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Spring 2018 | Issue 43 | Issue 2018 Spring

SavingSaving thethe EarthEarth Hollywood-styleHollywood-style

INSPIRE ISSN: 1818-0353 www.scienceinschool.org ISSN: 1818-0353 www.scienceinschool.org Becoming an astronaut: interview with Matthias Maurer

UNDERSTAND Titanic and the iron-eating bacteria EIROforum by funded and Published Iaroslav Neliubov/Shutterstock.com ESA/Stephane Corvaja, 2017

DECODING DNA WITH 17 BECOMING AN ASTRONAUT: 26 A POCKET-SIZED SEQUENCER INTERVIEW WITH MATTHIAS MAURER USB-powered sequencers smaller than your The European Space Agency’s newest astronaut smartphone could revolutionise the way recruit talks about his exhilarating experiences we decode DNA – in hospitals, in remote in astronaut training and what the future has in locations and even in space. store for space flight. geralt/pixabay.com

SAVING THE EARTH HOLLYWOOD-STYLE 46 Challenge your students to save the Earth from an asteroid collision, using calculations based on the Hollywood sci-fi fantasy film Armageddon.

UNDERSTAND INSPIRE 04 News from the EIROs: Dinosaur discovery, 26 Becoming an astronaut: self-sufficient space flight and structural interview with Matthias Maurer biology for students TEACH 08 Titanic and the iron-eating bacteria 31 Turning dandelions into rubber: 12 Ten things you might not know the road to a sustainable future about fracking 37 Further fantastic feats: falling and bouncing 17 Decoding DNA with a pocket-sized sequencer 41 Colourful chemistry: redox reactions with lollipops 21 Is science true? 46 Saving the Earth Hollywood-style 51 Solutions to further fantastic feats

2 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org EDITORIAL vexworldwide/Shutterstock.com

Eleanor Hayes Editor-in-Chief Science in School [email protected]

Welcome to the spring issue of Science in School. Traditionally, spring is the season of renewal and a time to freshen things up. So while you might be thinking about decluttering your classroom, now might also be a good time to ‘spring clean’ your lesson plans and introduce some new activities into your teaching. In this issue, there are plenty of fun activities to engage your students, including a colourful chemistry demonstration exploring redox reactions (page 41). In a Hollywood-themed physics lesson, students investigate whether events in the sci-fi action film Armageddon could really happen (page 46). We also bring you the latest article in the ‘Fantastic feats’ series (page 37). For those who are keen to get planting this season, we have an activity involving growing an unusual species of dandelion (page 31). With a high proportion of rubber in its roots, this plant offers a potentially sustainable way to meet the increasing global demand for rubber. We also investigate the science behind the environmentally controversial IS SCIENCE TRUE? 21 technology known as fracking, which is used to extract shale gas from Should we believe what science rocks deep underground (page 12). tells us? A philosopher of This issue’s coverage of new discoveries and developments in science science comments on teachers’ includes a species of bacterium that is accelerating the decay of the responses to this challenging question. Titanic shipwreck (page 8), and a pocket-sized DNA sequencer that was recently used to identify microbes in space (page 17). For more space- related reading, astronaut Matthias Maurer shares his story of becoming the European Space Agency’s newest space recruit in this issue’s scientist profile (page 26). Finally, what do you say when a student asks whether we should believe what science tells us? We share some real responses from teachers to such challenging questions, followed by a philosopher of science’s expert opinion on each response (page 21). We would love to hear what you think of these opinions – and how you deal with any similar challenges in your own classrooms. Eleanor Hayes

Interested in submittingSee: your own article? www.scienceinschool.org/submit-article

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 3 Biology, Chemistry, Physics | UNDERSTAND

Dinosaur discovery, self-sufficient space flight and structural biology for students

CERN EMBL The past, present and future of ‘Seeing is believing’ the Large Hadron Collider Insight Lecture attended by students worldwide In March 1992, CERN launched the Large Hadron Collider (LHC) experimental programme, revealing to the public its initial ideas for building the world’s largest particle accelerator. Last year marked the 25th anniversary of this debut, and to celebrate, CERN hosted a commemorative symposium. As well as looking back at the history of the LHC, the event reflected on the bold decisions that led to the development of this remarkable facility and its collaborative experiments. The symposium concluded

with a review of recent experimental results from the four EMBL large LHC experiments: ALICE, ATLAS, CMS and LHCb.

It was a particularly successful year for the LHC in 2017, Students listening to the EMBL Insight Lecture by Dr Thomas Schneider as the accelerator produced 5 million billion (1015) proton- proton collisions – exceeding its target, and collecting huge Around 1500 students from 18 countries participated in amounts of data that scientists will continue to analyse the 2017 European Molecular Biology Laboratory (EMBL) this year. Insight Lecture, an annual talk aimed at 15–19-year-old 2018 will be the final year of data collection for the LHC students that highlights cutting-edge developments in life before a ‘technical stop’, set to last from 2018 to early sciences research. 2021. This will allow CERN’s technicians, engineers and The interactive event, entitled ‘Seeing is believing – how physicists to renovate and improve the accelerator, and technology enables structural biology’, took place at to prepare the detectors to fully exploit the improved EMBL Heidelberg, Germany, in December and was live- performance of the machine. streamed to schools worldwide. EMBL senior scientist Based in Geneva, Switzerland, CERN is the world’s largest particle Dr Thomas Schneider took the students on a journey physics laboratory. See: www.cern.ch to learn about the basic principles of macromolecular crystallography and synchrotron radiation. Throughout the event, students and teachers put questions to the speaker via Twitter, which were answered at the end of the lecture. EMBL extends a warm invitation to anyone interested in taking part in the 2018 Insight Lecture.

To stay informed, subscribe to receive updates from the European Learning Laboratory for the Life Sciences (ELLS) website. See:

Julien Ordan/CERN http://emblog.embl.de/ells/subscribe-to-emblog Recordings of all EMBL Insight lectures produced between 2010 and 2017 can be viewed on the EMBL website. See: http://emblog.embl. de/ells/eil EMBL is Europe’s leading laboratory for basic research in molecular To celebrate the 25th anniversary of the LHC experimental programme, CERN biology, with its headquarters in Heidelberg, Germany. See: hosted a commemorative symposium. www.embl.org

4 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Biology, Chemistry, Physics

Science in School is published by EIROforum, a collaboration Dinosaur discovery, self-sufficient between eight of Europe’s largest inter-governmental space flight and structural biology scientific research organisations (EIROs). This article reviews some of the latest news from the EIROs. for students

ESO Planetarium and visitor centre

A microscope image to open in April of Arthrospira, commonly On 26 April 2018, a new attraction will open at the known as spirulina headquarters of the European Southern Observatory (ESO) in Garching, Germany. The ESO Supernova Planetarium and Visitor Centre will provide visitors with an immersive ESA experience to learn about our Universe, as well as presenting them with ESO-specific scientific ­results, Recycling oxygen for self-sufficient projects and technological breakthroughs. space flight At the heart of the new ESO centre is a digital planetarium In the harsh environment of space, resources are with state-of-the-art projection technology and a limited. To live on-board the International Space Station scientifically accurate three-dimensional astronomical (ISS), supplies must be regularly restocked by cargo database that allows you to fly to the stars and even vessels. Self-sufficient space flight is a possibility for to the edge of the Universe. The programme of shows the future, but it will require precious resources, such is displayed on a 360° dome that is 14 m in diameter, as oxygen, to be recycled and reused. Astronauts on and an interactive exhibition space hosts a variety of the ISS are now investigating how to do just that, with ­permanent and temporary exhibitions. help from a single-celled microalga called Arthrospira, The centre also offers a variety of opportunities for teachers commonly known as spirulina. and schools. Teachers can participate in teacher training In December 2017, samples of the bacteria were sessions and access free educational material. Curriculum- delivered to the ISS by the Space-X Dragon cargo centred visits for school groups include workshops for a vessel and loaded into a photobioreactor – a variety of ages, learning-focused planetarium shows and cylindrical container bathed in light. When the algae inspirational guided tours. photosynthesise, carbon dioxide is used up, producing oxygen and edible biomass. The experiment will run for To keep informed about the developments of the ESO Supernova one month to measure the amount of oxygen produced, Planetarium and Visitor Centre, visit the ESO website. See: https://supernova.eso.org before the microalgae samples return to Earth in April. ESO is the foremost inter-governmental astronomy organisation The algae’s genetic information will then be analysed to in Europe and the world’s most productive ground-based build a clearer picture of the effects of weightlessness astronomical observatory, with its headquarters in Garching, and radiation on the plant cell. near Munich in Germany, and its telescopes in Chile. See: www.eso.org The experiment is part of an initiative named MELiSSA (Micro-ecological Life Support System Alternative), The ESO Supernova Planetarium which is developing regenerative technologies for and Visitor Centre life support. To learn more, visit the ESA website. See: www.esa.int/Our_Activities/Space_ ESO Engineering_Technology/Melissa ESA is Europe’s gateway to space, with its headquarters in Paris, France. See: www.esa.int ESA

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 5 Biology, Chemistry, Physics | UNDERSTAND

ESRF Synchrotron sheds light on the lifestyle of a new dinosaur EUROfusion World’s largest fusion experiment A study of an exceptionally well-preserved fossil skeleton reaches halfway point from Mongolia has led to the discovery of a new species of bird-like dinosaur related to Velociraptor. With a neck similar Fusion is the process that powers the Sun and stars, to a swan’s, and flipper-like forelimbs, the new dinosaur but replicating the process on Earth to meet our energy species (which also represents a new genus) combines an needs has proven to be one of the greatest scientific unexpected mix of features. These demonstrate that some and engineering challenges. The key to overcoming predatory dinosaurs adopted a semi-aquatic lifestyle. these challenges, as shown by the world’s largest fusion The fossil was first smuggled out of Halszka, Mongolia, and experiment, ITER, is collaboration on a global scale. kept in private collections around the world before it was With its seven member states (the European Union, offered to palaeontologists for study. Since the skeleton is India, Japan, China, Russia, South Korea and the United largely covered by stone and thus much of it cannot be seen States), the ITER organisation is building the world’s directly, an international team of researchers at the European biggest fusion device in Cadarache, France. And, at the Synchrotron Radiation Facility (ESRF) used synchrotron end of 2017, the project announced that it had reached analysis to visualise and reconstruct the bizarre 75-million- an important milestone: ITER is now halfway towards year-old predator, named Halszkaraptor escuilliei, in three completion, when it will be able to begin its first dimensions. experiments. The experiments revealed that this amphibious dinosaur This is a significant step, not only for ITER but for the walked on two legs on land, but used its flipper-like forelimbs entire fusion community. Once operational, ITER will to manoeuvre itself in water (similar to how penguins and prove that fusion electricity is feasible and not just other aquatic birds move), while relying on its long neck for a vision. This aim lies at the heart of EUROfusion’s foraging and ambush hunting. roadmap, which outlines how the European fusion community will reach the goal of obtaining fusion For more information on the study, read the original research paper published in Nature. See: power. Cau A et al. (2017) Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs. Nature 552: EUROfusion manages and funds European fusion research activities, 395–399. doi: 10.1038/nature24679 with the aim to realise fusion electricity. The consortium comprises 30 members from 26 European Union countries as Download the article free of charge on the Science in School website. well as Switzerland and the Ukraine. See: www.euro-fusion.org See: www.scienceinschool.org/2018/issue43/eironews, or subscribe to Nature today: www.nature.com/subscribe Situated in Grenoble, France, ESRF operates the most powerful synchrotron radiation source in Europe. See: www.esrf.eu

Aerial view of ITER, which is currently under construction in Illustrative Cadarache, France reconstruction of Halszkaraptor escuilliei L Panzarin ITER

6 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Biology, Chemistry, Physics

ILL European XFEL New insight into enzyme useful Impressions from the first for drug development users of new X-ray laser A recent study has used neutrons to successfully visualise the facility structure of aspartate aminotransferase, an enzyme vital to the metabolism of certain amino acids. This could open avenues for new antibiotics and drugs to battle diseases such as drug- resistant tuberculosis, malaria and diabetes.

Matthias Vogt’s organic Aspartate aminotransferase is one of a group of vitamin LED experiment at the B6-dependent proteins – a diverse group of enzymes that FXE instrument conduct over a hundred different chemical reactions in cells. Carried out at the Institut Laue-Langevin (ILL), the study used neutron crystallography on the ILL LADI instrument to study a vitamin B6-dependent protein for the first time. By exposing delicate protein crystals to neutrons using the ILL beamline, scientists determined the location of hydrogen atoms in the enzyme. Knowing the precise location of hydrogen atoms can help to explain why the behaviour of B6-dependent enzymes

European XFEL is so specific. This study highlights how neutrons are an unrivalled probe for identifying the location of hydrogen atoms in biological systems, providing us with an unprecedented level of structural detail for this important enzyme.

From mid-September to early December 2017, the first Based in Grenoble, France, ILL is an international research centre at the external scientific researchers from across the world leading edge of neutron science and technology. See: www.ill.eu visited the European X-ray Free-electron Laser (European XFEL). They were there to carry out experiments at the LADI instrument at the Institut Laue-Langevin first two operational instruments: FXE, which studies chemical reactions on extremely short timescales, and SPB/SFX, which has a strong focus on structural biology and the imaging of tiny particles. Alexandra Ros from Arizona State University, USA, was excited to have the chance to work at the brand- new facility as one of the first user groups. “I was really amazed that we got accepted. We didn’t know what R Cubitt to expect before coming – every day has been a steep learning process”, she said. For Matthias Vogt, a researcher from the University of Bremen, Germany, working with the scientists at European XFEL will be crucial for developing his group’s luminescence compound into a material applicable in organic LEDs. “We’re very grateful for the outstanding support of the FXE scientists on site; their expertise is key to the success of our experiment”, he said. European XFEL is looking forward to welcoming the EIROforum combines the resources, facilities and expertise second round of users in May 2018. of its member organisations to support European science in reaching its full potential. See: www.eiroforum.org For a list of EIROforum-related articles in Science in School, To read stories from the first users of the facility, visit the European see: www.scienceinschool.org/eiroforum XFEL website. See: www.xfel.eu/news_and_events/news/ To browse the other EIRO news articles, see: index_eng.html?openDirectAnchor=1344 or use the direct link www.scienceinschool.org/eironews https://tinyurl.com/ycm74xo2 European XFEL is a research facility in the Hamburg area in Germany. Its extremely intense X-ray flashes are used by researchers from all over the world. See: www.xfel.eu

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 7 Biology, Chemistry, Physics | UNDERSTAND

Titanic and the iron-eating bacteria A species of bacterium discovered on the decaying wreck of the Titanic is providing new insights into how to protect living cells from damage.

