea surface is much smoother than most land it still generates turbulence, and so sails also need to be tested in air flow that resembles the natural wind over the sea. However, there is a further complication with sailing yachts. Because sailing yachts are not stationary, unlike buildings, and move through the wind, they create their own relative wind. This relative wind has to be simulated for any tests in a wind tunnel as the model itself is stationary (see Figure 5). In the wind tunnel at the University of Auckland this has been simulated by basically adding some vertical vanes to the end of an air duct. The vanes can be twisted to direct the air in the correct direction at each height (see Figure 6). Note: When the Twisted Flow Wind Tunnel was built in 1994 it was the twisted vanes that were the unique aspect. While we are mainly interested in measuring the overall forces on the model produced by the wind, for research purposes we are also interested in finding out what is going on in more detail such as the wind or air pressure on the surface of the sail. We have carried out some experiments to examine this in the wind tunnel and on the water. Air flowing over the sail affects its shape, and this is important, especially if we want to model the sail using computer simulation, as it is vital to have the correct shape (see Figure 7). The Yacht Research Unit has developed software to compute the sail shape automatically from the shape of the coloured stripes. This technique is being developed further so that the same system can be used on full-scale racing yachts to enable

Figure 6: A 1/5th scale model of a Tornado catamaran is being tested at a small heel angle so that the windward hull is raised above the water (wind tunnel floor). The air flows through the vertical slots and then onto the model. Photograph courtesy of

Figure 7: Sail stripes show the curvature in the sail and the curves have been fitted to the stripes by the computer software.

the sail trimmers to set the sail to the optimum shape. One final word on our yacht investigations: we are not interested exclusively in the most modern sailing boats. The Polynesian explorers had settled the Pacific many centuries before European explorers sailed its waters using wind (air) powered craft. There are many intriguing questions about how well these outrigger canoes could sail; it is known from the time of Captain James Cook that some were very fast. This has led us to begin a study of their aerodynamics and sailing ability. The sail is made of platted material to allow the ‘air’ to leak through, thus reducing the effectiveness of the sail.

Looking ahead... This article has focused on ‘air’, and how wind tunnels and other techniques can be used to understand and measure how the air flow and air pressures vary around different shapes and affect the loads that have to be carried. At the University of Auckland we have become quite good at this type of study. However, we would like to now build a towing tank to pull models of boat hulls through the water to understand how to build faster yachts; how to make more efficient tidal turbines; and so on. But that’s another story... For further information contact: r.flay@auckland.ac.nz New Zealand Association of Science Educators

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atmospheric emissions and health Is there a relationship between our car usage and respiratory disease levels? Ian Longley, Senior Air Quality Scientist, National Institute of Water & Atmospheric Research (NIWA) explains: In 2007, children were denied the opportunity to start attending a gleaming new Early Childhood Centre in south Auckland which had been officially opened by the prime minister (NZ Herald, 23 Sep 2007). Parents were among those surprised to learn that the Centre was denied an official licence to operate because its location on a major road intersection meant it was not a safe and healthy environment for children. Not because of fears of an accident, but because of the threat to children’s health from toxic vehicle emissions. To potentially deny children access to the crucial years of early education is not a step taken lightly. Was this case an overreaction? Or is our children’s health really at risk? Thousands of us spend substantial amounts of our time in, or close to, traffic without (apparently) suffering any ill effects. On the other hand, New Zealand is one of the world’s most car-bound societies, and also has internationally leading levels of respiratory disease. The implications of this risk could be profound, if the risk is actually real. How can we judge if the risk is real? What led to the suspicion that it might be? The answer is far from simple. Note: the Centre had never opened for business, so no children actually became ill from attending it. Quantifying the risk posed to the general population, or vulnerable members within it (such as children), by air pollution is a very active area of research around the world, and has been for several decades. Simply dosing volunteers with pollutants until they get ill, and perhaps die, would accelerate ‘Air Quality Science’ considerably, but is unlikely to be permitted! In practical terms we need to combine a wide range of imperfect evidence from a wide range of sources and disciplines to piece together a plausible understanding of the effects of air pollution. Progress in air quality science occurs when life scientists work in combination with physical scientists. In New Zealand, several major research programmes combining the skills of different life and physical scientists from NIWA, Landcare Research and the Universities of Auckland, Canterbury and Otago are in their early stages, with the question of whether traffic emissions present a particular threat to children being one of our major priorities. Impact of combustion products How do we know that combustion products present a hazard to health? Why do we suspect there might be a problem with vehicle emissions? Most school chemistry courses teach us that ideal combustion of the simplest fuel – methane – in oxygen leads to only two products: non-toxic CO2 and water. Real combustion of fuels in air is very different: carbon dioxide is inevitably accompanied by a wide range of forms of carbon. The proportions of these carbon compounds depend upon the fuel and how it was burned. However, important harmful combustion products include the poisonous carbon monoxide

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(CO), soot (elemental carbon), polycyclic aromatic hydrocarbons (PAHs, many of which are known carcinogens) and numerous other organic compounds including benzene (a carcinogen) and toluene (an irritant). These organic compounds are rarely emitted as discrete gaseous molecules, but mostly as clusters; for example, chains of soot particles of sizes in the tens to hundreds of mm, coated in an organic ‘soup’, which we collectively call ‘particles’. While the emission of soot is gradually being reduced through various technologies, this means that the role of organic compounds, especially in the liquid phase, has become more significant, and particles have tended to become smaller (organics don’t form chains as readily as soot). These different forms of carbonaceous pollution have a correspondingly wide range of effects on different body systems and on a wide range of timescales. But how do we know? It is extraordinarily difficult to determine what is happening in the body when we inhale pollutants, and our knowledge is probably very far from comprehensive. What we do know has arisen from combining lots of bits of evidence from disparate sources. Some combustion products have relatively immediate effects. For example, there is a large body of evidence of the near-instant neurotoxic effect of carbon monoxide available from cases of accidental poisoning, evidence backed up by limited experimental studies on volunteers. At the other extreme, other products, such as benzene, and some PAHs, have been revealed to be carcinogens based largely on evidence from industrial and occupational exposures over many, many years. In between these very short- and long-term effects there are the subtle effects of episodic exposures (e.g. a few hours or days, repeated regularly or erratically over months or years) to elevated levels of urban air pollution in general. That urban air in general can be toxic is based on evidence that particles sampled from the air on such occasions can cause inflammation in in-vitro cell cultures or animal models, although how this works, and how inflammation of cells leads to detectable illness is still the subject of intense research. In New Zealand we are used to the presence of wood smoke in our air on winter evenings. Surely, many think, vehicle emissions present a much less serious hazard? Evidence is growing that the opposite is true. Particles from vehicle emissions are typically much smaller than from wood-burning, and less sooty. These smaller particles (called ultrafine or nanoparticles) are less visible, but more able to penetrate deep into our lungs when inhaled. Once inhaled they are also more likely to remain in the lungs, and there is substantial experimental evidence showing that some particles even translocate into the circulatory systems and appear to trigger various forms of cardiovascular effects. New Zealand has a relatively ‘dirty’ fleet of vehicles, with old polluting vehicles staying on the road for longer than in many other countries. Aucklanders are reliant on their cars, while nationwide each generation of children is exposed to more traffic than the one before.


term hospitalization and death rates in industrial versus non-industrial cities, or comparing the worst and least polluted days in large cities.This requires us to characterize air quality in a city as a whole. This is (apparently) rather simple these days; many cities around the world have air quality monitoring stations, and at the time of writing Auckland has around a dozen and Wellington and Christchurch have about half as many each. A necessary assumption is made that the monitor records data which is a reasonable proxy for the true exposure of people who live near it (which can be several kilometres away). Based on the data from these monitors, which operate continuously 24 hours a day, air quality in this country is mostly good by international standards, except for elevated levels of particles in some towns on winter nights. Levels of traffic pollutants are relatively low compared to many European or Californian cities. It is because of this data that any skepticism about the applicability of Californian studies to New Zealand is understandable. The suitability of data from fixed monitors for exposure assessment depends very much on their location. Locations are generally chosen for the needs of compliance with air quality legislation and logistical practicalities, not epidemiology. In the case of exposure to traffic emissions, we know that comparing one city to another is not going to adequately represent the contrast between high and low exposures. A wide range of studies has shown that concentrations of traffic pollutants are strongly elevated within about 150m of a major road. This is the first clue to distinguishing more- and less-exposed groups, based on whether they live (or work) within 150m of major roads.

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Vulnerability to the effects of air pollution Let’s go back to the Early Childhood Centre in Auckland. The decision to deny its licence was not solely due to the presence of an environmental hazard – toxic vehicle emissions – but because of the exposed population i.e. children under the age of 5. A hazard only translates into a risk if people are exposed to the hazard. We are (nearly) all exposed to these urban air emissions every day. So why aren’t we dropping ‘like flies’? First, it is well-established in medicine that not all people respond to a given hazard (e.g. a dose of a toxin) in the same way or to the same degree. Some are more susceptible, vulnerable or sensitive than others. In terms of air pollution, we know that those with pre-existing cardiovascular and respiratory disease, including asthmatics, can be more vulnerable to some air pollutant doses. The immature lungs of children – and especially infants and unborn foetuses – are all especially prone, and pollutant exposure can lead to more serious and lasting lung impairment. Furthermore, children’s noses are closer to vehicle tailpipe height (NIWA is investigating just how much difference this makes), and are more physically active. This translates into more rapid and deeper breathing which accelerates the rate at which air pollutants are delivered to the lower lungs. Air pollution epidemiology When a hazard is presented to a population, especially a vulnerable population, we have a potential risk. But is there any evidence that potential translates into actual risk? This requires an epidemiological study. The science of epidemiology plays a major role in air quality science. Epidemiology studies some forms of ill-health distributed across society (as distinct from studying, say, a pathogen in the lab) and tries to determine what the sufferers have in common in order to trace both the cause, and who may be susceptible to it. Air pollution epidemiology, in one way or another, tests the hypothesis that people who are systematically more-exposed to a pollutant (or particular mixture of pollutants) than others suffer greater ill-effects, thus suggesting (not proving – epidemiology cannot do that alone) that the pollution causes those effects. In the case of children and vehicle emissions, most of the epidemiological evidence to date comes from the United States, where researchers have found that children living (or schooled) near major highways are more likely to suffer from a range of respiratory conditions. They are also more likely to have stunted lung development which can lead to increased susceptibility to respiratory disease right throughout adulthood. This has profound implications for health costs to society, as we are all exposed to traffic. These studies are far from conclusive and they rely on many assumptions about exposure which can (and have) been challenged. Exposure assessment Who is more exposed to air pollution? The crucial part of air pollution epidemiology is the ability to identify the more-exposed subjects and be able to quantify their exposure. This is known as exposure assessment, and is currently one of the weak links in understanding the effects of air pollution. In the 1980s and 1990s exposure assessment consisted of comparing the outcomes arising from rather crude contrasts in exposure, for example differences in long-

Personal exposure Fixed monitors, however, cannot possibly pick up the inter-personal variation in exposure which is the key to understanding health effects. Real people do not spend all their time rooted in one spot, like a monitoring station. Citizens are not all equally exposed, even those who live in the same suburb, street, or even the same home. We are regularly on the move, spending time in many different buildings in different parts of town, or moving between cities. We spend different amounts of time outside, in different places, doing different things. We travel in different ways for different durations, sometimes walking quiet streets, sometimes driving in congested traffic. It is not just exposure to traffic emissions to which this applies. Exposures to solvents, pesticides, moulds and heavy metals can also vary hugely between people living in the same community, street or home. Until 2007 almost no personal exposure measurements had been made in NZ. It was in 2007 that NIWA began its long-term commitment to making a major leap forward in exposure science in this country. NIWA has now been joined by collaborators at the Universities of Auckland and Canterbury in a range of co-ordinated research projects in this area. One of our first objectives has been to identify where and when most people are exposed to traffic emissions. This has led us to identify how, where and when one commutes as a factor which is at least as important as where one lives or works. In 2009, a study compared personal exposure of subjects during peak time journeys in Christchurch and Auckland made by car, cycle, bus, and train (in Auckland). Each subject carried a bag (see Figure 1) containing three miniature instruments. A GPS-enabled mobile New Zealand Association of Science Educators

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phone which constantly reported their location allowed us to explore how pollution levels change along the route (e.g. Figure 2). Journeys were conducted simultaneously in both morning and evening peak hours, and repeated for over 20 days in both cities. The results very clearly showed that, although exposures were high for all compared to the rest of their day (at home or in offices) the cyclist was the least exposed and the car driver the most, even though they took almost identical routes at the same time as each other. This conclusion has been investigated further by filling a NIWA company car with a wide range of instruments and driving it around a set of carefully chosen roads in

Figure 1: The air sampling equipment bag used in a commuting exposure project conducted by the Universities of Canterbury and Auckland, and NIWA in 2009. In this image, the bag is mounted on the front of a bicycle as it travels on a preset route in Auckland, simultaneously with similar bags travelling by car, bus and train over approximately the same route. The bag contains devices to measure carbon monoxide and particles every second, some meteorological parameters, location and forward-facing images.

