tag:theconversation.com,2011:/fr/topics/magnetism-13256/articlesMagnetism – The Conversation2023-10-02T19:11:50Ztag:theconversation.com,2011:article/2088592023-10-02T19:11:50Z2023-10-02T19:11:50ZWhat has the Nobel Prize in Physics ever done for me?<figure><img src="https://images.theconversation.com/files/551265/original/file-20230930-15-nkkytb.jpeg?ixlib=rb-1.1.0&rect=53%2C0%2C6000%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/luminous-white-led-bulb-on-wooden-2096282497">Shutterstock</a></span></figcaption></figure><p>Each October, physics is in the news with the awarding of the Nobel Prize. The work acknowledged through this most prestigious award often seems far removed from our everyday lives, with prizes given for things like “<a href="https://www.nobelprize.org/prizes/physics/1966/">optical methods for studying Hertzian resonances in atoms</a>” and “<a href="https://www.nobelprize.org/prizes/physics/1999/">elucidating the quantum structure of electroweak interactions</a>”.</p>
<p>However, these lauded advances in our basic understanding of the world often have very real, practical consequences for society.</p>
<p>To take just a few examples, Nobel-winning physics has given us portable computers, efficient LED lighting, climate modelling and radiation treatment of cancer. </p>
<h2>Thin magnets and portable computers</h2>
<p>In 2007, the physics Nobel was awarded jointly to Peter Grünberg and Albert Fert for the discovery of “<a href="https://www.nobelprize.org/prizes/physics/2007/press-release/">giant magnetoresistance</a>”. </p>
<p>In the late 1980s, Grünberg and Fert (and their research groups) were independently studying very thin layers of magnets. They both noticed that electricity flowed through the layers differently depending on the direction of the magnetic fields.</p>
<p>These teams were looking to understand fundamental properties of very thin magnets. However, their findings led to something we now take for granted: portable computers. </p>
<figure class="align-center ">
<img alt="A photo of an opened hard drive on a yellow background." src="https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551266/original/file-20230930-27-sxcuty.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The ‘giant magnetoresistance’ effect won its discoverers the 2007 Nobel Prize in Physics – and made portable hard drives possible.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hard-disk-drive-open-cover-computer-2115380288">Shutterstock</a></span>
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<p>At the time, most computers stored information on a hard disk drive made of a magnetic material. To read the information from the drive, a very small and very accurate magnetic field sensor is needed. </p>
<p>The discovery of giant magnetoresistance allowed for the development of far more sensitive sensors, which in turn made hard disk drives and computers smaller. (Today, magnetic hard disk drives are being overtaken by even smaller <a href="https://en.wikipedia.org/wiki/Solid-state_drive">solid state drives</a>.)</p>
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Read more:
<a href="https://theconversation.com/how-to-store-data-on-magnets-the-size-of-a-single-atom-82601">How to store data on magnets the size of a single atom</a>
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<p>In short, we would not have laptops without the discovery that won the 2007 Nobel Prize in Physics. </p>
<p>The effect of this research – like that of so much fundamental research – was completely unanticipated.</p>
<h2>A light bulb moment</h2>
<p>Sometimes, however, physics research does have a practical goal all along. One such example is the quest for energy-efficient lighting.</p>
<p>Old-fashioned incandescent light bulbs are highly inefficient. Because they work by heating a wire until it glows, they waste a lot of energy as heat. In fact, less than 10% of the energy they consume goes to producing light. </p>
<p>In the 1980s, scientists realised light emitting diodes, or LEDs – small electronic components that emit light of a specific colour – would make more efficient light sources. But there was a problem. Although red and green LEDs had been developed in the middle of the twentieth century, nobody knew how to make a blue LED.</p>
<p>LEDs are thin sandwiches of materials that respond to electricity in a very particular way. When an electron moves from one energy level to another inside the material, it emits light of a specific colour. </p>
<p>All three colours of light (red, green and blue) would be needed to produce the kind of white light people want in their homes and workplaces. </p>
<figure class="align-center ">
<img alt="A photo of a strip of blue LED lights against a dark background." src="https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551274/original/file-20231001-19-qlom3i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The invention of blue LEDs made it possible to create white light far more efficiently than with incandescent bulbs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/vertical-shot-blue-led-tape-glowing-2101501642">Shutterstock</a></span>
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<p>In the early 1990s, in the culmination of almost 30 years of work by many groups, the missing blue LEDs were found. In 2014, Isamu Akasaki, Hiroshi Amano and Shuji Nakamura <a href="https://www.nobelprize.org/prizes/physics/2014/press-release/">received the physics Nobel</a> for the discovery. </p>
<p>The layers of material chosen to make up the sandwich, plus the quality of each layer, had to be refined in order to make the first blue LED. Since the initial discovery, materials scientists have continued to improve the design and manufacture to make blue LEDs more efficient.</p>
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Read more:
<a href="https://theconversation.com/your-phone-screen-just-won-the-nobel-prize-in-physics-32456">Your phone screen just won the Nobel Prize in physics</a>
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<p>Lighting accounts for up to 20% of total electricity consumption. LEDs use roughly <a href="https://www.sustainability.vic.gov.au/energy-efficiency-and-reducing-emissions/save-energy-in-the-home/lighting/choose-the-right-led-lighting">one sixth as much energy</a> as incandescent light bulbs. They also last much longer, with a lifetime of around 25,000 hours. </p>
<h2>Climate models, radiation and beyond</h2>
<p>Environmental endeavours are probably not what springs to mind when you think of the Nobel Prize in Physics. Yet another example also comes to mind, the study of a chaotic and complex system with great importance to us all: Earth’s climate.</p>
<p>Half of the 2021 Nobel Prize in Physics was given to Syukuro Manabe and Klaus Hasselmann, scientists who developed <a href="https://www.nobelprize.org/prizes/physics/2021/summary/">early models for Earth’s weather and climate</a>. Their work also linked global warming to human activity.</p>
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<img alt="A black and white photograph portrait of a woman." src="https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=815&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=815&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=815&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1025&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1025&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551275/original/file-20231001-17-ef6emp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1025&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Marie Curie was awarded the Nobel Prize in Physics in 1903 for her work on radioactivity.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Marie_Curie#/media/File:Marie_Curie_c._1920s.jpg">Wikimedia</a></span>
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<p>Of the 222 people awarded the physics Nobel since 1901, <a href="https://theconversation.com/and-then-there-were-three-finally-another-woman-awarded-a-nobel-prize-in-physics-104323">only three have been women</a>. The most famous of those three is perhaps Marie Curie, who took home one quarter of the prize in 1903. </p>
<p>Curie’s work on understanding how atoms can decay into other kinds of atoms, producing nuclear radiation, profoundly changed life in the twentieth century.</p>
<p>The study of nuclear radiation led to the development of nuclear weapons, but also to radiation treatment for cancer. And further, it has led to carbon dating to determine the age of artefacts, allowing us to better understand <a href="https://www.ansto.gov.au/news/radiocarbon-dating-supports-aboriginal-occupation-of-south-australia-for-29000-years">ancient civilisations</a>. </p>
<p>So when we find out who is awarded the 2023 Nobel Prize in Physics, no matter what it’s for – and prospects include research on quantum computing, “slow light” and “self-assembling matter” – we can be sure of one thing. The awarded research will likely end up affecting our lives in extraordinary ways that may not at first be apparent.</p><img src="https://counter.theconversation.com/content/208859/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Livesey does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The science that wins the Nobel Prize in Physics each year can be hard to get your head around – but it often has real everyday implications.Karen Livesey, Senior Lecturer of Physics, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1966002022-12-19T16:39:25Z2022-12-19T16:39:25ZLondon Underground polluted with particles small enough to enter the human bloodstream – new research<figure><img src="https://images.theconversation.com/files/501579/original/file-20221216-17-ukf8o7.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C5455%2C3628&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Roughly 2 million people use the London Underground each day.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-november-14-2018-train-arriving-1235340622">Tom Eversley/Shutterstock</a></span></figcaption></figure><p>The London Underground is key to the functioning of England’s capital city. Roughly <a href="https://www.london.gov.uk/your-commute?">2 million people</a> use it each day. But it is <a href="https://www.sciencedirect.com/science/article/pii/S0160412019313649#b0120">polluted</a> with small particulate matter from heavy metals, including iron oxide, that may be damaging to human health. </p>
<p>These particles range in size, but so-called <a href="https://www.blf.org.uk/taskforce/data-tracker/air-quality/pm25">PM2.5</a> particles are typically less than two and a half micrometres (2,500 nanometres) in diameter and can cause asthma, lung cancer, cardiovascular diseases and neurological problems. If it was classified as an outdoor environment, concentrations of particulate matter on the underground would exceed the <a href="https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health">air quality limits</a> set by the World Health Organisation.</p>
<p>My colleagues and I recently conducted <a href="https://www.nature.com/articles/s41598-022-24679-4">research</a> at ten underground stations across seven different lines: the Northern, Piccadilly, Victoria, District, Bakerloo, Jubilee and Central. We found that users of the London Underground may be inhaling more airborne particles than previously recorded. </p>
<p>The majority of these particles are also smaller than those identified by previous research and represent a particularly <a href="https://link.springer.com/article/10.1007/s00038-019-01202-7">serious health concern</a> for humans. Between 60% and 70% of the iron-bearing particles sampled were 0.02 micrometres (20 nanometres) or less in diameter. Particles of this size can pass from the lungs into the bloodstream.</p>
<h2>Magnetic particles</h2>
<p>Metallic particulate matter is <a href="https://oem.bmj.com/content/62/6/355">generated</a> in underground rail systems through interaction between brakes, wheels and rails. Poorly ventilated platforms and tunnels then mean that underground users are exposed to <a href="https://www.sciencedirect.com/science/article/abs/pii/S1352231010002852?via%3Dihub">high concentrations</a> of these particles.</p>
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<a href="https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A woman seated and scrolling through her phone while a train moves past in the background." src="https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501580/original/file-20221216-11-8bg4cj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Poor ventilation means Underground users are exposed to high concentrations of airborne particulates.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-woman-wearing-protective-face-mask-2100516343">DavideAngelini/Shutterstock</a></span>
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<p>But as many of these particulates are metallic, they have magnetic properties. The underground is therefore a suitable location to test whether magnetism can be an effective method for monitoring airborne particulate pollution.</p>
<p>Our study employed magnetic and microscopic techniques including magnetic fingerprinting, 3D imaging and nanoscale microscopy. These methods represent a cost-effective way of characterising the harmful particulate matter in underground transport systems.</p>
<p>Traditional methods instead involve recording the concentration of bulk particles, such as <a href="https://www.gov.uk/government/statistics/air-quality-statistics/concentrations-of-particulate-matter-pm10-and-pm25">PM2.5</a>, by mass or volume – for example, in micrograms per cubic metre. Yet the fine particles that we identified weigh very little and may be too small to be detected using such a metric.</p>
<p>Examination of these fine particles under a microscope also revealed that they naturally clump together and give the appearance of larger particles. This means that traditional monitoring methods may not account for the true abundance of these smaller and potentially more harmful particles.</p>
<h2>Mitigation routes</h2>
<p>Our study also revealed that these fine particles have likely been present in the underground for months or years, but further research is needed to obtain a more accurate estimate.</p>
<p>The chemical structure of iron oxide moves through phases depending on its exposure to air. We recorded concentrations of highly oxidised iron-rich particulate matter. This suggests that the particulates have been exposed to prolonged low temperature contact with oxygen and makes it unlikely that they were freshly generated but instead circulated over time.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A busy underground train platform with passengers about to board a train." src="https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501849/original/file-20221219-12-122a43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Air quality is up to 40% worse on platforms than in ticket halls.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-uk-october-6-2018-passengers-1197949861">Matthew Ashmore/Shutterstock</a></span>
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<p>These particles will settle over time but are lifted into the air again as trains move through underground tunnels and arrive at platforms. We found that the air quality on some platforms is up to 40% worse than in ticket halls as a result.</p>
<p>But a set of systematic mitigation measures can be used to limit the recirculation of old particles. These measures include the periodic removal of accumulated dust from underground tunnels and the regular cleaning of tracks, which at present are cleaned solely for operational reasons and not in the interest of public health. </p>
<p>Another strategy would be to install magnetic filters in ventilation shafts to trap magnetic particles before they come into contact with humans. This strategy has been trialled in <a href="https://doi.org/10.1021/es404502x">Seoul’s subway system</a> in South Korea. Using a 60Hz fan frequency and double magnetic filters, 46% of the PM2.5 particles were successfully removed from a subway tunnel. This decreased, however, to 38% for smaller particles.</p>
<h2>Understanding the risk</h2>
<p>There is conflicting evidence over whether particulate matter pollution in underground train systems is in fact more dangerous than exposure to outdoor air pollution. More definitive toxicological research is needed to evaluate the impact of airborne particulates on human health.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A queue of road traffic pouring exhaust fumes into the cold sky." src="https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501581/original/file-20221216-27-i3bmwd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">It is unclear whether exposure to airborne particles in underground rail systems is more dangerous than outdoor air pollution.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pollution-exhaust-cars-city-winter-smoke-1301806378">NadyGinzburg/Shutterstock</a></span>
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<p>Research into the health impacts of exposure to air in underground rail systems shows mixed results. <a href="https://www.sjweh.fi/show_abstract.php?abstract_id=1142">Toxicological testing</a> of particulate matter in the Stockholm subway system in 2005 concluded that subway drivers were no more likely to suffer a heart attack than other manual workers in the city.</p>
<p>But more recent <a href="https://www.sciencedirect.com/science/article/pii/S2352396422002444">laboratory studies</a>, using particles from the London Underground’s Bakerloo and Jubilee lines, indicate that users are susceptible to pneumococcal infection (including pneumonia and bloodstream infections). Further research in Stockholm found that the air on the subway is <a href="https://pubs.acs.org/doi/10.1021/tx049723c">40-80 times</a> more damaging to human DNA compared with the air in an urban street environment.</p>
<p>Our characterisation of the London Underground’s particulate matter pollution complements traditional monitoring. Detailing the size, structure and chemical composition of particulate matter will better enable health experts and toxicologists to limit any potential health impacts associated with travelling on the underground.</p><img src="https://counter.theconversation.com/content/196600/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hassan Aftab Sheikh receives funding from Cambridge Trust</span></em></p>New research reveals that the London Underground is polluted with small particles which may carry negative health effects for humans.Hassan Aftab Sheikh, PhD Researcher in Earth Sciences, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1771612022-02-23T13:49:27Z2022-02-23T13:49:27ZNuclear fusion: how excited should we be?<figure><img src="https://images.theconversation.com/files/446778/original/file-20220216-13-f3zlzq.jpg?ixlib=rb-1.1.0&rect=65%2C14%2C2371%2C1674&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fusion could create more energy than any other process that could be produced on Earth.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-render-fusion-reactor-nuclear-tokamak-1666800238">Shutterstock</a></span></figcaption></figure><p>There’s been tremendous excitement about <a href="https://www.nature.com/articles/d41586-022-00391-1">recent results</a> from the <a href="https://ccfe.ukaea.uk/research/joint-european-torus/">Joint European Torus (JET) facility</a> in the UK, hinting that the dream of nuclear fusion power is inching closer to reality. We know that fusion works – it is the process that powers the Sun, providing heat and light to the Earth. But for decades it has proved difficult to make the transition from scientific laboratory experiments to sustained power production. </p>
<p>The fundamental aim of fusion is to bring atomic nuclei merging together to create a different, heavier nucleus – releasing energy in the process. This is different to nuclear fission, in which a heavy nucleus such as uranium is split into smaller ones while also releasing energy.</p>
<p>A significant difficulty has been the process of fusing light atoms, isotopes of hydrogen or helium, together. As they are electrically charged, repulsing each other, they resist fusing unless nuclei are moving fast enough to get physically very close to each other – requiring extreme conditions. The Sun achieves this at its core thanks to its immense gravitational fields and its huge volume. </p>
<p>One approach used in labs on Earth is “<a href="https://www.nature.com/articles/nphys3736">inertial confinement</a>”, whereby a tiny fusion fuel pellet around one-tenth of a centimetre in diameter is heated and compressed from the outside using laser energy. In recent years, some encouraging progress on this technique has been made, perhaps most notably by the <a href="https://lasers.llnl.gov/">National Ignition Facility</a> in the USA where a 1.3 million Joules (a measure of energy) fusion yield <a href="https://www.llnl.gov/news/national-ignition-facility-experiment-puts-researchers-threshold-fusion-ignition">was reported last year</a>. While this produced an <a href="https://lasers.llnl.gov/news/nif-experiment-puts-researchers-threshold-fusion-ignition">10 quadrillion Watts of power</a>, it only lasted for a fraction (90 trillionths) of a second.</p>
<p>Another technique, “<a href="https://www.ipp.mpg.de/15072/mageinschluss">magnetic confinement</a>”, has been deployed more broadly in laboratories worldwide, and is thought to be one of the most promising routes to realising fusion power stations in the future. It involves using fusion fuel contained in the form of a hot plasma – a cloud of charged particles – confined by strong magnetic fields. In creating the conditions for fusion reactions to take place, the confinement system needs to keep the fuel at the appropriate temperature and density, and for sufficient time. </p>
<p>Herein lies a significant part of the challenge. The small amount of fusion fuel (typically just a few grams) needs to be heated to huge temperatures, of the order of 10 times hotter than the centre of the Sun (150 million °C). And this needs to happen while maintaining confinement in a magnetic cage to sustain an energy output. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Internal view of the JET tokamak superimposed with an image of a plasma." src="https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446779/original/file-20220216-23-1jju31d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Internal view of the JET tokamak.</span>
<span class="attribution"><span class="source">EFDA-JET/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Various machines can be used to try to retain this magnetic confinement of the plasma, but the most successful to date is the so-called “<a href="https://www.iter.org/mach/Tokamak#:%7E:text=The%20tokamak%20is%20an%20experimental,the%20walls%20of%20the%20vessel.">tokamak” design</a>, which uses a torus (doughnut shape) and complex magnetic fields to confine the plasma, as employed at the JET facility.</p>
<h2>Small step or big leap?</h2>
<p>The recent results mark a real stepping stone in the quest for fusion power. The 59 million Joules of energy in total, produced over a five second period, gave an average fusion power of around 11 million Watts. While this is only enough to heat about 60 kettles, it is nevertheless impressive – creating an energy output 2.5 times the <a href="https://www.euro-fusion.org/fusion/history-of-fusion/">previous record</a>, set back in 1997 (also at the JET facility, achieving 22 million Joules). </p>
<p>The success at JET is the culmination in years of planning and a highly experienced team of dedicated scientists and engineers. JET is currently the largest tokamak in the world, and the only device that is able to make use of both deuterium and tritium fuel (both isotopes of hydrogen). </p>
<p>The design of the machine, using copper magnets which heat up rapidly, means that it can only operate with plasma bursts of up to a few seconds. To make the step to longer sustained high-power operations, superconducting magnets will be needed.