By Giuseppe Zaccai

The wreck of Titanic lies on the ocean floor, nearly 4 km located in the deep sea. However, these organisms have now below the surface of the dark, salty water of the North become the focus of scientific research for another reason: to Atlantic. Divers on expeditions to the site have noticed find out how they manage to thrive in conditions with high ‘rusticles’ – icicle-like growths rich in rust – covering parts and varying salt concentrations. of the damaged and corroded hull. In 2010, scientists investigating rusticles taken from the Titanic site discovered a Salts and the living cell new species of bacteria within these growthsw1. They named The term halo- means ‘salt’ in Greek. Bacteria of the genus the new species Halomonas titanicae. Halomonas live in salty environments, such as sea water The scientists have also discovered that Halomonas or salt marshes, where salt concentrations vary over a wide titanicae bacteria are involved in the rusting process and are range. All members of the genus are strongly ‘halotolerant’: accelerating the wreck’s decay. The decay is happening at they have evolved ways of coping with wildly fluctuating salt quite a rapid rate: estimates suggest that the wreck may have concentrations outside the cell, surviving over a huge range disappeared completely by 2030. These bacteria could thus of salinity from 0.5% (w/w) sodium chloride right up to 25%. pose a significant threat to oil rigs and other iron structures This may seem like a trivial issue, but it is not.

The RMS Titanic at the docks at Southampton, UK in April 1912 Wikimedia Commons (public domain)

8 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Biology, Chemistry, Physics

Microbiology Chemistry Image courtesy of Lori Johnston, RMS Titanic Expedition 2003, NOAA-OE Biochemistry Archaeology Ecology Ages 16–19

The wreck of the Titanic is very well known, so this article can be used to excite students about science. It can also act as an incentive A view of the bathtub in the captain of the Titanic’s bathroom. Rusticles can be seen growing over most to delve deeper into of the pipes and fixtures in the room. the world of bacteria and their usefulness to Cells are protected from the outside from the more dilute side to the more human beings – despite world by very thin membranes that concentrated side. their normally negative associations. control traffic in and out of the Cell membranes cannot cope with The article would cell, creating and supporting huge osmotic pressure differences. Red be useful in biology differences in composition between blood cells will burst when placed in teaching to explore how the inside and outside of the cell. For pure water, illustrating the effect of prokaryotic organisms example, cells maintain an electrical osmotic pressure – and the fragility can survive in extreme potential of about 100 millivolts across of cell membranes. Clearly, to keep environments, and how the membrane, which is typically just their membranes intact, Halomonas substances are transferred 10 nanometres thick. For all types of bacteria must be able to regulate across the cell membrane. the concentration of solutes in the It could also be used cytoplasm in response to changing in chemistry teaching external salt concentrations, without All Halomonas about hydrogen bonds disrupting the biochemistry within the “ REVIEW and the interactions bacteria have evolved cell (see Zaccai, 2009). How between water and do they do this? ways of coping with other molecules. wildly fluctuating salt Halomonas bacteria produce large Finally, recycling using amounts of a substance called ectoine Halomonas titanicae concentrations outside (see figure 1). To counterbalance the is relevant to ecology the cell. external salt concentrations, they and the study of the ” adjust the concentration of this soluble energy balance within compound within their cells. This keeps ecosystems. the cell’s fluids in osmotic balance cell, sodium chloride (NaCl) is the with the outside, protecting the cell Alina Giantsiou-Kyriakou, dominant salt outside the cell (for against shrivelling up or bursting even biology teacher, example, in blood serum), whereas in extreme conditions. Remarkably, Livadia High School, potassium chloride (KCl) is dominant ectoine appears to act differently Cyprus inside the cell. Yet, while the salt types from most salts and solutes, which are different, the total salt concentration can interfere with the role of water on either side of the cell membrane in metabolic processes. Ectoine is a should match exactly. The reason for ‘compatible solute’, and so preserves this is osmosis: if two solutions of the normal biochemistry within the cell. different concentration are separated It also increases the stability of proteins by a membrane that is permeable to and membranes. So how does this water but not to solutes, water will flow unusual solute achieve these results?

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Ectoine and the membrane surfaces (Zaccai et al., The attraction between water molecules hydrogen-bond network 2016). Normally, water molecules is also the basis of the ‘hydrophobic interact with each other through a effect’, which makes oil and water Clues as to exactly how ectoine works network of hydrogen bonds. The atoms separate. The hydrophobic effect is on the molecular level have recently in a water molecule interact with important in many biological processes, been discovered using the advanced neighbouring molecules, with each including the three-dimensional folding experimental technique of neutron oxygen atom acting as a receiver of two of protein molecules and the formation scattering (see text box). Carried out hydrogen bonds and each hydrogen of membranes. Hydrogen bond by an international collaborationw2 atom as a donor of one bond. This dynamics are thus an essential factor in involving the Institut Laue-Langevin results in a highly dynamic network how living cells are organised. (ILL)w3, the experiments showed how of intramolecular bonding, with the ectoine influences the layer of water molecules changing partners a billion around protein molecules and on (109) times a second. “ Hydrogen-bond dynamics are an Neutron scattering essential factor in Neutron scattering is a powerful method for studying the structure of how living cells are materials, including water and its interactions with other compounds. organised. The nucleus of a hydrogen atom is a single proton. Neutrons and protons ” are very similar particles (apart from their electric charge), and neutrons strongly scatter off protons, rather like snooker balls bouncing off each other. The neutron scattering pattern provides information on the Other substances in the water, location of oxygen and hydrogen atoms in nearby water molecules, and such as salts, can interfere with this thus on the dynamic network of hydrogen bonds that links them. organisation. But, as the neutron Another useful trick is used in neutron scattering. The nuclei of experiments have revealed, ectoine deuterium atoms (an isotope of hydrogen with one proton and seems to enhance hydrogen-bond one neutron in its nucleus) scatter neutrons in a very different way dynamics – at least in part – rather than from normal hydrogen nuclei. Replacing the hydrogen in a specific hindering it. This molecule contains a compound (ectoine, for example) with deuterium makes it possible positively charged group (shown in blue to see the contribution of only this compound to the scattering signal, in figure 1) and a negatively charged distinct from that of the surrounding water molecules. This in turn helps group (shown in red). These charged to reveal the details of their interaction. groups interact with water molecules, Neutron scattering with deuterium labelling has provided a rich crop making the hydrogen bond network of results in structural biology. These include insights into the complex nearby a little less dynamic – but also interactions between protein molecules, and those between proteins and creating a more dynamic network of nucleic acids (DNA, RNA). water molecules further away.

CH3 N

NH

OH

H ©ILL/L. Thion

BACKGROUND 0

Figure 1: The chemical structure of ectoine. In water, The D22 instrument at ILL, which revealed how water and ectoine interact with the red group becomes negatively charged (by losing + protein surfaces. The door of the apparatus has been opened to show a view of the one H ion) and the blue group becomes positively + neutron detector. charged (by gaining one H ion). The charged groups then form hydrogen bonds with adjacent water molecules.

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Outside the bacterial context, ectoine References w3 The Institut Laue-Langevin (ILL) is an international research centre at the leading is proving to be a useful ingredient Zaccai G (2009) The intracellular environment: edge of neutron science and technology, in cosmetics and clinical treatments, not so muddy waters. Science in School 13: based in Grenoble, France. See: www.ill.eu because it can reduce inflammation in 19-23. www.scienceinschool.org/2009/ issue13/water mammalian cells. The likely reason for Resource this is that by stabilising proteins and Zaccai G et al. (2016) Neutrons describe ectoine effects on water H-bonding and Find out more about microbes that live on membranes, ectoine protects human hydration around a soluble protein and a shipwrecks and the role of ectoine in an cells from damage, thus reducing cell membrane. Scientific Reports 6: 31434. accessible article on the BBC website. See: inflammation and providing remedies doi:10.1038/srep31434 www.bbc.com/earth/story/20170310-the- for conditions such as allergies, eczema, wreck-of-the-titanic-is-being-eaten-and- may-soon-vanish and cough and cold symptoms. Web references ______w1 Halomonas titanicae bacteria were discovered Return to the Titanic by scientists from universities in Seville, Spain, and Toronto and Halifax, Canada. Joe (Giuseppe) Zaccai is Emeritus Although the neutron experiments Read a scientific account of the discovery on Director of Research at the National have helped scientists to understand the UNESCO website. See: www.unesco.org/ new/fileadmin/MULTIMEDIA/HQ/CLT/pdf/ Centre for Scientific Research (Centre how Halomonas bacteria thrive in the Henrietta_Mann_Paper.pdf National de la Recherche Scientifique, potentially hostile environment around w2 The collaborating organisations included the CNRS) in France. He spent his research the sunken Titanic, the exact role of Institut Laue-Langevin (ILL) and Institut de career based at ILL, where he developed Halomonas titanicae in rust formation Biologie Structurale in Grenoble, France, and neutron scattering methods and applied remains unclear. But there is some the Max Planck Institute of Biochemistry them to the structural biology of good news here: these iron-eating and biotechnology company Bitop in Munich, adaptation to extreme environments. bacteria could have a role in future Germany. See the online supplementary information section in Zaccai et al. (2016) for waste management, speeding up the more information. decomposition of metallic litter – aside from historic wrecks – on the ocean floor.

Deepsea Delta oil drilling rig in the North Sea. Like the wreck of the Titanic, oil rigs are at risk of damage from rust-eating bacteria. Erik Christensen/Wikimedia Commons

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Ten things you might not know about fracking

Fracking is a hugely controversial technology, so it’s worth taking a closer look at the science behind the headlines.

By Rosemary Wilson

In the USA, fracking is big business. A surge in fracking Oil resources over the last few years means that it now accounts Earth science for more than 50% of all US gas production – but as levels of fracking have risen, so too have public Earthquakes opposition and concern. In Europe, governments and communities are currently weighing up the costs Environmental impacts and benefits of fracking, and some governments Citizenship have already banned it. But what exactly is fracking, and how does it work? Here we explore some of the Ages 14–19 science behind the current discussions. This article provides an interesting way to introduce the topic of fracking into lessons in different Shale landscape in the Languedoc-Roussillon

REVIEW subjects. For example, it could be used in earth region, France science to explore the idea of human-induced earthquakes compared to the natural phenomena. Fracking is also a suitable topic for discussion about citizenship and science communication, including the involvement of citizens in decisions about environmental matters, and the relationships between science, politics, environmental protection and economic interests. The article could be used as a role-play activity, with different students taking the roles of scientists, politicians, environmental activists and citizens. Students would use and follow up the information in the article to defend their points of view in a debate.

Teresita Gravina, science teacher, Istituto Comprensivo Luigi Vanvitelli, Italy Basicdesign/Wikimedia Commons

12 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Earth science, Engineering, Science and society

Conventional extraction Unconventional extraction

Borehole Borehole

Cap rock Fracking zone

Source rock Reservoir rock (shale)

Source rock Nicola Graf (shale)

Figure 1: Comparison between conventional and unconventional gas extraction. In conventional extraction (left), gas moves upwards until it reaches an impermeable layer (cap rock). It collects within the reservoir rock, from where it is extracted by drilling. In unconventional extraction (right), the gas is extracted directly from the source rock, which must be fractured to obtain the gas. (Source: Hans-Martin Schulz, GFZ Potsdam)

1. Fracking means sedimentary rocks called shales. Shale deposits are located all over ‘hydraulic fracturing’. As sediments of sand and mud the world, but the shales that contain were converted into rocks over the most gas formed in marine Fracking is an example of millions of years under high environments, particularly in slow- unconventional gas extraction. In this temperature and pressure, the plant moving, poorly oxygenated water such process, water (mixed with sand and and animal remains associated with as ancient sea basins. Here, the plants chemicals) is injected into rocks under the sediments were converted into shale and animals could not decay before they very high pressure to fracture them gas, which consists predominantly of were buried, providing organic material – hence the name hydraulic fracturing, methane. that was later converted into fossil fuel. or fracking. In conventional extraction of natural gas reserves, such as those under the North Sea, the gas migrates upwards from the source rocks where it was formed and collects under an impermeable rock layer, from where it can be pumped out by drilling (see figure 1). Unconventional gas resources are trapped in the source rocks themselves, which have to be broken to release the gas. Sand particles are used to prevent the fractures from closing again, allowing the gas to escape and migrate to the surface. Adam Welz/CREDO 2. Fracking is used to extract shale gas. Currently, fracking is mainly used to extract the gas found in fine-grained Anti-fracking demonstration in New York, USA (October 2012)