Auckland. This has allowed us to observe on a second-bysecond basis how cars collect and trap the emissions from the vehicle in front. This indicates that, even though the air may, in general, be clean, the air inside your car may be a ‘hotspot’ of pollution. This has never been previously considered in an air pollution epidemiology study and something we aim to put right in the near future. After our focus on commuting and the interior of the typical car, the next phase of our work, starting in 2010, is to focus on an Auckland community clustered around one of its busiest stretches of motorway. Within this area, we intend to study the impact of the motorway on local air quality in unprecedented detail, and also observe its impact on air quality inside typical homes and at least one school. By deploying a range of survey techniques we will then determine how people move in and around the community, moving from one ‘microenvironment’ to another, developing exposure ‘profiles’ that allow us to create personal exposure assessments for residents and distinguish the more-exposed individuals. At his point we will join forces with colleagues in public health research here, and in Australia, to conduct New Zealand’s first air pollution epidemiological studies based on local observations of real personal exposures. By 2016, we have a commitment to reporting to the relevant government agencies, as well as the global science community, on the scale and seriousness of emerging air quality health risks, particularly the effect of vehicle emissions on children’s health. We shall also be reporting on a range of policies and measures that will match the scale of risk. At this point we will have much better, locally-based evidence to judge whether the decision to withhold a licence from the Auckland ECEC was an overreaction, or an admirable precaution. For further information contact: i.longley@niwa.co.nz Acknowledgement: The research conducted by NIWA and collaborators is funded by the Foundation for Research, Science and technology, the Health Research Council and the New Zealand Transport Agency.

Figure 2: An example of the data generated by the equipment seen in Figure 1. The coloured dots indicate concentrations of carbon monoxide measured as the cycle passed that location (yellow = low, purple = high). This plot shows an on-road route (the lower line) and an off-road route (upper line) between downtown Christchurch (point A) and the University of Canterbury (point B). 28 New Zealand Association of Science Educators


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Over 1000 species of algae are aerophytic (or air plants) and can be divided into two groups: freeliving, or with a lichen association, as Phil Novis, Phycologist – Allan Herbarium, Landcare Research explains: Algae tend to be regarded as slimy, aquatic organisms in streams and lakes that dry out, stink, and perish – except for their resistant spores – when water disappears. However, it might surprise you to learn of vast hordes (over 1000 species) of algae that are aerophytic. Aerophyte literally means ‘air plant’; these don’t have to be immersed, and are able to obtain all the water they need directly from the atmosphere, in the form of rain or condensation. The obvious challenge of the aerophytic lifestyle is, nonetheless, capturing enough water to survive and grow. This means either storing it or surviving long periods of dehydration. Add intense light (which is greatly reduced in submerged habitats) to the water stress and life becomes really tough. Only specially adapted, tenacious organisms will thrive on the surface of a rock, leaf, tree trunk, or building. A wide range of aeorphytes also occurs in the top 5cm of soil, where the presence of water between soil grains is often very temporary. Here, however, I will focus on the harsher end of the spectrum: surfaces found above the soil. There are two main types of aerophytic lifestyle. Some species are free-living, and cope alone with the extreme demands of their terrestrial habitats. Others overcome these demands through partnership with a fungus in a lichen association. Some algae can adopt both lifestyles. Note that ‘lifestyles’ doesn’t say anything about diversity,

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and indeed both kinds of aerophytes include algae of diverse evolutionary lineages. In other words, terrestrial habitats were colonised not once but many times – and similar adaptations can be found in each case, as examples of convergent evolution.These adaptations include means to retain water – frequently through the production of jelly-like mucilage or thick, solute-rich cytoplasm – and pigments that screen out harmful radiation.

Free-living lifestyles Trentepohlia is a very common and obvious aerophyte, as well as being one of the most misidentified algae in the world; it is routinely mistaken for a lichen. It also exemplifies the production of protective pigments, forming a powdery red coating on rock and wood surfaces (Figure 1). If you sit on such a rock, you may find the red powder transfers its allegiance to the seat of your pants. The red pigment masks the colour of the photosynthetic pigments, chlorophylls a and b, which are grass green. Trentepohlia is thus a green alga and only distantly related to the group known as red algae, which is composed mostly of marine species. One instructive site to visit is Castle Rock, above Christchurch. The damper southern aspects, much slower to dry, are extensively covered with Trentepohlia, whereas the sunnier northern side is relatively bare. This is a nice illustration of the importance of water availability, even to these hardiest of plants. Phycopeltis (Figure 1) is a relative of Trentepohlia, but its growth form is quite different. It forms small discs on the leaves of certain plants, such as Blechnum ferns on Banks Peninsula and the Canterbury foothills. Another relative is the parasitic Cephaleuros; this genus steals carbon from a host plant by growing beneath its epidermis. Also intriguingly, DNA sequence data show that the order Trentepohliales is part of the same class as Ulva, the sea lettuce, and the other groups in this class are either purely marine or a mix of marine and freshwater taxa. Trentepohliales is the only one of these groups lacking any aquatic representatives; all hints Figure 1: Aerophytic algae of the Trentepohliales. Left, Trentepohlia on a rock of Trentepohlia’s origins from any surface from Arthur’s Pass. Right, Phycopeltis on a leaf of Blechnum from Banks aquatic environment are lost in Peninsula. the mists of time. One final perplexing attribute of Trentepohliales is that, during cell division, a kind of plate (phragmoplast) forms between the daughter cells, and develops into the new cell wall separating them. Remarkably, phragmoplasts are otherwise known only in the land plants. This is yet more evidence of the uniqueness of Trentepohliales, Figure 2: Common morphologies – cells embedded in a gelatinous matrix – among and the difficulty of figuring out aerophytic algae from (left to right) the Chlorophyta (Coccomyxa, a green just where they fit in the tree of alga), Chrysophyceae (Chrysocapsa, a golden-brown alga), and Cyanobacteria life. (Gloeocapsa).

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The land plant lineage itself includes some aerophytic green algae. A recent paper on the genus Klebsormidium features images of aerophytic growths on damp walls and around drains. This is not the only free-living alga to occur in such a habitat: another green alga, Prasiola, may be found in the alleyways where drunks stagger out of pubs and urinate against the walls. Not only water, but plenty of salts and nitrogen thrown in for free! Other green algae occur as free-living aerophytes, although often in less extreme habitats. For example, in a recent survey on Rangitoto Island, Coccomyxa was found living on moss communities as epiphytic colonies of cells embedded in jelly-like mucilage. Many soil algae also possess this adaptation. The mucilage slows the drying process, and has been evolved many times in different groups, including several lineages of eukaryotic green algae, golden-brown algae, and the prokaryotic cyanobacteria (Figure 2). Cyanobacteria (also known as the blue-green algae) are very common in aerophyte communities. The relationship between these prokaryotes and other (eukaryotic) algae, and why they are regarded as algae, are complicated. Both obtain energy through photosynthesis. However, Trentepohlia is classified in the domain Eukaryota: each cell has a nucleus, chloroplast, mitochondria, and other membrane-bound organelles. Cyanobacteria, as prokaryotes belonging in the domain Eubacteria, lack such organelles. The nuclear genome of Trentepohlia bears little resemblance to the genome of a bacterium. So ‘algae’ is a useful ecological term that has been retained, although it is not particularly useful in describing relationships between groups. However, life gets more complicated. Scientists who have examined nuclear DNA in photosynthetic eukaryotes (such as Trentepohlia) have encountered thousands of cyanobacterial genes in the nuclear genome. These originated from the chloroplast, or photosynthetic organelle, that has another (greatly reduced) genome of its own. If a chloroplast was free-living, it would

Figure 3: Cyanobacteria on limestone. Top, runoff from a bolt installed by rock climbers has killed the algal epiliths; bottom, a recently fractured boulder shows the difference between colonised and uncolonised surfaces. Images courtesy of Paul Broady, University of Canterbury.

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be classified as a prokaryote closely related to the cyanobacteria, and this is in fact the modern theory for the origin of chloroplasts – sometimes described as an endosymbiotic event and sometimes as an enslavement – in which a photosynthetic bacterium was engulfed by a eukaryote. Hence, a eukaryotic cell can be thought of as a community of components with different evolutionary origins. In the harshest conditions, cyanobacterial aerophytes are some of the most successful. The closest nunataks – large rock outcrops – to the South Pole have been colonised by cyanobacteria, including the genus Ammatoidea. Others, such as Gloeocapsa, inhabit the surfaces of limestone boulders, such as those in Castle Hill Basin, giving a purplish-grey colour to the rocks, adding further to their elephant-like appearance. The white streaks below the bolts installed by rock climbers show where metals washed off the bolt have killed the algae; white uncolonised surfaces can also be seen where boulders have split and fractured (Figure 3). Similar cyanobacterial communities on limestone may be found around the mouths of caves. Gloeocapsa occurs on other rock surfaces too, such as scree boulders in the high mountains. After rain, the purple colour of the colonies can be especially apparent as the algae ‘come alive’ to mop up all the water they can. Microscopic examination of Gloeocapsa reveals that the cells are embedded in a robust mucilage that retains water during dry spells – a similar adaptation to Coccomyxa mentioned above, and highlighting again the constraints and challenges imposed by particular habitats, leading to common solutions in distantly related species. This, of course, is convergent evolution.

Symbiotic (lichenised) lifestyles Green algae and cyanobacteria are the most common aerophytic algae. It is not surprising, therefore, that it is these two groups that form symbiotic associations with fungi to produce lichens. Although lichens are classified with a Latin binomial (genus and species),

Figure 4: Two lichen morphologies shown by Placopsis (a crustose lichen that includes cyanobacteria) and Usnea (a fruticose lichen).


Fungi that discovered agriculture The ability to lichenise has evolved multiple times in both algae and fungi. Most mycobionts are ascomycetes, but a few are basidiomycetes (the group that includes the common edible mushroom). These mycobionts have been described as ‘fungi that have discovered agriculture’. This is a closer analogy than it may appear at first glance. The selection of increasingly successful photobionts by mycobionts is similar to the domestication of crops by humans, in which crops with desirable attributes are selected and passed to other farmers. Clearly, a fungus might prefer some strains of algae over others; one that photosynthesises more efficiently than another in the lichen environment – and therefore provides the fungus with more fixed carbon – will promote a faster rate of lichen growth. Over much

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they are ‘compound organisms’ and best thought of as communities of fungi (the mycobionts) and algae (the photobionts). Each benefits from the relationship: the mycobiont derives fixed atmospheric gases from the photobiont, which receives shelter and nutrients in return from the fungal mycelium. There may be more than one algal partner in a lichen. For example, the lichen Lobaria may have a green alga as the main photobiont, but also produces structures called cephalodia that house balls of cyanobacteria. The mycobiont is thus able to acquire fixed carbon from both photobionts, and nitrogen from the cyanobacteria (nitrogen fixation from the atmosphere being a strictly prokaryotic invention). This co-operation, which combines the strengths of several functional groups, has resulted in spectacularly successful aerophytic communities. Lichens can dominate the aerophytic habitat, from tropical rainforests to the deserts of Antarctica. In the latter, lichens may be absent from valley floors, but found partway up the mountainsides where clouds commonly form from condensing water vapour, providing the moisture needed for lichen growth. However, growth rates in such environments are painfully slow. Lichenologist Allan Green, from Waikato University, has revisited the same lichens in Taylor Valley over decades and found no detectable change in their diameters. Given such slow growth rates, it is not surprising that some large polar lichens are thought to be very old – up to 5000 years. Lichen colonisation can therefore be used to date events such as landslides and glacier retreats. Lichens usually most resemble the fungal partner in their shape. However, on occasion the lichen more closely resembles the photobiont. This is the case in Mastodia, which includes Prasiola as a green algal partner, and also the ‘secret writing’ lichens such as Graphia, in which Trentepohlia is the photobiont. Different lichens form a huge variety of shapes, including crustose (flat mats or crusts), foliose (leaf-like), fruticose (strands or branching stems), and squamulose (scale-like). Two of these are shown in Figure 4. Some lichens have more than one growth form – the vegetative thallus of Cladonia is squamulose, but the fruiting structures are fruticose. Lichens reproduce in a variety of ways. The individual partners have their own reproductive mechanisms, but the partners may also propagate together. Soredia are balls of algae wrapped in fungal mycelium, which disperse by wind from a structure called a soralium. Other less specialised structures simply fragment, allowing dispersal and colonisation of a new site by the lichen.

Figure 5: An aerophytic ‘land’ plant: Tillandsia, a Central American bromeliad. Image from: http://tinyurl.com/ydtne3e

time, this will result in a dominance of lichens having that particular photobiont. This does indeed seem to have happened: a large lineage called Rhizonema, only recently discovered, comprises cyanobacteria that are found exclusively as the photobionts of lichens. Thanks to its success in lichen partnerships, this lineage has effectively been ‘cultivated’ by several different fungi. Similarly, and probably through the same mechanism, green algae in the genus Trebouxia are very common lichen partners, occurring in 50–70% of all lichens. In some places, however, photobiont partners are at a premium. Mycobionts in these areas cannot always afford to be so picky; some fungi that form associations with very specific cyanobacteria in temperate regions have been shown to recruit any passing cyanobacterium in maritime Antarctica. ‘Proto-lichens’ occur at some Antarctic sites, in which layers of fungi, algae and bacteria grow inside porous rocks; these were described in an earlier issue of this magazine. Another remarkable feature of Antarctic mycobionts is their ability to alter the temperature optimum of photosynthesis. If the photobiont is extracted from the lichen and grown alone in culture, its temperature optimum is likely to be around 20ºC. In the lichen thallus, however, the optimum is close to 0ºC, similar to the temperature of the outside air. The trick is done by the fungus; by altering the fungal biomass relative to the photobiont biomass, the temperature optimum becomes depressed. This works because respiration and photosynthesis respond to temperature change in different ways.