Luckily, this is the case at the <a href="https://www.iter.org/">ITER facility</a>, currently being built in the south of France as part of an international effort involving 35 nations, which is now 80% complete. The recent results have therefore given great confidence in the engineering design and physics performance for the ITER machine design, also a magnetic confinement device, which is designed to produce 500 million Watts of fusion power. </p>
<p>Other important challenges remain, however. These include developing appropriately durable materials that are able to withstand the intense pressure within the machine, handling the huge power exhaust and, most importantly, generating energy that is economically competitive with other forms of energy production. </p>
<p>Achieving notable power outputs and sustaining them for more than very short periods of time has proved to be the major challenge in fusion for decades. Without this ultimately being solved, an eventual fusion powerplant simply cannot be made to function. This is why the JET results represent a significant landmark, albeit just marking a step along the way.</p>
<figure class="align-center ">
<img alt="Image of ITER construction in 2018." src="https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=386&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=386&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=386&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=485&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=485&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446780/original/file-20220216-27-y6r3k8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=485&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">ITER construction in 2018.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/ITER#/media/File:ITER_construction_in_2018_(41809718461).jpg">Oak Ridge National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The giant leap will come with scaling up of the current fusion achievements in subsequent fusion systems, such as ITER and then in demonstration power plants beyond this. And this should be within reach in the not too distant future, aiming for operation by the 2050s or possibly slightly earlier.</p>
<h2>Crucial benefits</h2>
<p>There’s a lot at stake. Fusion produces more energy per gram of fuel than any other process that could be achieved on Earth. Some of the main benefits of fusion are that the products of the process are helium and neutrons (particles which make up the atomic nucleus, alongside protons) – no carbon dioxide or other greenhouse gases are released. The raw fuels are <a href="https://www.iter.org/newsline/167/631">deuterium</a>, which can be found in seawater, and lithium - which is also abundant and found in vast salt flats. The potential fusion energy released from the <a href="https://www.rsc.org/periodic-table/element/3/lithium">lithium</a> contained in one laptop battery and a bathtub of water is estimated to be equivalent to around 40 tonnes of coal.</p>
<p>Fusion does produce some radioactivity in the materials comprising the reactor. But this isn’t expected to be anywhere near as long-lived or intense as the
radioactive waste produced by nuclear fission – making it potentially a safer and more palatable choice than conventional nuclear power.</p>
<p>Ultimately, Rome wasn’t built in a day. Various other aspects of human ingenuity, such as aviation, have historically taken significant amounts of time to progress to fruition. That means steps along the way which make progress are hugely important and should rightly be celebrated. </p>
<p>Fusion is creeping inexorably forward and we are getting closer and closer to achieving that once distant dream of commercial fusion power. One day, it will provide a near limitless supply of low-carbon power for many future generations to come. So while it is not quite there yet, it is coming.</p><img src="https://counter.theconversation.com/content/177161/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lee Packer receives funding from the European Physical Sciences Research Council and the European Consortium for the Development of Fusion Energy</span></em></p><p class="fine-print"><em><span>Paul Norman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Fusion produces more energy per gram of fuel than any other process that could be achieved on Earth.Paul Norman, Senior Lecturer in Nuclear Physics, University of BirminghamLee Packer, Applied Radiation Physics Section Leader, Culham Centre for Fusion EnergyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1550402021-02-15T04:00:08Z2021-02-15T04:00:08ZWe found the first Australian evidence of a major shift in Earth’s magnetic poles. It may help us predict the next<figure><img src="https://images.theconversation.com/files/384156/original/file-20210215-21-1bbrzt.jpg?ixlib=rb-1.1.0&rect=20%2C37%2C2227%2C1085&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>About 41,000 years ago, something remarkable happened: Earth’s magnetic field flipped and, for a temporary period, magnetic north was south and magnetic south was north. </p>
<p><a href="https://www.nature.com/subjects/palaeomagnetism">Palaeomagnetists</a> refer to this as a geomagnetic excursion. This event, which is different to a complete magnetic pole reversal, occurs irregularly through time and reflects the dynamics of Earth’s molten <a href="https://www.nationalgeographic.org/encyclopedia/core/">outer core</a>. </p>
<p>The strength of Earth’s magnetic field would have almost vanished during the event, called the Laschamp excursion, which lasted a <a href="https://www.frontiersin.org/articles/10.3389/feart.2019.00086/full">few thousand years</a>. </p>
<p>Earth’s magnetic field acts as a shield against high-energy particles from the Sun and outside the solar system. Without it the planet would be bombarded by these charged particles. </p>
<p>We don’t know when the next geomagnetic excursion will happen. But if it happened today, it would be crippling. </p>
<p>Satellites and navigation apps would be rendered useless — and power distribution systems would be disrupted at a cost of <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016SW001491">between</a> US$7 billion and US$48 billion each day in the United States alone.</p>
<p>Obviously, satellites and electric grids didn’t exist 41,000 years ago. But the Laschamp excursion — named after the lava flows in France where it was first recognised — still left its mark. </p>
<p>We recently detected its signature in Australia for the first time, in a 5.5 metre-long sediment core taken from the bottom of Lake Selina, Tasmania. </p>
<p>Within these grains lay 270,000 years of history, which we unpack in <a href="https://www.sciencedirect.com/science/article/abs/pii/S1871101421000030">our paper</a> published in the journal Quaternary Geochronology. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-happens-when-magnetic-north-and-true-north-align-123265">Explainer: what happens when magnetic north and true north align?</a>
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</em>
</p>
<hr>
<h2>How sediment can record Earth’s magnetic field</h2>
<p>Rock and soil can naturally contain magnetic particles, such as the iron mineral <a href="https://www.sciencedirect.com/topics/engineering/magnetite">magnetite</a>. These magnetic particles are like tiny compass needles aligned with Earth’s magnetic field. </p>
<p>They can be carried from the landscape into lakes through rainfall and wind. They eventually accumulate on the lake’s bottom, becoming buried and locking in place. They effectively become a fossil record of Earth’s magnetic field. </p>
<p>Scientists can then drill into lake beds and use a device called a magnetometer to recover the information held by the lake sediment. The deeper we drill, the further back in time we go.</p>
<p>In 2014 my colleagues and I travelled to Lake Selina in Tasmania with the goal of extracting the area’s climate, vegetation and “paleomagnetic” record, which is the record of Earth’s magnetic field stored in rocks, sediment and other materials.</p>
<p>Led by University of Melbourne Associate Professor <a href="https://findanexpert.unimelb.edu.au/profile/6089-michael-shawn-fletcher">Michael-Shawn Fletcher</a>, we drilled into the lake floor from a makeshift floating platform rigged to two inflatable rafts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Lake Selina, Tasmania." src="https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384153/original/file-20210215-15-1accaw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lake Selina is a small sub-alpine lake located near the west coast of Tasmania. Sediment from the lake was sampled in the form of 2x2cm cubes, each containing a few hundred years’ worth of magnetic field history.</span>
<span class="attribution"><span class="source">Michael-Shawn Fletcher</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The first Australian evidence of Laschamp</h2>
<p>Our dating of the core revealed that the biggest shift in magnetic pole positions and the lowest magnetic field intensity at Lake Selina both occurred during the Laschamp excursion.</p>
<p>But for a core that spanned several glacial periods, no single dating method could be trusted to precisely determine its age. So we employed numerous scientific techniques including radiocarbon dating and beryllium isotope <a href="https://www.cerege.fr/fr/equipements/ln2c">analysis</a>.</p>
<p>The latter involves tracking the presence of an isotope called beryllium-10. This is formed when high-energy cosmic particles bombard Earth, colliding with oxygen and nitrogen atoms in the atmosphere. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-evidence-for-a-human-magnetic-sense-that-lets-your-brain-detect-the-earths-magnetic-field-113536">New evidence for a human magnetic sense that lets your brain detect the Earth's magnetic field</a>
</strong>
</em>
</p>
<hr>
<p>Since a weaker magnetic field leads to more of these charged particles bombarding Earth, we expected to find more beryllium-10 in sediment containing magnetic particles “locked-in” during the Laschamp excursion. Our findings confirmed this.</p>
<p>The interaction between charged cosmic particles and air particles in Earth’s atmosphere is also what creates auroras. Several generations of people would have witnessed a plethora of spectacular auroras during the Laschamp excursion. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Aurora borealis over the Gulf of Finland." src="https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384141/original/file-20210214-19-1q3v064.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The interaction between charged cosmic particles and the highest air particles in Earth’s atmosphere is what creates auroras. During the Laschamp excursion, several generations of people would have witnessed a plethora of spectacular auroras.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Building on work from the 1980s</h2>
<p>Only two other lakes in Australia — Lake Barrine and Lake Eacham in Queensland — have provided a “full-vector” record, wherein both the <a href="https://academic.oup.com/gji/article/81/1/103/674602">past directions</a> and <a href="https://academic.oup.com/gji/article/81/1/121/674627">past intensity</a> of the magnetic field are obtained from the same core. </p>
<p>But at 14,000 years old, the records from these lakes are much younger than the Laschamp excursion. Four decades later, our work at Lake Selina with modern techniques has revealed the exciting potential for similar research at other Australian lakes. </p>
<p>Currently, Australia is considered a paleomagnetic “blind spot”. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Stalactites hang from cave ceiling." src="https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384170/original/file-20210215-23-1eo00yc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Speleothems’ such as stalactites (pictured) and stalagmites are mineral deposits that form in caves.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>More data from lake sediments, archaeological artefacts, lava flows and mineral <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/speleothem">cave formations</a>, including stalagmites and stalactites, could greatly improve our understanding of Earth’s magnetic field. </p>
<p>With this knowledge, we may one day potentially be able to predict the next geomagnetic excursion, before our phones stop working and the birds overhead veer off-course and crash into windows.</p>
<p>Our dating of the Lake Selina core is just the start. We’re sure there are more secrets embedded beneath, waiting to be found. And so we continue our search.</p>
<hr>
<p><em>This work was carried out in collaboration with <a href="http://www.archaeomagnetism.com/taal-lab-facilities">La Trobe University</a>, the <a href="http://rses.anu.edu.au/research/facilities/palaeomagnetic-laboratory">Australian National University</a>, The University of Wollongong, the Australian Nuclear Science and Technology Organisation and the European Centre for Research and Teaching in Environmental Geosciences (<a href="https://www.cerege.fr/fr/equipements/ln2c">CEREGE</a>).</em></p><img src="https://counter.theconversation.com/content/155040/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Agathe Lise-Pronovost receives funding from the Australian Research Council. </span></em></p>Researchers have found the first Australian evidence of this global event, during which people on Earth would have witnessed a multitude of spectacular auroras.Agathe Lise-Pronovost, McKenzie Research Fellow in Earth Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1484042020-11-02T20:01:34Z2020-11-02T20:01:34ZMagnetism of Himalayan rocks reveals the mountains’ complex tectonic history<figure><img src="https://images.theconversation.com/files/365671/original/file-20201026-17-199ct3j.jpg?ixlib=rb-1.1.0&rect=155%2C0%2C2993%2C1999&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Himalayan rocks hold magnetic clues about their origins.</span> <span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Breathing quickly in the thin mountain air, my colleagues and I set down our equipment. We’re at the base of a jagged outcrop that protrudes upwards out of a steep gravel slope.</p>
<p>The muffled soundscape of the spectacular Himalayan wilderness is punctuated by a military convoy roaring along the Khardung-La road below. It’s a reminder how close we are to the long-disputed borders between India, Pakistan and China which lie on the ridgelines just a few miles away.</p>
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<p>This area also contains a different type of boundary, a narrow sinuous geological structure that stretches along the length of the Himalayan mountain range. Known as a suture zone, it’s only a few kilometers wide and consists of slivers of different types of rocks all sliced together by fault zones. It marks the boundary where two tectonic plates fused together and an ancient ocean disappeared.</p>
<p>Our team of geologists traveled here to collect rocks that erupted as lava more than 60 million years ago. By decoding the magnetic records preserved inside them, we hoped to reconstruct the geography of ancient landmasses – and <a href="https://doi.org/10.1073/pnas.2009039117">revise the story of the creation of the Himalayas</a>.</p>
<h2>Sliding plates, growing mountains</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="artist's rendering of two tectonic plates colliding at a subduction zone" src="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At a subduction zone, two tectonic plates collide, with one slowly sliding beneath the other.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/tectonic-plates-world-map-royalty-free-illustration/889618718">VectorMine/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>Tectonic plates make up the surface of Earth, and they’re constantly in motion – drifting at the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tectonic-plate">imperceptibly slow pace</a> of just a few centimeters each year. Oceanic plates are colder and denser than the mantle beneath them, so they sink downward into it at subduction zones.</p>
<p>The sinking edge of the ocean plate drags the ocean floor along behind it like a conveyor belt, pulling the continents toward each other. When the entire ocean plate disappears into <a href="https://www.nationalgeographic.org/encyclopedia/mantle/">the mantle</a>, the continents on either side plow into each other with enough force to uplift great mountain belts, like the Himalayas.</p>
<p>Geologists generally thought that the Himalayas formed <a href="https://doi.org/10.1130/0016-7606(2000)112%3C324:TOTHAS%3E2.0.CO;2">55 million years ago in a single continental collision</a> – when the Neotethys Ocean plate subducted under the southern edge of Eurasia and the Indian and Eurasian tectonic plates collided. </p>
<p>But by measuring the magnetism of rocks from northwest India’s remote and mountainous Ladakh region, our team has shown that the tectonic collision that formed the world’s largest mountain range was actually a complex, multi-stage process involving at least two subduction zones.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of interior of Earth and magnetic field stretching from pole to pole" src="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=646&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=646&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=646&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=811&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=811&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=811&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Earth’s magnetic field is generated by movement within the planet’s outer core. Magnetic north and south drift and sometimes flip over time.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/earth-magnetic-field-scientific-vector-royalty-free-illustration/932342344">VectorMine/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Magnetic messages, preserved for all time</h2>
<p>Constant movement of our planet’s metallic outer core creates electric currents which in turn generate <a href="https://cosmosmagazine.com/geoscience/what-creates-earth-s-magnetic-field/">Earth’s magnetic field</a>. It’s oriented differently depending where in the world you are. The magnetic field always points toward the magnetic north or the south, which is why your compass works, and averaged over thousands of years it points toward the geographic pole. But it also slopes downward into the ground at an angle which varies depending on how far you are from the equator. </p>
<p>When lava erupts and cools to form rock, the magnetic minerals inside lock in the direction of the magnetic field of that location. So <a href="https://doi.org/10.1016/B0-12-369396-9/00106-4">by measuring the magnetization of volcanic rocks</a>, <a href="https://scholar.google.com/citations?hl=en&user=aD8WioMAAAAJ">scientists like me</a> can determine what latitude they came from. Essentially, this method allows us to unwind millions of years of plate tectonic motions and create maps of the world at different times throughout geologic history.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Member of our research team collecting samples in Ladakh." src="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=884&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=884&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=884&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1111&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1111&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1111&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Geologist collects core samples using a water-cooled electric core drill.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Over multiple expeditions to the Ladakh Himalayas, our team collected hundreds of 1-inch diameter rock core samples. These rocks originally formed on a volcano active between 66 and 61 million years ago, around the time that the first stages of collision began. We used a hand-held electric drill with a specially designed diamond coring bit to drill approximately 10 centimeters down into the bedrock. We then carefully marked these cylindrical cores with their original orientation before chiseling them out of the rock with nonmagnetic tools.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cylindrical rock core samples with markings" src="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A few rock core samples, with the sample orientation line marked on their sides.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The aim was to reconstruct where these rocks originally formed, before they were sandwiched between India and Eurasia and uplifted into the high Himalayas. Keeping track of the orientation of the samples as well as the rock layers they came from is essential to calculating which way the ancient magnetic field pointed relative to the surface of the ground as it was over 60 million years ago.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="View of magnetometer equipment at MIT." src="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The magnetometer sits inside a magnetically shielded room at the MIT Paleomagnetism Laboratory.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We brought our samples back to the <a href="http://www.benweiss.mit.edu/">MIT Paleomagnetism Laboratory</a> and, inside a special room that’s shielded from the modern-day magnetic field, we heated them in increments up to 1,256 degrees Fahrenheit (680 degrees Celsius) to slowly remove the magnetization.</p>