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There are potential shale gas reserves across Europe, including the Posidonia Shale in Germany (see 4 on the map, figure 2), and the Bowland Shale in the north of England (see 8, figure 2). The Posidonia Shale was formed about 200 million years ago, at the bottom of the 2 1 ancient Tethys Sea. Fossils of molluscs are common in these rocks, and those 8 of larger animals such as dinosaurs have 19 4 3 also been found here. 7 5 14 18 6 11 12 3. Fracking has been 10

used for decades. 9 13 16 Fracking is not a new method of extraction: it has been used since the 1940s, but mostly in conventional 15 extraction as a way of obtaining any last remaining gas. The type of fracking used 1. Sweden 11. Austria to extract shale gas is more challenging, Alum shale Upper Jurassic shales, Vienna Basin as shales are found at shallower 2. Denmark 12. Hungary depths closer to groundwater supplies Alum shale Cenozoic shales, Mako Trough and require greater volumes of fluid 3. Poland 13. Bulgaria Paleozoic shales Mesozoic shales, northeast Bulgaria injection than conventional reserves. 4. Germany 14. Ukraine More recently, engineers have worked Mesozoic shales including Posidonia Lower Carboniferous shales, out how to drill sideways into shale shale, Lower Saxony Basin Dnepr Donets Basin deposits, thereby fracking more rocks 5. Germany 15. Turkey with only one borehole. In the USA, this Namurian shales Silurian shales, southeast Turkey development has led to a rapid increase 6. Germany 16. Spain Permocarboniferous shales, Lower Jurassic shales, in shale gas production over the last Bodensee-Trog Basque-Cantabrian Basin decade. In Europe, however, while there 7. England 17. Italy are a few test sites, fracking for shale gas Weald Basin Tertiary shales, Ribolla Basin is very limited. 8. England 18. Czech Republic Namurian shales, including Bowland Tertiary shales, Western Carpathian shale Basin 4. Fracking needs 9. France 19. Ireland Mesozoic shales, Southeast Basin Clare shales, Upper Carboniferous, Clare Basin a lot of water… 10. Switzerland Nicola Graf Lower Jurassic shales, Fribourg, Vaud Some states in the USA have run dangerously low on drinking water, due to fracking. A single fracking borehole Figure 2: Map showing location of potential shale gas reserves across Europe. can use as much as 43 000 m3 of water (Source: Hans-Martin Schulz, GFZ Potsdam) – enough to supply a small town for about a month. Some boreholes use only a tiny percentage of this amount, 5. …and a lot of sand. 6. Fracking can cause but in the USA a large percentage of Fracking uses vast amounts of sand earthquakes. fracking boreholes are in areas prone to – up to 8000 tonnes per borehole. While fracking can cause earth tremors, drought, such as Texas and California. In fact, fracking now accounts for these are generally too small to notice. In addition, fracking uses drinking water approximately 60% of the sand used However, there is evidence that the taken from reservoirs and groundwater industrially in the USA. The sand disposal of fracking fluids causes more aquifers, which must be disposed of needed is quite special: it is carefully problems and larger earthquakes afterwards rather than returned to the sorted to select grains with a particular than fracking itself. For example, in water cycle. This puts added strains on shape and size, and also with a high Oklahoma, USA, which has a large local water resources and is causing a quartz content to withstand high number of disposal sites, there were lot of concern. pressures. just a few tremors every year until

14 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Earth science, Engineering, Science and society

2008, increasing to 20 in 2009 and casing near the shales, and the fracking bustling European metropolis would not 105 in 2013. The largest tremor had a fluid is forced through these holes be easy. magnitude of 5.6 on the Richter scale into the rocks under extremely high and destroyed several homes. pressures – some 680 atm (69 million 9. Beer brewers in Germany Scientists at the US Geological Survey Pa). As a comparison, professional have worked out that the strength of racing bike tyres have pressures of are opposed to fracking. these earthquakes depends on the about 10 atm, or 1 million Pa. The German beer purity law states amount of liquid pumped into the rocks. that German beer should be brewed They calculated that injecting a volume 8. In Europe, many potential using only hops, yeast, malt and water. 3 of some 10 000 m (enough to fill about fracking sites are Pure, clean water is therefore a crucial four Olympic-sized swimming pools) ingredient of beer brewing, and many could result in an earthquake with a near cities. breweries in Germany obtain the water maximum magnitude of 3.3. However, In the north of England, the shale gas they use from their own wells. Any this is no prediction as to whether an reserves are beneath the large cities of contamination of water supplies with earthquake will occur or not. Manchester and Leeds. In Germany, the methane or fracking fluids would be a Posidonia shale deposits are located threat to this important industry, and 7. It takes a lot of pressure to near the city of Hanover, which has beer brewers in Germany have publicly a population of over half a million. A declared their anti-fracking position. fracture the rocks. couple of bore holes would require Fracking advocates argue, however, Shale deposits that can yield gas are an area about the size of a football that there are thick, impermeable usually found at depths of between field, including space for drilling rigs, layers of rock above shale deposits, 1000 m and 5000 m. After the borehole equipment and trucks; somewhere to which would act as a protective has been drilled down to the rocks, store and dispose of water and waste; barrier during fracking, protecting it has to be carefully encased with as well as gas storage and cabins for shallow groundwater supplies from concrete to protect the surrounding the workers. Setting up these sites and potential contamination. In addition, environment before fracking can begin. the associated infrastructure, such as fracking must always take place Holes are then made in the borehole transport routes, near or around any at a defined distance away from Annie and Andrew/Flickr

Beer drinkers at the Oktoberfest in Munich, Germany. German beer producers have voiced concerns about the effect fracking could have on the purity of their products.

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groundwater. Another safety factor Acknowledgement is that if any fracking fluids were to The author would like to thank Professor escape, they would sink downwards, Dr Ernst Huenges and Dr Hans-Martin rather than migrating upwards Schulz from the German Research Centre for Geosciences (GFZ), and Dr Clement Uguna from the University of Nottingham, UK, for their helpful input “ Beer brewers in and comments on this article. Germany have publicly Resources declared their anti- Read a study about how earthquakes can be fracking position. induced by fracking. See: ” Ellsworth WL (2013) Injection-induced earthquakes. Science 341(6142): 1225942-1–7 doi: 10.1126/ science.1225942 towards the groundwater level. But Information and an interactive map of induced while groundwater supplies might be earthquakes can be found on HiQuake, a database of human-induced earthquakes. protected from any contamination See: http://inducedearthquakes.org occurring at depth, there have been The US Geological Survey recently published cases of groundwater contamination a study on water consumption used by caused by spills on the surface, so fracking. Find out more in this article careful handling of extraction chemicals from Scientific American. See: and waste around the fracking site is www.scientificamerican.com/article/ also needed. water-use-rises-as-fracking-expands To learn about the current state of shale gas production in Germany, visit the Shale Gas 10. Scientists are using a Information Platform website. See: www. similar technique to shale-gas-information-platform.org/areas/ the-debate/shale-gas-in-germany-the- produce geothermal current-status.html energy. Information about shale gas geology, resources and production in the UK are available on A method known as enhanced the British Geological Survey website. geothermal systems (EGS) exploits See: www.bgs.ac.uk/shalegas naturally occurring fractures in rocks, Learn more about fracking and current public and uses high-pressure water to create opinion in the UK with this article published by The Guardian. See: www.theguardian.com/ even more fractures deep down, where environment/2017/dec/25/fracking-start- the rocks are naturally hot. This creates 2018-shale-gas-uk-industry-protests a geothermal reservoir, which heats up Watch a TEDed lesson entitled ‘How does water pumped down into the rocks, and fracking work?’ to learn about the the resulting steam is used to generate technology behind fracking, and why it is electricity. Once the water has cooled, so controversial. See: https://ed.ted.com/ it is then pumped back down into the lessons/how-does-fracking-work-mia- rocks to be heated again. nacamulli Unlike in fracking for shale gas, no sand or other chemicals are needed ______for this process. The process is still controversial, however: an EGS project Rosemary Wilson is a science in Basel, Switzerland, was cancelled communicator and writer based in after it caused significant tremors, North Germany. leading to insurance claims totalling millions of euros. But development and research continue: in Europe, there are EGS test facilities in Portugal, France and Germany, and projects are planned in Cornwall, UK that are expected to be operational by around 2020.

16 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | Biology, Health

A new method of genetic sequencing is making it easier than ever to decode DNA. Iaroslav Neliubov/Shutterstock.com

Decoding DNA with a pocket-sized sequencer USB-powered sequencers smaller than your smartphone could revolutionise the way we decode DNA – in hospitals, in remote locations and even in space.

By Kerstin Göpfrich and Kim Judge

What were the biggest technological developments of the Now, another technology is being revolutionised in a 20th century? Computers may be the first thing that comes similar way: the DNA sequencer. to mind: early computers for military and commercial DNA stores the genetic information that is passed down use took up a whole room before they were transformed between generations. Similar to the way computers store into smaller, affordable consumer products in the 1980s. information as a string of zeros and ones, the information Computing power has advanced at such a rate that the in DNA is stored as a code of four bases: A, T, C and G smartphones we use today can perform tasks that even the (adenine, thymine, cytosine and guanine). most powerful computers could not achieve decades ago.

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In 2003, the first human genome – the How does nanopore nanopore sequencer, which is plugged complete set of genetic information – sequencing work? into a laptop via a standard USB cable was sequenced. It took seven years, 150 (figure 1). scientists and 3 billion US dollars (2.5 Portable DNA sequencers have been on Inside the nanopore sequencer, an billion euros) to complete the mammoth the market since 2015. The sequencing enzyme unwinds the DNA double helix project. Today, the same task can be process is straightforward and, unlike and passes one of the strands through a achieved in just over a day for around earlier methods of DNA sequencing, nanopore – a microscopic channel in 1000 dollars (850 euros). What’s more, scientists do not need to make millions the centre of a protein molecule sited decoding the DNA doesn’t need to take of extra copies of the DNA or to label in a membrane. A voltage is applied place in a large-scale laboratory: it can the DNA with fluorescent or radioactive across the nanopore, causing ions in be done with a portable sequencer that tags. First, the DNA is extracted – for the solution to move through the pore fits in your pocket. This remarkable example, from a swab or blood sample and generate an ionic current. The reduction in cost and size is thanks – and mixed with an ionic solution to channel is just the right size for the to a new technique called nanopore prepare it for sequencing. This DNA DNA strand to pass through. Since each sequencing. liquid is then pipetted directly into the of the four DNA bases is different in size, it blocks a different proportion of the nanopore as it passes through. This means there is more or less space for ions to pass through the nanopore, and so more or less current can flow across the gap (figure 2). The ionic current is measured and the data is transferred to Biology the computer and analysed by specialist Biochemistry software that converts the measurements in real time into the DNA sequence – a Biotechnology text file with the letters A, T, C and G. Depending on how much DNA Health sequence data you want to generate, Ages 16–19 the sequencer can run for minutes or days. One way to analyse the data is to This interesting article addresses one of the main topics in biology: the upload it to an online DNA database DNA molecule. In particular, it focuses on a new technique that allows and compare it to known sequences. faster and cheaper sequencing of DNA using a powerful but small This way, you can find out which device. species the DNA belongs to, whether

REVIEW This new tool, called nanopore sequencing, has the potential to open there were pathogens in the sample, doors to a variety of applications. In the near feature, it could be as and what genes are present. Nanopore simple to use as smartphones are today. However, the ease with which sequencing is remarkably fast, but the public’s DNA could be sequenced raises important ethical issues. typically generates a smaller amount of Together with images and graphics, the article could be used to explain the molecular biology techniques involved in reading and sequencing the DNA double helix, and how nanopore sequencing could replace earlier sequencing methods. It could also be used for discussions on the ethical issues and problems of privacy regarding genetic profiles. Comprehension questions could include: · Why does each nucleotide cause a different ionic signal in the nanopore sequencing device? · What types of molecule could help to move the DNA through

the nanopore? Oxford Nanopore Technologies · How does the DNA nanopore sequencer work? · Explain two or three novel applications for the nanopore sequencer. · What are the ethical issues surrounding the use of DNA sequencers?

Ana Molina, natural science teacher, IES Gil y Carrasco High School, Spain Figure 1: A nanopore sequencer connected to a laptop via USB. The DNA solution (yellow) is added with a pipette.

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data than other sequencing methods. Sequencing centres will therefore remain important for obtaining large DNA double helix amounts of data. DNA base Ammeter Applications of nanopore sequencing Voltage source Nanopore sequencers are opening Unwinding enzyme up many new possibilities for DNA C C A A sequencing. They have already been T T G G used to identify viruses, bacteria and Current parasites in a hospital environment. Nanopore Time Most notably, in 2015 a team of scientists took the first sequencing field kit to West Africa and sequenced blood samples from 142 patients

during the Ebola outbreak to track the Membrane Kerstin Göpfrich emergence of new strains (see Bryk, Ionic current 2017). Scientists identified the viral DNA in each sample after just 15 minutes of sequencing, showcasing the potential of the new technology to Figure 2: Illustration of the working principle of a nanopore DNA sequencer. A strand of DNA is passed monitor epidemics and to help identify through a nanopore, and an ionic current is measured and translated into the DNA sequence. drug and vaccine targets to instantly inform control measures. In the future, nanopore sequencing could also speed up the identification of cancers, which is particularly important for aggressive tumours; currently, it can take weeks from collecting a patient’s DNA sample to receiving the result from a laboratory. Portable DNA sequencers have also been used to identify unknown species in remote areas, such as on high mountains and in the deep sea. Even further afield, it was announced at the start of 2018 that NASA astronauts had successfully identified microbes found on board the International Space Station using nanopore DNA sequencing. This means that astronauts could potentially Karl Christoph Gödel diagnose infections using a sequencer to identify viral or bacterial DNA from their own mouth swabs. One day, nanopore sequencers may even be used to analyse DNA on other planets. A portable nanopore sequencer Using the same technology, DNA sequencing can now be carried out by students in the classroomw1 – for Ethics of DNA sequencing analyse only specific genes, and the example, sequencing the DNA of Nanopore sequencing is the only results are sometimes questionable. fruits in a smoothiew2. While the cost technology to enable portable DNA As whole-genome DNA sequencing of portable DNA sequencers may sequencing of use genomes. Currently, becomes increasingly accessible due to still be prohibitive for widespread anyone can use a home genetic-testing nanopore sequencing, it will be crucial use, this technology opens up many kit for less than 150 euros. But unlike to consider the ethical questions. The new opportunities for citizen science nanopore sequencing, which can more DNA we sequence, the better we projects and education. provide a base-by-base result, these kits will understand the health implications

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 19 Biology, Health | UNDERSTAND University of Birmingham