Final reflections Sometimes it is worth reflecting on the discrete categories that humans define and impose upon nature. There is a sense in which all land plants – which also happen to be a branch of green algae – are aerophytes, having left behind the strictly aquatic habitat of their progenitors. They have been referred to as the ‘drier algae’. Also, some land plants are as aerophytic as any alga, as shown by some members of the pineapple family: bromeliads in South America, such as Tillandsia, grow not only as epiphytes on other plants but even balanced precariously on telephone lines (Figure 5), and are known as ‘air plants’ in their own right. Nonetheless, in the harshest conditions – the alpine zone, bare rock surfaces, nunataks nearest the South Pole – the only aerophytes are microbes. For further information contact: NovisP@landcareresearch.co.nz

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lifelong science learning Written by Miles Barker (University ofWaikato) Introduction

numbers of students continuing to study science in the senior secondary school.”5 Nevertheless, if school science is to be an indispensable springboard for learning science lifelong – and one meets few adult citizens who are passionately engaged with science but who profess to have found school science less than meaningful – then the point about school science experiences is a valid one. On the face of it, the point about having inspiring science teachers is hard to deny. Very few people seem to be set on a lifelong orientation towards science quite independently of their schooling. An exception is British neurologist Oliver Sacks who, as he describes in his classic book Uncle Tungsten: Memories of a Chemical Boyhood, resonated lovingly with everything scientific in his youthful world, whether teacher-inspired or not.6 By contrast, interactions with teachers are more evident in the biography of New Zealand’s greatest astronomer, Beatrice Tinsley, but in her case awe on the part of the teachers is more in evidence that the benefits gained by Tinsley at school: “Already, at the age of 13, Beatrice knew about energy, and force. She had a gift for perceiving and linking things which went well beyond anything her teacher had ever encountered, and she did this while going directly to the heart of the matter and expressing herself in the simplest and most precise way.”7 These two moved into professional science, but New Zealand economics commentator Brian Easton didn’t, despite an exceptionally gratifying science schooling: “I almost became a chemist. In the upper forms at Christchurch Boys’ High School I had an inspiring chemistry teacher, Alan Wooff … (there was) a chemistry section of the library which I devoured … I still read science for leisure.”8 For my own part, it was probably the influence of senior biology teacher Stewart Christie in Form Six at Hamilton Boys’ High School and his view that evolution by natural selection “… is a whole lot of arrows pointing in the same direction. There are just a few arrows pointing in the opposite direction.” I thought, “If ‘Sam’, who takes the conservative Christian Crusaders group, can apparently accommodate and reconcile the diverse scientific and theological influences in his mind in this way, maybe it is possible for me too.” It’s a challenge I’ve cherished lifelong. But I believe we need to dig deeper. Not everyone relishes

There is a story doing the rounds about two English schoolboys taking time out and commiserating about the state of their lives. One says, “More bad news from school.” “What?” wails the other. “Now they’ve discovered LIFELONG learning!”1 These days in New Zealand, where ‘lifelong learning’ is seen as an indisputably desirable outcome of schooling, that story has a somewhat antiquated feel to it. The New Zealand Curriculum of 2007 makes this clear even in its ‘Forward’, where it outlines what is to follow: “It defines five key competencies that are critical to sustained learning and effective participation in society and that underline the emphasis on lifelong learning.”2 ‘Lifelong learning’, or equivalent phrases, then appear like a mantra through its pages.3 Interestingly, however, what lifelong learning actually looks like or – crucially for teachers of science – how you would teach students in such a way that they will continue science learning in the uncharted world of the rest of their lives, is not elaborated.

Two preliminary thoughts Asking people about what might create a fruitful setting for lifelong learning in science (and I am not thinking here about the small proportion of students who will go on to be professional scientists) is likely to bring forward two preliminary thoughts: that science experiences need to afford sustained enrichment right through schooling; and, more specifically, that having inspiring science teachers is hugely important. On the first point, there is of course a disquieting body of international research that suggests that at senior levels these days, when students have the option of relinquishing science, they tend (either out of disappointment with school science, or for career-strategic reasons) to choose business-related subjects and ICT. Schools in many countries are therefore struggling to “… slow, stop and reverse the decline in science enrolments at year 12 and 13”4. How far this is true of New Zealand is a moot point. Actually, from a very comprehensive study, Rosemary Hipkins, Rachel Bolstad and Josie Roberts concluded that “caution is needed when interpreting (New Zealand) data that lament a sharp decline in overall 1a

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Figure 1: Responses to the ‘draw a scientist’ task from three Middle Schoolers - a student in South India (1a), and two New Zealanders, Nicole (1b) and Victor (1c) - and from three Kenyan teacher educators (1d). 32 New Zealand Association of Science Educators


Lifelong science learning – what is it? What do we actually mean by ‘lifelong learning in science’? What visible forms does it take: reading widely in science all your life; watching science documentaries; trying to understand new science theories; attending lectures and evening classes; using science knowledge to stay employed; or making money from science? And when we have decided that, how might an anticipatory platform be laid in school to ensure that science learning does persist lifelong? The lens I bring to this is a very pragmatic one. Although science speaks to me about some of the deepest things in the cosmos, I am no dilettante hobbyist. Rather, I believe that we are increasingly living in a world fraught with urgencies and issues, a world of new directions and new responsibilities, where science learning can empower us and help us to be vital lifelong contributing citizens. With this in mind, I am suggesting that lifelong science learning might entail three major capabilities.

Capability One: Owning, adapting and applying the big stories of science Adults who are lifelong science learners usually, it seems to me, have one clear characteristic – rather than their science knowledge consisting of isolated fragments, illremembered from schooling, they can instead offer you extended explanatory stories in science. More specifically, in response to the big, simply worded questions that arise in our everyday lives, they can give you an articulate and coherent account from the science perspective.9 They don’t claim that their stories are definitive, or even complete, but they have been running these stories in their minds since school, and they have been keeping them up to date, as best they can, and they have been finding them useful to engage with life’s complexities. Here are some examples of such questions – questions that beg for such a narrative: how did we get here; how did Aotearoa/New Zealand get here?; why are there so many types of plants and animals?; where does energy come from and go to?; what are rocks and how are they made?; what causes disease?; what is learning?; how do trees grow?; how old is the Earth?, and how did it come to be?; why is water so special?; how do we change as we get older?; what is air?; why does the moon keep going around the Earth?; what are fossils and how are they made?; how does the heart work?; and so on … But how do these stories become profoundly sustaining in the living of our adult lives? Let me give you four examples: Example 1: The New Zealand Herald ran a story in 200810 about a water bottling company which claimed that the processing of its Energised Distilled Water and Energised Mineral Water “neutralises the harm caused by toxins through reprogramming the water’s polarity and restoring it to its ‘primordial’ or natural state.” Now water, especially bottled water, is a dominant and controversial aspect of the lives of most of us these days, and the water companies assail us with apparently persuasive scientific justifications for the superiority of their various products. However, any citizen who has been running the ‘Why is water so special?’ science story since

school days, can readily unravel this gobbledegook. They can explain to themselves and others that water simply IS water – that its H2O molecules, since the Earth was young, have had a fixed negative side and a fixed positive side; that there is simply no way by which this natural condition can be demonically reversed; and that we therefore are awaiting rescue from this pervasive catastrophe by a water bottling company. Incidentally, the company in question was fined $25,000 for breaching the Fair Trading Act. Example 2: In 2009, The New Zealand Herald11, under the headline ‘Garlic offered for hypertension’ told how, in an experiment, a 53-year-old man visited 26 randomly selected health food shops. Although he was complaining of supposed high blood pressure, he “was referred to a doctor by only one … If asked, he told the employee his blood pressure was 160/120. In 25 of the shops he bought a wide range of products, with the most popular being garlic.” For us citizens, correctly understanding this situation really could be a matter of life and death; but those who run the science narrative ‘How does the heart work?’, especially as it explains the cardiac cycle and the prescient significance of ‘160/120’, would seemingly be at an enormous advantage in the survival stakes. Example 3: Earlier in 2009, The New Zealand Herald12 added a new twist to the question of whether or not, around 23 million years ago, Aotearoa/New Zealand was completely submerged for a period, drowning all animal life. In 2007, Earth scientists Hamish Campbell and Gerard Hutching had controversially claimed that this HAD occurred.13 Now, The Herald was reporting a Central Otago tuatara fossil find that suggests to Earth scientist Trevor Worthy that tuatara have had a continuous existence on an Aotearoa/New Zealand land mass (but of greatly varying size) since well before 30 million years ago. Those citizens who run the ‘How did Aotearoa/New Zealand get here?’ science story are well placed to appreciate how intriguingly open-ended this story of our homeland’s generation currently is. But there is more to it than that. For Pasifika people, this is a science story that deeply intersects with another narrative that is foundational to deep questions of human identity: the role of the great ancestral trickster and demi-god Maui in the creation of Aotearoa. Understanding the tuatara find cuts right down to the bedrock of our national identity. Example 4: Also in 2009, the New Zealand Geographic reported14 a story which would have shaken the foundations of those Pakeha citizens who run the ‘How did we get here?’ science story. It announced that a human skull found near Featherston in 2004 was now known to have a radiocarbon age of 296 plus or minus 35 years before the present. The journal commented that, “… mitochondrial molecules have spoken, science has triumphed over common sense and now the historical record had to account for a European woman roaming the banks of the Ruamahunga River centuries before the first record of white women15 anywhere in New Zealand.” Apprehending this science story, and its intersections with the story of Pakeha social history in New Zealand, again strikes at the very identity of New Zealanders, especially the conventional story of Pakeha women and the New Zealand Company’s arrival in 1839. There are three key points about these great stories of science: 1. Knowledge structure: The stories overlap between themselves – for example, in the case of the Central Otago tuatara fossil find, the ‘What are fossils?’ and the ‘How did Aotearoa/New Zealand get here?’ stories

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twelve or thirteen enriching years of science at school; and which teacher one gets for science is often a notorious lottery. In this article, I would like to explore how schools can much more deliberately and systematically offer a form of science learning that both meets the needs of contemporary learners, but is also tailor-made to sustain lifelong science learning.

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clearly intersect. Also, the science stories intersect with stories from beyond science, for example, with the social science narrative in the case of the Ruamahunga skull. And in later life, of course, the knowledge in the science stories more and more takes on a new ambience. No longer is the knowledge novel, raw and school-bound – rather, as we confront life’s science–related situations (anything from managing a household energy budget within a low income, to raising a child born with Down’s syndrome) the science stories increasingly and properly take on the sophisticated, contextual flavour of ‘citizen thinking’.16 In conclusion, one could well suggest that learning itself is the facility to make immediate, fruitful and novel connections between the big stories. 2. Pedagogy: Because the science stories are evidencebased, handing them on intact and unmodified is not one of their features; rather, the stories are being perpetually modified as new evidence comes to hand. Science learning in school therefore has the crucial task of explicating this evidence-seeking aspect of science for students with a clarity that will endure for a lifetime. (I talk more about this below.) Again, what we know about how students construct their knowledge suggests that teachers need to take account of three dimensions in their science teaching: an appropriate form of the story itself, the students’ own existing ideas, and a vigorous interrogation of the evidence. 3. Curriculum: A wise science curriculum will be paced so that students’ science stories are further enriched as they pass through school. This successive enrichment is, of course, modelling a habit of mind people will hopefully possess for a lifetime. And just as the pacing the ideas is important so, too, is the pacing of the cognitive demand on learners. In summary, the capability of owning, adapting and applying the big stories of science requires school-fostered expertise in two of the four banner headings that subsume each page of our science curriculum: • Investigating in science – constructing the story as an amalgam of ideas and evidence • Communicating in science – articulating the story with clarity and confidence

Capability Two: Understanding the nature of science itself Another characteristic of adults who are lifelong science learners, it seems to me, is that they have a shrewd idea of what science is like. Not only do they have ideas in science (its big ideas) but they also have ideas about science: what science knowledge is and how it is special; who scientists are and how they do their work; and how scientists and the rest of us affect each other. I’ve been exploring people’s ideas in this area by inviting them to respond to an imaginary task and to draw a scientist.17 Usually, students interpret the task as requiring some kind of archetypal scientist, but I’ll show you a delightful example of a particular scientist that a Middle School student in South India drew for me earlier in the Darwin Bicentenary year of 2009 (Figure 1a). She has alluded to Darwin’s tropical sea voyaging, and she has suggested how seminal were Charles’s ideas about tortoises and bird life in creating the Voyage of the Beagle and The Origin of Species. A letter “to sweetheart” also acknowledges Darwin’s private life – his relationship with Emma. I’m convinced that it is essential to explore and clarify ideas about science with school students because for the rest of their lives they are sure to be exposed to a maze of often quite contradictory ideas about this profound aspect of 34 New Zealand Association of Science Educators

their lives.18 Having students ‘draw a scientist’ can lead to fruitful learning. For example, Middle Schoolers Nicole and Victor suggested somewhat contradictory images: Nicole’s sunny upbeat scientist (Figure 1b) bears a test tube, but her rainbow-drenched surroundings19 comprise symbols of her private life, including a (curiously bespectacled) puppy. By contrast, the environment of Victor’s more severe male scientist (Figure 1c) is dominated by aspects of his professional life: a giant nucleic acid, and a skull and crossbones-labelled chemical flask. These images could well lead into class discussion of a classic proposition20 about the way “scientists participate in public affairs both as specialists and as private citizens.” Perhaps an even more fundamental question that arises from Nicole’s and Victor’s images is ‘How do scientists actually make discoveries?’ On the one hand, some explanations appeal to a scientist’s inexplicable flash of genius – a ‘eureka’ moment – like the story of Archimedes and the discovery of density. At the other extreme, the fundamental importance of persistent careful observation is seen as the key, for example, Edward Jenner’s prolonged observations of milkmaids, their susceptibility to cowpox, but their relative exemption from smallpox. Clearly, both explanations about the discovery process are simplistic parodies of how most scientists work.21 But, perhaps Victor’s teacher and his class actively pursued the question of how that DNA molecule was actually discovered. Exploring the Watson and Crick story can show us that even those most eminent of scientists deliberately used a number of very standard heuristics, or discovery-seeking techniques in combination. They: found out everything that was already known about DNA; did more experiments and thought about other people’s experiments; worked out what DNA should be like in theory; and built models in the basement until they were PRETTY sure … And, with further schooling, Victor may well appreciate that, as Derek Hodson describes it, “real scientific inquiry is holistic, fluid, flexible, reflexive, context-dependent and idiosyncratic. It is characterised by frequent false starts, blind alleys and improvised modifications; it can be, and often is, redirected by unexpected events and by unanticipated technical problems … by the publication of a research paper in the same field or chance conversation with another researcher.”22 Yes, inquiry in science is a blend of logic and imagination, there is no single ‘scientific method’, and everyday thinking processes like seeking an analogy and analysing its pros and cons can all play their part. Perhaps, Nicole and Victor, we should now go and visit some scientists, and ask them how they do their work! Beyond school classrooms, ‘drawing a scientist’ can raise wonderfully reflective discussions about the science enterprise. I recall how a group of three Kenyan primary school teacher educators – admittedly, being deliberately provocative – drew me a one-year-old scientist (Figure 1d), deeply engrossed in questioning, hypothesising, experimenting, and communicating. By contrast, when scientists self-report, it seems, they often emphasise a socially interactive and environmentally aware view of ‘doing science’.23 I shall return to this aspect below. In summary, being capable of understanding the nature of science itself requires school-fostered expertise in another of the banner headings that subsume every page of our science curriculum: • Understanding about science – appreciating that science is a way of explaining the world; that science