<p>Different mineral populations acquire their magnetization at different temperatures. Incrementally heating and then measuring the samples in this way enables us to extract the original magnetic direction by removing more recent overprints that might hide it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagrams depicting India colliding with Eurasia either in a single stage or multiple stages" src="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=239&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=239&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=239&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=301&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=301&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=301&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Black lines mark boundaries between tectonic plates. Black lines with triangular tick marks show subduction zones, with the direction of subduction. The Trans-Tethyan Subduction Zone is the additional subduction zone not accounted for in the single-stage collision model. The Trans-Tethyan Subduction Zone is where the volcanic island chain formed before the Indian continent collided into it and pushed it into Eurasia, forming the Himalaya.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1073/pnas.2009039117">Martin et al 'Paleocene latitude of the Kohistan-Ladakh arc indicates multi-stage India-Eurasia collision,' PNAS 2020</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<h2>Magnetic traces build a map</h2>
<p>Using the average magnetic direction of the whole suite of samples we can calculate their ancient latitude, which we refer to as the paleolatitude.</p>
<p>The original single-stage collision model for the Himalaya predicts that these rocks would have formed close to Eurasia at a latitude of around 20 degrees north, but our data shows that these rocks did not form on either the Indian or the Eurasian continents. Instead, they formed on a chain of volcanic islands, out in the open Neotethys Ocean at a latitude of about 8 degrees north, thousands of kilometers south of where Eurasia was located at the time.</p>
<p>This finding can be explained only if there were <a href="https://doi.org/10.1038/ngeo2418">two subduction zones</a> pulling India rapidly toward Eurasia, rather than just one. </p>
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<p>During a geologic time period known as the Paleocene, India caught up with the volcanic island chain and collided with it, scraping up the rocks we eventually sampled onto the northern edge of India. India then continued northward before <a href="https://doi.org/10.1016/j.epsl.2013.01.023">ramming into Eurasia around 40 to 45 million years ago</a> – 10 to 15 million years later than was generally thought.</p>
<p>This final continental collision raised the volcanic islands from sea level up over 4,000 meters to their present-day location, where they form jagged outcrops along a spectacular Himalayan mountain pass.</p><img src="https://counter.theconversation.com/content/148404/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig Robert Martin receives funding from the National Science Foundation (NSF).</span></em></p>Earth’s magnetic field locks information into lava as it cools into rock. Millions of years later, scientists can decipher this magnetic data to build geologic timelines and maps.Craig Robert Martin, Ph.D. Student in Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology (MIT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1481112020-10-15T11:38:47Z2020-10-15T11:38:47ZLife on Earth: why we may have the Moon’s now defunct magnetic field to thank for it<figure><img src="https://images.theconversation.com/files/363663/original/file-20201015-19-16azo0e.jpg?ixlib=rb-1.1.0&rect=44%2C36%2C4928%2C3238&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Photo of a nearly full Moon shining brightly on the Earth's atmosphere, taken from the International Space Station.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>The habitability of a planet depends on many factors. One is the existence of a strong and long-lived magnetic field. These fields are generated thousands of kilometres below the planet’s surface in its liquid core and extend far into space – shielding the atmosphere from harmful solar radiation.</p>
<p>Without a strong magnetic field, a planet struggles to hang on to a breathable atmosphere – which is bad news for life as we know it. A new study, <a href="https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.abc0865">published in Science Advances</a>, suggests that the Moon’s now extinct magnetic field may have helped protect our planet’s atmosphere as life was forming around 4 billion years ago.</p>
<p>Today, Earth has a strong global magnetic field <a href="https://theconversation.com/earths-magnetic-field-may-change-faster-than-we-thought-new-research-142752">that protects the atmosphere</a> and low-orbiting satellites from harsh solar radiation. In contrast, the Moon does not possess either a breathable atmosphere or a global magnetic field.</p>
<p>Global magnetic fields are generated by the motion of molten iron in the cores of planets and moons. Keeping the fluid moving requires energy, such as heat trapped within the core. When there is insufficient energy, the field dies.</p>
<p>Without a global magnetic field, the charged particles of the solar wind (radiation from the Sun) passing close to a planet generate electric fields that can accelerate charged atoms, known as ions, out of the atmosphere. This process is <a href="https://theconversation.com/how-did-mars-lose-its-habitable-climate-the-answer-is-blowing-in-the-solar-wind-50258">happening today</a> on Mars and it is losing oxygen as a result – something that has been directly measured by the <a href="https://mars.nasa.gov/maven/">Mars atmosphere and volatile evolution (Maven) mission</a>. The solar wind can also collide with the atmosphere and knock molecules into space. </p>
<p>The Maven team estimates that the amount of oxygen lost from the Martian atmosphere throughout its history <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103517306917">is equivalent</a> to that contained in a global layer of water, 23 metres thick.</p>
<h2>Probing ancient magnetic fields</h2>
<p>The new research investigates how the Earth’s and Moon’s early fields may have interacted. But probing these ancient fields isn’t easy. Scientists rely on ancient rocks that contain small grains that got magnetised as the rocks formed, saving the direction and strength of the magnetic field at that time and place. Such rocks are rare and extracting their magnetic signal requires <a href="https://theconversation.com/are-the-earths-magnetic-poles-about-to-swap-places-strange-anomaly-gives-reassuring-clue-142859">careful and delicate laboratory measurement</a>. </p>
<figure class="align-center ">
<img alt="A picture of the ancient moon with magnetic field lines." src="https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/363444/original/file-20201014-21-b9ysdx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Our Moon, four billion years ago generated its own magnetic field.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Such studies have, however, unveiled that Earth has generated a magnetic field for at least <a href="https://pubmed.ncbi.nlm.nih.gov/20203044/">the last 3.5 billion years</a>, and possibly <a href="https://pubmed.ncbi.nlm.nih.gov/26228145/">as far back as 4.2 billion years</a>, with a mean strength <a href="https://www.nature.com/articles/s41561-018-0288-0?proof=t">just over half</a> of the present-day value. We don’t know much about how the field was behaving any earlier than that. </p>
<p>By contrast, the Moon’s field was perhaps even stronger than Earth’s around 4 billion years ago, before <a href="https://pubmed.ncbi.nlm.nih.gov/25477467/">precipitously declining</a> to a weak field state by 3.2 billion years ago. At present, little is known about the structure or time-variability of these ancient fields, though.</p>
<p>Another complexity is the interaction between the early lunar and geomagnetic fields. The new paper, which modelled the interaction of two magnetic fields with north poles either aligned or opposite, shows that the interaction extends the region of near-Earth space between our planet and the Sun that is shielded from the solar wind. </p>
<p>The new study is an interesting first step towards understanding how important such effects would be when averaged over a lunar orbit or the hundreds of millions of years that are important for assessing planetary habitability. But to know for sure we need further modelling and more measurements of the strengths of the Earth and Moon’s early magnetic fields.</p>
<p>What’s more, a strong magnetic field does not guarantee the continued habitability of a planet’s atmosphere – its surface and deep interior environments matter too, as do influences from space. For example, the brightness and activity of the Sun <a href="https://theconversation.com/mission-to-the-sun-will-protect-us-from-devastating-solar-storms-and-help-us-travel-deeper-into-space-78583">has evolved</a> over billions of years and so has the ability of the solar wind to strip atmospheres.</p>
<p>How each of these factors contributes to the evolution of planetary habitability, and hence life, is still not fully understood. Their nature and how they interact with each other are also likely to change over geological timescales. But thankfully, the latest study has added another piece to an already fascinating puzzle.</p><img src="https://counter.theconversation.com/content/148111/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Earth’s magnetic field was most likely weaker when life evolved on our planet than it is today.Christopher Davies, Associate Professor in Theoretical Geophysics, University of LeedsJon Mound, Associate Professor of Geophysics, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1135362019-03-18T17:01:05Z2019-03-18T17:01:05ZNew evidence for a human magnetic sense that lets your brain detect the Earth’s magnetic field<figure><img src="https://images.theconversation.com/files/264258/original/file-20190317-28505-1b1zf7w.jpg?ixlib=rb-1.1.0&rect=17%2C247%2C2849%2C1818&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Do you have a magnetic compass in your head?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/moral-compass-career-path-concept-human-115938361">Lightspring/Shutterstock.com</a></span></figcaption></figure><p>Do human beings have a magnetic sense? <a href="https://www.springer.com/us/book/9783642797514">Biologists know</a> <a href="https://doi.org/10.1016/S0959-4388(00)00235-X">other animals do</a>. They think it helps creatures including bees, turtles and birds <a href="https://doi.org/10.1016/S0959-4388(02)00389-6">navigate through the world</a>.</p>
<p>Scientists have tried to investigate whether humans belong on the list of magnetically sensitive organisms. For decades, there’s been a back-and-forth between <a href="https://www.worldcat.org/title/human-navigation-and-the-sixth-sense/oclc/11022691&referer=brief_results">positive reports</a> and <a href="https://www.jstor.org/stable/1685499">failures to demonstrate</a> the trait in people, with <a href="https://www.springer.com/us/book/9781461379928">seemingly endless controversy</a>.</p>
<p>The mixed results in people may be due to the fact that virtually all past studies relied on behavioral decisions from the participants. If human beings do possess a magnetic sense, daily experience suggests that it would be very weak or deeply subconscious. Such faint impressions could easily be misinterpreted – or just plain missed – when trying to make decisions.</p>
<p>So our research group – including a <a href="https://maglab.caltech.edu/">geophysical biologist</a>, a <a href="https://neuro.caltech.edu">cognitive neuroscientist</a> and a <a href="http://www.isp.ac/index_e.html">neuroengineer</a> – took another approach. <a href="https://maglab.caltech.edu/human-magnetic-reception-laboratory/">What we found</a> arguably provides the first concrete neuroscientific <a href="https://doi.org/10.1523/ENEURO.0483-18.2019">evidence that humans do have a geomagnetic sense</a>. </p>
<h2>How does a biological geomagnetic sense work?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=515&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=515&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=515&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=648&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=648&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=648&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Life on Earth is exposed to the planet’s ever-present geomagnetic field that varies in intensity and direction across the planetary surface.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/illustration-physics-magnetic-field-that-extends-1165968205">Nasky/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>The Earth is surrounded by a magnetic field, generated by the movement of the planet’s liquid core. It’s why a magnetic compass points north. At Earth’s surface, this magnetic field is fairly weak, <a href="https://nationalmaglab.org/about/maglab-dictionary/tesla">about 100 times weaker</a> than that of a refrigerator magnet.</p>
<p>Over the past 50 years or so, scientists have shown that hundreds of organisms in nearly all branches of the bacterial, <a href="https://www.livescience.com/54242-protists.html">protist</a> and animal kingdoms have the ability to detect and respond to this geomagnetic field. In some animals – <a href="https://doi.org/10.1007/BF00611096">such as honey bees</a> – the geomagnetic behavioral responses are <a href="https://pdfs.semanticscholar.org/750f/ce1b8f4723b09dd2fb1324fc916c9578c77b.pdf">as strong as the responses</a> to light, odor or touch. Biologists have identified strong responses in vertebrates ranging from <a href="https://doi.org/10.1038/37057">fish</a>, <a href="http://jeb.biologists.org/content/205/24/3903.full">amphibians</a>, <a href="https://doi.org/10.1126/science.1064557">reptiles</a>, numerous birds and a diverse variety of mammals including <a href="http://jeb.biologists.org/content/120/1/1.short">whales</a>, <a href="https://doi.org/10.1038/srep09917">rodents</a>, <a href="https://doi.org/10.1371/journal.pone.0001676">bats</a>, <a href="https://doi.org/10.1073/pnas.0803650105">cows</a> and <a href="https://doi.org/10.7717/peerj.6117">dogs</a> – the last of which can be trained to find a hidden bar magnet. In all of these cases, the animals are using the geomagnetic field as components of their homing and navigation abilities, along with other cues like sight, smell and hearing.</p>
<p>Skeptics dismissed early reports of these responses, largely because there didn’t seem to be a biophysical mechanism that could translate the Earth’s weak geomagnetic field into strong neural signals. This view was dramatically changed by the <a href="https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/73/4/435/5435">discovery that living cells</a> have the <a href="https://doi.org/10.1126/science.472725">ability to</a> build nanocrystals of the <a href="https://doi.org/10.1126/science.201.4360.1026">ferromagnetic</a> <a href="http://jeb.biologists.org/content/140/1/35.short">mineral magnetite</a> – basically, tiny iron magnets. Biogenic crystals of magnetite were first seen in the teeth of one group of mollusks, later in <a href="https://doi.org/10.1126/science.170679">bacteria</a>, and then in a variety of other organisms ranging from protists and animals such as insects, fish and mammals, <a href="https://doi.org/10.1073/pnas.89.16.7683">including within tissues of the human brain</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chains of magnetosomes from a sockeye salmon.</span>
<span class="attribution"><span class="source">Mann, Sparks, Walker & Kirschvink, 1988</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Nevertheless, scientists haven’t considered humans to be magnetically sensitive organisms.</p>
<h2>Manipulating the magnetic field</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=596&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=596&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=596&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=749&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=749&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=749&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Schematic drawing of the human magnetoreception test chamber at Caltech.</span>
<span class="attribution"><span class="source">Modified from 'Center of attraction' by C. Bickel (Hand, 2016).</span></span>
</figcaption>
</figure>
<p>In our new study, we asked 34 participants simply to sit in our testing chamber while we directly recorded electrical activity in their brains with electroencephalography (EEG). Our modified <a href="https://science.howstuffworks.com/faraday-cage.htm">Faraday cage</a> included a set of 3-axis coils that let us create controlled magnetic fields of high uniformity via electric current we ran through its wires. Since we live in mid-latitudes of the Northern Hemisphere, the environmental magnetic field in our lab dips downwards to the north at about 60 degrees from horizontal. </p>
<p>In normal life, when someone rotates their head – say, nodding up and down or turning the head from left to right – the direction of the geomagnetic field (which remains constant in space) will shift relative to their skull. This is no surprise to the subject’s brain, as it directed the muscles to move the head in the appropriate fashion in the first place.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=513&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=513&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=513&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=645&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=645&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=645&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Study participants sat in the experimental chamber facing north, while the downwards-pointing field rotated clockwise (blue arrow) from northwest to northeast or counterclockwise (red arrow) from northeast to northwest.</span>
<span class="attribution"><span class="source">Magnetic Field Laboratory, Caltech</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In our experimental chamber, we can move the magnetic field silently relative to the brain, but without the brain having initiated any signal to move the head. This is comparable to situations when your head or trunk is passively rotated by somebody else, or when you’re a passenger in a vehicle which rotates. In those cases, though, your body will still register vestibular signals about its position in space, along with the magnetic field changes – in contrast, our experimental stimulation was only a magnetic field shift. When we shifted the magnetic field in the chamber, our participants did not experience any obvious feelings.</p>