Portable DNA sequencers are being used to monitor epidemics, as shown here during the Zika outbreak in Brazil

of genetic predispositions. But while our lives – but we must work together To learn more about nanopore sequencing, visit genes may predict the probability of across society to ensure that we the Oxford Nanopore Technologies website. certain diseases, lifestyle factors often maximise the opportunities, while also See: https://nanoporetech.com/how-it-works decide the outcome. Private companies mitigating the risks of DNA sequencing. For up-to-date information about the NASA project on DNA sequencing in space, are already marketing dubious ‘health visit the Oxford Nanopore Technologies horoscopes’ based on DNA testing – Reference blog, or listen to an interview with Dr often neglecting the complexity and Byrk J (2017) Evolution in action: pathogens. Aaron Burton. See: https://dna.space probabilistic nature of genomic data. Science in School 42: 8–13. and www.thenakedscientists.com/sites/ www.scienceinschool.org/content/ default/files/media/Naked_Scientists_ evolution-action-pathogens Show_16.11.29_1006004_1.mp3 or use the direct link https://tinyurl.com/y9qwng3q Web references The Wellcome Genome Campus provides In principle anyone detailed information, including classroom “ w1 For a podcast on DNA sequencing in the resources, about everything related to DNA. could own such a classroom involving both authors of this See: www.yourgenome.org article, visit the Naked Scientists website. device and sequence See: www.thenakedscientists.com/sites/ ______DNA as they choose. default/files/media/Naked_Scientists_ ” Show_16.11.29_1006003_1.mp3 or use Dr Kerstin Göpfrich is a science the direct link https://tinyurl.com/ycrwge5t communicator and a postdoctoral w2 Learn more about an interactive DNA researcher at the Max Planck Institute sequencing challenge set up by the authors, for Medical Research in Heidelberg, The data may also be misused for new titled ‘DNA my smoothie’. See: www. Germany, with experience in nanopore kinds of discrimination. For example, thenakedscientists.com/articles/features/ dna-my-smoothie technologies. She established the Ring- will health insurance companies w3 Visit the Oxford Nanopore Technologies a-Scientist platform to connect scientists pick their customers depending on website to read about the latest DNA and teachers using video conferencing. genetic profiles? Could DNA records sequencer under development. See: https:// Dr Kim Judge is a senior staff scientist be available to the police? In light of nanoporetech.com/products/smidgeon the sudden miniaturisation of DNA at the Sanger Institute in Cambridge, UK, working on DNA sequencing sequencers, in principle anyone could Resources own such a device and sequence DNA using nanopores and other sequencing Schedule a discussion between the authors and technologies. as they choose – in fact, a smartphone your students by making an appointment DNA sequencer is already under via the Ring-a-Scientist website – a project developmentw3. We all leave traces of supported by Wikimedia Deutschland, DNA everywhere we go, so privacy is Stifterverband and the Volkswagen now an increasing concern. Foundation within the Open Science Fellows Program. The authors can take you through Like computers and smartphones, DNA sequencing experiments live via a video sequencers have the power to change conference. See: www.ring-a-scientist.org

20 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | General science, History, Science and society vexworldwide/Shutterstock.com

A relative view of truth deprives people of a shared platform for communication – as suggested in this illustration, based on the drawing entitled ‘Relativity’ by artist MC Escher.

Is science true? Should we believe what science tells us? A philosopher of science comments on teachers’ responses to this challenging question.

By Thomas Uebel and Susan Watt

As a science teacher, do your students sometimes put you on examples where scientific advice has changed based on new the spot – not just about the details of what you are teaching, evidence. but about the value of scientific knowledge itself? Compared So how should educators respond to the question, ‘Is science to previous generations, people are now more sceptical about true?’ Which responses support the validity of science – and institutions and expert opinions in all fields of knowledge – which could undermine it? young people perhaps even more so. And we can all think of

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Teachers’ responses in that it is 22 °C? If they are both right, esty about our knowledge: it just makes defence of science they would then have no common ref- knowledge of the world impossible. erence on which to base any decisions In this article, we look at some (for example, whether to turn the heat- Response 2: “Science is about responses used by actual science ing on or off). Having no disagreements models – it’s not about reality.” teachers in the classroom as they sounds nice, but in reality, no one could attempt to defend scientific knowledge rely on what anyone else said, and there It’s certainly true that science provides against challenges from students, would be no way of telling how things models of what the world is like. But such as ‘Why should we believe what actually are. it’s a misunderstanding to think that because science provides models, it’s science tells us?’ These responses are There is one aspect of truth relativism not about reality. followed by comments and suggestions that appeals to many people, because it from a philosopher of science to add an seems to fulfil our wish to avoid claim- Whenever we think about anything, we expert’s view on the issue. ing too much. This is even more so if do so by means of a medium – whether we put the contrast in terms of ‘relative this is words in a language or images Response 1: “Truth is relative: vs. absolute truth’ – after all, who wants that are drawn or imagined. Either way, your truth isn’t my truth.” to be an absolutist anymore? But to say we always need a means of representa- tion. Scientific thought is no different: This type of response is often tempting that there is a truth on a given matter is it provides models of reality that are to use against challenges to any knowl- not to say that we know what the truth meant to represent just those aspects edge claims, not just in science. The is. If we want to be modest in making that are under investigation. aim is to sidestep the question of truth knowledge claims, then we should just entirely – but does this work? be very careful about the claims that we Obviously, models cannot be reality make, and the uncertainty associated itself: they are merely representations The problem with seeing truth as rela- with them. Denying that there can be of it. Reality itself is what we bump tive is that, without a notion of truth as objective truth does not express mod- our heads on or burn our fingers something objective, it becomes impos- sible to understand how learning about the world around us is even possible. If what we hold to be true can only be true for us individually, could we ever Nature of science Science and society “Without a notion of truth Ages 14–19 as something objective, In this 21st century, the age of technology, is such an article it becomes impossible necessary? Unfortunately, yes. Many European science curricula to understand how at secondary-school level do not pay much attention to the construction of scientific knowledge. learning about the This very interesting article leads us to reflect on two crucial world around us is even dimensions of science: the link to factual reality, and the search for reliable and testable patterns in our comprehension of the cosmos.

possible. REVIEW After a discussion of the central ideas in this text, science teachers ” could involve their students in a semi-structured inquiry around a question from the recent history of science, as illustrated in the article. agree or disagree with each other? I Whatever approach science teachers take, I believe that this article would always be right, and so would will help them to consider the most important questions here: is you – or rather, there would no longer the scientific endeavor well understood by science students in be any ‘being right’. secondary education? Probably not. Can the misunderstanding of its Imagine two people are sitting in a goals and methods put a truly democratic and open society at risk? room, which one says feels cold and the Definitely, yes. other thinks feels warm. This is under- standable: one person may simply feel Luis M Aires, biology teacher, Antonio Gedeao Secondary School, cold more easily than the other. But Portugal what if one person says that, based on a thermometer reading, the temperature of the room is 19 °C, and the other says

22 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org UNDERSTAND | General science, History, Science and society Enzymlogic/Flickr

Model of the DNA molecule. Once Crick and Watson Nicolas Copernicus (www.bj.uj.edu.pl; public domain)/Wikimedia Commons had built the first model of DNA structure, the double-helical form rapidly led to new theories about DNA’s role in heredity.

with. Given that scientific models and theories are representations, all that we can ever ask of them is to predict and explain phenomena as precisely as possible. So is the criticism here that science uses bad models? Certainly, scientists argue over whether a model makes the right assumptions, uses the correct Page from the manuscript of De Revolutionibus Orbium Coelestium (1543) by Nicolaus parameters, has included all the Copernicus, showing the Sun at the centre of the planetary orbits relevant features, and so on. Thus, the criticism cannot be of science itself, because science makes it its business to deal with such problems. Models can be tested and their results compared, leading to gradual refinements. their only role is to make observable predictions – has been influential, Response 3: “Scientific theories are It’s a misunderstanding “ although it is no longer very popular just a way of fitting the data: all to think that because among philosophers of science. we have is observations.” science provides In any case, in science as in everyday This is an interesting thought that has life, observations very rarely stand on a long history. In the century when the models, it’s not about their own, but are part of networks of geocentric view of our Solar System was reality. related observations, generalisations being replaced by the heliocentric one, ” and expectations – in other words, it was often useful (for reasons to do theories. And the beauty is that just with society at the time) to say that all as theories lead to predictions of new that mattered was ‘saving appearances’. descriptions of the Earth circling the observations, so observations help to In the book in which Copernicus put Sun: the descriptions are merely there confirm or disconfirm theories. Both of forward his heliocentric account, the to account for the observations. And in these elements of science correct each preface warns readers not to assume more recent times, the ‘instrumental’ other, and together they make scientific any claims about reality from the view of scientific theories – in which knowledge possible.

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Furthermore, most scientific theories are very complex, and they undergo strin- gent testing – not only from advocates, but also from opponents. It is because of these internal dynamics that we can regard science as a self-correcting enter- prise. For this reason, it’s quite persua- sive to point to the practical successes of science (in terms of the technology we use) to demonstrate that science is an integrated and robust system of Larry Qian/Flickr knowledge. What lies behind this success is that, in principle, every scientific knowledge Electronics inside a mobile phone. The complex technology has been developed over many decades, based on claim can be questioned – and certainly robust scientific theories and new technological developments. will have been in the past. If a theory survives at all, there is likely to be a good deal of truth about it. Even old theories are rarely discarded in their What we call scientific knowledge Response 4: “If science is just a entirety. While Newtonian physics are theories that are confirmed to the theory, why does your mobile was superseded by relativistic physics, phone work?” highest degree that it seems reasonable to demand. But certainty is not required It is difficult to respond directly to the throughout: within science we have challenge that “science is just a theory”, many different degrees of acceptance Even old scientific as it’s not entirely clear what the com- – from theories that are extremely well “ plaint is. Science provides descriptions confirmed, to models that have a more theories are rarely that allow us to explain what happens, hypothetical status, or are even just discarded in their and to make correct predictions. What speculative. Typically, scientists would more could be expected of these explan- only count the first category here as entirety. atory descriptions that we call theories? reliable knowledge. ”

The ALMA (Atacama large millimeter/submillimeter array) telescopes in the Chilean Andes. Astronomers use data from different wavebands of the electromagnetic spectrum to inform and develop new theories about the Universe.

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______the older theory continues to apply to Resources objects within our ordinary experience, Read a classic introduction to the philosophy of Thomas Uebel is a professor in the with degrees of deviation so tiny they science, see: Department of Philosophy at the are mostly undetectable. So there is Chalmers A (2013) What is this Thing discontinuity in scientific progress, but Called Science? 4th edition. Indianapolis, University of Manchester, UK. He also continuity. USA: Hackett Publishing Company. ISBN: teaches and researches philosophy of 162466038X science and its history, and is the author For a recent and accessible introduction to of several books and numerous journal philosophy of science, see: articles. Okasha S (2016) Philosophy of Science. A Very Short Introduction. 2nd edition. Oxford, UK: Susan Watt is a science writer and Oxford University Press. ISBN: 0198745583 editor for Science in School. She holds For a comprehensive and up-to-date online a degree in natural sciences from the resource on philosophy, look for various University of Cambridge, UK, and articles under ‘science’ and ‘scientific’ postgraduate degrees in philosophy and

Eric Erbe, Chris Pooley (public domain)/Wikimedia Commons in The Stanford Encyclopaedia of psychology. Philosophy. See: https://plato.stanford.edu/ contents.html

Scanning electron micrograph of a yellow mite, Lorryia formosa, magnification about 850 x. The wave-particle theory regards particles such as electrons as also having wave properties. This theory has led to the development of electron microscopy, with exquisitely high resolution. S. Guisard/ESO

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 25 Scientist profile | INSPIRE

Becoming an astronaut: interview with Matthias Maurer The European Space Agency’s newest astronaut recruit talks about his exhilarating experiences in astronaut training and what the future has in store for space flight.

Wearing a training spacesuit, Matthias Maurer is submerged in a water tank at the Neutral Buoyancy Laboratory in Houston, Texas, USA. ESA/Stephane Corvaja, 2017

26 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org INSPIRE | Scientist profile ESA/Sabine Grothues

Matthias Maurer at the European Astronaut Centre in Cologne, Germany

By Hannah Voak

After a challenging year-long selection was triggered partly by coincidence. I When did you decide that process to become one of the European was completing my military service as you wanted to become an Space Agency’s newest astronaut an ambulance driver when the Berlin recruits, Matthias Maurer made it to the wall came down in Germany. So, in astronaut? final group of ten candidates. But, with the summer of 1990, I received a letter When I left school at the age of 19, I only six places available to fly to space, informing me that I was relieved of my did not have a clear plan for my career. his aspiration to become an astronaut service ahead of time – I could start When the European Space Agency was put on hold at the final hurdle. my studies a year earlier than planned. (ESA) announced in 2008 that it would Science in School spoke to Matthias But the deadlines for applying to study begin the selection for a new class of about his unforeseen path to becoming aerospace engineering had closed six an astronaut, and what he can expect if months before. Only a few universities astronauts, I immediately realised that it he ultimately travels to space. in Germany reopened applications for was exactly what I wanted to do. special cases like mine, so I decided The preferred age range for an astronaut How did you first become to study the next best thing – material is between 27 and 37. By that time, you science engineering. interested in science? have finished studying and have at least My plan was to change to aerospace three years’ experience as an engineer, From an early age, I was fascinated by engineering later, but after one year scientist or doctor, or a certain number engineering. My uncle is an engineer, so of studying at my home university in of flight hours as a pilot. When I applied I was always interested in the stories he Saarbrücken, Germany, I discovered for the selection process, I was already told me about his job. As a very small that material science engineering was 37. That said, Italian ESA astronaut Paolo kid, I wanted to become a pilot, or a so rich and interesting that I wanted to Nespoli has just returned from space, and Formula One racing driver – so there was continue. In the years that followed, I he is 60 years old. We now understand a technical interest right from the start. studied in the UK, France and Spain, that space flight is not so hard on the My initial plan was to study aerospace and completed my PhD in material body, so the health requirements for flying engineering, but I guess my career path science engineering in 2004. to space are changing, too.

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 27 Scientist profile | INSPIRE ESA/S Sechi

Practical courses, which include learning about microorganisms and where best to look for signs of life, prepare astronauts for assisting with scientific studies on the ISS (Matthias Maurer, left).