Capability Three: Engaging in socio-scientific issues Adults who are lifelong science learners, it seems to me, are generally not people who take things sitting down. As we have seen above, they respond personally to news media items that speak to them about their own health and identity. However, they are also often people who respond and react in a much wider societal and environmental sense to science-related media items. And, of course, those issues are many, they are frequently complex, and the statements made can be utterly contradictory. One day, we are told that climate change is now near irreversible: “scientists sound dire warning on governments to act quickly to cut greenhouse gases.”24 Another day, we learn that “carbon dioxide, the evil stuff that CGW [Church of Global Warming] wants to outlaw, is actually the compound we exhale every breath we take.”25 How, if at all, do we respond? If taking action on socio-scientific issues is desirable in adult life, and if school science is a preparation for life, does this mean that school science education should model such action-taking? Hugely respected, now Auckland-based, science educator Derek Hodson says, ‘yes’: “It is not enough for (science) students to learn that science and technology are influenced by social, political and economic forces; they need to learn how to participate, and they need to experience participation.”26 But, given the complexity of some of the issues, would it not be wise to postpone action-taking until senior secondary school, when students’ understandings will be appropriately mature? Derek Hodson says ‘not necessarily – it depends on the context.’“For example,” he says, “it is easier to take action on recycling than to reach a considered and critical judgement of recycling versus reduced consumption versus alternative materials.”27 Yet should we be advocating social participation of this sort as a basic aspect of school science? Derek Hodson’s response is absolutely in line with The New Zealand Curriculum’s position on values: “Many teachers avoid confronting the political interests and social values underlying the scientific and technical practices they teach about, and seek to avoid making judgments about them, or influencing students in particular directions. This makes no sense … It asks teachers to do the impossible. Values are embedded in every aspect of the curriculum.”28 But how do teachers actually approach the teaching of socio-scientific issues? Kathy Saunders, a faculty member of the School of Education at the University of Waikato, has very recently completed a major study29 investigating this. The secondary school teachers whom she interviewed expressed a number of doubts, hesitancies and even avoidance strategies: “I don’t see it as an issue – just facts”; “I teach the science and let the students discuss and make up their own minds on subjects”; “I don’t understand the issues myself to the degree I would like.” Next, Kathy surveyed teachers about what they felt was constraining their teaching of controversial science issues. Lack of time in their current programmes (68%), lack of personal background knowledge (50%), lack of time to plan (35%), lack of teaching resources (35%), and – significantly for Kathy – lack of knowledge of effective teaching and learning strategies (23%) turned out to be major factors in

the teachers’ minds. Only 20% cited lack of interest by the students. Kathy decided to channel her research towards developing and trialling a novel teaching and learning model to help teachers navigate through the process. Evolving from international research, especially in the United Kingdom, Kathy’s ‘Model for ethical inquiry into scientific issues’ draws the class through processes of engagement, backgrounding, reflection, discussion, and question identification. Then comes, what is for Kathy, the key step: introducing a choice from five ethical frameworks or lenses (‘the right to choose’, ‘pluralism’, etc.) by which students can focus on their question and generate processes of ethical decision-making, with justification, from which actiontaking (Derek Hodson’s key point) results. Kathy presents persuasive evidence that students considered her approach to be a gratifying exploration of, as one student put it, “the reasons why people think differently”; and teachers were attracted to the security of the stepwise process30 and the clear action-generating outcomes. Yes, Kathy’s work was in secondary schools, but she is convinced that the approach would be equally effective with much younger learners.31 In summary, being capable of engaging with socio-scientific issues requires school-fostered expertise in another of the banner headings that subsume every page of our science curriculum: • Participating and contributing – linking science learning to daily living, using science knowledge when considering issues of concern, exploring various aspects of an issue, drawing evidence-based conclusions, making decisions about possible actions (both personal and societal), and taking action where appropriate.32

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knowledge changes over time; identifying ways in which scientists work together and provide evidence to support their ideas; knowing about the relationship between investigation and theory and the processes of logical argument; exploring the connections between new and existing knowledge; and understanding the importance of peer review.

Living science lifelong: What do we need to do in school? I have suggested three capabilities that lifelong learners in science might need to have, and which therefore need to be a focus of school science programmes. Fortunately, these three capabilities are legitimised by the banner headings, the Nature of Science, across every page of our school science curriculum: Capabilities for Lifelong Science Learning

NZ Science Curriculum: The Nature of Science

1. Owning, adapting and applying the big stories of science

• Investigating in science • Communicating in science

2. Understanding the nature of science itself

• Understanding about science

3. Engaging in socioscientific issues

• Participating in science

It turns out, on this view, that preparing our students for lifelong science learning entails no big additional new directions and responsibilities. What is needed is simply a willingness to accept wholeheartedly the radical course that our new science curriculum has already set us on: to accept that our science curriculum actually means what it says.

Living science lifelong and The New Zealand Curriculum at large Thinking about school science learning as an anticipation of life encourages us to take even more seriously the underpinnings of our science curriculum in the front half of The New Zealand Curriculum.33 Take the ‘Values’ section (page 10). A fundamental aspect in living science lifelong is surely never to forget the question “What do we value, and why?” Another angle is for we teachers of science to New Zealand Association of Science Educators

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ask ourselves which of the eight listed values (‘excellence’, ‘integrity’, etc.) does science learning, in school and lifelong, provide an especially fruitful context for developing? I would say that ‘integrity’ has a high loading for science. An invaluable lifelong habit of mind might be to be to perpetually have at the ready the question: “How do I bring scientific integrity” (objectivity, respect for evidence, openmindedness, willingness to suspend judgement, logic and analysis, attention to variables) “to whatever situation is in front of me?” The ‘Vision’ section on page 8 (which is about “What we want for our young people”) is highly relevant. Living science, lifelong, could be seen as the working out of visionary, science-related questions like: “What kind of world do we want to live in?”, and “What kind of people do we want to be?” And more serious thinking needs to be done about how the ‘Key Competencies’ (page 12) relate to the ‘Nature of Science’ banner on each page of the science curriculum. Given some obvious resonances (both catalogues contain ‘participating and contributing’; clearly, ‘using language symbols and text’ channels specifically into ‘communicating in science’) let me propose the following alignment: KEY COMPETENCIES Capabilities for Living and Lifelong Learning, p.12

NATURE OF SCIENCE Level One – Eight Science ‘The New Zealand Curriculum’

Participating & Contributing

Participating & Contributing

Using Lang., Symbols & Text

Communicating in Science

Thinking Relating to Others Managing Self

Understanding about

Investigating in

Science

Science

Here, I am thinking of ‘Investigating in science’ not only as students carrying out traditional experiments but, rather, the very broad range of technical, mental and social processes involved in students ‘finding out’ in science. Construed this way, ‘Investigating in science’ demands broadly competent ‘thinking’, ‘relating to others’ and ‘managing self’. And, of course, this column of descriptors for students engaged in science has intriguing similarities and differences with what happens when professional scientists engage in science (‘Understanding about science’). Thought about this way, living science throughout adult life calls for a lifelong application of all of the Key Competencies learned in school.

Living science lifelong: a final word A quotation attributed to Mohandas Gandhi deserves to stand as a final word on what we might hope for in a world where school science learning and lifelong science learning would be seamless: “Be the change you want to see in the world. Live as though you were to die tomorrow. Learn as though you were to live forever.”34 For further information contact: mbarker@waikato.ac.nz

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Acknowledgements This article has grown out of an invitation to speak to the national Middle Schools conference, Hamilton, June 2009. I am grateful for that opportunity. I am also indebted to Kathy Saunders, Derek Hodson, Sally Birdsall and Chanadda Poohongthong.

Footnotes 1 I am indebted to Guy Claxton for this anecdote. 2 Ministry of Education (2007), The New Zealand Curriculum. Wellington: Learning Media, p.4. 3 Refer pp.6, 7, 8, 20, 37, 41 and 42. 4 Jonathan Osborne, speaking at the Australian Council for Educational Research Conference, Canberra, quoted in: Foster, G. (2006). Boosting science learning – What will it take? New Zealand Science Teacher, 113, 15-18. 5 Hipkins, R., Bolstad, R., & Roberts, J. (2006). Encouraging a greater range of students to stay in science: What can teachers do? New Zealand Science Teacher, 113, pp.7-11. 6 Sacks, Oliver (2001). Uncle Tungsten: Memories of a Chemical Boyhood. London: Picador. 7 Catley, Christine Cole (2006). Bright Star: Beatrice Hill Tinsley, Astronomer. Auckland: Cape Catley, p.64. 8 New Zealand Listener’ January 24, 2009, p.54. 9 This notion is certainly not all my own. It was first persuasively voiced in Millar, R., & Osborne, J. (1998) (Eds.), Beyond 2000: Science Education for Future. London: King’s College, section 5.2.1. 10 14th January 2009. 11 24th April 2009. 12 23rd January 2009. 13 Campbell, H., & Hutching, G. (2007). In search of ancient New Zealand. London: Penguin Books. 14 Yarwood, Vaughan (2009). Written in blood: How a chance discovery shook our notions of the past. New Zealand Geographic, 96 (March-April), 36-47. 15 The article cites this as 1806, with the arrival of two escaped convicts, Kathleen Hargety and Charlotte Edgar, from the New South Wales colony. 16 Jenkins, E. W. (1999). School science, citizenship and public understanding of science. International Journal of Science Education, 21(7), 703-710. 17 “Draw a geneticist” or “Draw an ecologist” are interesting variants on this task. See: Jordan, R., & Duncan, R. G. (2009). Student teachers’ images of science in ecology and genetics. Journal of Biological Education, 43(2), 62-69. 18 On my recent flight to India I was bemused by the wrapping on my serving of ‘Gourmet Ice Cream’ which promoted itself by claiming to be “created by connoisseurs not chemists.” 19 The original drawing is in colour (as is Fig. 1d). 20 Rutherford, J., & Ahlgren, A. (1990). Science for all Americans. New York: Oxford University Press, p.11. 21 These two accounts of how discovery occurs in science are often dignified by the names ‘hypothetico-deductive’ and ‘inductive’ respectively. See There is a beautifully clear explanation of this in: French, S. (2007). Science – Key Concepts in Philosophy. London: Continuum, pp.8-23. 22 Hodson, Derek (2008). Towards scientific literacy: A teachers’ guide to the history, philosophy and sociology of science. Rotterdam: Sense Publishers, p.133. 23 Barker. M. (2009). Draw a scientist. New Zealand Science Teacher, 121, 33-36. 24 New Straits Times, 14th March 2009. 25 Hamilton Press, 6th May 2009 26 Hodson, Derek (2003). Time for action. International Journal of Science Education, 25(6), 645-670. 27 Ibid. 28 Ibid. 29 Saunders, Kathy (2009). Engaging with controversial scientific issues – a professional learning programme for secondary school teachers in New Zealand. Unpublished DScEd, Curtin University of Technology, Perth, Australia. 30 Kathy was even more gratified by the way many teachers skilfully adapted the model to their own circumstances, without losing any of its intent. 31 In fact, Kathy (Kathy@waikato.ac.nz) is very keen to work alongside any teachers who would like to develop the model further with her. 32 Two excellent discussions about science education as societal participation are: Lee, S., & Roth, W.-M. (2003). Science and the “good citizen”: communitybased scientific literacy. Science, Technology and Human Values, 28, 403-424, and Roth, W.-M. (2007). Towards a dialectical notion and praxis of scientific literacy. Journal of Curriculum Studies, 39(4), 377-398. 33 See also: Barker, M. (2009). Science and the NZ curriculum. New Zealand Science Teacher, 120, 29-33. 34 Quoted in Australasian Yoga (2004). Programmes for Satyananda Yoga, p.25.