<p>The EEG data, on the other hand, revealed that certain magnetic field rotations could trigger strong and reproducible brain responses. One EEG pattern known from existing research, called alpha-ERD (event-related desynchronization), typically shows up when a person suddenly detects and processes a sensory stimulus. The brains were “concerned” with the unexpected change in the magnetic field direction, and this triggered the alpha-wave reduction. That we saw such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6Y4S2eG9BJA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video shows the dramatic, widespread drop in alpha wave amplitude (deep blue color on leftmost head) following counterclockwise rotations. No drop is observed after clockwise rotation or in the fixed condition. <i>Connie Wang, Caltech</i></span></figcaption>
</figure>
<p>Our participants’ brains only responded when the vertical component of the field was pointing downwards at about 60 degrees (while horizontally rotating), as it does naturally here in Pasadena, California. They did not respond to unnatural directions of the magnetic field – such as when it pointed upwards. We suggest the response is tuned to natural stimuli, reflecting a biological mechanism that has been shaped by natural selection.</p>
<p>Other researchers have shown that animals’ brains filter magnetic signals, only responding to those that are environmentally relevant. It makes sense to reject any magnetic signal that is too far away from the natural values because it most likely is from a magnetic anomaly - a lighting strike, or lodestone deposit in the ground, for example. One early report on birds showed that robins stop using the geomagnetic field if the strength is more than about <a href="https://doi.org/10.1126/science.176.4030.62">25 percent different from what they were used to</a>. It’s possible this tendency might be why previous researchers had trouble identifying this magnetic sense – if they <a href="https://doi.org/10.1016/S1388-2457(02)00186-4">cranked up the strength of the magnetic field</a> to “help” subjects detect it, they might have instead ensured that subjects’ brains ignored it.</p>
<p>Moreover, our series of experiments show that the receptor mechanism – the biological magnetometer in human beings – is not electrical induction, and can tell north from south. This latter feature rules out completely the so-called <a href="https://doi.org/10.1146/annurev-biophys-032116-094545">“quantum compass” or “cryptochrome”</a> mechanism which is popular these days in the animal literature on magnetoreception. Our results are consistent only with functional magnetoreceptor cells based on the <a href="https://doi.org/10.1016/0303-2647(81)90060-5">biological magnetite hypothesis</a>. Note that a magnetite-based system <a href="https://doi.org/10.1098/rsif.2009.0491.focus">can also explain</a> <a href="https://doi.org/10.1098/rsif.2009.0435.focus">all of the behavioral effects in birds</a> that promoted the rise of the quantum compass hypothesis.</p>
<h2>Brains register magnetic shifts, subconsciously</h2>
<p>Our participants were all unaware of the magnetic field shifts and their brain responses. They felt that nothing had happened during the whole experiment – they’d just sat alone in dark silence for an hour. Underneath, though, their brains revealed a wide range of differences. Some brains showed almost no reaction, while other brains had alpha waves that shrank to half their normal size after a magnetic field shift.</p>
<p>It remains to be seen what these hidden reactions might mean for human behavioral capabilities. Do the weak and strong brain responses reflect some kind of individual differences in navigational ability? Can those with weaker brain responses benefit from some kind of training? Can those with strong brain responses be trained to actually feel the magnetic field? </p>
<p>A human response to Earth-strength magnetic fields might seem surprising. But given the evidence for magnetic sensation in our animal ancestors, it might be more surprising if humans had completely lost every last piece of the system. Thus far, we’ve found evidence that people have working magnetic sensors sending signals to the brain – a previously unknown sensory ability in the subconscious human mind. The full extent of our magnetic inheritance remains to be discovered.</p><img src="https://counter.theconversation.com/content/113536/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shinsuke Shimojo received funding from Human Frontier Science Program (HFSP), Japanese Science and Technology Agency (JST), and currently receives funding from DARPA. </span></em></p><p class="fine-print"><em><span>Daw-An Wu receives funding from DARPA. </span></em></p><p class="fine-print"><em><span>Joseph Kirschvink receives funding from the RadioBio program of DARPA, and previous support for this work was from the Human Frontiers Science Program (HFSP).</span></em></p>Your brain’s sensory talents go way beyond those traditional five senses. A team of geoscientists and neurobiologists explored how the human brain monitors and responds to magnetic fields.Shinsuke Shimojo, Gertrude Baltimore Professor of Experimental Psychology, California Institute of TechnologyDaw-An Wu, California Institute of TechnologyJoseph Kirschvink, Nico and Marilyn Van Wingen Professor of Geobiology, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1018992018-11-11T23:23:26Z2018-11-11T23:23:26ZCurious Kids: How and why do magnets stick together?<figure><img src="https://images.theconversation.com/files/232825/original/file-20180821-30608-boid1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Every magnet has two sides: a north pole and a south pole.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/76099968@N00/5115486246/">Helena/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Hi my name is Dean and I am 7 years old. My question is: How and why do magnets stick together? – Dean, age 7, Vermont Sth.</strong></p>
</blockquote>
<hr>
<p>Hi Dean!</p>
<p>This is a good question and a bit tricky to answer, but I’ll try my best. </p>
<p>Every magnet has two sides: a north pole and a south pole. We use these names because if you hang a magnet from a thread, the magnet’s north pole points (almost) towards the north direction. </p>
<p>This is because the Earth’s core (its centre) is a large, weak magnet. Your little, strong magnet lines up with Earth’s magnetic core, so it points north. That’s how a magnetic compass works.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=322&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=322&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=322&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=404&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=404&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232831/original/file-20180821-30602-yybzcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=404&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">If you sprinkle <em>iron filings</em> (a fine powder of iron) around a magnet, you can see an image of the magnetic field.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-blue-bar-magnet-physics-magnetic-791214841?src=nh4OXG8yLf5OWMA6UD7-MQ-1-6">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Magnets don’t always stick together.</h2>
<p>If you hold two magnets the <em>wrong way</em> around, they push apart - they repel! In other words, if you hold two magnets together so that like-poles are close together (two norths OR two souths), they repel. Try it! It feels like the magnets are surrounded by an invisible rubber layer pushing them apart. That invisible layer is called a magnetic field.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=145&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=145&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=145&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=182&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=182&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243236/original/file-20181031-76405-1x2l3r0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=182&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><strong>Like-poles repel:</strong> We can use curvy arrows (called field lines) to draw the shape of the magnetic field around magnets. The arrows always start at the magnet’s north pole and point towards its south pole. When two like-poles point together, the arrows from the two magnets point in OPPOSITE directions and the field lines cannot join up. So the magnets will push apart (repel). Image credit: Author provided.</span>
</figcaption>
</figure>
<p>It’s only when you hold unlike-poles together (a north pointing to a south) that magnets stick together (they are attracted). Now, the magnetic field acts like a stretched rubber band pulling the magnets together. (Be careful; two strong magnets can pinch your skin).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=154&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=154&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=154&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=193&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=193&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243240/original/file-20181031-76396-iycnzp.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=193&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><strong>Unlike-poles attract:</strong> When a north pole and south pole point together, the arrows point in the SAME direction so the field lines can join up and the magnets pull together (attract). Image credit: Author provided.</span>
</figcaption>
</figure>
<h2>So, why do magnets attract or repel?</h2>
<p>You have probably heard of energy. Energy is needed to create movement. </p>
<p>A car that’s sitting still will start to move when the petrol inside it burns. That’s because petrol contains stored-up energy which is released when it burns. </p>
<p>When this stored-up energy is released, some of it changes into movement energy. Scientists call this stored-up energy “potential energy” and call movement energy “kinetic energy”.</p>
<p>When you start running, it’s because energy stored in your food is released and some of it changes into movement energy.</p>
<p>What’s this got to do with magnets? Well, the magnetic field that surrounds all magnets contains stored-up energy. But there’s a way to change the amount of stored-up energy surrounding the magnet. And the <em>way</em> you change it will tell you which way the magnet will move.</p>
<h2>A rule to remember</h2>
<p>Everything in the universe follows a rule. I will tell you the rule in a moment, but first I have to say that it’s not easy to explain <em>why</em> the universe follows this rule without complicated mathematics. The best I can say is “that’s just how the universe behaves”. (I’m sorry. I don’t like answers like that either).</p>
<p>The rule is: wherever there is stored-up energy in an object (and the object is not tied down or stuck in place), then the object will be pushed in the direction that causes the stored-up energy to decrease. The stored-up energy will be reduced and replaced by movement energy. </p>
<p>So if two magnets are pointing with unlike-poles together (north pole to a south pole), then bringing them closer together <em>decreases</em> the energy stored up in the magnetic field. They will be pushed in the direction that decreases the amount of stored-up energy. That is, they are forced together (this is called attraction).</p>
<p>If two magnets are pointing with like-poles together (a south pole to a south pole OR north to north), then stored-up energy will decrease if they move apart.</p>
<p>So our rule says the magnets will be pushed in the direction that decreases the amount of stored-up energy. That is, they are forced apart (repelled).</p>
<p>I should also say that when dropped objects are attracted to Earth and fall down, it’s NOT because of magnetism. It’s because of <em>gravity</em>. Earth is <em>also</em> surrounded by a gravitational field which <em>also</em> contains stored up energy. </p>
<p>Unlike magnetism, gravity never repels because gravity only points one way. There are no north and south poles for gravity.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/earths-magnetic-heartbeat-a-thinner-past-and-new-alien-worlds-59442">Earth's magnetic heartbeat, a thinner past and new alien worlds</a>
</strong>
</em>
</p>
<hr>
<h2>Can I keep taking stored-up energy from the magnetic field forever?</h2>
<p>No. </p>
<p>Once two magnets stick together, you’ll need to put some stored-up energy back into the field by pulling the magnets apart again. You can’t get energy for nothing.</p>
<p>The energy needed to pull the magnets apart comes from you, and you get it from the food you eat. And the plants or animals you eat get their energy from other plants and animals, or from the Sun. All energy comes from somewhere. </p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/101899/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen G Bosi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The energy needed to pull magnets apart comes from you, and you get it from the food you eat. And the plants or animals you eat get their energy from other plants and animals, or from the Sun. All energy comes from somewhere.Stephen G Bosi, Senior Lecturer in Physics, University of New EnglandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/887542017-12-07T19:28:31Z2017-12-07T19:28:31ZRare glimpse of a black hole’s magnetic field could help us to understand how it feeds<figure><img src="https://images.theconversation.com/files/198145/original/file-20171207-5016-1ddmuro.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Black hole Cygnus X.</span> <span class="attribution"><span class="source">NASA/CXC/M.Weiss</span></span></figcaption></figure><p>Encountering a black hole would be a <a href="https://theconversation.com/what-would-happen-if-earth-fell-into-a-black-hole-53719">frightening prospect for our planet</a>. We know that these cosmic monsters ferociously devour any object that strays too close to their “event horizon” – the last chance of escape. But even though black holes drive some of the most energetic phenomena in the universe, the physics of their behaviour, including how they feed, remains hotly debated. </p>
<p>In particular, the conditions close to the black hole and the role of its magnetic fields are thought to be key, but are notoriously difficult to probe in distant cosmic systems. Now an international team of astronomers have for the first time measured the precise magnetic field properties close to a black hole in our own Milky Way galaxy. </p>
<p>The results of study, <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aan0249">published in Science</a>, could help us better understand the mysterious process by which black holes swallow matter and grow.</p>
<p>Predicted mathematically from Einstein’s theory of general relativity, we now think that black holes come in a range of sizes. Supermassive black holes – with a million to a billion times the mass of our sun and about the size of our solar system in extent – are thought to lie at the heart of all massive galaxies and are likely to play a decisive role in the formation and evolution of galaxies.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198148/original/file-20171207-5077-1ccojnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of the surroundings of the supermassive black hole.</span>
<span class="attribution"><span class="source">ESO/M. Kornmesser</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>At the other extreme, there are black holes just a little more massive than our sun but contained in a region only a few kilometres across. They form in the cataclysmic death throes of massive stars or the merger of dense stellar remnants such as neutron stars or a neutron star colliding with another stellar black hole. When they merge, they <a href="https://theconversation.com/explainer-what-are-gravitational-waves-53239">produce gravitational waves</a>.</p>
<p>Studies of gamma ray bursts (bursts of light with very high energy) <a href="https://www.nature.com/articles/nature12814">have previously suggested</a> that large-scale magnetic fields could form close to black holes and cause jets of charged gas to escape from them. A similar mechanism is expected for supermassive black hole systems, which launch jets that spread over distances of millions of light years and are visible to networks of radio telescopes such as the <a href="https://public.nrao.edu/visit/very-large-array/">Very Large Array</a>. However, even the nearest supermassive black hole is nearly 30,000 light years away from us, so it is technically challenging to probe their magnetic fields.</p>
<h2>Cosmic burp</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=883&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=883&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=883&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1109&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1109&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122526/original/image-20160513-10674-bvt5gm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1109&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cygnus.</span>
<span class="attribution"><span class="source">Till Credner/wikimedia</span></span>
</figcaption>
</figure>
<p>The new study looks at a black hole that lies only 8,000 light years from Earth, part of a “binary system”, dubbed <a href="https://en.wikipedia.org/wiki/V404_Cygni">V404 Cygni</a>. This consists of a black hole with the mass of ten suns and a star similar to our own sun (but slightly cooler), which orbit each other every 6.5 days. In such systems, material from the star can fall towards the companion black hole to be gradually swallowed by it. </p>
<p>On its journey, the matter heats up, shines brightly and – in the presence of magnetic fields – some of it may be ejected back into space in the form of a focused beam of charged gas (plasma) or jets at bulk speeds close to that of light. Exactly how the magnetic fields cause this effect is still unknown. Luckily, the flares tend to be long-lived and their brightness can be monitored from Earth.</p>
<p>On June 15, 2015, V404 Cygni produced such an outburst – analogous to flares seen from the sun – that lasted for two weeks. The team, which immediately pointed a number of different telescopes at it, then noticed that the brightness of the system decreased suddenly and unexpectedly around June 25 across light frequencies ranging from X-rays to infrared. </p>
<p>They realised that this precipitous drop in brightness signalled that the system was cooling. By comparing this drop in brightness with models that predict how electrons produce light and lose energy – cool – when they spiral around magnetic field lines, the team were able to make a very precise estimate of the strength of the magnetic field. At 461 Gauss (a measurement of magnetism), this is much weaker than expected – only ten times stronger than a typical fridge magnet. </p>
<p>By studying how the properties of the light depended on frequency and time, they showed that the region from which the light was emitted was not expanding, as would be expected if the matter in this region formed part of a jet outflow. Instead, the research shows that there is a hot halo of charged particles held in place by a magnetic field around the black hole. The long-term fate of this halo gas is unknown, but it could be considered one of the last staging posts for fuel to reach the black hole and, if cooled further, may ultimately feed the black hole itself. </p>