What advice would you give Tell us about how you got to “ You would find to someone who wants to be an astronaut. hundreds of people become an astronaut? The selection process took one year. The who have the One of the biggest problems is that you more I progressed, the more I believed can’t plan your life around becoming I could actually do it. We went from foundation to become an astronaut. Even if you have all the 8500 candidates to only ten. But, at a good astronaut – right experience, the limiting factor is the final stage, we were told there was the number of available spots to fly to room for only six of us to fly to space. then it’s down to luck space – but this could change in the I was not among the six, and instead, I whether there is a next 20 years, thanks to commercial was put on a reserve list. It was a massive space flight. disappointment – a bit like at Christmas selection process at In Europe, you would find hundreds when you receive your dream present, the right time. of people who have the foundation only for your parents to tell you the next ” to become a good astronaut – then day that it wasn’t actually for you. it’s down to luck whether there is a After the selection process, I joined ESA selection process at the right time. Don’t in 2010 as a member of their ground let anyone tell you that you can’t do it, personnel, communicating between though. Astronauts aren’t unique in the the control centre on Earth and the sense that we are smarter; we are just astronauts in space. But a couple of unique in that we were a bit luckier years ago, ESA had the capacity for than others. more space flights and astronauts. They Lastly, always have fun, pursue the immediately came to me and asked ‘Do subjects you like best, and maybe it will you still want to become an astronaut?’ add up, as it did in my case. I said yes.

28 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org INSPIRE | Scientist profile

You began astronaut training However, I can imagine that losing What would teachers find in 2015. What did it involve? sight of Earth, for example in the case most interesting about of flying to Mars, would be difficult We currently fly on Russian Soyuz psychologically. your job? spacecraft, so the training began Often, the most fascinating part about with intensive language courses in Would you fly to Mars? space is how things differ from Earth. Russian. Since then, I have also started I would do it if I had the confidence For example, how does a candle burn learning Chinese in anticipation of that it would be safe for me to return. in space? When a flame burns on our cooperation with China. In basic I would never do it on a one-way Earth, heated gases rise from the flame, astronaut training, you learn all the mission. forming the elongated shape we are skills to become an astronaut, from knowing how to react quickly to failures on the International Space Station (ISS), to collecting valuable samples for scientific studies. We are Matthias Maurer jumping from a trained as paramedics and we can also Chinese Shenzou capsule during pull out teeth and do fillings. Survival sea survival training in 2017 training is also a big part – recently I was in China practising an emergency capsule landing in the open sea. I was hoisted out of the water by a helicopter hovering above me – I felt like I was in a James Bond movie!

When will you fly to space? I am now ready to be assigned to a ESA/Stephane Corvaja, 2017 space mission at any time. There are currently six astronauts on board the ISS, but in future there will always be seven. ESA usually has only one space flight per year to the ISS and the next free spot is in 2020. I’m really hoping to be on that flight and to represent Europe in space.

What do you think will be the hardest part about living and working in space?

Physically, the most difficult part will be ESA/Helmut Rueb the spacewalk – working six hours in a space suit is really tough. It is difficult being away from your family, but it is only for half a year and I will be able to To prepare for work on the exterior of the ISS, call them every day. Another thing that Matthias Maurer performs tasks wearing a training I will miss will be the fresh air – jogging spacesuit at the ESA Neutral Buoyancy Facility in Cologne, Germany. in the forest or along the beach.

The space station is more or less the ESA/Stephane Corvaja, 2017 size of a football pitch so you can easily go the entire day without seeing another astronaut. But your sleeping quarter is as small as a cupboard, so that’s all you have for privacy.

The astronaut training means we are Matthias Maurer is lifted out of the sea during well prepared for living in space. survival training in Yantai, China

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 29 Scientist profile | INSPIRE ESA/Anneke Le Floc’h

ESA astronauts Matthias Maurer (centre) and Samantha Cristoforetti (left) during a parabolic flight, which allows astronauts to experience weightlessness for 20 seconds at a time used to seeing. In space, hot air doesn’t Finally, what is the future Resources rise, so the flame is like a ball. We can of space flight? Watch a video showing Matthias Maurer then investigate why this happens. in astronaut training. See: www.esa. It is an exciting time for space flight int/spaceinvideos/Videos/2017/01/ In that sense, astronauts act as – lots of changes are happening. The Introducing_ESA_s_new_astronaut_ facilitators for scientists. One of my ISS will operate for a few more years, Matthias_Maurer favourite projects was developing new and ESA is already studying potential Visit the ESA education website for classroom alloys in space for the next generation resources, hands-on projects for pupils, and space platforms for the post-ISS period. of aeroplane turbine engines, so information about teacher training. See: The Chinese space station will be they can fly further with less petrol. www.esa.int/Education ready by 2023, and the Americans Protein crystallisation in space is also Learn more about human space flight and are talking about a commercial space exploration by visiting the ESA website. fascinating – the weightlessness means station that could replace the ISS. We See: www.esa.int/Our_Activities/Human_ that the crystals grow perfectly, so also have long-term international plans Spaceflight/Astronauts scientists fly proteins to space to be to return to the Moon and eventually crystallised, before they are brought ______– in the next few decades – put the back to Earth for X-ray analysis. first people on Mars. Space flight is Space research also has applications Hannah Voak is an editor of Science a truly international endeavour, and for medicine, for example testing in School. With a bachelor’s degree in it is essential that we have people medication to slow down or stop biology and an enthusiasm for science from different countries, different osteoporosis. And we also address communication, she moved to Germany backgrounds and different fields, in 2016 to join Science in School at the fundamental questions such as where working together. life comes from, whether we are unique European Molecular Biology Laboratory. on Earth, and what organisms can survive in space.

30 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Biology, Chemistry, Engineering

Turning dandelions into rubber: the road to a sustainable future

A species of dandelion is leading the way towards sustainable rubber. Find out how, by growing this unusual plant yourself and extracting the rubber from the roots. Mareike Göbel

Russian dandelion, Taraxacum kok-saghyz

By Mareike Göbel and Martin Gröger

Look around you: what objects can you see that are made but underestimated, dandelion: Taraxacum kok-saghyz, from rubber? You might spot an elastic band, a pencil commonly known as the Russian dandelion. eraser, or perhaps one of the biggest users of rubber – car To help students understand more about sustainability and tyres. In fact, over 40 000 everyday products are produced this unusual source of rubber, we developed two simple from natural and synthetic rubber. With this material in methods to extract the rubber from the dried roots of the such high demand, scientists are exploring an alternative Russian dandelion. In the first method, students grind the source of rubber from a particular species of the familiar, roots into a powder to extract the rubber particles and create

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 31 Biology, Chemistry, Engineering | TEACH

The roots of the Russian dandelion contain a high proportion of rubber. Mareike Göbel

their own eraser. In the second method, sodium hydroxide is used to erode the Chemistry woody parts of the root, and students can stretch out the fine strands of Biology rubber that remain. The activities can be Environmental sciences carried out by students aged 11–14 or older, in small groups of three or four, Design technology and will take about two hours. History Ages 11–19 Rubber: sources and structure We live in a time when we must reconsider our habits and how we use natural resources. This article, which provides information on how The majority of the world’s natural rubber can be made using a species of dandelion, can be used for rubber comes from plantations REVIEW chemistry, biology and environmental sciences lessons. It is particularly of the tropical rubber tree Hevea suitable for discussing sustainability issues related to technological brasiliensis – over 90% of which are development, and for considering global questions regarding cultivated in Southeast Asia. Natural biodiversity. rubber production is responsible for widespread deforestation, and most The article also describes a novel activity using the roots of the of this rubber is used to make tyres. dandelion. The Taraxacum species must be grown well in advance, Relying on natural rubber to meet rising but teachers could grow the plants with students in the spring, and complete the experiment in autumn. It would be interesting to follow demands is not only unsustainable, the whole process, from seeds to rubber. but also risky: yields of natural rubber are falling due to a decline in prices, Ingela Bursjöö, science teacher and science education researcher, which has resulted in farmers switching Johannebergsskolan Elementary School, Sweden to more profitable plantations such as palm oil. Climate change and crop

32 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Biology, Chemistry, Engineering

diseases pose additional threats. These Russian dandelion as an alternative Structure and properties of rubber challenges make the future of natural source of rubber. Rubber is used in so many products rubber production uncertain. Producing Compared to tree-sourced rubber, the because of its unique chemical and rubber synthetically can help, but it Russian dandelion is extremely resilient physical characteristics. An elastomer (a requires the use of crude oil – so it is and can be grown in moderate climates polymer with elastic properties, such as important to find an environmentally on poor soils. This means that it can be rubber) can be stretched to over 100% friendly and sustainable alternative. grown locally, reducing dependence of its original length without breaking. on imports. It is also much quicker to Natural rubber consists of long chains The discovery of Russian dandelion grow dandelions than trees – Russian of cis-1,4-polyisoprene (figure 1), each dandelions can be harvested twice a comprising up to 30 000 isoprene The Russian dandelion, Taraxacum year, whereas natural rubber trees take monomers. The chains are interwoven kok-saghyz, was discovered in Eastern 7–10 years to mature before the sap, with one another like a plate of cooked Kazakhstan in 1931. The plant has the which is processed into rubber, can first spaghetti. When you stretch rubber, yellow flowers characteristic of the be collected. What’s more, the Russian the chains are pulled apart but do not dandelion genus, but the roots contain dandelion produces inulin (a sugar break, due to the linkages between the a higher percentage of rubber than the substitute and potential biofuel) as a entangled chains (figure 2). familiar species of dandelion found by-product. in Europe. Soon after its discovery, the Soviet Union began large-scale cultivation of T. kok-saghyz to extract the rubber and end the country’s dependence on imports (see Göbel & Gröger, 2016). When the Japanese seized rubber plantations in Southeast Asia during World War II, other countries, including the USA and Smokefoot/Wikimedia Commons Germany, started farming the dandelion as an alternative. When the war ended and supplies from the rubber tree, H. brasiliensis, became available again, research on the Russian dandelion ceased – until recently. Figure 1: Chemical structure of cis-1 ,4-polyisoprene, the main constituent of natural rubber

“Compared to tree- sourced rubber, the Russian dandelion is extremely resilient and can be grown in moderate climates on poor soils.”

A replacement for natural rubber Today, research into the Russian dandelion is growing. The Fraunhofer

Institute for Molecular Biology and Mareike Göbel Applied Ecologyw1, based at the University of Münster, and the tyre company Continentalw2 are just two of the organisations working on using Figure 2: Model showing the structure of rubber when relaxed (left) and stretched (right)

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 33 Biology, Chemistry, Engineering | TEACH David Edelstein/Unsplash

The tyre industry is the biggest consumer of natural rubber.

Preparing the plant material 2. Show students a photo of the them to carefully break the root In preparation for the following Russian dandelion and ask them to in half so they can see the very activities, you will need to grow the find the connection between the fine elastic rubber threads within Russian dandelion plant and harvest dandelion and the rubber products. the root (figure 3). Note that these the roots to dry. The whole preparation To prompt them, ask where natural threads can rip easily if the root is process will take approximately seven rubber usually comes from. broken too forcefully. months from February to September, 3. Give each student one dried but teachers could use this opportunity Russian dandelion root. Instruct to teach students about plants and the requirements for growing them. Seeds can be purchased onlinew3 and should be sown in February in a window- sill greenhouse. After two months, transfer the plants into flower boxes. You can harvest the roots from August onwards. To dry them, place the roots on paper towels and leave them at room temperature for 3–4 weeks.

Introductory activity Before carrying out the two main activities, spark your students’ interest with this starter activity introducing the topic of rubber and the Russian dandelion.

Procedure Mareike Göbel 1. Ask your students to list rubber products that they use in their everyday lives. Figure 3: Breaking the Russian dandelion root reveals the net of white rubber threads.

34 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Biology, Chemistry, Engineering

Activity 1: Making a dandelion root eraser In this activity, students physically extract rubber from dried Russian dandelion roots to produce a small eraser.

Materials Each group of 3–4 students will need: · 3–4 pieces of dried Russian dandelion root. Note: you should choose roots with a diameter of about 1 mm, and break them into pieces of about 2–3 cm in length. · Pestle and mortar · Tweezers · Watch glass · Water Mareike Göbel

Procedure 1. Place the dried dandelion roots into the mortar (figure 4). The greater the Figure 4: Dried dandelion roots in the mortar number of roots you have, the more time and effort is required to grind them. 2. Using the pestle, grind the roots for 5–10 minutes until they become a homogeneous powder (figure 5). 3. As you grind the roots, remove any small, globular brown particles

in the mortar using tweezers, and Mareike Göbel place aside on the watch glass. These are the rubber particles. 4. Continue grinding the roots until no further brown particles are formed Figure 5: Dried roots are ground until they become Figure 6: Individual rubber particles a powder. in the powder. 5. Wash out the mortar with some water to remove the woody powder. Place the rubber particles back into the mortar, which should still be slightly wet (figure 6). 6. Grind the rubber particles until they stick together (figure 7) and form a

piece of rubber about 0.5–1 cm in Mareike Göbel length (figure 8). 7. You can now test the piece of rubber as an eraser. Students can Figure 7: Individual rubber particles come together Figure 8: Grinding three pieces of dried rubber merge the rubber from multiple to form one piece of rubber. produces an eraser roughly 1 cm in length. groups to create a bigger eraser.