How we use contexts and the part we expect them to play in conceptual learning and in engagement with learning may need to be rethought, as Rosemary Hipkins, NZCER explains: Introduction At the Science Education Research Symposium (SERS) in November 2009, participants in the introductory panel discussion were asked to give their thoughts on the problem of student engagement in science. Issues and questions that kept popping up included the following: Is there actually a problem with keeping students engaged? How do we know? (What is our evidence?) What do we do about it? Why should we change? (What could happen if we don’t?) Anyway what do we actually mean by engagement? Discussing these issues and questions over the course of the two days of SERS brought up a range of related questions: What do we mean by the “nature of science”? What difference (if any) should it make to teaching and learning in science? What do good explanations look like? What are our expectations of what students will gain from their science learning? Listening to the debate flow back and forth, I pondered on the many ways we could answer such questions, depending on what we actually mean by terms such as engagement and explanation. In this article I’m going to use three small learning episodes, each of which is just a moment-in-time snapshot but raises an interesting learning dilemma, to try and address some of the above questions – if only by asking even more questions! I think we need much wider debate about the issues I plan to raise, so this article is just a ‘toe in the water’ of what I hope might become a debate amongst teachers, not just our small science education research community.

The ‘engaging’ nature of practical work The first incident I have chosen was documented during the Learning in Science Project (LISP) (for a discussion of the implications for teaching questioning skills see Osborne and Freyberg, 1985). I was aware that the observer in question was Ross Tasker, the first project officer for the Hamilton-based LISP team and by all accounts an extraordinarily good researcher of classroom action. Sadly Ross died in January 2009, so this is my small salute to his legacy, and that of the whole LISP team. What are you doing now? Observer: Keith: Heating this. Observer: I see, what for? Keith: Well (races off to desk on other side of room bringing back book). We are doing No. 5. What did you do before you started Observer: heating it? Keith: These ones here (points to Nos. 3 and 4 of instructions). Can you tell me what you have found Observer: out? Keith: We got this yellow stuff. Observer: Can you tell me the purpose of this activity? Keith: No…not really.

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This incident popped into my mind at SERS when someone claimed, with a certain level of passion, that practical work must be continued because it is so engaging for students (we were discussing the challenges of new lab safety regulations at the time). This has a ring of truth. All of us know how attention-grabbing practical work of a certain sort can be. The messier, noisier, more dramatic it is, the more students like it. The entertainment value is without doubt, and students often see this as science’s point of difference from other subjects. But what is the educative value of memorable practical work? Let’s assume that Keith was burning sulphur, although we can’t be sure. Burning sulphur, with its purple flame, yellow and brown mess, and distinctive smell, is certainly a memorable experience for students and it is highly likely that Keith was engaged in the moment. But what would he take away from this learning, if all he could say was that this was “number 5” of a series of steps? Who owned the sense of purpose for this activity? Fredricks, Blumenfeld, and Paris (2004) carried out a comprehensive review of research on student engagement. They identified three discrete dimensions: behavioural engagement, emotional engagement and cognitive engagement. They said that each of these exists as a continuum of possible responses from compliance in response to extrinsic factors to deep intrinsic engagement with learning for its own sake: • Students show they are behaviourally engaged by being involved and participating. This engagement is more likely to be extrinsically motivated when the student is mainly responding to input (e.g. from the teacher or a ‘fun’ activity). Behavioural signs of more intrinsic engagement include autonomous and self-regulated participation. • Evident interest and enjoyment are indicators of emotional engagement. Again this can be in response to extrinsic factors but becomes more internally motivated when the learning is valued by the student as worthwhile and/or challenging and therefore worthy of their personal effort and attention. • Cognitive engagement at a surface level occurs when students show what they have learned, when requested to do so, via a task shaped by someone else (i.e. learning as a performance). As cognitive engagement deepens, they are more likely to want to demonstrate deeper thinking and they may choose to use metacognitive strategies such as goal setting, study strategies, setting and solving own problems and challenges etc. What can we say about Keith in the light of this summary? Clearly he was behaviourally engaged, and probably emotionally also, but we could speculate that his willingness to carry out the work was purely extrinsically motivated. Cognitive engagement appears to have been minimal, if not non-existent, and his behavioural engagement did not appear to have any intrinsic dimension or he would have been able to explain what he personally was trying to achieve by the actions he was carrying out. I think this episode raises lots of questions about what engagement looks like and who it matters for. If students are active and on task, can we take this as sufficient evidence of their engagement? (It certainly makes life easier for teachers, as we all know to our cost when we don’t achieve it.) But should we be aiming for something more, and if so what and why? New Zealand Association of Science Educators

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Please don’t think I’m arguing here that students don’t need to do practical work. In another telling moment at SERS, one contributor expressed sadness that ‘inquiry learning’ is now depriving many younger students of hands-on investigations in favour of a dominant focus on information-based research. If we don’t want children’s active explorations to decline yet further, we do need to be clear about the educative purposes we have for specific practical episodes. I don’t think entertainment value, on its own, is a strong argument, especially given the complexities and uncertainties of life in the 21st century, for which we need to prepare our students as best we can. Contemporary education researchers (Gilbert, 2005; Young, 2009) say that school is where, in our complex networked society, students are most likely to be introduced in carefully structured ways to powerful types of knowledge, and how it is organised. The learning experiences we shape and support need to help students understand something bigger about the complex conditions of knowing in the world of the 21st century, with all its uncertainties and risks. With this in mind, could we introduce a ‘nature of science’ dimension to this and other similar practical activities to help students like Keith learn something meaningful about the work science does in constructing ways we see the world? What would it look like if we did add such a dimension? How would Keith know this was what he was supposed to be learning? The way we should develop the Nature of Science strand was another area of strong debate at SERS, and these are questions you might like to explore as you unpack the nature of science strand of the curriculum and its relationship to traditional science content. (See also Miles Barker’s article in this edition.)

Playing the explaining game? My next small episode comes from a research our NZCER science team undertook to inform the development of Assessment Resource Bank items related to the concept of interdependence. This episode has already been discussed elsewhere (Hipkins, Bull, and Joyce, 2008). My plan here is to reframe that earlier discussion to pose some questions about relationships between engagement and explanation – that stalwart of traditional assessment questions! Figure 1 shows how one Year 8 student completed a simple outline drawing of a stream to demonstrate his knowledge of what might be found there. (The mistake in putting the outline of a saltwater fish in the stream, which Matt has simply labelled “fish”, was ours and illustrates how much we take contextual knowledge for granted when clearly we should not.) The text is the explanation Matt wrote to accompany his drawing. He was asked to describe two direct relationships and an indirect relationship between things he identified when completing the drawing. I’ve shown this drawing and text to many groups now. Asked to identify something not quite right with Matt’s explanations many people scratch their heads. Matt certainly understands the nature of direct and indirect relationships and he has heard the message of the “Waterways”1 programme loud and clear! His conceptual knowledge, which is what we typically assess when we ask students to explain science ideas, is very good for his age. However, people with experience of freshwater fishing, or of streams more generally, quickly spot his learning challenge – knowledge of context. Trout don’t eat reeds. Eels don’t eat algae. Both are carnivores so Matt’s whole argument unravels in practice at this point. Yet he does seem 38 New Zealand Association of Science Educators

to know what trout look like because he didn’t make our mistake of adding a dorsal fin, which we didn’t know is only a feature of saltwater fish. (We certainly do now!) And, unlike many other students, Matt knew the kingfisher is a bird and correctly labelled its outline. Somehow his new conceptual knowledge and his existing contextual knowledge have not come together in a critically integrated way so that he could describe valid consequences of certain actions in the world. Matt has created a flowing lucid explanation. But who has he done this for, and why? This question circles us back to the engagement dilemma. Probably Matt has answered only because he was asked to do so. He has played the explaining game exactly as he expects that he should. Unlike Keith, there is certainly evidence that Matt is cognitively engaged, but again it seems likely this is extrinsically motivated. The explanation he has shaped was an answer to someone else’s question – it appeared to have no authentic purpose for Matt. We can possibly say that Matt would have been more likely to check his own contextual assumptions if he wanted to use his knowledge to address an issue of real concern for him. But we can’t be certain about this, having fallen into the same trap ourselves! Does any of this matter? How might Matt come to understand the business of knowledge construction in science if he is not challenged to check his ideas? We’ve been working for some time on a new Kick Start resource that explores what the Nature of Science strand of the curriculum could look like in the primary school (Bull, Joyce, Spiller, and Hipkins, in press). It includes the following quote from some well-known Canadian science educators, which could give quite a powerful steer to possible ways to reshape both Keith’s and Matt’s learning experiences so they might learn something about what makes science a specific way of explaining natural phenomena: The real job of science is to produce better explanations – and no matter how they are formulated, explanations are structures of ideas. Everything else is secondary. Myth, common sense, and imagination also produce explanations. What sets science apart is the sustained effort to improve on the available explanations; in short, science is theory building. Careful observation, methodical testing, marshalling of evidence – these are all important parts of scientific practice, but theories are the goal and the guides. (Bereiter and Scardamalia, 2009). If we believe that “the real job of science is to produce better explanations” then it does matter that Matt checks the evidence he has marshalled to support his explanation. He needs to have his confident explaining challenged in ways that help him come to understand that a very important function of investigation (both hands-on and research varieties) is to test our explanations against evidence, to see if they stand up. This is an important nature of science idea and it would have been so easy for Matt to do as a next step. With our own blooper in mind, awareness of the need to check contextual components of explanations seems to be the main issue here (for a discussion of the implications for developing question-asking skills see Joyce and Hipkins, 2009). It would certainly help if Matt had been invited to shape an explanation for a question or issue he cared deeply about (and we need to remind ourselves that this was not likely to be the case here – he was simply completing a worksheet on request). There is no doubt that intrinsically motivated (‘authentic’) learning is much more engaging for all of us. But when this idea is applied to curriculum it is often unhelpfully posed as an either/or matter: should Matt or the teacher decide what is important for him to learn?


If we accept Young’s argument that an important purpose for school is to provide students with powerful experiences and ideas to which they would not otherwise have access, (Young, 2009) then the onus is on us to convert this either/ or engagement dilemma to a both/and resolution. Matt should have opportunities to learn about the powerful concepts and skills that the adults in his education world know are centrally important to his educational growth, and to his ability to create cogent explanations for what he sees around him in the world (see Barker this edition). But he should also experience learning that gives him more control over directions and pace – that is, he should experience chances to learn about, and shape explanations for, things that matter to him. Finding a way to balance both is a tightrope all of us need to learn to walk.

Engaging contexts? My final anecdote brings together elements of the previous two. By now Keith’s and Matt’s stories have come to stand for something more than the minor incident each represented in the reality of the moment. Keith, obliging if not able to explain when challenged, and Matt who is both obliging and a confident explainer come now to represent that body of ‘good’ students whom we expect to do what we ask and to do it well. They play the school game and “get on”. Whether what they actually learn has real value for them is a moot question, as we have seen, but let’s set that reservation aside and ponder this next episode. We (the NZCER science team) have been working on developing a new assessment tool to help teachers determine next learning steps in certain areas of the nature of science related to the key competency thinking. As I have already noted, science centrally involves checking 1

An educational initiative of the New Zealand Royal Society, in conjunction with regional councils (www.royalsociety.org.nz)

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Figure 1: The algae is eaten by the eel. The rainbow trout feeds on the reeds. Companies by water drop oil waste into waterways therefore killing the trout and other fish. The reeds will overgrow, algae will spread and this will cause blockage of drains.

our assumptions and explanations against the evidence of the real world. We have created a nationally benchmarked assessment tool called Thinking with Evidence that is designed to give teachers of Years 7-10 students formative assessment information concerning how well their students can do this already – and where their next learning steps might be. The 160 items across the four tests are all set in contexts that we chose because we thought they would be interesting for students and would help them engage with the questions, so that they would take the opportunity to show us what they could do. As part of the development process around 8000 students from 62 different schools took part in the trials. My final anecdote comes from feedback comments made by teachers whose classes participated. A number of teachers commented on how engaged some students had been, especially those they had not expected would try so hard. Feedback from these teachers often expressed concerns about the reading level of the information in the tests, yet the statistical analysis of all the responses showed us that students did rather better than anticipated across the board. One teacher commented on a group of students (mainly boys) who had achieved at a much higher level than their reading track record would have predicted. What’s going on here? We’re not sure yet and we want to do more work to answer our own question. We think that the types of questions we asked tapped into a different way for students to use their knowledge and skills and clearly some of them rose to that challenge, when their past track record might have been predicted them to be disengaged. (We also note in passing that, like both Matt and Keith, all the trial students were answering questions that someone else asked them to address, not working to their own agenda!) We don’t know where the balance lies between tapping into a different type of learning skill and being more engaged to begin with, but we suspect there are strong cross-links between these. Research predicts that seeing links between what is taught and these types of real issues and concerns is key to ongoing student engagement (for a summary see Bolstad and Hipkins, 2008). What we can say for certain is that the contexts in the questions we shaped were chosen for their links to real word issues and concerns. These were not necessarily contexts students would know about in advance, but they all raised issues and questions that matter for more than just providing a chance to assess learning. Examples included whether or not New Zealand should introduce dung beetles as part of our efforts to clean up farming practices, the bodily challenges of surviving in space, and how to avoid getting dengue fever if you visit affected areas of the Pacific. Perhaps the most important point to make is that the contexts were integral to the item sets. Without them, the questions we shaped simply could not have been asked. This stands in contrast to what I think about as the ‘candy wrapping’ way of using contexts to support learning – the intended learning is essentially unchanged but the context wraps around the outside to provide an attractive veneer of ‘relevance’. Many of us tried this out when the 1993 curriculum was introduced. It was a lot of work and sometimes confused students about what was important (Hipkins and Arcus, 1997). I now think we need to rethink how we use contexts and the part we expect them to play in conceptual learning and in engagement with learning. That’s another question you might like to discuss as part of your ongoing curriculum planning and debates. For further information contact:

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References Bereiter, C., & Scardamalia, M. (2009). Teaching how science really works. Education Canada, 14-17. Bolstad, R., & Hipkins, R. (2008). Seeing yourself in science: The importance of the middle school years. Wellington: New Zealand Council for Educational Research. http://www.nzcer.org.nz/default.php?cpath=139_133&products_ id=2261 Bull, A., Joyce, C., Spiller, L., & Hipkins, R. (in press). Kickstarting the Nature of Science. Wellington: New Zealand Council for Educational Research. Fredricks, J., Blumenfeld, P., & Paris, A. (2004). School engagement: Potential of the concept, state of the evidence. Review of Educational Research, 74(1), 59-109. Gilbert, J. (2005). Catching the Knowledge Wave? The Knowledge Society and the future of education. Wellington: NZCER Press.