<p>This work is important as it lays the foundations for future studies of this intriguing system to discover how black holes feed and how, if overfed, they may “burp” by launching focused beams or jets. Fortunately, V404 Cygni is sufficiently close to be <a href="https://theconversation.com/how-we-caught-a-black-hole-emitting-intense-wind-59423">an ideal laboratory</a> for future studies of black hole feeding and cosmic indigestion, but far enough from Earth not to be a threat to us.</p><img src="https://counter.theconversation.com/content/88754/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carole Mundell receives funding from the Science and Technology Facilities Council. However, the views expressed here are her own.</span></em></p>A sudden flare and cooling of gas around a black hole has enabled astronomers to measure the magnetic field of a black hole for the first time – finding it much weaker than expected.Carole Mundell, Head of Physics, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/790702017-07-19T06:44:08Z2017-07-19T06:44:08ZProtecting your smartphone from voice impersonators<figure><img src="https://images.theconversation.com/files/177937/original/file-20170712-19675-910rmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is this an impostor trying to break into your phone with his voice?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-recording-voice-message-smartphone-541649137">Georgejmclittle/Shutterstock.com</a></span></figcaption></figure><p>It’s a lot easier to talk to a smartphone than to try to type instructions on its keyboard. This is particularly true when a person is trying to log in to a device or a system: Few people would choose to type a long, complex secure password if the alternative were to just say a few words and <a href="https://thenextweb.com/apps/2015/03/25/wechat-on-ios-now-lets-you-log-in-using-just-your-voice/">be authenticated with their voice</a>. But voices can be recorded, simulated or even imitated, making voice authentication vulnerable to attack.</p>
<p>The most common methods for securing voice-based authentication involve only ensuring that analysis of a spoken passphrase is not tampered with; they securely store the passphrase and the <a href="https://www.technologyreview.com/s/428970/securing-your-voice/">authorized user’s voiceprint in an encrypted database</a>. But securing a voice authentication system has to start with the sound itself.</p>
<p>The easiest attack on voice authentication is impersonation: Find someone who sounds enough like the real person and get them to respond to the login prompts. Fortunately, there are automatic speaker verification systems that <a href="http://dx.doi.org/10.1121/1.4879257">can detect</a> <a href="https://doi.org/10.1109/TMM.2014.2300071">human imitation</a>. However, those systems <a href="https://doi.org/10.1016/j.specom.2014.10.005">can’t detect more advanced machine-based attacks</a>, in which an attacker uses a computer and a speaker to simulate or play back recordings of a person’s voice.</p>
<p>If someone records your voice, he can use that recording to create a computer model that can generate any words in your voice. The consequences, from impersonating you with your friends to dipping into your bank account, are terrifying. The research my colleagues and I are doing uses <a href="https://pdfs.semanticscholar.org/6be6/00d60f4d3210d20567c0ab8f3d78324ab5d4.pdf">fundamental properties of audio speakers, and smartphones’ own sensors</a>, to defeat these computer-assisted attacks.</p>
<h2>How speakers work</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/175656/original/file-20170626-29070-1tmcqg1.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The architecture of conventional loudspeaker showing the magnet, coil and cone used for loudspeaker operations.</span>
</figcaption>
</figure>
<p>Conventional speakers contain magnets, which vibrate back and forth according to <a href="http://www.physics.org/article-questions.asp?id=54">fluctuations of electrical or digital signals</a>, converting them into sound waves in the air. Putting a speaker up against the microphone of a smartphone, for example, means moving a magnet very close to the smartphone. And most smartphones contain a magnetometer, an electronic chip that can detect magnetic fields. (It comes in handy when using a compass or navigation app, for example.)</p>
<p>If the smartphone detects a magnet nearby during the process of voice authentication, that can be an indicator that a real human might not be doing the talking.</p>
<h2>Making sure it’s a person talking</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=851&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=851&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=851&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1070&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1070&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178145/original/file-20170713-18558-rh6r8z.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1070&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An outline of how our process works.</span>
<span class="attribution"><a class="source" href="https://pdfs.semanticscholar.org/6be6/00d60f4d3210d20567c0ab8f3d78324ab5d4.pdf">The Conversation (via Lucidchart), after Kui Ren et al.</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>That’s just one part of our system. If someone uses a smaller speaker, like a set of headphones, the magnetometer might not detect its smaller magnets. So we use machine learning and advanced mathematics to examine physical properties of the sound as it arrives at the microphone.</p>
<p>Our system requires a user to hold the smartphone in front of his or her face and move it from side to side in a half-circle while speaking. We combine the sound captured by the microphone with movement data from gyroscopes and accelerometers inside the smartphone – the same sensors apps use to know when you’re walking or running, or changing direction. </p>
<p>Using that data, we can calculate how far away from the microphone the sound is being generated – which lets us identify the possibility of someone using speakers at a distance so its magnets wouldn’t be detected. And we can compare the phone’s movement to the changes in the sound to discover whether it is created by a sound source roughly the size of a human mouth near the phone.</p>
<p>All of this, of course, could be defeated by a skilled impersonator – an actual human who mimics a user’s voice. But recall that existing speaker verification methods can catch impersonators, using machine learning techniques that identify <a href="http://dx.doi.org/10.1121/1.4879257">whether a speaker is modifying or disguising</a> his or her normal voice. We include that capability in our system as well. </p>
<h2>Does detection work?</h2>
<p>When we put our system to the test, we found that when the sound source is 6 centimeters (2 inches) from the microphone, we can always distinguish between a human and a computer-controlled speaker. At that distance, the magnet in a normal loudspeaker is strong enough to clearly interfere with the phone’s magnetometer. And if an attacker is using earphone speakers, the microphone is close enough to the sound source to detect it.</p>
<p>When the sound source is farther from the microphone, it’s harder to detect magnetic interference from a speaker. It’s also more difficult to analyze the movement of the sound source in relation to the phone when the distances are greater. But by using multiple lines of defense, we can defeat the vast majority of speaker- and human-based attacks and significantly improve the security of voice-based mobile apps. </p>
<p>At the moment, our system is a stand-alone app, but in the future we’ll be able to integrate it into other voice authentication systems.</p><img src="https://counter.theconversation.com/content/79070/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kui Ren receives funding from US National Science Foundation. </span></em></p>You can log in to your smartphone by talking to it. Current security systems don’t protect enough against imitators. The best way to ensure voice authentication is secure is to start with the sound.Kui Ren, Professor of Computer Science and Engineering, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/576612016-08-08T20:07:17Z2016-08-08T20:07:17ZExplainer: the mysterious missing magnetic monopole<figure><img src="https://images.theconversation.com/files/132937/original/image-20160803-12207-vsll31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">All the magnets we've ever seen have a north and a south, but there might be some out there that have only one end.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>You’ve probably heard of the <a href="https://theconversation.com/au/topics/higgs-boson">Higgs boson</a>. This elusive particle was predicted to exist long ago and helped explain why the universe works the way it does, but it took decades for us to detect.</p>
<p>Well, there’s another elusive particle that has also been predicted by quantum physics, and it’s been missing for an even longer time. In fact, we still haven’t spotted one, and not through lack of trying. </p>
<p>It’s called the magnetic monopole, and it has a few unique properties that make it rather special.</p>
<h2>Parallels</h2>
<p>Those with an interest in physics are probably already familiar with an <em>electric</em> monopole, although you may know it by its more common name: electric charge. </p>
<p>Opposite electric charges attract and like charges repel through the interaction of electric fields, which are defined as running from positive to negative. These are the somewhat arbitrary labels for the two opposing electric charges. </p>
<p>Electric monopoles exist in the form of particles that have a positive or negative electric charge, such as protons or electrons.</p>
<p>At first glance, magnetism seems somewhat analogous to electricity, as there exists a magnetic field with a direction defined as running from north to south. </p>
<p>However, the analogy breaks down when we try to find the magnetic counterpart for the electric charge. While we can find electric monopoles in the form of charged particles, we have never observed magnetic monopoles. </p>
<p>Instead, magnets exist only in the form of dipoles with a north and a south end. When a bar magnet is split into two pieces, you don’t get a separate north part and a south part. Rather you get two new, smaller magnets, each with a north and south end.</p>
<p>Even if you split that magnet down into individual particles, you still get a magnetic dipole. </p>
<p>When we look at magnetism in the world, what we see is entirely consistent with <a href="https://www.theguardian.com/science/2013/sep/15/maxwells-equations-electrify-world">Maxwell’s equations</a>, which describe the unification of electric and magnetic field theory into classical electromagnetism. </p>
<p>They were first published by James Maxwell during 1861 and 1862 and are still used daily on a practical level in engineering, telecommunications and medical applications, to name just a few.</p>
<p>But one of these equations – Gauss’s law for magnetism – states that there are no magnetic monopoles.</p>
<p>The magnetism we observe on a day-to-day basis can all be attributed to the movement of electric charges. When an electrically charged particle moves along a path, such as an electron moving down a wire, this is an electrical current. This induces a magnetic field that wraps around the direction of the current.</p>
<p>The second cause of magnetism involves a property from quantum mechanics called “spin”. This can be thought of in terms of an electrically charged particle rotating on an axis rather than moving in a particular direction. </p>
<p>This generates an angular momentum in the particle, causing the electron to act as a magnetic dipole (i.e. a tiny bar magnet). This means we can describe magnetic phenomena without the need for magnetic monopoles.</p>
<p>But just because our classical electromagnetic theories are consistent with our observations, that does not imply that there are no magnetic monopoles. Rather, this just means that there are no magnetic monopoles anywhere that we have <em>observed</em>. </p>
<p>Once we start to delve into the murky depths of theory, we begin to find some tempting arguments for their presence in the universe. </p>
<h2>The lure of duality</h2>
<p>In 1894, Nobel Laureate <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1903/pierre-curie-bio.html">Pierre Curie</a> discussed the possibility of such an undiscovered particle and could find no reason to discount its existence. </p>
<p>Later, in 1931, Nobel Laureate <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/dirac-bio.html">Paul Dirac</a> showed that when Maxwell’s equations are extended to include a magnetic monopole, electric charge can exist only in discrete values. </p>
<p>This “quantisation” of electric charge is one of the requirements of quantum mechanics. So Dirac’s work went towards showing that classical electromagnetism and quantum electrodynamics were compatible theories in this sense.</p>
<p>Finally, there are few physicists who can resist the beauty of symmetry in nature. And because the existence of a magnetic monopole would imply a duality between electricity and magnetism, the theory suggesting magnetic monopoles becomes almost intoxicating. </p>
<p>Duality, in the physical sense, is when two different theories can be related in such a way that one system is analogous to the other. </p>
<p>If it were the case that the electric force was completely analogous to the magnetic force, then perhaps other forces would also be analogous to one another. Perhaps then there would be some way to relate the strong nuclear force to the weak nuclear force, paving the way to a grand unification of all physical forces.</p>
<p>Of course, just because a theory has an appealing symmetry doesn’t make it correct. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132938/original/image-20160803-12196-16cpxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A single magnetic monopole might be hiding out there somewhere.</span>
<span class="attribution"><a class="source" href="http://moedal.web.cern.ch/images">CERN/MoEDAL</a></span>
</figcaption>
</figure>
<h2>Monopole mirage</h2>
<p>Scientists have come close to seeing magnetic monopoles by producing <a href="http://phys.org/news/2014-01-physicists-synthetic-magnetic-monopole-years.html">monopole-like structures</a> in the lab using complex arrangements of magnetic fields in Bose-Einstein condensates and superfluids. </p>
<p>But, while these show that a magnetic monopole is not a physical impossibility, they are not the same as discovering one in nature. </p>
<p>Particle physics experiments have, on occasion, announced <a href="http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.35.487">possible</a> <a href="http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.48.1378">monopole</a> candidates, but so far none of these discoveries have been shown to be irrefutable or reproducible. </p>
<p>The Monopole and Exotics Detector at the Large Hadron Collider (<a href="http://moedal.web.cern.ch/">MoEDAL</a>) has taken up the search, but has found no monopoles to date. </p>
<p>As a result, magnetic monopole enthusiasts have turned their sights to explaining why we <em>haven’t</em> seen any monopoles. </p>
<p>If the current generation of particle accelerators have failed to detect a magnetic monopole, perhaps the mass of a monopole is simply greater than we are able to create at present. </p>
<p>Using theory, we can estimate the maximum possible mass for the magnetic monopole. Given what we already know about the structure of the universe, we can estimate that the monopole mass could be up to an enormous 10<sup>14</sup> TeV. </p>
<p>An object this massive may have been produced only in the very early stages of the universe after the Big Bang, before cosmic inflation began. If the universe cooled to a point that monopole creation was no longer energetically possible before expanding, perhaps the monopoles are out there. Just few and far between. The trick is to find one.</p><img src="https://counter.theconversation.com/content/57661/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>T'Mir Danger Julius does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Physicists have theorised about the existence of a magnetic monopole for decades, but we have yet to find one.T'Mir Danger Julius, Data Scientist, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/547962016-06-03T01:02:30Z2016-06-03T01:02:30ZUsing lasers to make data storage faster than ever<figure><img src="https://images.theconversation.com/files/124210/original/image-20160526-22083-afpj7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Optical elements of the experimental setup allowing to obtain visible-spectrum laser pulses as short as 10 femtoseconds.</span> <span class="attribution"><span class="source">Courtesy of Dr. R. Borrego-Varillas and Prof. G. Cerullo, University Politecnico Milan (Italy)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>As we use <a href="https://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/mobile-white-paper-c11-520862.html">more and more data every year</a>, where will we have room to store it all? Our rapidly increasing demand for web apps, file sharing and social networking, among other services, relies on information storage in the “cloud” – always-on Internet-connected remote servers that store, manage and process data. This in turn has led to a pressing need for faster, smaller and more energy-efficient devices to perform those cloud tasks. </p>
<p>Two of the three key elements of cloud computing, microchips and communications connections, are getting ever faster, smaller and more efficient. My research activity has implications for the third: data storage on hard drives.</p>
<p>Computers process data, at its most fundamental level, in ones and zeroes. Hard disks store information by changing the local magnetization in a small region of the disk: its direction up or down corresponds to a “1” or “0” value in binary machine language.</p>
<p>The smaller the area of a disk needed to store a piece of information, the more information can be stored in a given space. A way to store information in a particularly tiny area is by taking advantage of the fact that individual electrons possess magnetization, which is called their spin. The research field of spin electronics, or “spintronics,” works on developing the ability to control the direction of electrons’ spins in a faster and more energy efficient way.</p>
<h2>Shining light on magnets</h2>
<p>I work to control electrons’ spins using extremely short laser pulses – one quadrillionth of a second in duration, or one “femtosecond.” Beyond just enabling smaller storage, lasers allow dramatically faster storage and retrieval of data. The speed comparison between today’s technology and femtosecond spintronics is like comparing the fastest bullet train on Earth to the speed of light.</p>
<p>In addition, if the all-optical method is used to store information in materials that are transparent to light, little or no heating occurs – a huge benefit given the economic and environmental costs presented by the need for <a href="http://dx.doi.org/10.1063/PT.3.3022">massive data-center cooling systems</a>.</p>
<h2>Ultrafast laser-control of magnetism</h2>
<p>A decade ago, <a href="http://dx.doi.org/10.1038/nature03564">studies</a> first demonstrated that laser pulses could control electron spins to write data and could monitor the spins to read stored data. Doing this involved measuring tiny oscillations in the electrons’ magnetization. After those early investigations, researchers believed – wrongly, as it turned out – that lasers could not affect or detect fluctuations smaller than the wavelength of the lasers’ own light. If this were true, it would not be possible to control magnets on a scale as short as one nanometer (one millionth of a millimeter) in as little time as a femtosecond. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/124212/original/image-20160526-22050-q96qun.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artistic representation of laser-induced modulation of electronic spins, which are represented by the red arrows.</span>
<span class="attribution"><span class="source">Courtesy of Dr. D. Afanasiev and Prof. A.V. Kimel, Radboud University Nijmegen (The Netherlands)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Very recently an international team of researchers of which I am a member has provided an <a href="http://dx.doi.org/10.1038/ncomms10645">experimental demonstration</a> that such a limitation does not actually exist. We were able to affect magnets on as small as one nanometer in length, as quickly as every 45 femtoseconds. That’s one ten-millionth the size, and more than 20,000 times as fast as today’s hard drives operate.</p>
<p>This suggests that future devices may be able to work with processing speeds as fast as 22 THz – 1,000 times faster than today’s GHz clock speeds in commercial computers. And devices could be far smaller, too.</p>