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Activity 2: Refining the References rubber threads Göbel M, Gröger M (2016) Kautschukforschung am russischen Löwenzahn in der Zeit The rubber from fresh dandelion roots is um den Zweiten Weltkrieg. Praxis der an emulsion of polymer micro-particles, Naturwissenschaften – Chemie in der Schule similar to the sap from a rubber tree. In 8(65): 19–22 the dried roots, however, the rubber is a Göbel M, Gröger M (2017) Alternative Kautschukquellen am Beispiel des solid aggregate. In this activity, students russischen Löwenzahns experimentell dissolve the outer, woody material of erschließen. Praxis der Naturwissenschaften – the dried roots to gain access to the Chemie in der Schule 2(66): 26–30 inner net of rubber. Web references Materials w1 Understand how researchers are using Russian dandelion rubber as an

Each group of 3–4 students will need: Mareike Göbel environmentally friendly alternative to the · 1–2 pieces of dried Russian natural rubber tree in this video from the dandelion root. Note: you should Fraunhofer Institute. See: www.youtube. choose roots with a diameter of com/watch?v=bvVJL2GYRHY about 0.5 cm, and break them into Figure 9: Gently pulling the net of rubber threads w2 Learn how rubber from the Russian pieces of about 3–4 cm in length. apart highlights the elastic properties of rubber. dandelion can be used to produce tyres · 5 ml of sodium hydroxide (NaOH) in this video from the tyre company Continental. See: www.youtube.com/ solution (3%) watch?v=H8XODAJAmmg · Test tube w3 Seeds of Russian dandelion, Taraxacum kok- · Water bath set to approximately 90 °C Discussion questions saghyz, can be purchased from the All Good · Tweezers Things Organic Seeds website. See: www. Alongside the activities, discuss the plantgoodseed.com Safety note: following questions with your students This procedure involves the use of to teach them about different types of Resources sodium hydroxide solution. Students rubber, the properties of rubber, and the Understand more about rubber and inulin should wear lab coats and safety importance of sustainability. production from the Russian dandelion goggles. See also the general safety note · What are the advantages and in an article from Owlcation. See: https:// on the Science in School website and at disadvantages of rubber from Hevea owlcation.com/stem/Natural-Latex-and- Rubber-From-Common-and-Russian- the end of this print issue. brasiliensis and synthetic rubber? Dandelions · Why is it important to look for Read about the European DRIVE4EU project, Procedure alternative sources of rubber like the which is working to make Russian dandelion 1. Place a piece of dandelion root in a Russian dandelion? rubber a serious alternative to natural test tube. · When you break a dandelion root in rubber. See: www.wur.nl/nl/nieuws/ Rubber-from-Russian-dandelions-a- half, what can you see? 2. Cover the root with the sodium serious-European-alternative-to- hydroxide solution. · What form does the rubber take in rubber-tree-plantations.htm 3. Place the test tube in the water bath dried dandelion roots? The gene editing technique CRISPR-Cas9 has for about one hour. The colour of · What are the advantages and been used to increase the rubber content the sodium hydroxide solution will disadvantages of dandelion rubber? of Russian dandelion plants. Read more in an article from Chemical & Engineering change from clear to brown, but the · What are the properties of rubber? solution will remain transparent. News. See: https://cen.acs.org/articles/94/i30/ Explain its elasticity. Dandelions-scourge-lawns-fount-rubber.html 4. After one hour, remove the root ______from the test tube using tweezers. The root will now be soft. Extension activity 5. Using tweezers, carefully wash the Seeing and experiencing the elasticity Mareike Göbel is a PhD student in root by dipping it into the water from of rubber from the Russian dandelion Professor Dr Martin Gröger’s Chemistry the water bath. The woody material is sufficient proof of natural rubber. Didactics group at the University of of the root will wash away, but if To extend the activities, however, Siegen, Germany. In her thesis, she needed, you should remove any you could chemically detect the develops experimental approaches for remaining tissue using the tweezers double bonds in polyisoprene, for extracting rubber and inulin from the until you are left with only the bright example using bromine, potassium roots of Russian dandelion and tests and white net of fine rubber threads. permanganate (Baeyer test) or the evaluates them with students. 6. Gently extend the threads by Burchfield colour reaction (see Göbel & pulling them apart (figure 9). Gröger, 2017).

36 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org solutions revealed. the principlesofNewtonianmechanics, asthe as thetablecloth-snatch trick – werebasedon 2016). All thetricks –even familiarones,such tricks totryathomeorintheclassroom(Featonby, In apreviousarticle,Ipresentedsomeintriguing By David Featonby fantastic feats tochallengeandentertain – Roll up, roll up!We bringyou somemore and toshowcase somephysics, too. ALN BOUNCING FALLING & FANTASTIC FURTHER FEATS page 51. physics principles,asrevealed inthesolutionson you’ll beabletosolve by applyingsomesimple Here, Ipresentanotherselectionofchallenges that www.scienceinschool.org IScience inSchoolIIssue43: Spring2018I 37

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Engineering, Physics

FishCoolish/Shutterstock.com Photo: Photo: Engineering, Physics | TEACH

Feat 1: Tunnel ball Procedure W-shaped path, but usually returns to the sender as if it has struck a The challenge here – to make a ball Make a tunnel with the book lying reflecting wall in the tunnel. bounce through a tunnel – may seem across the drinking glasses (or other easy, but it’s more difficult than it supports), as shown in figure 1. So how can you make the ball pass through the tunnel as required? And appears at first. The challenge is to try to make the ball can you explain what’s going on? bounce in the following way, forming Materials a W-shaped path (figure 2): This feat can be performed using different-sized tunnels – for example, · First bounce: in front of the tunnel · One high-bounce rubber ball a table with a flat underside (with the · Second bounce: on the underside · One heavy, large-format floor as the lower surface). hardback book of the tunnel (book) · Third bounce: outside the · Two tall drinking glasses (or Feat 2: Cork bounce other similar-sized supports for tunnel the book) It comes as a surprise to most people Here, the trick is quite easy to do; the · A table or other level surface that the ball does not follow a challenge is to explain why it works. David Featonby/Nicola Graf David Featonby

Figure 1: Tunnel arrangement formed by a Figure 2: How the ball should bounce through the tunnel: the challenge is to make it follow this path. book and two glasses

Physics Dynamics Engineering Ages 11–16 Mechanics

This article describes some simple but enjoyable Questions could include: experiments that illustrate important principles of · How does spin affect the movement of a ball? mechanics and dynamics. It shows how bouncing balls · Does spin depend on the type of surface? or cylindrical objects move, depending on their spin · How do spin and friction depend on each other? or applied forces, and how this movement depends · What applications are connected to the experiments on friction and other factors. These experiments are

REVIEW described in the article? simple to perform, and show interesting effects. The article could also be used as a comprehension Gerd Vogt, physics and technology teacher, exercise. Higher Secondary School for Environment and Economics (Yspertal), Austria

38 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org position. bounced intoavertical standing shown infigure4 weresuccessfully you cantrythiswith:alltheobjects there areplentymoretube-shapeditems toilet rolltubethanwiththecork. And In fact,thischallenge iseasierwiththe or any slightlyflexibletube. the cardboardinnertubeofatoiletroll, with othercylindrical objects–such as make itbounceupright,you cantryit worked outhow besttodropthecork to Once you’ve masteredthisfeatand 2. 1. Procedure · · Materials A tableorotherlevel surface preferably madefromrealcork One standardwine-bottlecork, eut Ad a yu xli why? explain you can And result? before you dropittoachieve this How shouldyou holdthecork standing ononeend(figure3). Try todropthecorksothatitlands the table. Hold thecorkabout10cmabove Figure 4:Tubes suitablefor dropping Figure 3:Cork standingupright afterbeingdropped www.scienceinschool.org IScience inSchoolIIssue43: Spring2018I 39

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David Featonby David David Featonby David |

Engineering, Physics

FishCoolish/Shutterstock .com FishCoolish/Shutterstock Photo: Photo: Engineering, Physics | TEACH

______Feat 3: Card drop David Featonby is a retired physics The aim of this challenge is to find a teacher from Newcastle, UK, reliable way to drop a playing card with 35 years experience in the into a hat, from a height of about classroom. He is the author of 1.5 m. various hands-on articles in Science Materials in School and Physics Education, and is on the executive committee · Some standard-sized playing of Science on Stage. David has cards a keen interest in unusual things · A hat with a crown that keeps its connected with physics, and in shape when placed upside down, revealing the physics in everyday or a similar-sized bowl, box or things to everyone, whatever their other open container age. He has presented exciting · A table or other level surface physics workshops all over Europe, to both children and teachers. Procedure

1. Place the hat upside down on David Featonby the table. 2. Take a card and hold it about 1.5 m above the hat (figure 5). Figure 5: Attempting to drop a playing card into an 3. Try to drop the card so that upturned hat. As you can see from the photograph, it lands inside the hat. How this is not as simple as it seems. should you hold the card before you drop it to achieve this result? And can you explain why? Philippa Willitts/Flickr

40 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Chemistry

The chemical chameleon demonstration produces vivid colour changes as a result of redox reactions. IanRedding/Shutterstock.com

Colourful chemistry: redox reactions with lollipops Use a lollipop to activate colour-changing redox reactions in this simple but eye-catching activity.

By Marisa Prolongo and Gabriel Pinto

Teaching oxidation-reduction (redox) reactions is part of from a lollipop is used as the reducing agent. When glucose all secondary-school chemistry curricula. In this article, we is added to a solution containing OH– ions, the alcohol groups describe a vivid colour-changing demonstration to illustrate in the glucose donate electrons, giving rise to ketone groups: a chain of redox reactions, whereby electrons are transferred between different compounds and ions. The activity is –C(H)(OH)– + 2OH– à –C(=O)– + 2H O + 2e– suitable as a teacher demonstration, or older students could 2 (secondary alcohol) (ketone group) carry out the experiment themselves. In our experiment, glucose is added to a permanganate Oxidising and reducing agents solution together with sodium hydroxide (NaOH), so electrons from glucose (C6H12O6) are first donated to – A redox reaction is any chemical reaction in which a permanganate ions (MnO4 ). The oxidation products of the molecule, atom or ion loses or gains electrons, altering its reducing sugar are mainly glucuronic acid (C6H10O7,), plus oxidation state. An oxidising agent gains electrons (and is some arabinonic acid (C5H10O6) and formic acid (CH2O2). reduced in the reaction) and a reducing agent loses electrons If the lollipop is made from fructose, which is an isomer of

(and is oxidised in the reaction). In this experiment, glucose glucose, the main product is fructonic acid (also C6H10O7).

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 41 Chemistry | TEACH

In a series of redox reactions, electrons are donated continually from glucose to successive compounds of manganese. At each step in the chain, a colour change is visible. Manganese is ideal for this experiment, as it has more stable oxidation states than any other transition metal (from +2 to +7), each of which has a different colour. You may be familiar with the classic ‘chemical chameleon’ demonstrationw1, of which this experiment is an adaptation. In the original version, you begin with a potassium permanganate and glucose solution, which changes colour upon mixing with a spatula. By using a lollipop instead, the glucose is added more gradually to the solution, Marisa Prolongo which makes it easier to follow the colour changes. Using a miniature electric whisk means the lollipop is stirred faster than by hand. Figure 1: Materials required for the lollipop experiment

Materials Procedure Chemistry You will need the following materials The activity is suitable for a single Redox reactions (see figure 1): lesson. The experiment takes only about

· Potassium permanganate (KMnO4) 15 minutes and can be followed up by a Ages 16–19 crystals set of discussion questions. · Spherical lollipop containing glucose The steps are as follows: The redox chemistry of (or other reducing sugar, 1. Fill the flask or beaker with 200 ml manganese is a fascinat- e.g. fructose) of distilled water. ing aspect of transition · 3–4 sodium hydroxide (NaOH) metal chemistry. This 2. Stir in the NaOH pellets with the pellets (approximately 0.5 g) simple practical exercise spoon until they have dissolved · helps students to famil- 200 ml distilled water completely. iarise themselves with the · 250 ml conical flask or beaker 3. Using the spatula, add a few variable oxidation states (glass or plastic) REVIEW potassium permanganate crystals of manganese and their · Spoon and spatula (not too many, or the colour will be respective colours. · Miniature electric whisk, too dark to see the changes). When

Observing the different e.g. hand-held milk frother potassium permanganate (KMnO4) colours will elicit discus- · Adhesive tape is added to the alkaline NaOH sion and will be a point solution, it dissolves into potassium Safety note: of focus for understanding + – (K ) and permanganate (MnO4 ) what is happening in the A lab coat, gloves and safety goggles ions. should be worn. Teachers should redox steps in the reaction. 4. Attach the stick of the unwrapped follow their local health and safety lollipop to the mini electric whisk rules, in particular concerning the use Andrew Galea, chemistry using adhesive tape (see figure 1). of potassium permanganate and the lecturer, Giovanni Curmi disposal of the resulting solution. See 5. Insert the lollipop into the solution Higher Secondary School, also the general safety note on the and switch on the whisk to start Malta Science in School website and at the mixing. end of this print issue.

42 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Chemistry

As the lollipop dissolves into the 1. The first colour (purple) corresponds has an oxidation state of +5 and a – solution, you will observe colour to permanganate ions (MnO4 ). blue colour. changes for each redox reaction. The Manganese has the oxidation state – – MnO4 (aq) (purple) + 2e first two changes happen very rapidly +7 (figure 2). 3– → MnO4 (aq) (blue) (3–5 seconds), while further changes 2. The permanganate ions (MnO –) are 4 3. The manganate ions (MnO 2–), take a little longer. Students can take then reduced to manganate ions 4 which have an oxidation state photos (e.g. with the camera of a (MnO 2–). The oxidation state of 4 of +6, are further reduced to mobile phone) at various time points manganese changes from +7 to +6, manganese dioxide (MnO ), with to better compare and follow the and the colour changes from purple 2 an oxidation state of +4, causing changes in colour. A video from the to green (figure 4). authors demonstrating the experiment is a colour change from green to MnO –(aq) (purple) + e– w2 4 yellow-brown (figure 5). available in Spanish . 2– → MnO4 (aq) (green) MnO 2–(aq) (green) + 2 H O(l) + 2e– An intermediate blue stage occurs 4 2 → MnO (s) + 4OH–(aq) between steps 1 and 2 (figure 2 What happens in the (yellow-brown) 3). One explanation is that the experiment? mixture contains both the purple 4. Finally, when even more glucose – As the lollipop dissolves in the solution permanganate (MnO4 ) and the is incorporated into the solution, 2– containing manganese ions, at least five green manganate ions (MnO4 ), brown-black manganese dioxide different colours can be distinguished which combine to produce a blue (MnO2) forms a colloidal (as shown in figures 2–6), which solution. Another explanation is that suspension in alkaline solution, correspond to different oxidation states a part of permanganate is reduced which (if fairly dilute) can appear 3– of manganese. to hypomanganate (MnO4 ), which orange (figure 6).