Hipkins, R., & Arcus, C. (1997). Teaching science in context: Challenges and choices. In B. Bell & R. Baker (Eds.), Developing the Science Curriculum in Aotearoa New Zealand. Auckland: Addison Wesly Longman. Hipkins, R., Bull, A., & Joyce, C. (2008). The interplay of context and concepts in primary school children’s systems thinking. Journal of Biological Education, 42(2), 73-77. Joyce, C., & Hipkins, R. (2009). Assessment dilemmas when “21st century” learning approaches shift students into unfamiliar terrain. http://www.iaea2009.com/ abstract/34.asp. Osborne, R., & Freyberg, P. (1985). Learning in Science: The implications of children’s science. Auckland: Heinemann. Young, M. (2009). What are schools for? In H. Daniels,H. Lauder & J. Porter (Eds.), Knowledge, Values and Educational Policy (pp. 10-18). London: Routledge.

inaugural Freemasons’ Reel Science Film Festival Years 11 to 13 secondary school students are invited to make a two-minute film about an interesting aspect of science. The Freemasons’ Reel Science Film Festival is a new competition aimed to get all Years 11 to 13 students involved and excited about science! Unsure how to make a film? During March, Masters’ students from Otago University’s Centre for Science Communication will be running one-hour workshops at venues throughout New Zealand. The workshops will provide budding filmmakers (and their teachers) with information about how to make a great short film using very basic equipment such as their cell phones. Students will also be given useful technical tips on editing, lighting and sound techniques. Judged on their two-minute film, winning film makers will be invited to spend five days in Dunedin where they will work with professional film makers and scientists to make a high quality film on a given science topic. The best judged film will win the Freemasons’ Reel Science Film Festival.

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For further information visit: www.reelsciencefilm.org.nz or email: debbie.woodhall@royalsociety.org.nz

continued from page 42 commitments stand as conditions for the possibility of that cultural form, and to wrap into philosophy or science the task of evidencing or otherwise warranting those commitments will on that account fail. However strongly disposed I am, given my culture, to think that nature completes my situation, still I will struggle to fit meaning itself or mindedness or ethics or mathematics, or anything of which the original touch of infinity is defining, quite under its fold. Naturalising intentionality, naturalizing ethics, naturalising mathematics, all to me seem fraught philosophical projects, however fully the impulses resonate with me that draw other philosophers into such pursuits. Yet the agony when naturalism is tried, but founders, is to me no inducement to have truck with the supernatural. Rather, I see the naturalising urge as an original instability of my culture (and yet a creative one). Some aspects of the vaulting investment in reason itself are much like faith, and God as metaphor is even helpful in some degree as explanation of their directedness. Yet the condition in question, being thoroughly cultural, seems to me not in the end to tell about the world as it is in itself. It tells at most about us, we Westerners, who are in the circumstance of philosophy, and science.

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Newton’s consideration of time seems to me on this account not the best philosophy but nonetheless a giant step towards it. As a philosopher he examines honestly and fairly the conceptual presuppositions concerning time of the empirically learned, robustly evidenced laws of motion that he himself enunciated. It is faithful to that science to defend as he does a transcendental (or ‘absolute’) conception of time, yet Newton steps beyond what is necessary, or scientifically warranted, to fashion his high transcendentalism as directed to God. A more critical perspective is possible, by which Kant would help issue in the Enlightenment. Still, of the four alternatives mentioned at the beginning, the assessment of Newton’s consideration that time is absolute must be that this represented good science and good philosophy. All very Western in the bearings which define it, Newton’s consideration that time is absolute represents in its day high sensitivity to conditions for the possibility of physics as exact science. For further information contact: philip.catton@canterbury.ac.nz


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If we understand Newton’s determination to think time absolute then we are well on the path to understanding what is “Western” about Western science. (Note: I will address, ‘why “Western” science?’ in a subsequent issue of the NZST.) Newton has deep reasons to make out time as absolute, and they are connected to his thinking that physics can be an exact science. By considering Newton’s views about absolute time, we can glimpse the defining difference of the West to the East (the latter having produced a lot of wisdom, but not burgeoning exact science). The West lays upon our shoulders the search for ‘The View from Nowhere’. High literal-mindedness is the essence of this search. Western rationalism is of a pitch or intensity that Eastern rationalism is not. Some considerable commitment to reason is needed before you get (East or West) traditions of deep reflection and theoretical rumination; but in the West, the commitment to reason runs to such an extreme as to have been (originally) theological. The West has its extraordinary God; Eastern thoughtforms, such as Confucianism and Buddhism, are, by contrast, godless. When in the Scholium to the Definitions in his Principia Newton produces his discussion of ‘absolute’ versus ‘relative’ time, he provides us with reasons to be ideally literal minded about temporal durations. Time is not to be reckoned with in terms of human conventions, Newton determines. (And yet this reflects in its way something singular about the ambient cultural form.) Any material process to which we might look practically as a clock, if adopted as our standard for duration, would lead us to conclude inconveniently that order everywhere is subtly defiled.

Duration – a rationalistic ideal To explain, let us begin at the beginning. As events unfold, they do so over a certain interval of time. The first and last events in any such series are separated by a certain duration. We who possess Western philosophy and thus have literal minds in far accentuated degree expect that any such duration is somehow universally significant. Our thinking concerning duration is connected with an exacting, rationalistic ideal. For we are disposed to seek some practical, material measure for duration, the adoption of which as the standard for duration is consistent with the following universal understanding: that every process whatsoever should be found, relatively to that standard of duration, to speed up or slow down only ever for a reason, a reason that can be found within material conditions. Otherwise we are disposed to think that the chosen material measure for duration is faulty and that we therefore need to seek a better one. Thus, for example, when the Romans adopted as their fundamental measure of duration the time from sunrise to sunset (one twelfth of which was called a ‘daylight hour’),

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they were not at first significantly inconvenienced by this choice, living at the latitude of Rome. But at the latitude of Hadrian’s Wall in Britain, the Romans had to concede that soldiers marched a great deal further per daylight hour in the summer than in the winter, with no sufficient material reason why this was so. Similarly, with a ‘night hour’ (one twelfth of the time from sunset to sunrise), candles were found to burn a whole lot faster per night hour in the winter than in the summer, with no sufficient material reason why this was so. So those were reasons to seek a better standard of duration. Romans are less noted than, say, Greeks for their dedication to inquiry, but it was within the reach of what they did for them to discover the imperfection of their own official measure of duration. To be on the lookout at all for such a measure was to be really very concertedly rationalistic. Rationalism in its extreme Western guise enforces upon time an outright ideality. An ideal clock would measure perfectly a universal time, so that by its lights all material processes whatsoever would only ever speed up or slow down for a reason that could be discovered in those material processes themselves. The rationalistic orientation to such an ideal presupposes that material processes all are exquisitely well attuned to one another, so that they are all coherently embraced within a single truly universal temporal order. To frame in the first place such a conception of time is to embrace the concept of nature or the natural, or thus of cosmos, that is, of an All that is at the same time a unitary Order. We know that only special cultures possess the concept thus of nature or the natural; only in the context of philosophy is such a concept even possible. We next explore how the philosophy of the West better nurtures than the philosophy of the East the orientation of mind that can give us physics as an exact science.

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What explains Sir Isaac Newton’s readiness to contend that time is absolute? What did he mean by this contention? Was this bad science, good philosophy; good science, bad philosophy; bad science, bad philosophy; or, good science, good philosophy? Philip Catton, who helps co-ordinate the programme in History and Philosophy of Science (HAPS) at the University of Canterbury, answers these questions:

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Astronomy and duration Astronomy provides many different candidate measures for duration, but also discovers to us the disturbing fact that none of these measures coheres fully with any of the others. For example, astronomy discovers to us that a (24-hour) solar day should not be measured as the time from sunrise to sunrise because that interval is very variable across the seasons. It is considerably better to measure such a day as the time from the Sun’s crossing the meridian (the line in the sky through zenith that runs directly north-to-south) to its next crossing the meridian. Yet even this interval is, to a certain extent, variable across the seasons. Astronomy discovers to us this variability partly by comparing the solar day to the sidereal day − a sidereal day being the time it takes a star, such as Sirius, to run about from meridian to meridian. Because of the Sun’s daily progression along the zodiac, the two measures differ in length by an amount (of roughly four minutes) that, as the Babylonians discovered, itself varies seasonally, in a way that is necessitated by the fact that the number of days (of either sort) from vernal equinox (when the Sun is on one side of the zodiac) to autumnal equinox (when the Sun is on diametrically the opposite side) differs considerably from the number of days from autumnal equinox to vernal equinox. In the face of this astronomical fact, astronomers long ago adopted the duration that a solar day averages relatively New Zealand Association of Science Educators

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to the sidereal day, itself regarded as constant, as defining a 24-hour period. Notice how very much concerning the astronomical motions needed to be learned before this measure could even be defined, let alone adopted. Because of all the uses of measurement in the acquisition of those astronomical understandings, the work in question illustrates quite handsomely what I choose to call ‘the pursuit of a measured understanding’. This pursuit concerning time encountered an obstacle which I shall next discuss, an obstacle that people could not pass until the ignition of physics as a science in Newton’s hands roughly 350 years ago.

Astronomy’s search for understanding The imperfections as a standard of duration of the 24-hour measure of duration that is referenced to a sidereal day are so slight that people could not possibly detect them in their experience say of humans marching or of candles burning. But looking to other astronomical phenomena, the constancy or otherwise of this measure was moot. Measures of time by the moon’s motion are various, and each varies appreciably relatively to one another and to the standardised 24-hour day. Thus we may consider the time from full moon to the next full moon, or the time it takes for the moon to run once around the zodiac, or the time it takes for the moon to move in effect from one perigee (point of closest approach to the Earth) to the next (which we remark by the variation in how angularly fast the moon moves per day against the background of the stars). These measures are notably inconstant both relatively to one another and to the standardised 24-hour day. There are complexities in what a ‘year’ is also – is it the time for the Sun to progress once around the zodiac, or is it the time from, say, vernal equinox to the next vernal equinox? The choice of neither measure as a standard for duration turns out to be fully coherent with the other, nor either with the choice of days or months (however defined) as such a standard. Ultimately astronomers realised that they needed a theory of the physics that underlies the motion of the heavenly bodies. In its light alone could they hope to determine which astronomical motions are subject to variation and are on that account inadequate as the standard for temporal duration. The figure who first provided a thoroughgoing physics of the astronomical system was Newton. Newton articulated, defended and ably employed the three laws of motion (namely, the law of inertia, the law that F = ma, and the law of the equality of action and reaction) plus the law of universal gravitation. These laws proved to be very telling about the motions of the heavenly bodies. In particular, they accounted not only for why Kepler’s laws about the motion of the heavenly bodies are approximately true, but they also accounted in amazingly accurate quantitative detail for some tiny departures that there are from Keplerian motions in the true motions of the heavenly bodies. Indeed by assuming the Keplerian motions to be approximately true, and by assuming also both the three laws of motion and that Euclidean geometry holds at the scale of the heavenly motions, Newton actually outright deduced the form of the law of gravitation. So in light of this impressive, impressively cogently argued physical knowledge, was Newton in a position to point at last to an ideal yet material measure of time? That is, could Newton point to a material measure of time, the adoption of which as a standard for duration would mean that every other process in nature only ever speed up or slow down for a reason? The fact is that Newton did not. Moreover, he knew that he could not. For, his three laws of motion,

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together with the law of universal gravitation, imply that there is no material process whatsoever that runs thus absolutely smoothly. For example, the sidereal day, although quite highly constant, is bound not to be absolutely constant, because it will be subject to variation owing to tidal friction upon the Earth from the moon, the sun and other bodies. The sidereal year will be affected by the tidal influence on the Earth-Sun system of other bodies, chiefly Jupiter. And so on. Newton realised therefore, that it would be disastrous for our theorising if we were to fix the meaning of temporal duration by choosing an actual material process and stipulating that it shall serve as our standard for duration. Newton contended that the adoption of any such ‘sensible measure’ as a standard for duration would ‘defile the purity’ of the known laws of motion, that is, of the laws that reveal to us the fundamental dynamic of the system of matter. In other words, if you adopt any actual material process as the standard for duration, then you cannot contend that Newton’s laws hold perfectly true. For if you adopt any actual material process as the standard for duration then you would have to say that other processes speed up and slow down for no material reason. This would make a nonsense of Newton’s dynamical laws. Yet Newton was disposed to think that it is at least possibly the case that his laws of motion are literally true. If it is at least possibly the case that they are literally true, then we must not rule out that they are by wantonly adopting some sensible measure of duration as our standard of time. Thus Newton cleaved to the rationalist ideal concerning time even though no material measure could possibly exist for duration. Newton insisted that relatively to true time all material processes whatsoever only ever speed up or slow down for a reason, a reason that can be discovered in the material conditions themselves. This insistence emblematises his literal-mindedness, among other things about his own principles of physics.