<h2>Novel scientific frontiers</h2>
<p>In addition to the practical effects on modern computing, the scientific importance of this research is significant. Conventional theories and experiments about magnetism assume that materials are in what is called “equilibrium,” a condition in which the quantities defining a system (temperature, pressure, magnetization) are either constant or changing only very slowly.</p>
<p>However, sending in a femtosecond laser pulse disrupts a magnet’s equilibrium. This lets us study magnetic materials in real time when they are not at rest, opening new frontiers for fundamental research. Already, we have seen <a href="http://dx.doi.org/10.1103/PhysRevLett.76.4250">exotic phenomena such as loss</a> or even <a href="http://dx.doi.org/10.1103/PhysRevLett.99.047601">reversal of magnetization</a>. These <a href="http://dx.doi.org/10.1038/nature09901">defy our current understanding of magnetism</a> because they are impossible in equilibrium states. Other phenomena are likely to be discovered with further research.</p>
<p>Innovative science begins with a vision: a scientist is a dreamer who is able to imagine phenomena not observed yet. The scientific community involved in the research area of ultrafast magnetism is working on a big leap forward. It would be a development that doesn’t mean just faster laptops but always-on, connected computing that is significantly faster, smaller and cheaper than today’s systems. In addition, the storage mechanisms won’t generate as much heat, requiring far less cooling of data centers – which is a significant cost both financially and environmentally. Achieving those new capabilities requires us to push the frontier of fundamental knowledge even farther, and paves the way to technologies we cannot yet imagine.</p><img src="https://counter.theconversation.com/content/54796/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Davide Bossini does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The speed comparison between today’s technology and femtosecond spintronics is like comparing the fastest bullet train on Earth to the speed of light.Davide Bossini, Postdoctoral Researcher in Experimental Condensed Matter Physics, University of TokyoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/592902016-05-12T18:01:15Z2016-05-12T18:01:15ZNASA flies satellites through explosion in space – and starts to unravel mystery of magnetism<figure><img src="https://images.theconversation.com/files/122172/original/image-20160511-18140-5apkik.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Four identical NASA spacecraft fly near the sun-facing boundary of Earth's magnetic field (the blue wavy lines).</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>There’s a lot we don’t know about many of the magnetic effects we see throughout the universe. The familiar, beautiful northern lights, for example, are actually a bit of an enigma. They are driven by a mysterious magnetic process in which a huge amount of energy is explosively released when particles from the sun hit the Earth’s magnetosphere. This is so powerful it can even break down the Earth’s magnetic shield that normally protects us from harmful, charged particles.</p>
<p>Exactly how this fundamental process works has long been a puzzle to physicists. Now a <a href="http://science.sciencemag.org/lookup/doi/10.1126/science.aaf2939">new study</a> published in Science has finally made a breakthrough by analysing data from a NASA mission flying through a region of space where these explosions occur. The findings boost our understanding of phenomena ranging from faraway astrophysical events to local <a href="http://www.metoffice.gov.uk/publicsector/emergencies/space-weather">space weather</a> and nuclear fusion. </p>
<p>Plasmas, known as the “<a href="http://pluto.space.swri.edu/image/glossary/plasma.html">fourth state of matter</a>”, are composed of electrically charged particles – loose electrons (negatively charged) and atoms that have lost electrons (positively charged), which have no overall charge. You may not be as familiar with plasmas in your everyday life as you are with solids, liquids and gases, but they are by far the most common form of ordinary matter in the universe, making up 99.9% of it. They are a bit like a hot gas and can indeed be created by heating a gas or subjecting it to a strong electromagnetic field.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_SoKuW1-Yf4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Plasmas made easy.</span></figcaption>
</figure>
<p>Plasmas are used in fluorescent lamps, supersonic combustion engines, <a href="http://www.explainthatstuff.com/plasmatv.html">plasma TV</a> and during the production of electronics. And although they have plenty of further technological potential, there are still some unknown properties of the plasma state that we need to figure out before we can get any further, such as in harnessing new energy sources or safeguarding our technological infrastructure.</p>
<p>One of these is a process called “<a href="http://www.nasa.gov/content/goddard/science-of-magnetic-reconnection/">magnetic reconnection</a>”, which can occur when plasmas with different magnetic fields collide. As the magnetic fields of each plasma get close to each other, the entire pattern of magnetic field lines changes and everything realigns into a new magnetic configuration – releasing huge amounts of energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=548&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=548&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=548&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Two plasmas (with magnetic fields coloured blue and red) move towards one another where they meet and they reconnect, changing their magnetic field lines.</span>
<span class="attribution"><span class="source">ChamouJacoN</span></span>
</figcaption>
</figure>
<p>This process fuels the northern lights and many space weather events, from solar flares and <a href="https://www.spaceweatherlive.com/en/help/what-is-a-coronal-mass-ejection-cme">coronal mass ejections</a> to the geomagnetic storms they can cause on Earth. These events influence our technological systems (both in space and on the ground) and can endanger property and human health. The huge power unleashed in this process is also one of the reasons why you probably <a href="https://theconversation.com/why-lightsabers-would-be-far-more-lethal-than-george-lucas-envisioned-55726">shouldn’t try to make a real-life lightsaber</a> and take part in a duel with it. </p>
<h2>Physics on a tiny scale</h2>
<p>Over very large scales, plasmas can be treated as fluids which can conduct electricity. This is true even of very weak plasmas, like those in space, where we have only a few charged particles within the size of a sugar cube. By comparison the same volume of the air you breathe contains 27 quintillion (or 27 followed by 18 zeros) molecules.</p>
<p>But our theories of this large-scale behaviour can’t quite explain reconnection. For that, we need to look at the physics happening at the small scale of particles. This becomes a very a complicated problem, even with our most advanced computing facilities. Nevertheless, we have been able to make some predictions about <a href="https://www2.warwick.ac.uk/fac/sci/physics/research/cfsa/people/valery/teaching/px420/handouts/mag_rec_flares.pdf">what we think happens within reconnection</a> – namely that the entire process is in fact controlled by electrons within a very small region of space, the heart of the reconnection site as it were. But the true test is to observe what actually occurs in nature.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122166/original/image-20160511-18144-1k0f7o6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The four spacecraft of the MMS mission getting prepared for stacking operations.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/gsfc/13960820999">NASA/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>NASA’s Magnetospheric Multiscale Mission is a set of four identical satellites separated by only 10km and flying in a pyramid formation with advanced instruments on board. This configuration, designed to fly through magnetic reconnection sites, allows us to probe the physics of the electrons in the process. The study found that this mission flew through the very heart of a reconnection site on the edge of Earth’s magnetic shield, allowing the researchers to observe exactly how the energy from the magnetic fields is converted to energy of the particles in the plasma. This is the first mission to directly observe how reconnection happens, which is impressive as researchers have tried to do this for half a century.</p>
<p>Some of our previous theoretical predictions were confirmed with this finding, including that electrons drive the reconnection process, however a number of surprises were also found. The acceleration and amount of energy given to the electrons was greater than expected.</p>
<p>Since the process is fundamental to all plasmas, this is a major milestone for physicists working in many different areas. For example, it could in the future improve our ability to predict when and where space weather may affect us. Understanding when magnetic reconnection can occur and how it happens is key to making such forecasts.</p>
<p>We will also be able to apply this knowledge universally to environments far from Earth out in our plasma universe or indeed much closer to home – particularly to within nuclear fusion reactors. Such reactors, which enable atomic nuclei (atoms that have no electrons) in a hot plasma to collide to form a new nucleus while releasing energy in the same way as the sun. Reconnection can disturb the strong magnetic fields we use to keep this extremely hot plasma at bay.</p>
<p>So while flying spacecraft into an explosion in space may sound like the plot of a terrible science fiction movie or the scheme of a nefarious super villain, it is an incredibly exciting feat for plasma physicists that may allow us to jump the technological hurdles we currently face.</p><img src="https://counter.theconversation.com/content/59290/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Archer does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After half a century of trying, scientists have finally caught a glimpse of the magnetic process that fuels space weather and the northern lights.Martin Archer, Space Plasma Physicist, Queen Mary University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/580062016-04-29T10:06:06Z2016-04-29T10:06:06ZA new state of matter: quantum spin liquids explained<figure><img src="https://images.theconversation.com/files/120548/original/image-20160428-28040-ojld52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spin, liquid – just add quantum.</span> <span class="attribution"><span class="source">Panom Pensawang/shutterstock.com</span></span></figcaption></figure><p>Magnetism is one of the oldest recognised material properties. Known since antiquity, records from the 3rd century BC describe how <a href="http://www.oceannavigator.com/January-February-2003/Lodestone-and-needle-the-rise-of-the-magnetic-compass/">lodestone</a>, a naturally occurring magnetised ore of iron, was used in primitive magnetic compasses. Today, thanks to the theory of quantum mechanics we now understand the nature of magnetism, too, with the concept of spin explaining the behaviour of elementary particles such as electrons in the material that make it magnetic.</p>
<p>Spin, a property of sub-atomic particles such as electrons and quarks, makes each individual electron behave as if it were a tiny magnetic compass needle. The millions or billions of electron spins in a piece of material interact with each other in various ways and stabilise to form the different possible magnetic states found in solid matter. Taken together in such large numbers, the spin of the material’s electrons grants the same magnetic properties to the material itself.</p>
<p>Magnetism is essential for the basic trappings of modernity: magnetic materials form the basis of modern electronics and information storage. With this in mind, scientists have pursued the discovery of materials with entirely new magnetic behaviours or new states of matter with unprecedented and potentially beneficial properties. </p>
<p>One is that of a <a href="http://iopscience.iop.org/1367-2630/focus/Focus%20on%20Quantum%20Spin%20Liquids">quantum spin liquid</a>, first proposed by the Nobel Prize-winning theoretical physicist PW Anderson in the early 1970s. In a paper published in the journal Nature Materials, a research team led by Professor Stephen Nagler at the Oak Ridge National Laboratory in the US has <a href="http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4604.html">demonstrated the quantum spin liquid nature</a> of the magnetic material ruthenium trichloride (α-RuCl₃).</p>
<h2>How do quantum spin liquids form?</h2>
<p>Quantum spin liquids are frequently found in a class of materials known as <a href="http://phys.org/news/2015-04-frustrated-magnets-reveals-clues-discontent.html">frustrated magnets</a>. In a conventional magnet, the interactions between spins result in stable formations, known as their <a href="http://www.britannica.com/science/long-range-order">long-range order</a>, in which the magnetic directions of each individual electron is aligned.</p>
<p>In a frustrated magnet, the arrangement of electron spins prevents them from forming an ordered alignment, and so they collapse into a fluctuating, liquid-like state. In a true quantum spin liquid, the electron spins never align, and continue to fluctuate even at the very lowest temperatures of absolute zero, at which the spins in other magnetic states of matter would have already frozen.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/120520/original/image-20160428-28044-1rvjot9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Herbertsmithite, a candidate quantum spin liquid source.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Herbertsmithite-herb03a.jpg">Rob Lavinsky/iRocks.com</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The conditions required for a quantum spin liquid to form are often found in nature. The most famous example is the copper-based mineral <a href="http://www.mindat.org/min-26600.html">Herbertsmithite</a>, for which there is significant evidence to suggest that a quantum spin liquid state exists within the frustrated magnetic layers of copper ions that make up its structure. </p>
<h2>Where do we find quantum spin liquids?</h2>
<p>A challenge for scientists is to recreate the conditions required to synthetically grow candidate quantum spin liquid materials in the laboratory to allow for a complete understanding of their properties.</p>
<p>Quantum spin liquids’ evasive character make it notoriously difficult to confirm their existence and pinpoint their exact nature. The presence of a quantum spin liquid can be inferred from a lack of alignment of electron spins, but definitive confirmation is tricky: absence of evidence is not evidence of absence, as the adage goes. A more sophisticated approach is to uncover the more distinctive and unique characteristics of the quantum spin liquid to allow for a positive confirmation.</p>
<p>This is why Nagler’s study is particularly noteworthy. In experiments using <a href="http://www.spectroscopyonline.com/neutron-spectroscopy">neutron spectroscopy</a>, the team revealed that α-RuCl₃ realises something extremely close to a special flavour of quantum spin liquid called a <a href="http://www.esrf.eu/home/news/spotlight/content-news/spotlight/spotlight236.html">Kitaev spin liquid</a>. A prerequisite for this particular quantum spin liquid state is that the spins of the magnetic ruthenium ions form a frustrated honeycomb network: a layered, two-dimensional hexagonal structure, similar to that assumed by carbon atoms in graphite.</p>
<p>In their experiment, a beam of neutron particles created by a particle accelerator was scattered from the sample of α-RuCl₃ transferring energy between the neutrons and the sample in the process. This energy transfer was quantified by a set of detectors surrounding the sample, and the response observed fits that described by the theory developed for the Kitaev quantum spin liquid in particular.</p>
<h2>What can we do with quantum spin liquids?</h2>
<p>We now recognise that the quantum spin liquid comes in several different varieties with subtly different properties, but that they all share the ability to support peculiar quantum mechanical phenomena. This is exciting, and not just from a purely scientific perspective: these states could be used in the development of quantum computers and other transformative quantum technologies that are expected to provide revolutionary changes to how we process and store data throughout the 21st century. </p>
<p>In the age of quantum computing, we will be able to perform calculations that are currently unsolvable on even the most powerful supercomputers of today. This will allow for breakthroughs in a vast array of fields in which we are tackling some of the biggest challenges of our time, from drug discovery to the design of smarter materials for a whole host of applications. As we discover more candidate quantum state liquid materials and better understand their behaviour, we will unravel ever more exotic physics and discover ways to manipulate and control this novel state of matter to our advantage.</p><img src="https://counter.theconversation.com/content/58006/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lucy Clark receives funding from The Leverhulme Trust. </span></em></p>Here’s how they could revolutionise science.Lucy Clark, Research Fellow, University of St AndrewsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/557262016-04-04T11:24:19Z2016-04-04T11:24:19ZWhy lightsabers would be far more lethal than George Lucas envisioned<figure><img src="https://images.theconversation.com/files/116957/original/image-20160331-6126-1fronht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You may want to be careful with that, Darth!</span> <span class="attribution"><span class="source"> Kenny Louie/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Research is an unpredictable process. Sometimes you end up making a really cool discovery that you didn’t see coming. I recently uncovered a fundamental property of lightsabers (that’s right – the awesome weapons from Star Wars) while doing my regular plasma physics research. I found that, while it is in theory possible to build a lightsaber, it’s likely it would be the most dangerous weapon ever created – both for the perpetrator and the victim.</p>
<p>With <a href="https://theconversation.com/the-force-awakens-a-sugar-high-but-not-a-great-movie-49543">Star Wars: The Force Awakens</a> being released on DVD after breaking all kinds of records at the box office, I figured it was a good time to share the news. </p>
<p>Despite the name, it has been established in <a href="http://starwars.wikia.com/wiki/Lightsaber">Star Wars canon</a> that these ancient weapons of the Jedi are, in fact, not laser swords but blades of plasma. Plasma is often known as the “<a href="http://pluto.space.swri.edu/image/glossary/plasma.html">fourth state of matter</a>” in addition to the solids, liquid and gases that we’re all familiar with here on Earth. However, plasmas are by far the most common state of all visible matter in the universe (excluding the mysterious “dark matter” or “dark energy”) comprising some 99%.</p>
<p>The thing that makes plasmas different from the other states is that they are composed of electrically charged particles – loose electrons (negatively charged) and atoms that have lost electrons (positively charged), despite having no overall charge. Any moving electric charge, such as those inside a plasma, creates magnetic fields and can also be manipulated using magnetic or electric fields – unlike a neutral gas.</p>