Figure 2: The first colour in Figure 3: Before the colour Figure 4: Permanganate ions Figure 5: Manganate ions Figure 6: The final colour the chain of redox reactions changes from purple to are reduced to manganate are reduced to manganese change is to orange, when is purple, which corresponds green, there is a blue ions, resulting in a colour dioxide, causing the colour to manganese dioxide forms a to the permanganate ions. intermediate stage. change to green. change from green to yellow- colloidal suspension in the brown. alkaline solution. Marisa Prolongo

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 43 Chemistry | TEACH

Variations in colour Permanganate ions (MnO -) Manganate ions (MnO 2-) Manganese dioxide (MnO ) The food colours used in lollipops do 4 4 2 not have a big impact on the colours you see in this experiment, but some other factors do play a role. Once the reactions start, there are always mixtures of ions in the solution, resulting in mixtures of colours that are not always easy to interpret (see figure 7). Another factor is that the colour of manganese ions in solution is Nicola Graf generally different from the colour of their corresponding solid salts. This is because manganese ions form complexes with water due to Figure 7: Colours of the three main manganese compounds (top row) and example mixtures of these compounds as the redox reactions proceed (bottom row) the electron-accepting capacity of their atomic d-orbitals. In addition, the tendency for molecules to accept electrons varies with pH and temperature, so if you change these Electron configuration and transition metals variables or the quantities of the chemicals, the colours will vary, and the Electrons are arranged in energy levels called shells. Each shell is divided colour changes will occur at different into subshells, which are made up of orbitals. Transition metals have one times between experiments. or more electrons in their outermost d-orbital. The difference in energy between individual d-orbital electrons is relatively small, so all transition metal cations have a variety of ways of forming chemical bonds involving different numbers of d-orbital electrons. This is why transition Discussion metals have several oxidation states. To link the lollipop demonstration to When electrons absorb certain frequencies of electromagnetic radiation, the chemistry of redox reactions, ask they jump to a higher energy level. In many transition metals, the your students some of the following difference in energy between d-orbitals corresponds to the energy questions: of radiation of the visible light spectrum. For example, the d-orbital · In the experiment, what is the electrons of permanganate ions absorb electromagnetic radiation from reducing agent that donates the yellow part of the visible spectrum, but what we see as the colour electrons in the redox reactions? of permanganate ions is the colour complementary to yellow – that is, This depends on which reducing purple. We see the colour of the remaining wavelengths that were not sugar you use, but in our experiment, absorbed (figure 8). the reducing agent is glucose

BACKGROUND 750 nm 400 nm (C6H12O6). · What is the oxidising agent that accepts the electrons? The first oxidising agent in the 630 nm 430 nm reaction is the permanganate ions. After that, electrons are donated to manganate ions. · Does potassium permanganate in solution absorb the part of

visible light that corresponds to Nicola Graf the colour we see (green) or to its 590 nm 480 nm complementary colour (red)? Potassium permanganate absorbs electromagnetic radiation 560 nm from the red part of the visible spectrum, but what we see as the Figure 8: The colour of the solution is the colour that is complementary (i.e. opposite on the colour wheel) to the wavelength of light absorbed by d-orbital electrons. colour of manganate ions is the complementary colour, green.

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· Do you know of any other chemical Acknowledgements Resources elements that show different colours This article is based on a presentation For ideas on introducing redox reactions using in different oxidation states in everyday examples, see: at the Spanish Science on Stage festival solution? Voak H (2016) Redox resources. Science (Ciencia en Acción) in 2014. This work Examples include: chromium in School 36. www.scienceinschool.org/ was first carried out by students at IES content/redox-resources (Cr O 2–, orange; CrO 2–, yellow) and 2 7 4 Manuel Romero Secondary School in vanadium (V2+, violet; V3+, green; To try a colour-change experiment involving Málaga, Spain. We are grateful for the pH-sensitive plant dyes, see: VO2+, blue; VO 3–, yellow) 4 support of the Technical University of Shimamoto GG, Vitorino Rossi A (2005) An · What are the main uses of Madrid (Universidad Politécnica de artistic introduction to anthocyanin inks. manganese, for example in biology Madrid) for the projects ‘Promotion of Science in School 31: 32–36. or industry? experimental learning of chemistry’ www.scienceinschool.org/content/ Manganese compounds are used and ‘Chem-Innova’, and of the Spanish artistic-introduction-anthocyanin-inks in stainless steels and batteries, Royal Society of Chemistry (Real ______and as fuel additives and pigments. Sociedad Española de Química, RSEQ). Manganese is also an essential Marisa Prolongo is a physics and cofactor for many enzymes, such Web references chemistry teacher currently working as photosystem II in chloroplasts. w1 For variations of the experiment, visit at Principia, an interactive science However, in large amounts it is toxic the Science Brothers website and the museum in Málaga, Spain. She has to humans. Hobby Chemistry website. See: www. more than two decades of teaching sciencebrothers.org/the-chemical- chameleon/ and https://hobbychemistry. experience, including a variety of Variations of the experiment wordpress.com/2015/03/31/ student-centred learning methods and chemical-chameleon/ activities. This experiment can be performed in a w2 A video of the experiment is available in number of different ways. For example, Gabriel Pinto is a professor at the Spanish on YouTube and the IES Manuel Technical University of Madrid, Spain, rather than using a lollipop, you could Romero Secondary School website. See: where he has been teaching chemistry use a chewing gum containing sugar www.youtube.com/watch?v=1pE3U7UkIqc as the reducing agent; or instead of or http://iesmanuelromero.es/index.php/es/ to engineers for 32 years. He has been adding the glucose to a flask, you noticias/132-noticias-curso-2013-14/519- involved in a number of STEM outreach could add it to a plastic bottle and experimentos-de-ciencias programmes and activities for students. shake it to observe the colour changes Marisa and Gabriel are Scientix (see figure 9). Your students could use ambassadors and have taken part in their creativity to think of alternative many national and international science experiments. festivals and workshops presenting experiments for STEM education. Marisa Prolongo

Figure 9: An alternative experimental setup using chewing gum and a plastic bottle

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Saving the Earth Hollywood-style Challenge your students to save the Earth from an asteroid collision, using calculations based on the Hollywood sci-fi fantasy film Armageddon.

By Mike Follows

What would students prefer to discuss: Hollywood films or Armageddon: the story physics? In my physics classes, I try to combine these topics by using scenarios from Hollywood sci-fi films as a source In the film, astronomers spot an asteroid the size of Texas of problem-solving exercises – in a similar way to using heading towards Earth when it is only 18 days away from the adventures of superhero characters (see Follows, 2017). impact. A plan is devised to detonate a nuclear warhead Even if students have not seen the films, they seem to enjoy beneath the surface of the asteroid, to split it into two equal engaging with the inventive and fantastical scenarios, which halves along a fault line. The two halves would then move they can use as a basis for doing real science – as long as the apart – and miss the Earth. To execute the plan, NASA flies ideas and assumptions are set out clearly. oil-driller Harry Stamper (Bruce Willis) and his team to In this article, I present some exercises based on the film the asteroid on board two space shuttles, which perform a Armageddon (1998) – a Hollywood movie about a heroic slingshot around the Moon and come up behind the mission to save the Earth from a giant asteroid heading asteroid. Once they reach the asteroid, to avert disaster they straight towards it. The film was criticised for being rather must detonate the bomb before the asteroid reaches ‘zero unrealistic, but it still offers an interesting plot to use as a barrier’, a point reached eight hours after the asteroid passes basis for calculations. the Moon.

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· The asteroid is heading towards Earth at a speed of 22 000 miles per hour. · Each half of the asteroid misses the Earth’s surface by 400 miles (640 km). The other information we need is as Astronomy follows: · Texas has an area of 696 200 km2. Linear motion · The average density of the four Ages 14–19 largest known asteroids is 2760 kg m-3. (For comparison, the Earth has a This activity is very density of 5520 kg m-3.) interesting and fun for · The distance of the Moon from Earth students. What better way is 384 400 km. to trigger students’ curiosity · Earth has a radius of 6400 km. and to prompt them to · The energy of a nuclear warhead think creatively? Verifying is up to 50 megatons of TNT. (This or disproving facts derived

is the energy of the most powerful REVIEW from fictional films allows thermonuclear weapon known: the students to generate their Soviet warhead called Big Ivan.) own questions about them, · 1 megaton of TNT is 4.18 x 1015 J and to think of how these questions can be answered Let’s also assume that: by applying their knowledge · The asteroid is heading for the centre of physics and mathematics. of the Earth, so that both halves of No matter how surreal the asteroid need to move ‘sideways’ some scenes in these films by the same distance. are, there will always be a scientific principle that can help explain their possibility

geralt/pixabay.com Student questions and worked calculations or impossibility. The use of science to Students are asked to investigate explain fictional movies whether the plan is likely to succeed in can also lead to some saving Earth from the collision. This can very elaborate discussions be done as a sequence of calculations, when students think about as set out below. Students work in the facts stated in films groups, and are encouraged to discuss and do not just take them the way forward with each other. for granted. Students can Creating a classroom activity be motivated to expand 1. Show that the asteroid has a radius their area of research Students can carry out a variety of of 470.8 km. calculations based on the information as needed, and to back We assume that the approximately in the film, supplemented by some up their arguments with circular cross-section of the asteroid reasonable assumptions. The fun lies mathematical evidence. has an area A equal to that of Texas, in seeing whether the quantities and This exercise can also make i.e. approximately 696 200 km2. assumptions in the film make sense – students aware that science 2 or not. A = pr where r = radius of asteroid. facts are everywhere, in real So: life as well as in fiction. From the film, we know that: A · The asteroid is ‘the size of Texas’. r = p Let’s assume that this refers to the Catherine Cutajar, 696 200 km physics lecturer, St Martin’s cross-sectional area through the = centre of the approximately p College, Malta spherical asteroid. = 470.8 km

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 47 Astronomy/space, Mathematics, Physics | TEACH

2. At what speed is the asteroid Method 2 travelling in metric units For those students who are more (i.e. in m s-1)? confident with maths, we can use Encourage the students to perform proportionality. As in the method the change of units formally: above, in the time t that it takes the asteroid to travel 101 000 km to 22 000 miles per hour (mph) Earth, the two pieces must move 1609 m = 22000 x apart by a distance equivalent to the 3600 s radius of the Earth plus 640 km, R. = 9833 m s-1 So using algebra:

s D R 3. How far from Earth is ‘zero barrier’? t = = = u v v To answer this question, we first need 1 2 D = v t to work out how far the asteroid 1 R so v2 = v1 would travel in eight hours, as the D 3 -1 3 ‘zero barrier’ is a distance equal to = 9.83 x 10 m s x (6400 + 640) x 10 m eight hours travel from the Moon: 1.01 x 108 m Distance = speed x time = 685 m s-1

-1 distance = 9833 m s x 8 x 3600 s time = speed = 2.83 x 108 m D R Then, we subtract this distance from so = = R = v t v v the overall Earth–Moon distance 2 1 2 8 (3.84 x 10 m) to calculate how much Rearranging for v2 gives:

further the asteroid would need to Nicola Graf R v = v travel to collide with the Earth. 2 1 D

3 -1 3 3.84 x 108 m – 2.83 x 108 m = 9.83 x 10 m s x (6400 + 640) x 10 m = 1.01 x 108 m Figure 1 (not to scale): The yellow line shows the 1.01 x 108 m asteroid’s original direction of travel. The black = 685 m s-1 line shows how far one half of the asteroid has to 4. How fast do the two pieces of the move to miss the Earth by 640 km; the blue line shows the resultant path that the half-asteroid 5. What is the mass of the asteroid asteroid need to move apart to needs to take. (assuming it has a density typical avoid impact with Earth? of asteroids)? The two halves of the asteroid must The mass m is equal to density r travel 1.01 x 108 m from the zero Method 1 times volume V, so m = r x V barrier to reach Earth. In the time this First, we calculate how long it would takes, each half-asteroid must also take (time t) for the asteroid to travel The asteroid is approximately 4 move in a direction perpendicular from the zero barrier to Earth: spherical, so V = p R3 3 to the original direction of travel, far D t = From question 1, R = 470.8 km enough to miss the Earth by at least v1 So M = r p R3 640 km on each side (see figure 1). 1.01 x 108 m = 4 Here: 9.83 x 103 m s-1 = 2760 kg m-3 x p x (4.71 x 105 m)3 3 D = distance between zero barrier = 10 274.7 s = 1.21 x 1021 kg and Earth = 171.2 min, or 2 h 51 min R = radius of the Earth plus the 6. How much kinetic energy must 640 km by which each half We can now work out the speed that be given to the two halves of the asteroid to prevent a collision misses the Earth each half of the asteroid needs to move in a direction perpendicular to with Earth? v = speed of the asteroid moving 1 its original path to miss the Earth with Note: you will get the same answer towards Earth a margin of 640 km. whether the asteroid is treated as one v = perpendicular (sideways) speed 2 lump or two separate pieces. of each half-asteroid needed to R v = 1 2 2 t E = mv miss the Earth with a margin of 2 (6400 + 640) x 103 640 km 1 = = x 1.2 x 1021 kg x (685 m s-1)2 10 274.7 s 2 The speed v2 can be calculated in two ways. = 685 m s-1 = 2.84 x 1026 J

48 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Astronomy/space, Mathematics, Physics

7. How many nuclear weapons of the same size as Big Ivan would be needed to provide this energy? One Big Ivan is equivalent to 50 megatons of TNT = 50 x 4.18 x 1015 J = 2.09 x 1017 J So the energy required to change the path of the asteroid sufficiently to miss the Earth is equivalent to: 2.84 x 1026 J = 1.36 x 109 Big Ivans 2.09 x 1017 J

8. How fast will the two halves of the asteroid move apart if only one Big Ivan bomb is used? E = 1 mv2 2 Jack W. Aeby (public domain)/Wikimedia Commons 2E so v = m