Reason-in-the-world In order for there to be temporal duration in such literal respects, every last process must be exquisitely rationally harmonized with all the other processes; everything must unfold as it does for reasons, reasons across which there is likewise harmony or coherence. We are a hair’s breadth from theism in the making of such a vaulting assumption. Cross, moreover, anywhere in the West, a philosopher or a scientist or a mathematician, on the question whether literal-mindedness is itself an acceptable commitment, and in the glowering agony of their response, you will see how you palpably do insult to an article of faith. These are the reasons why burgeoning theoretical science is ‘Western’. It is hubris perhaps for the West so far originally to have wrapped the infinite (God) into its cultural fold, that we should become with Newton literal minded in ‘absolute’ degree about temporal duration. But we do at least have burgeoning exact science to show for it. I am myself disposed to view our vaulting commitment to reason-in-the-world ‘critically’ in Immanuel Kant’s sense of that word. The God concept may, to deep-going degree, be regulative of Western culture including Western philosophy and science, but I frame no belief with it on that account of anything beyond the natural. Only on account of my culture’s rationalism is the very concept of nature or the natural fully available to me, so that in its very culturally emergent quality, the concept of nature will not be able to cover quite everything. Some

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what’s new on the shelves? New titles appear on National Library shelves on a regular basis as ordering is done on a monthly cycle. Staff in the Schools Collection have regular meetings at which subject needs are reported. These may be related to requests from teachers that haven’t been adequately resourced, material that is getting dated and needs replacement, or new emerging topics. Reference librarian/selectors source and order relevant material in each curriculum area. It is a challenging task trying to keep ahead of the needs of schools and their changing curricula. Topics with a New Zealand flavour, and/or at a school level, are often difficult to resource. However, our selectors have access to numerous databases, review journals and publisher catalogues. Suggestions and recommendations from schools to the selection process are also welcome (email me at: melva.jones@natlib.govt.nz). Teachers need to be aware that something that is unavailable for their studies on one occasion may well be available next time they visit the topic. Here is a sample of new titles that we acquired in 2009. Atmosphere (The habitable planet) (DVD – Marcom) Aimed at a secondary audience, this DVD explains the atmosphere as a critical system that helps to regulate Earth’s climate and distribute heat around the globe. Includes descriptions of: climate zones, weather patterns, climate change and global warming.

Seven Natural Wonders of the Arctic, Antarctica, and the Oceans by Michael and Mary Woods (Twenty-first Century Books, 2009) An interesting look at seven wonders of the natural world including: the Mariana Trench, The Gulf Stream, Hydrothermal Vents, The Great Barrier Reef, Bay of Fundy, and the North and South Poles. It includes facts, historical information and photographs.

Which Native Tree?: New Ecology Edition by Andrew Crowe (Penguin, 2009) This NZ title in a series, has been re-written with more detail and more colour. Information on each entry is split into three sections with details on cultural uses, growing tips and general data (such as insects/birds associated with the particular plant). Some pages have small images of birds, insects or other wildlife that have a relationship with the tree.

resources

by Melva Jones

Climate Change by Eve Hartman, Wendy Meshbesher (Raintree, 2010) Aimed at a younger audience, and could be used to provide a simple overview. Chapters include: Evidence of change, The greenhouse effect, The carbon cycle, and Adapting to climate change. Godwits: Long-haul champions by Keith Woodley (Penguin, 2009) Keith Woodley, manager of the Miranda Shorebird Centre in NZ, traces the fascinating journey of the godwits as they fly the huge distances from NZ to their breeding grounds in Alaska. Woodley documents the changes the birds undergo, and the innate skills they use to navigate across such huge distances. Photographs are liberally scattered throughout the book. A great read for senior students or teachers. Our Changing Planet: The View from Space (Cambridge University Press, 2007) Written for adults (but useful for senior secondary students) this book is a compilation of amazing photos, satellite and remote sensing images and essays which give a compelling history of Earth changes and the impact human activity is having on the land, the seas and the atmosphere. Planetary Motion by P.Andrew Karam (Chelsea House, 2009) The scientific discoveries of early scientists including Kepler, Hally, and Newton provide a foundation for modern scientists to build on. This book, one of the series ‘Science Foundations’, shows how scientists further extend our understanding of the Universe as they work to discover new planets and explore the possibility of the existence of others similar to our Earth. Feel the G’s: The Science of Gravity and G-Forces by Suzanne Slade (Compass Point, 2009) An interesting book which explains the concept of g-forces through real life examples including: roller coaster rides, bobsledding, space travel and flying in a fighter jet. How Does it Happen?- a series of books (Raintree, 2010) How Does An Earthquake Become A Tsunami? How Does A Volcano Become An Island? (both by Linda Tagliaferro) and How Does a Cloud Become a Thunderstorm? (Mike Graf ) are part of a great new series suitable for younger or reluctant readers. Each title explores the causes and effects that shape the world, using simple language, photographs and clear, easy to follow diagrams. New Zealand Association of Science Educators

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chemistry news by Suzanne Boniface, Chair of NZASE Standing Committee (Chemistry) Communicating Chemistry − formulae and vocabulary? It’s easy to assume that communicating chemistry is all about using the right vocabulary, symbols, and equations. But chemistry is an ‘imagined’ science, and understanding chemistry requires a learner to develop the ability to integrate their observations with the imagined world of atoms, ions and molecules. The causes of observable changes of matter can only be understood at the particulate, sub-microscopic level. An experienced chemist moves easily between the observable macroscopic behaviour − the symbolic representations − and the sub-microscopic world. For learners, misconceptions often arise from an inability to visualise (or imagine) what it happening at the sub-microscopic level.1 Bucat and Mocerino (2008) recommend an effective way to help students visualise what is happening by the careful use of language to distinguish the macro- and sub-micro levels. Scientists, textbook writers, and teachers are all guilty of using loose language that blurs, rather than sharpens, the distinction between these two levels. For example, C6H14 is not hexane, although the composition of hexane can be represented as C6H14; nylon is not a long molecule although its molecules are long; in a Daniell cell zinc does not lose electrons but zinc atoms do; and hydrogen is not the smallest element but it is the element with the smallest atoms. Taking the trouble to be more precise, even though to do so means using more words, will help encourage students’ awareness of the distinction between the two levels, and will go a long way to reducing the confusion and misconceptions that develop in students’ minds. Understanding the conventions and styles of molecular representations is also important if students are to visualise the spatial and structural features of a molecule and consider the reactivity implications of these features. Chemists do not make things easy for a novice; molecules of a substance can be represented in a variety of ways to illustrate particular features, and to the novice these can seem to be different structures (Bucat and Mocerino, 2008). A molecule of propane could be represented in a number of ways (see Figure 1).

Figure 1: Molecular representations of propane. To read any of these structural representations one needs to understand the conventions. A chemist, who has absorbed these conventions, will subconsciously interpret all these diagrams as being equivalent, but the same cannot be assumed for students. Teaching the conventions of molecular representations is an important part of helping to develop students’ visualisation skills in chemistry. Ultimately 1

Bucat, R., & Mocerino M. (2008) Learning at the Sub–micro Level: Structural Representations. In J.K. Gilbert & D. Treagust (Ed.), Multiple Representations in Chemical Education, Springer.

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we want them to be able to translate the representation of a given macro phenomenon to, and between, the sub-micro and symbolic types of representations. For a good understanding of chemistry it is critical that students are able to visualise the sub-microscopic world. Teachers and chemists can aid students’ understanding through using precise language to distinguish the macro from the sub-microscopic levels. Instilling an understanding of the conventions of representation will also remove some of the confusion for students.

News from Carbon Chemistry − Graphene Graphite and diamond are well-known allotropes of carbon. The striking differences in their physical properties provide an excellent illustration of the dependence of the properties of a substance on its structure and bonding at the molecular level. In the mid–1980s, new forms of carbon (the fullerenes), were discovered. The most stable of these, C60, is sometimes known as a ‘buckyball’ as its structure is made up of 20 hexagons and 12 pentagons, resembling a soccer ball. In 1991, extremely thin graphite-like tubes, with fullerenetype ends, were discovered (see NZST Issue 120 - Ed). They are called nanotubes because they have a diameter of about 1 nanometre. Along their length they are stronger than steel and conduct electricity. For templates to make buckyballs and information about buckyballs and nanotubes visit: www.nottingham.ac.uk/nanocarbon.

(a)

(b)

Figure 2: (a): C60 or a ‘buckyball’ and (b): Carbon nanotubes – rolled-up sheets of graphite capped with half a bucky–ball. In 2004 , it was discovered that single layers of hexagonal rings of carbon, such as is found in a single layer of graphite, could exist by themselves. Known as graphene, this material has a breaking strength 200 times greater than steel, making it the strongest substance ever tested. It is electrically and thermally conducting, similar to carbon nanotubes. This is not surprising given that a graphene sheet is basically an unrolled carbon nanotube (see Figure 3). Electrons pass through graphene with less resistance than through silicon, which makes it a potential replacement for silicon in microchip electronics. However, before graphene can be widely used, the cost of mass-producing it will need to be lowered. Initially, small pieces of graphene were prepared using sticky tape. Flecks of graphite were stuck to sticky tape; the sticky sides were folded against the crystals and pulled apart, cleaving the flakes in two. Repeating this

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more ideas for physics demonstrations byPaulKing

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physics

Rocket and Helicopter Balloons

Missing Mass

Francis Bryden (St Cuthbert’s) enthused us at Physicos ‘09 about rocket balloons and balloon helicopters. Both of these remarkable tools/toys are available from: www. profbunsen.com.au for only A$2.10 for a helicopter (endlessly reusable with care) and A$4.50 for a 12 pack of rocket balloons (they do eventually burst). Try these: Rocket balloons: The rocket balloons can be used to practise measuring and recording basic information such as time of flight, height reached, range achieved etc. Although I am sure there will be plenty of ‘noisy’ discussion about the impacts of uncontrolled variables such as the wind! The balloons produce a delightfully disgusting noise and the students will need to discover for themselves as to how this noise is made, and in the process will be prepared for an easy understanding of any sound wave content of their courses. Try shoving a short length of plastic tube into the rubber neck of the balloon to get rid of most of the sound and less randomness in the direction of flight. Balloon helicopter: The balloon helicopter is even more useful than the rocket balloons. Stored elastic energy is converted into rotational kinetic energy, which in turn is converted into gravitational potential energy. Try covering the whistle with a tiny piece of tape and the helicopter flies higher, gaining GPE instead of losing sound energy. Rocket and helicopter balloons: With your Year 13s try attaching a rocket balloon to a helicopter. The long thin rocket has a smaller moment of inertia than the standard fat party balloon. How does it affect the flight?

Also at Physicos ‘09 Gorazd Planinsic, Associate Professor at the University of Ljubljana, Slovenia, weighed a balloon, inflated it with a known mass of CO2 (delivered by a capsule held in a compressed air bicycle pump) and showed that: Weight of balloon + weight of gas =/ weight of balloon with gas inside “Experiences from everyday situations tell us that mass (obtained by measuring the weight) is an additive quantity. If I step on the scales and hold a chair in my hand, the scales will show the reading which is equal to the sum of the weights of the chair and me if measured separately. The following experiment shows an apparent paradox and sets a scene for lively discussion and exploration.” His experiment can be downloaded at: http://www.if.uj.edu. pl/Foton/100/pdf/gorazd-planinsic.pdf ( or go to: http:// tinyurl.com/y9yv6jf ) and will be invaluable for the study of buoyancy and the distinction between mass and weight.

Electricity and Magnetism Lectures We all use balloons to illustrate charge separation, but it had not occurred to me that water bomb balloons might be so much more effective than standard sized ones. Walter Lewin from MIT demonstrates a heap of simple electrostatic demonstrations in a video lecture that can be down loaded for free from: http://ocw.mit.edu/OcwWeb/ Physics/8-02Electricity-and-MagnetismSpring2002/ VideoAndCaptions/detail/embed01.htm (or go to: http://tinyurl.com/c3d9lb) Lewin’s lectures will give teachers some great ideas for putting on a show for our students, and clear any misunderstandings we may have about this topic.

continued from Chemistry page 44 process prepared thinner and thinner slices until atom– thick sheets were formed. Now much research is going into trying to find a low-cost method of making sheets of graphene.

Graphene-based electronic components conduct electrical current even when they are flexed and stretched. Manufacturers are working to incorporate this property into advanced wearable and flexible personal electronic systems.

PD opportunities in 2010

Figure 3: Graphene – a single layer of carbon atoms arranged in an hexagonal pattern.