<p>Magnetic fields are the key to containing the plasma in a blade, they can counteract the pressure of the hot plasma trying to expand into its surroundings. This is exactly one of the approaches that have been developed in trying to harness nuclear fusion power, in which atomic nuclei (atoms that have no electrons) collide to form a new nucleus while releasing huge amounts of energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=506&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=506&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=506&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=635&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=635&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=635&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wendelstein X - a nuclear fusion reactor in Germany.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Wendelstein_7-X">Max Planck institute/wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Fusion requires incredible temperatures so that the positively charged atomic nucleii can overcome their tendency to repel each other. We create these hot plasmas in <a href="https://theconversation.com/for-decades-a-distant-dream-the-countdown-to-nuclear-fusion-may-have-finally-begun-17801">doughnut-shaped fusion reactors</a> (“tokamaks”) which use strong electromagnets in the reactor walls to keep this plasma at bay. The largest <a href="https://theconversation.com/nuclear-fusion-the-clean-power-that-will-take-decades-to-master-41356">of these such experimental reactors</a> will be <a href="https://www.iter.org/">ITER (International Thermonuclear Experimental Reactor)</a> construction of which will finish in 2019 and which aims to finally be able to produce more energy via fusion than is put in to create, sustain and control the plasma itself.</p>
<h2>Mysterious glow</h2>
<p>There are two ways plasmas can emit light. The first is by being incredibly hot. The sun, for instance, is a ball of hot plasmas whose heat source comes from the fusion taking place in its core. All hot objects emit electromagnetic radiation with specific wavelengths. Their perceived colour depends solely on their temperature, going from red for lower temperatures and blue for higher temperatures. This is likely the source of a lightsaber’s glow – if you want a really dangerous lightsaber, you need a blue one.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0Nt16ZvGjAM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Lightsaber discovery.</span></figcaption>
</figure>
<p>The other way plasmas may glow is very similar to how a fluorescent bulb works. By running an electrical current through a plasma, electrons can collide with the positively-charged atoms (dubbed ions), which raises their energy. It’s similar to picking up a ball off the ground and putting it on one of many shelves – this raises the ball’s potential energy, whereby the shelves represent the energy levels of the ions. But nature is inherently lazy and will always strive to go back to the lowest possible state of energy. Eventually the ball will roll off of the shelf falling back to the ground. The ions do this by releasing their excess energy as light – which could create the lightsaber glow. This light will be of a specific colour depending on the composition of the plasma.</p>
<p>While lightsabers do seem feasible from a physics point of view, the power requirements for such a device would be immense, especially given that it needs to be contained within the small lightsaber hilt. Huge advances in technology would be required to make lightsabers a reality. But there’s an even bigger problem which would come about if you were to ever have a lightsaber duel like in the movies.</p>
<h2>Powerful magnetic effects</h2>
<p><a href="http://www.nasa.gov/content/goddard/science-of-magnetic-reconnection">Magnetic reconnection</a> is a fundamental plasma physics process which can occur when plasmas with different magnetic fields collide. As the magnetic fields of each plasma get close to each other, the entire pattern of magnetic field lines changes and everything realigns into a new magnetic configuration – releasing huge amounts of energy. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=548&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=548&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=548&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Two plasmas (with magnetic fields coloured blue and red) move towards one another where they meet and they reconnect, changing their magnetic field lines.</span>
<span class="attribution"><span class="source">ChamouJacoN</span></span>
</figcaption>
</figure>
<p>This is what essentially fuels the aurora or northern lights – energy from the solar wind is released when these particles collide with plasma inside Earth’s magnetic field under a specific set of conditions.</p>
<p>It’s from our studies of the conditions under which reconnection can occur in space that I was able to realise the problem with lightsaber battles. When two plasma blades clash it is almost impossible to avoid magnetic reconnection, with the results being an explosive release of the plasma contained in both sabers. This would mean that, if you were in a lightsaber duel, both you and your opponent would have body parts vaporised in a single clash! </p>
<p>Perhaps the makers of the coming two Star Wars films should make a note … then again who knows how “The Force” really works?</p><img src="https://counter.theconversation.com/content/55726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Archer does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Warning: you’ll never watch a lightsaber duel in the same way again after you read this …Martin Archer, Space Plasma Physicist, Queen Mary University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/465702015-09-07T13:34:16Z2015-09-07T13:34:16ZHow does the Lexus hoverboard actually work? A scientist explains<figure><img src="https://images.theconversation.com/files/93329/original/image-20150828-19916-9i5obf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Riding on air</span> <span class="attribution"><span class="source">Lexus</span></span></figcaption></figure><p>Marty McFly wouldn’t be surprised. Lexus <a href="http://www.lexus-int.com/amazinginmotion/slide/">recently announced</a> it had fulfilled the dreams of Back to the Future Part II fans everywhere by building a working hoverboard. And just in time for the October 2015 date that Marty visits in the film to discover kids have ditched skateboards in favour of their flying counterparts.</p>
<p>The Lexus “Slide” hoverboard isn’t set to go on sale but a prototype was recently put through its paces by pro-skateboarder Ross Mcgouran at a custom-built skate park in Barcelona. Now Lexus has also revealed how the device actually works, involving a special track that enables the board to magnetically levitate above it, in a very similar way to <a href="https://theconversation.com/the-future-of-rail-travel-and-why-it-doesnt-look-like-hyperloop-45354">maglev trains</a>.</p>
<p>It’s an amusing coincidence that, while Back to the Future featured technology called a flux capacitor, the Slide relies on something called flux pinning, as well as a principle called the <a href="http://www.supraconductivite.fr/en/index.php?p=supra-levitation-meissner-more">Meissner effect</a>. And this all works because of something called superconduction.</p>
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<p><a href="http://www.superconductorweek.com/what-is-superconductivity">A superconductor</a> is a material cooled to a very low critical temperature that, when you run a current through it, experiences no electrical resistance (the material doesn’t push back against the current). When a material becomes a superconductor it pushes away any magnetic fields inside it. This is known as the Meissner effect.</p>
<p>The Slide hoverboard contains a series of metal alloy superconducting blocks cooled to -197°C by reservoirs of liquid nitrogen. The track below contains three magnets that induce a current in the blocks, causing the Meissner effect to take hold and expel the magnetic field back towards the track in a mirror image.</p>
<p>These mirroring magnetic forces repel each other and so the board is lifted above the track. Even if someone stands on the board, the magnetic forces are strong enough to keep it levitating because the lack of electrical resistance in the superconductor means the magnetic field can adjust to deal with external pressure.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/ZwSwZ2Y0Ops?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>But another scientific phenomenon makes the hoverboard even more stable. When the cooling process is switched on and the blocks in the board become supercondutors, they effectively trap the lines of the magnetic field from the track. This causes the blocks to be pinned at a fixed height above the track, a process known as flux pinning, which provides much more stable levitation. Flux pinning ensures the hoverboard doesn’t deviate either horizontally or vertically from the track. </p>
<p>As a proof of concept, the Slide shows that constructing a hoverboard with stable levitation is entirely possible. Sadly, before we get too excited, the technology looks unlikely to hit the market in the near future for several reasons. The current board <a href="http://www.lexus-int.com/amazinginmotion/slide/">weighs 11.5kg</a>, including the superconducting material and the liquid nitrogen on board, making it rather cumbersome to carry. The liquid nitrogen also requires a top-up roughly every 10 minutes to ensure that the superconducting material remains at optimal temperature.</p>
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<p>On top of that, the board currently only works at one custom-built skate park. Lexus hasn’t disclosed the cost for this proof of concept, but it is safe to presume that superconducting blocks, supplies of liquid nitrogen and a custom-built park awash with permanent magnets could not have been cheap. </p>
<p>Despite these limitations – <a href="http://www.techtimes.com/articles/63215/20150624/lexushover-lexus-teases-a-real-and-rideable-hoverboard-video.htm">and as Lexus points out</a> – nothing is impossible. It is entirely plausible to imagine similar parks and guide-ways being constructed as part of future smart cities. Perhaps the hoverboard could even offer a greener travel alternative within the city as well as a leisure activity. In years to come, we could well find ourselves topping up our boards with liquid nitrogen at city-wide charging points, just as we fill up our cars today.</p><img src="https://counter.theconversation.com/content/46570/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tan Sharma does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The engineers who brought this science-fiction stable to life relied on some very well established science fact.Tan Sharma, Associate of Informatics, University of SussexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/429852015-06-30T10:16:25Z2015-06-30T10:16:25ZI’m stuck like glue: why I love magnets and you should too<figure><img src="https://images.theconversation.com/files/86641/original/image-20150628-1431-ac980z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The invisible force and visible effects of magnetism.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/archeon/12857404305"> Hans Splinter</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>I have a confession: I’m obsessed with magnets.</p>
<p>We rely on magnets every day, but seldom give them a second thought. There are magnets in your credit card, your cellphone, your car, microwave oven and computer – and perhaps also pasted all over your refrigerator. </p>
<p>Probably the last time you thought about a magnet was in <a href="https://www.nde-ed.org/EducationResources/HighSchool/Magnetism/twoends.htm">a high school science class</a>. But you should realize they’re the unsung heroes of our world. Someone needs to stand up for magnets, and that person is me.</p>
<p>Don’t get me wrong. I’m not a magnet stalker or a magnet groupie. I’m a scientist, and I study magnetism for a living.</p>
<h2>Universally magnetic</h2>
<p>My main interest is in “<a href="https://www.skatelescope.org/magnetism/">cosmic magnetism</a>” – magnets in outer space. </p>
<p>Incredibly, magnetism is everywhere in the cosmos: planets, stars, gaseous nebulae, entire galaxies and the overall universe are all magnetic. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=563&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=563&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=563&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=707&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=707&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86775/original/image-20150629-9054-170w15l.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=707&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Our planet is one big magnet.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Earths_Magnetic_Field_Confusion.svg">TStein</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>What does it mean to say that a heavenly body is magnetic? For a solid body like the Earth, the idea is reasonably simple: <a href="http://www.geomag.nrcan.gc.ca/mag_fld/fld-eng.php">the Earth’s core is a giant bar magnet</a>, with north and south poles.</p>
<p>But farther afield, things get weird.</p>
<p><a href="http://phenomena.nationalgeographic.com/2014/12/08/magnetic-milky-way/">Our entire Milky Way galaxy is also a magnet</a>. Just like for the Earth, the Milky Way’s magnetism is produced by electrical currents. But while the Earth has a molten core to carry these currents, our galaxy’s magnetism is powered by uncounted numbers of electrons, slowly drifting in formation through space. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86774/original/image-20150629-9102-wyi1lf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The magnetic field of our Milky Way galaxy as seen by the Planck satellite. Darker regions correspond to stronger polarized emission, and the striations indicate the direction of the magnetic field projected on the plane of the sky.</span>
<span class="attribution"><a class="source" href="http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1502_aaa/fig3.jpg">ESA and the Planck Collaboration</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The result is a magnet like nothing you’ve ever seen. </p>
<p>First, the Milky Way’s magnetism is unimaginably weak, around a million times weaker than the Earth’s. What’s more, instead of having a single north–south pole, there is seemingly <a href="http://www.mpifr-bonn.mpg.de/research/fundamental/cosmag">a separate magnet in each spiral arm</a> of our galaxy’s glowing pinwheel: different galactic neighborhoods have their own local definitions of north and south.</p>
<h2>Cosmic questions about cosmic magnets</h2>
<p>My own research has two focuses. First, what do galactic magnets look like? Where are all the north and south poles in our Milky Way, and in the millions of other galaxies scattered throughout the universe?</p>
<p>Second, and more importantly, where did all these magnets come from? How did the first cosmic magnets come into existence billions of years ago, and how have they survived through to the present day?</p>
<p>These questions are not quite as esoteric as they sound. </p>
<p>Magnetism is vital for <a href="https://www.cfa.harvard.edu/news/2009-20">stars like our sun to form</a>. The Earth’s magnetism <a href="http://www.esa.int/Our_Activities/Space_Science/Cluster/Earth_s_magnetic_field_provides_vital_protection">protects our atmosphere from harmful radiation</a>. And cosmic magnets generate energetic high-speed particles which, on arrival at Earth, <a href="http://www.space.com/7193-death-rays-space-bad.html">can cause random genetic mutations</a> and hence drive evolution.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DRR3IPfTXiE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Faraday rotation is an effect through which light is rotated as it passes through magnetized regions of space. (Swinburne Astronomy Productions / CAASTRO: The ARC Centre of Excellence for All-sky Astrophysics)</span></figcaption>
</figure>
<p>On the other hand, the answers are elusive. The big challenge is that magnetism is invisible: point a powerful telescope at a cosmic magnet, and you won’t see it. Instead, we use indirect approaches, relying on the fact that <a href="http://dunlap.utoronto.ca/%7Ebgaensler/papers/stories/301Gaensler-3.pdf">background light is subtly changed</a> as it passes through magnetic regions of foreground gas. I think of it as trying to do the ultimate cryptic crossword puzzle, but blindfolded and with your hands tied behind your back. </p>
<h2>A magnetic sixth sense</h2>
<p>Of course, one can’t spend one’s whole life just thinking about cosmic magnets. Every scientist has a secret unfulfilled ambition: a completely different scientific career that perhaps, if things had been different, they would have pursued instead.</p>
<p>So what’s my secret alternative vocation? </p>
<p>In a parallel universe, I would still be obsessed with magnets. But I would not be an astronomer. Instead I would study “magnetoreception.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86643/original/image-20150628-1438-3k8odr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Birds’ long migrations can be tied to their magnetic ‘sixth sense.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/wolfraven/3108329398">Jack Wolf</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Magnetoreception is the ability of some animals to <a href="http://www.the-scientist.com/?articles.view/articleNo/36722/title/A-Sense-of-Mystery/">respond or react to magnetism</a>: a “sixth sense” that allows them to see the unseen. The best-known examples are birds, some species of which <a href="http://www.nytimes.com/2012/04/27/science/study-sheds-light-on-how-pigeons-navigate-by-magnetic-field.html">navigate using the Earth’s magnetic field</a> during their spectacular globe-spanning migrations. </p>
<p>But in recent years, scientists have found that a whole host of other species can sense magnetism. Perhaps the most extraordinary case is that of <a href="http://www.nature.com/news/the-mystery-of-the-magnetic-cows-1.9350">magnetic cows</a>. Using images from Google Earth, researchers have claimed that cows around the world tend to align their bodies with the Earth’s magnetic field whenever they are grazing or resting.</p>
<p>Other studies, covering everything from <a href="http://www.smithsonianmag.com/smart-news/earths-magnetic-field-draws-sea-turtles-their-nests-180953926/?no-ist">the swimming patterns of sea turtles</a> to the <a href="http://www.pbs.org/newshour/rundown/dogs-poop-in-alignment-with-earths-magnetic-field-study-finds/">directions dogs face when they defecate</a>, have similarly revealed that animals can somehow sense magnetism. </p>
<p>Even humans might have some vestigial sensitivity to magnets. <a href="http://www.ncbi.nlm.nih.gov/pubmed/11976892">Vision quality seems to depend</a> on whether you’re facing north–south or east–west. Dreams are more likely to be <a href="http://www.newscientist.com/article/dn16871-sweet-dreams-are-made-of-geomagnetic-activity.html">mundane rather than bizarre</a> when the Earth’s magnetism is going through a period of high activity. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=386&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=386&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86645/original/image-20150628-1428-liw6y9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=386&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pluses of magnets.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bar_magnet.jpg">Aney</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Well-known but so mysterious</h2>
<p>It’s now been around 2,600 years since <a href="http://galileoandeinstein.physics.virginia.edu/more_stuff/E&M_Hist.html">the Greek philosopher Thales noticed that magnets attract iron</a>. We understand almost completely how magnets work, right down to <a href="http://magician.ucsd.edu/essentials/WebBookse16.html">the detailed atomic level</a>. Once a curiosity, magnetism is now at our beck and call, and <a href="http://www.northeastern.edu/sunlab/mom/technology.html">underpins our entire modern world</a> of convenience and technology. </p>
<p>We might have completely tamed magnets for our purposes, so much so that we almost never give them a moment’s thought. But both up in the heavens and down here on the ground, there’s still a huge amount we don’t understand about magnets. Where did magnets come from? How have they shaped the universe? And what roles do they play for life on Earth? </p>