2 x 2.09 x 1017 = 1.21 x 1021

= 1.85 x 102 m s-1 = about 2 cm s-1

9. How far apart will the two halves be when they collide with Earth, if only one Big Ivan bomb is used? The first nuclear explosion: the Trinity test at Los Alamos, USA on 16 July 1945 We have already shown (in question 4) that at the zero barrier, the asteroid is less than three hours away from their own thoughts on how to make impact. At a speed of 1.85 x 102 m s-1 the scenario more realistic – and on (question 8), in that time each half of which outcomes or assumptions are the the asteroid will have moved 190 m most absurd. For example, why did the away from its original path, so that the scientists fail to spot the asteroid until it two halves will have moved apart by was so close? And despite this failure, less than 400 m – far too little to avoid how did they work out that it had a fault a collision with Earth. In fact, under line running through it, exactly along the circumstances described in the the direction of travel? film, the team would need to intercept Here are some suggestions of other the asteroid when it was some 3.74 x points to consider: this out from the kinetic energy 1012 km away – 25 times the distance · The calculations did not include of the asteroid. They will find that of the Sun from Earth, out in space the energy required to break the its impact with the Earth would between Uranus and Neptune. chemical bonds to split the asteroid release 5.8 x 1028 J – equivalent to Which all goes to show that there in two: it included only the energy 276 billion (2.76 x 1011) Big Ivans. are times when you need something required to move the two halves For comparison, the asteroid that even bigger than a nuclear explosion apart, assuming that the asteroid was marked the end of the Cretaceous to make things happen. already conveniently fractured. If we (and the demise of the dinosaurs) 65 added the energy needed to fracture million years ago is estimated to have the asteroid, by how much would released only about 4 x 1023 J Discussion this affect the calculations? (2 million Big Ivans). There is plenty more here to discuss · If the asteroid were to hit the · Students can investigate real-life with students, after or alongside the Earth, what would be the energy objects that might strike the Earth, calculations. Students may well have of the impact? Students can work and find out how typical the asteroid

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FURTHER skeeze/pixabay.com

Planet in peril? Imaginative image of a planet with nearby comets and asteroids

in Armageddon is for asteroids Resources Perkowitz S (2010) Hollywood Science: -1 generally. At 9833 m s , its speed is Read about the ‘good’ and ‘bad’ science in Movies, Science, and the End of the World. New somewhat slower than asteroids on Armageddon by visiting the Bad Astronomy York, USA: Columbia University Press. ISBN: average, which have a mean velocity website. See: www.badastronomy.com/bad/ 0231142811 of 25 000 m s-1. (For comparison, movies/armpitageddon.html Weiner A (2007) Don’t Try This at Home! The Halley’s comet has a velocity of For information on asteroids and comets, visit Physics of Hollywood Movies. New York, USA: Kaplan Publishing. ISBN: 1419594060 53 600 m s-1 when it is closest to the Bill Arnett’s very comprehensive Nine Edwards R, Brooks M (2017) Science(ish): The Sun, at perihelion.) NASA’s NEOw1 Planets website. See: http://nineplanets.org/ smallbodies.html Peculiar Science Behind the Movies. London, (near-Earth object) programme Watch a TED talk explaining how we could UK: Atlantic Books. ISBN: 1786492210 searches for and tracks objects that defend the Earth from asteroids on the ______might strike the Earth: one candidate TED website. See: www.ted.com/talks/ is asteroid (29075) 1950 DA, which phil_plait_how_to_defend_earth_from_ has a diameter of about 1 km. Its asteroids Mike Follows is acting head of physics chances of hitting the Earth in 2880 The Spaceguard Centre (located in Knighton, at King Edward’s School in Birmingham, is currently estimated to be 1 in 300. Powys, UK) provides information about the UK. He has a PhD in ultralow- threat of asteroid and comet impacts, and temperature physics, and he enjoys the ways in which we can predict and deal Reference developing interesting ways of teaching with them. For more information, visit their physics to students, including finding Follows M (2017) Heroes and villains: the science website. See: https://spaceguardcentre.com unusual contexts (such as science fiction of superheroes. Science in School 40: 57-63. The Views of the Solar System website offers a www.scienceinschool.org/content/ catalogue of terrestrial impact craters. See: movies). He is also drawn to global heroes-and-villains-science-superheroes http://solarviews.com/eng/tercrate.htm issues and how physics helps to explain For other critiques and explorations of science in them – and might help solve them. Web reference the movies, see the following books: w1 To read the latest news stories from the Rogers T (2007) Insultingly Stupid Movie Center for Near Earth Object Studies, visit Physics. Naperville, IL, USA: Sourcebooks the NASA website. See: https://cneos.jpl. Hysteria. ISBN: 1402210337 nasa.gov

50 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org TEACH | Engineering, Physics

FURTHER FANTASTIC FEATS

SOLUTIONS TO THE CHALLENGES ON PAGE 37

Feat 1: Tunnel ball The reason that the ball usually bounces back towards the thrower, rather than continuing forward, is explained by one word: spin. The spin can be seen most easily using a ball with markings on it, such as a basketball. If you throw a basketball at an angle to the ground, after bouncing it immediately starts to spin. This is due to friction between the ball and the ground (see figure 1).

Figure 1: The ball’s first bounce, showing the spin directions. 1: the ball’s initial 1 3 direction of travel; 2: friction acts on one side of the ball only, producing spin; 3: the resulting direction of spin David Featonby/Nicola Graf

2

Figure 2: The ball hits the tunnel roof with backspin, which changes the ball’s path. 1: the ball’s initial direction of travel; 2: forward spin (relative to table) 3 after the first bounce; 3: backward spin (relative to roof); 4: final direction of 4 travel

1 David Featonby/Nicola Graf

2

www.scienceinschool.org I Science in School I Issue 43 : Spring 2018 I 51 Engineering, Physics | TEACH David Featonby/Nicola Graf

Figure 3: Path of the ball when friction is eliminated, so no spin is produced

In the challenge, friction between skid over the table and upper surface Feat 2: Cork bounce the ball and the table gives the of the tunnel without spin, and the ball ball a forward spin at the first will follow a W-shaped path through the The secret here is in how you hold the bounce, in the same direction in tunnel, as most people initially expect cork (or other cylinder) before you which the ball is travelling. So (figure 3). drop it. when the ball hits the tunnel roof, A challenging extension of this feat 1. Hold the cork horizontally but it has a backwards spin relative is to work out the direction and size at a very slight angle (it’s almost to the underside of the roof of the spin at different stages of the impossible not to do so), and at a (figure 2) – because the top part ball’s motion. Taking a film of a large, height above the table of about of a spinning ball must be turning patterned ball (such as a basketball) and 1.5 times the length of the cork in the opposite direction to the watching it in slow motion is a good (figure 4). bottom part. way to make this easier. This backspin causes the ball to return along its original path, back towards the thrower. So, how can you overcome this spin and make the ball pass through the tunnel as intended? For the ball to follow a W-shaped path through the tunnel, it must strike the table (and then the roof of the tunnel) without spin. The spin is caused by the friction at the point of contact, because friction opposes the motion between two surfaces in contact – so one side of the ball is slowed down, but not the other. To minimise the spin, the friction

also needs to be minimised. David Featonby The easiest way to do this is to change the surface of the ball. If the ball is immersed in water for a second, its wet surface will then Figure 4: Cork at the ready

52 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org Figure 7:Thecork rotates toavertical position–withluck! speed) andrebounds atthesamespeed,makingcork rotate intheoppositedirection. Figure 6:Thesecond end of thecork (2)hitsthetableatspeed2v(falling plusrotation the samespeed,makingcork rotate. oneendof thecorkFigure (1)hitsthetableandbounces upagainat 5:Falling atspeedv, v 1 1 v 1 2 2

2v

David Featonby/Nicola Graf Featonby/Nicola David Graf Featonby/Nicola David Graf Featonby/Nicola David www.scienceinschool.org IScience inSchoolIIssue43: Spring2018I 53 a vertical position (seefigure7). (here anticlockwise), sothatitrotatesto the corkrotateinoppositedirection The reboundmomentumof2vmakes rebound atspeed2v(seefigure6). plus vfromtherotation),andwillalso it ismoving atspeed 2v(fromitsfall So when end2ofthecorkhitstable, will beinthesamedirectionasitsfall. for end2,themovement duetorotation at thesamespeedaboutitscentre.But opposite end(end2)ofthecorkmove movement. This rotationmakesthe centre ofgravity, hereasaclockwise of thecorkcausesittorotateaboutits This change inmomentumatoneend back upwards atspeedv(seefigure5). an elasticcollision,thisendbounces first endhitsthetable. Assuming thisis The corkisfallingatspeedvwhen the illustrate. described above, asthediagrams here a morecomplexsequencethan watching itinslow motionhasrevealed However, videoingthefalland enough tostandonitsend. effect. This makesthecorkrotate end ofthecork,producingaturning results inaforce appliedtoonlyone table beforetherestofcork. This cork falls,oneofitsendswillstrikethe The basicexplanationisthatwhen the 3. 2. height foryour corkandtable. Keep practicing tofindthebest at least50%ofthetime. and finishupstandingonitsend– Drop thecork.Itshouldbounce

REVIEW TEACH the teacher. more common, are studentsandnot,asis because thebloggers particularly interesting university level. Itis science, namelyatpre- learning andteaching benefits ofbloggingfor testimony aboutthe The articleisanexcellent

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Betina daSilva Lopes, Engineering, Physics Ages 16–18 All sciences

Portugal Photo: Photo: Engineering, Physics | TEACH

Finding the best height for the drop and getting the cork to stand upright is very much a trial-by-experiment process. There are many factors involved that will vary significantly from cork to cork, and between different surfaces. All the other tubes can be made to stand on end in the same way. The ease with which this happens varies considerably – and the cork is probably the most difficult. What else could you bounce into a vertical position by producing a turning force?

Feat 3: Card drop When trying this challenge, most people will hold the card vertically before dropping it. From this position the card will invariably move sideways during its fall, and is much less chance of a significant it will usually miss the hat – even if sideways force, so the card’s fall is dropped from directly above it. almost vertical – directly into the hat below. This sideways shift is due to pressure from air movements caused by the For even greater theatrical effect, try falling card itself. Even though they performing this feat with banknotes. are very slight, these movements will produce enough force on the side of the card to move it sideways, away Resources from the hat. For a more detailed analysis of dropping cards from greater heights, read the The trick is to hold the card explanation on the Naked Scientists horizontally, as shown in figure website. See: www.thenakedscientists. 8. In this position, the area of the com/get-naked/experiments/ card that is exposed to sideways air falling-cards movements is much smaller – just the edge of the card. This means there David Featonby

Figure 8: Holding the card horizontally before dropping it

54 I Issue 43 : Spring 2018 I Science in School I www.scienceinschool.org Philippa Willitts/Flickr Photo: (CERN), Switzerland (CERN), Germany Luxembourg Education, 1818-0353 version: Print 1818-0361 Online version: I Issue 43 : Winter 2017 I 55 I Issue 43 : Winter in School I Science www.scienceinschool.org geralt/pixabay.com Imprint in School Science Biology Laboratory Molecular European 1 Meyerhofstrasse 69117 Heidelberg Germany [email protected] www.scienceinschool.org www.eiroforum.org Publisher: EIROforum, team: Editorial Editor-in-Chief Dr Eleanor Hayes, Editor Hannah Voak, Editor Susan Watt, Assistant Editorial Spilios Vasilopoulos, board: Editorial France Institut Laue-Langevin, Cicognani, Dr Giovanna Nuclear Research for Organization European Del Rosso, Antonella the Netherlands Agency, Space Barnes, European Rebecca Germany Southern Observatory, European Johnston, Tania France Radiation Facility, Synchrotron European Lacaze, Yannick EUROfusion, Germany Nieckchen, Dr Petra Germany XFEL, European Piergrossi, Joseph Biology Laboratory, Molecular European Szmolenszky, Agnes Astronomy Association for European Wagner, Dr Fernand Australia Inlexio, Hadley, editor: Dr Caroline Copy Germany Graf, Nicola Graphic Design Studio Composition: Germany Leimen, Printer: Colordruck Germany GmbH, Fulfillment Circle Distributor: CFG Germany KG, & Co Alperion GmbH development: Web ISSN image Cover Physics

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Practical work is carried out in a properly equipped and maintained science science and maintained equipped is carried out in a properly Practical work laboratory maintained is properly electrical equipment Any with normal laboratory operations such as heating is taken Care used are when chemicals or living organisms is observed Good laboratory practice risk to the eyes recognised is any there whenever is worn protection Eye activities such as handling techniques for safe taught are Pupils and students materials and equipment. hazardous living organisms, CC BY-NC-SA BY-NC-SA CC BY-NC-ND CC Attribution CC BY CC Attribution Attribution-NonCommercial-ShareAlike Attribution–NonCommercial-NoDerivatives Safety note note Safety tried to check that all have in School, we all of the activities published in Science For suggested. are and that suitable precautions been identified have hazards recognised and omissions can be made, and safety that errors however, should be aware, Readers within individual countries. and even Europe across vary standards carry out their should always readers activity, undertaking any before Therefore, or education employers local rules issued by any In particular, risk assessment. own in School articles. is suggested in the Science whatever authorities MUST be obeyed, it is assumed that: dictates otherwise, Unless the context · · · · · · Advertising: tailored to your needs to your tailored Advertising: journal, or in the print in School website on the Science to advertise of how details For [email protected] or contact see www.scienceinschool.org/advertising See: www.scienceinschool.org/copyright necessarily not are authors and advertisers by and opinions expressed Views those of the editors or publisher. 3. 2. is the only teaching journal to cover all sciences and target the whole and target all sciences in School is the only teaching journal to cover Science distributed in English and journal is printed quarterly The free and beyond. of Europe articles in 30+ languages. offering available, is also freely The website Europe. across a (www.eiroforum.org), EIROforum in School is published and funded by Science scientific inter-governmental largest of Europe’s eight partnership between organisations. research Creative published under in School are articles in Science exceptions, few With very not may You the text. and republish can copy so that you licences, Commons holder. of the copyright the images without the consent reproduce licences: copyright one of three in School articles carry Science Most 1. Science in School About Science

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