NZIC has invited Rick Moog, Franklin and Marshall College, USA and Peter Hollamby, University of Cardiff, Wales to present workshops to chemistry teachers. These workshops will be held in various locations throughout NZ. Free POGIL workshops: Rick Moog will be running POGIL three workshops in the latter half of Term 1 in Auckland (29 March), Wellington (31 March) and Christchurch (30 March). Improving Teaching and Learning using ICT: a ‘DIY’ approach: Peter Hollamby, who presented at ChemEd ‘09, will be running one-day workshops in: Auckland, Hamilton, Tauranga, Palmerston North, Wellington, Christchurch and Dunedin during the first 4 weeks of Term 2. The cost will be $125. For more information about these workshops and/or other chemistry matters please contact: Suzanne.Boniface@vuw.ac.nz New Zealand Association of Science Educators

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active learning Key messages from the NZASE 2009 Primary Science Conferences: “Active Learning: Science talk from the classroom to the dinner table” have been distilled into a series of questions that can be used by teachers to inform the teaching and learning of science in their classrooms, as Ian Milne, Conference Director, explains: A feature of this year’s conferences was the final forum where the teachers attending were challenged to formally identify the issues and challenges they had faced prior to coming to the conference and what actions they may take to enhance their children’s future learning in science as a result of their conference experiences. A summary of the key messages and issues presented at the forums, and any additional issues raised by the teachers during the forum evaluation process of each conference has been compiled below. The challenges and issues have been presented as a series of questions that could be used by teachers as they reflect on their classroom practices when involved in science education activities. The answer the teachers provide should assist them to identify issues and aspects of their teaching practices they may need to adjust.

When working with students, science teachers need to ask themselves: • Have they made the science explicit for their children; do their children know what makes the activity science? • Are they focusing on children doing science rather than just learning science? • Does the teacher belong to a supportive network where they can share ideas and talk about their (and their children’s) learning experiences? • Are they providing exploratory activities that generate a sense of wow and wonder that assist their children to develop a sense of engagement with the further learning that leads to the development of explanations and understanding? • During the science activity, how often do they apply active assessment, plus active teaching and learning strategies to their interactions with their children? • How do they use student talk within their classroom to promote engagement and learning in science in their classroom? • How often do they select student relevant contexts for science exploration and study? • How could they use a Science or Wonder Centre in their classroom as a focus for promoting children’s learning in science? The teachers attending the Dunedin and Christchurch Conferences suggested the following aspects that needed to be considered as well. Many of their suggestions are similar to, or are embedded in, the summary statements identified by the director above. Dunedin: Teachers talking to each other; having suitable equipment and resources carefully stored; role of questioning; importance of engagement; listening to the pupils’ ideas; variety of approaches to teaching science; role of thinking valuing children’s thinking; linking school science to science and scientists and to the real world. Christchurch: Teachers need to be passionate and have the wow factor; science must move from curiosity 46 New Zealand Association of Science Educators

to comprehension; create and use links between school and local science community; relating to reality, not just “doing it”; start out a lesson or activity with a question or context that makes the students want to find out; real world links; just focus on emphasis rather than complex assessment; cluster and local TRCC courses are a wonderful opportunity to network and share; need to find ways to sell science to school management who don’t see it as equal to literacy and numeracy; and science should be a higher priority in schools.

Inquiry focused learning The teachers want their science education programmes to have learning activities that foster the children’s involvement in doing and learning about science, and using relevant contexts that generate authentic inquiry. Inquiry focused learning approaches have become very popular within New Zealand primary schools’ curriculums. Inquiry and evidence, along with engagement, are key issues that are currently the focus of much attention in science education. Harlen (2007) provides a useful set of criteria for teachers evaluating whether they are using teaching strategies that truly value contextual relevant active inquiry learning in primary science. Clear links can be made between the focus aspects from the forum and the strategies and activities inherent in Harlen’s questions. The answers to the questions below could be very useful starting points for teachers involved in seeking to evaluate and improve their teaching and learning practices in science.

Does the teacher: • explain the aims of a lesson in ways appropriate to the children? • gather children’s ideas or experiences relevant to the topic under study? • use open questions and allow time for children to answer? • listen carefully to children’s answers? • encourage children to ask questions? • encourage children to talk to, and listen to, each other about their work? • arrange for children to work and discuss in groups? • expect children to use evidence to support their conclusions? • provide activities where children can look for relationships and patterns? • ask children to predict, test predictions and generate conclusions? • discuss alternative explanations and generalisations? • help children to apply what they learn in science to everyday experience? • help children to make records in notebooks or worksheets to help their learning? • discuss with children the quality of work expected? • encourage children to assess their own work, identifying what has been done well as well as what could be improved? • provide non-judgemental feedback that helps children know how to move forward? For further information about ideas expressed above, and other issues relating to primary science education, please contact: i.milne@auckland.ac.nz


The Planet Earth and Beyond curriculum changes can be a challenge to teachers and learners unfamiliar with the Earth Systems Science emphasis. The following are some useful ideas for Years 7 to 10. Also, visit the NZASE website SCIPEB page for PDFs of previous NZST reports. And did you know about the ‘The rare Earth hypothesis’? Visit: http://tinyurl. com/2ofmz7.

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Earth – the lucky planet byJennyPollock

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1. Distance from the sun Earth is the only planet in the Solar System known to have life, especially complex life, see: http://tinyurl.com/ycjq4yj Exercises: http://www.ucar.edu/learn/1_1_2_1t.htm

2. The Earth’s tilt and the seasons Seasons result from two important things: the revolution of Earth around the Sun each year; and the tilt of the Earth’s axis, which is 23.5 degrees. Note: the Earth always tilts the same way all the way around the sun. http://tinyurl.com/y932e5g A good worksheet on sun angles: http://tinyurl.com/ycmgfsk Activities on sun angles: http://tinyurl.com/y8fwhoh How to make a sundial: http://tinyurl.com/ycjhu7s, and http://tinyurl.com/yc3hok5 Activities about the seasons: http://tinyurl.com/yexsksn

3. The surprising effect of the Moon Earth is the only planet in our Solar System with a large moon compared to the size of the planet it orbits. This stops the Earth from wobbling on its axis. The Moon orbiting the Earth keeps the 23.5 degrees tilt of the Earth steady. A stable tilt means predictable weather patterns and seasons.

4. The effect of a big neighbour – Jupiter Jupiter is much larger than Earth and has a much greater gravity. It is possible that the gravity of Jupiter attracts meteors or comets which may shield Earth from being hit by them. Such collisions would devastate all living organisms, not just humans. In 1994 a comet, called Shoemaker-Levy 9, came too close to Jupiter. Jupiter’s gravity caused the comet to break up into many pieces which crashed into the surface of the planet leaving huge scars. Animations of this event: http://tinyurl.com/ye4xj48 and http://tinyurl.com/ybxov2d Animations about death of the dinosaurs: http://tinyurl.com/ye43ad5. (Although they are worth checking first as some are quite scary.) Article about ‘What killed the dinosaurs’, useful for a class debate: http://tinyurl.com/ycudv5m

5. Our atmosphere − Greenhouse gases Earth is the right size to have enough gravity to hold an invisible atmosphere around the planet. The atmosphere contains gases essential to life, such as oxygen, plus gases called greenhouse gases which act like an invisible blanket that traps just enough energy, in a similar way that glass traps heat inside a greenhouse. Without them the Earth’s average surface temperature would be a cold -18°C rather than the pleasant 15°C. Animation carbon dioxide absorption: http://www.ucar.edu/learn/1_3_1.htm Animation of how greenhouses work to retain heat: http://www.ucar.edu/learn/1_3_2_12t.htm Animation heat-trapping ability of a greenhouse: http://www.ucar.edu/learn/1_3_2_13t.htm

See: http://tinyurl.com/yae5uac Video hot air rising at the equator and cold air flows in to replace: http://tinyurl.com/ybyxjuk

7. The role of the oceans The oceans have two important roles in helping keep a stable climate on Earth: (1) The great ocean currents play a very important part in maintaining a steady climate system. They transport huge quantities of heat in enormous volumes of water. Video link of ocean circulation, especially the thermohaline: http://www.watchknow.org/Video. aspx?VideoID=176. Plus: http://tinyurl.com/y8ctl65 and http://tinyurl.com/yedvcfs. Practical exercises on convection in water: http://www.ucar.edu/learn/1_1_2_7t.htm (2) The oceans also influence the amount of carbon dioxide in the atmosphere. See: http://www.pmel.noaa.gov/ co2/OA/OA1.jpg

8. Lots of water Water is critical to life and Earth has abundant water. But scientists don’t know why Earth has so much water when other planets don’t. Two theories are that: • Early Earth was struck by a comet which may have left water behind on the surface or as water vapour in the atmosphere. • Water may have been part of the rocks that formed early Earth. When volcanoes erupt some of this water is erupted as water vapour. Exercise on three states of water: http://www.ucar.edu/learn/1_1_2_3t.htm

9. Tectonic plates and volcanoes Earth is the only planet in our Solar System with plate tectonics. This process has an important part to play in keeping the climate steady. The crust and the hard upper part of the mantle are broken into giant rock plates called tectonic plates which float on the softer, lower mantle. The core of Earth gives off an enormous amount of heat which keeps the rock in the lower part of the mantle soft and able to be moved along by giant convection currents. This moves the tectonic plates so that sometimes they collide and other times move apart from each other.

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CONSTANZ ‘09 Written by Beryl McKinnell, Chair of Constanz‘09 When asked if I would organise the next Constanz Conference way back in 2007, I thought: Organise a conference? Why not. I can do that – after all what do you need; some workshops, a few field trips and a couple of keynote speakers? And in Auckland, the happening place. Even better if we can show that South Auckland is not such a bad place – let’s do it here, nice and close to the airport. We have a lovely boarding school in South Auckland and it would be an ideal location. Did I just say yes to organising a conference? Me, a ‘back room’ kind of person, who dislikes being ‘front of house’… Okay, no need to panic...I can delegate the ‘on stage’ bit later and anyway, it’s all a long way off...it’ll be fine. First task: gather some like-minded folk who’d like to help... no shortage of capable volunteers here, and many of them members of the Technicians’ Cluster group from South Auckland. All agreed we’d try for a South Auckland venue, but further down the track we were to learn our ideal venue was not exactly that and the Conference was moved to another location – the lovely St Cuthbert’s College campus. After a brainstorming session, we came up with a keynote speaker or two, but further investigation told us that most were going to be way too expensive. No worries, let’s find someone who will do it for free! It’s not until you write a trial budget that you start to realise just how much money you need to run a conference. To charge a fee to cover payments of keynote speakers’ and workshop presenters’ expenses would price the conference registration fee beyond the budget of those we hoped would attend. How can we make some money to make this fly? Ask for sponsors – in these economic downturn times? Sell trade table space? Never has there needed to be such hard sell. Have inserts in our satchel? Yes…that seems easier, but it’s not bringing in the big bucks. Apply for grants? But who are we, and how do we describe this to anyone who wants to know? The juggernaut that was to be Constanz ‘09 was underway, and I along with a band of 13 willing helpers got into ‘full swing’. We discussed what we liked from previous conferences, had firm ideas about what we were not going to include, and generally formulated the direction we were heading. Along the way we formed a tight band of workers

who developed a lasting respect for each other. Constanz ‘09 had a theme of Earth Wind and Fire. It was disappointing the Fire Service, due to industrial action, could not attend with their Fire Safety Kitchen to start our Conference with a bang. Keynote speakers informed us about science in ancient Greece, and Auckland’s volcanoes. Plus, with 24 different workshops covering everything from Electronics to Geology, Living in Space to Chemical Magic, there was something for everyone. The enthusiasm of Professor Bunsen would have to have been a highlight for all, his shows were so informative. For those attending, the fellowship and networking opportunities are the most valuable things you get out of a conference and there are few opportunities for Technicians to get together. I would urge anyone who has not yet experienced the camaraderie of a conference to try to attend the Dunedin Conference in 2011. I extend a huge vote of thanks to the organising committee. So many people graciously gave their time to run workshops, speak, or assisted with funding – and to you all a big thank you. Without everyone doing their bit, big or small, we would not have had a Conference, and to all those who attended, I hope you were able to grow in some way from the experience, and have made enduring contacts within your colleagues. Would I do it again? I’m not sure…I did not manage to delegate the ‘on stage’ bit. I think organising a conference is a bit like giving birth – it takes a while to forget the pain and hard work, you need to do that before you go through it again. And, funnily enough, presenting the conference to the delegates is a bit like introducing your family to your newborn baby for the first time. You wonder: will it go well or will it all end in a screaming bundle? And after it’s all over there is that ‘empty nest’ feeling. Organising Constanz ‘09 has been an experience I won’t forget. My best wishes go to those who are organising Constanz 2011. For further information contact: BeMcKinnell@papatoetoehigh.school.nz

continued from science/PEB page 47 When plankton with shells made of calcium carbonate die the shells fall to the ocean bottom and become part of the sediment accumulating there. The sediment gets compacted and forms rock. Rock formed from compressed plankton shells is called limestone. Both the shells and limestone are made of calcium carbonate. This sediment will remain on the bottom of the ocean forming deeper and deeper layers of limestone. Eventually much of the limestone will become subducted when two tectonic plates collide, as is happening off the North Island. The limestone is subducted deep into the ground where it may be melted and become magma. Most of the volcanoes around the world occur along boundaries between tectonic plates. 48 New Zealand Association of Science Educators

When magma is erupted from a volcano vast amounts of carbon dioxide are released back into the atmosphere.

10. The Earth’s thermostat Carbon dioxide is cycled through the atmosphere, biosphere (living organisms), hydrosphere and geosphere, and acts as a very effective thermostat for Earth, keeping temperatures within a liveable range. Parts of this cycle happen over short periods of time, but some happen over millions of years. This cycle is a very effective thermostat. Diagram of global thermostat: http://tinyurl.com/y8aqmkr). For further information contact jenny.pollock@xtra.co.nz


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