<p>So please don’t overlook magnets. Magnets are marvelous, mysterious and magical, and deserve both your affection and your respect.</p><img src="https://counter.theconversation.com/content/42985/count.gif" alt="The Conversation" width="1" height="1" />
<h4 class="border">Disclosure</h4><p class="fine-print"><em><span>Bryan Gaensler receives funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p>I have a confession: I’m obsessed with magnets. We rely on magnets every day, but seldom give them a second thought. There are magnets in your credit card, your cellphone, your car, microwave oven and…Bryan Gaensler, Director, Dunlap Institute for Astronomy and Astrophysics , University of TorontoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/391542015-03-23T18:48:28Z2015-03-23T18:48:28ZMagnetic fields can control heat and sound<figure><img src="https://images.theconversation.com/files/75686/original/image-20150323-17699-e7afqt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Magnets have mysterious powers – now shown to influence heat and sound.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-206965711/stock-photo-horseshoe-magnet-isolated-on-white-background-back-view.html">Magnet image via www.shutterstock.com.</a></span></figcaption></figure><p>Sound is carried by periodic vibrations of atoms in gases, liquids and solids. When we talk to each other, the vocal chords of the speaker vibrate, causing the air coming from his lungs to vibrate as well. This creates sound waves, which then propagate through the air until they hit a listener’s eardrums and make them vibrate as well. From these vibrations, the listener can then reconstruct the speaker’s words.</p>
<p>Sound is affected by the surroundings in which it travels and by the frequency of the sound waves. We design musical instruments to manipulate the sound waves they produce. Further, we know that there are sound waves that are outside the range of human hearing, such as those produced by a dog whistle. As physicists have researched sound both inside and outside the range of human hearing, interesting properties have been discovered.</p>
<p>More than a hundred years ago, physicists understood that heat is simply the energy stored in the vibrations of atoms, and therefore realized that heat and sound are related. Now my lab showed experimentally for the first time that these atomic vibrations have magnetic properties too.</p>
<h2>Building our knowledge of sound</h2>
<p>In the 1930s, physicists started modeling atomic vibrations as particles. This is similar to the concept of light as both a wave and a particle we call a photon. Physicists called the sound wave particles “phonons,” derived from the Greek word for sound. </p>
<p>Today, physicists treat phonons as quasi-particles, having both wave and particle properties. Phonons carry both sound and heat. In metals, heat is carried primarily by the movement of electrons in the atoms. However, in all other materials, heat is carried almost exclusively by the phonons. </p>
<p>So the mechanical, acoustic and thermal properties of sound waves have long been established. Yet, before now, nobody ever imagined that sound waves might also have magnetic properties.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75680/original/image-20150323-17699-116cyry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A lopsided tuning fork, made of the semiconductor indium antimonide, used in the experiment.</span>
<span class="attribution"><span class="source">Kevin Fitzsimons, The Ohio State University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Heat, sound… and magnetism?</h2>
<p>In the <a href="http://dx.doi.org/10.1038/nmat4247">March 23 issue of Nature Materials</a>, we offer experimental proof that sound waves do interact with external magnetic fields.</p>
<p>The experiment was carried out on a large, single crystal of a very pure semiconductor, indium antimonide, which had been cut into two unequal sections and then cooled to about -445F (-265C). A controlled amount of heat was made to flow in each section separately. At these temperatures, the phonons can be thought of as individual particles, like runners on a racetrack each carrying a little bucket of heat.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=848&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=848&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=848&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1066&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1066&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75683/original/image-20150323-17709-1vbx8jz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1066&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Artist’s rendering of a phonon heating solid material. The phonon hits the center orange atom, which is attached to other atoms via spring-like bonds. The trail of the passing phonon is marked with increased magnetic field intensity, shown in green.</span>
<span class="attribution"><span class="source">Renee Ripley, The Ohio State
University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>In the small section, the phonons often run into the walls, which slows them down. The small section is used as a reference, to make the experiment independent of the other properties of the solid that might interfere. In the large section, the phonons can go faster, and they don’t run into the walls as much as into each other. When we apply a magnetic field, they tend to run into each other more frequently. Because the magnetic field increases the number of collisions, it also slows the phonons down and lowers the amount of heat they carry by 12%.</p>
<p>We think this is due to the electrons that rotate in orbits around each atom in the solid. The orbital motion of these electrons emits a very small intrinsic magnetic field that interacts with the externally applied field – an effect called “diamagnetism.” This property exists even in substances we don’t traditionally think of as magnetic, such as glass, stone or plastic. When the atoms vibrate due to the passing of the phonons, this interaction creates a force on the atoms that makes the phonons collide with each other more often.</p>
<h2>What can we do with these results?</h2>
<p>At this point, we’ve just described a new concept, something that had never been thought of before. Engineers can perhaps use this concept to control heat and sound waves magnetically. Sound waves can be effectively steered already by using multiple sources of sound, as is done in ultrasound imaging systems, but controlling heat conduction is much harder.</p>
<p>Conversion of heat into electrical or mechanical power, as is done in engines and in power stations, supplies over 90% of the energy humanity uses. Therefore, being able to control heat conduction at will could have an enormous impact on energy production, though, obviously, applications of this emergent concept are still quite a way in the future.</p><img src="https://counter.theconversation.com/content/39154/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The experiments were supported as part of the ARO MURI under award number W911NF-14-1-0016, US AFOSR MURI under award number FA9550-10-1-0533 (H.J.) and the NSF grant CBET-1133589 (J.P.H., R.C.M.). The theoretical work was supported by the NSF MRSEC program under grant DMR 1420451, as well as an allocation of computing time from the Ohio Supercomputing Center.</span></em></p>Sound waves are made of particles called phonons. New research shows they’re affected by magnetic fields, with researchers able to steer heat magnetically.Joseph Heremans, Professor of Mechanical and Aerospace Engineering, Physics, and Materials Science & Engineering, The Ohio State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/381222015-03-04T13:14:11Z2015-03-04T13:14:11ZExplainer: what is a superconductor?<figure><img src="https://images.theconversation.com/files/73507/original/image-20150302-15941-1fyapoc.jpg?ixlib=rb-1.1.0&rect=8%2C561%2C5591%2C3302&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Superconducting materials have strange and unusual properties including magnetic levitation.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-223876228/stock-photo-image-concept-of-magnetic-levitating-above-a-high-temperature-superconductor-cooled-with-liquid.html?src=eEzMrPe8SuI1P-se_WiMPQ-1-0&ws=1">Shutterstock</a></span></figcaption></figure><p>Materials can be divided into two categories based on their ability to conduct electricity. Metals, such as copper and silver, allow electrons to move freely and carry with them electrical charge. Insulators, such as rubber or wood, hold on to their electrons tightly and will not allow an electrical current to flow. </p>
<p>In the early 20th century physicists developed new laboratory techniques to cool materials to temperatures near absolute zero (-273 °C), and began investigating how the ability to conduct electricity changes in such extreme conditions. In some simple elements such as mercury and lead they noticed something remarkable – below a certain temperature these materials could conduct electricity with no resistance. In the decades since this discovery scientists have found identical behaviour in thousands of compounds, from ceramics to carbon nanotubes. </p>
<p>We now think of this state of matter as neither a metal nor an insulator, but an exotic third category, called a superconductor. A superconductor conducts electricity perfectly, meaning an electrical current in a superconducting wire would continue to flow round in circles for billions of years, never degrading or dissipating. </p>
<h2>Electrons in the fast lane</h2>
<p>On a microscopic level the electrons in a superconductor behave very differently from those in a normal metal. Superconducting electrons pair together, allowing them to travel with ease from one end of a material to another. The effect is a bit like a priority commuter lane on a busy motorway. Solo electrons get stuck in traffic, bumping into other electrons and obstacles as they make their journey. Paired electrons on the other hand are given a priority pass to travel in the fast lane through a material, able to avoid congestion. </p>
<p>Superconductors have already found applications outside the laboratory in technologies such as <a href="https://theconversation.com/the-science-of-medical-imaging-magnetic-resonance-imaging-mri-15030">Magnetic Resonance Imaging</a> (MRI). MRI machines use superconductors to generate a large magnetic field that gives doctors a non-invasive way to image the inside of a patient’s body. Superconducting magnets also made possible the recent detection of the <a href="https://theconversation.com/nobel-prize-in-physics-goes-to-discovery-of-the-higgs-boson-19014">Higgs Boson</a> at <a href="http://home.web.cern.ch/">CERN</a>, by bending and focusing beams of colliding particles. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=547&fit=crop&dpr=1 600w, https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=547&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=547&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=687&fit=crop&dpr=1 754w, https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=687&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/73506/original/image-20150302-15965-crkaoo.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=687&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Superconductors are used in medical Magnetic Resonance Imaging.</span>
<span class="attribution"><a class="source" href="http://pubs.acs.org/doi/abs/10.1021/nl5048175">Jan Ainali</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>One interesting and potentially useful property of superconductors arises when they are placed near a strong magnet. The magnetic field causes electrical currents to spontaneously flow on the surface of a superconductor, which then give rise to their own, counteracting, magnetic field. The effect is that the superconductor dramatically levitates above the magnet, suspended in the air by an invisible magnetic force.</p>
<p>What prevents more widespread use of these materials is the fact that the superconductors we know about operate only at very low temperatures. In the simple elements for instance superconductivity dies out at just 10 Kelvin, or -263 °C. In more complicated compounds, such as yttrium barium copper oxide (YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub>), superconductivity may persist to higher temperatures, up to 100 Kelvin (-173 °C). While this is an improvement on the simple elements, it is still much colder than the coldest winter night in Antarctica. </p>
<p>Scientists dream of finding a material where superconductive properties can be used at room temperature, but it’s a challenging task. Turning up the temperature tends to destroy the glue that binds the electrons into superconducting pairs, which then returns a material back to its boring metallic state. One of the great challenges in the field arises from the fact that we don’t yet understand very much about this glue, except in a few limited cases.</p>
<h2>From superatom to superconductor</h2>
<p><a href="http://pubs.acs.org/doi/abs/10.1021/nl5048175">New research</a> from the University of Southern California has taken a novel step towards improving our understanding of how superconductivity arises. Rather than study superconductivity in bulk materials like wires, Vitaly Kresin and his coworkers have managed to isolate and examine small clumps of a few dozen aluminium atoms at a time. These tiny clusters of atoms can act like a “superatom”, sharing electrons in a way that mimics a single, giant atom. </p>
<p>What is surprising is that measurements of these clusters reveal what may be the signature of electron pairing persisting all the way up to 100 kelvin (-173 °C). This is still a frosty temperature of course, but it is 100 times higher than the superconducting temperature of a piece of aluminium wire. Why does a small handful of atoms superconduct at a much higher temperature than the millions of atoms that form a wire? Physicists have some ideas but the effect is largely unexplored, and it might prove an interesting way forward in the quest for superconductivity at higher temperatures. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/73512/original/image-20150302-15984-ryxdbw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The need for speed: MagLev trains in Japan use superconductivity to achieve ultra-high speeds.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?searchterm=maglev&pl=il-lb&cr=back&page=1&inline=182442122">Shutterstock</a></span>
</figcaption>
</figure>
<h2>Hoverboards anyone?</h2>
<p>If physicists were able to achieve the goal of room temperature superconductivity in a material that was easy to fashion into wires, important new technologies would soon follow. For starters, devices which use electricity would become considerably more efficient and consume less power. </p>
<p>Transporting electricity over long distances would also become much easier, which is particularly useful for renewable energy applications – and some have proposed giant superconducting cables linking Europe with solar energy farms in North Africa. </p>
<p>The fact that superconductors will levitate above a strong magnet also creates possibilities for efficient, ultra-high speed trains that float above a magnetic track, much like Marty McFly’s hoverboard in Back to the Future. Japanese engineers have experimented with replacing the wheels of a train with large superconductors that hold the carriages a few centimetres above the track. The idea works in principle, but suffers from the fact that the trains need to carry expensive tanks of liquid helium with them in order to keep the superconductors cold. </p>
<p>Many superconducting technologies will probably remain on the drawing board, or too expensive to implement, unless a room temperature superconductor is discovered. It’s just possible however that the advances made by Kresin’s group might mark a milestone on this journey.</p><img src="https://counter.theconversation.com/content/38122/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Sutherland receives funding from the EPSRC and the Royal Society.</span></em></p>Just what is a superconductor? And what can it be used for? Research using superconductors at higher temperatures opens up more possibilities for this fascinating class of materials.Michael Sutherland, Royal Society University Research Fellow, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/333132014-11-04T01:33:42Z2014-11-04T01:33:42ZHere’s a brainwave – magnetic pulses could treat autism<figure><img src="https://images.theconversation.com/files/63378/original/rkh7ggq2-1414733932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Repetitive transcranial magnetic stimulation can help alleviate symptoms of autism, such as anxiety.</span> <span class="attribution"><a class="source" href="http://www.flickr.com/photos/j-aguila-photo/1510653401">AGUILA_JONATHAN/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Around <a href="http://www.cdc.gov/media/releases/2014/p0327-autism-spectrum-disorder.html">1 in 68 children</a> has an autism spectrum disorder (ASD), according to the US Centres for Disease Control – an extraordinarily high number. Although the prevalence rise is probably due mainly to changes in how we diagnose and classify ASD – autism was once considered a rare condition affecting only one among thousands – it has become a huge public-health challenge.</p>
<p>One way to help ASD patients may be with brain-stimulating magnets, which have recently been shown to <a href="http://www.sciencemag.org/content/345/6200/1054">boost memory</a>.</p>
<p>Our <a href="http://dro.deakin.edu.au/view/DU:30059359">research</a> using repetitive transcranial magnetic stimulation (rTMS) – a new type of brain stimulation – can improve some of the abnormalities in brain activity in ASD, but also reduce some of the social difficulties (including social understanding and anxiety).</p>
<p>So how does rTMS work, and what is it about ASD that makes it an attractive candidate for such treatment?</p>
<h2>Autism treatments – the story so far</h2>
<p>ASD involves difficulties in social understanding and communication, along with a narrow and repetitive range of interests and behaviours. </p>
<p>A big part of the treatment challenge is that we do not have any validated biomedical treatments that improve the core symptoms of ASD. This is in stark contrast to most other conditions in psychiatry and neurology, such as depression, anxiety, psychosis and Attention Deficit Hyperactivity Disorder (ADHD).</p>
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<p>Where medications are used for ASD, they are usually for less common associated features, such as aggression.</p>
<p>Early intervention in ASD is very important. The best outcomes generally come from getting children into intensive behavioural intervention programs as early as possible. This of course depends on an early diagnosis of ASD, ideally by about two or three years of age. </p>
<p>But this often isn’t the case where an individual with ASD has excellent language skills or high intelligence. These kids tend to attract a clinical referral much later, and a diagnosis is often not made until well into primary school.</p>
<p>Early childhood interventions also don’t meet the needs of adults with ASD who continue to experience significant social difficulties, yet find themselves estranged from both youth-focused autism programs or adult-focused psychiatric programs. </p>
<h2>A new hope for treatments</h2>
<p>For those who would like to have a biomedical option for the treatment of ASD, there is hope on the horizon.</p>
<p>In recent years we’ve seen encouraging results from preliminary clinical trials in ASD involving, for example, hormonal treatments (oxytocin) and medications that have been developed for other purposes, such as bumetanide, which is traditionally used to treat high blood pressure.</p>
<p>A handful of research groups around the world, including ours, have been conducting clinical trials using a new technique known as rTMS.</p>
<p>rTMS involves delivering strong but precise magnetic pulses to a part of the brain to stimulate brain activity. This is done by holding a rTMS “coil” against a person’s head, seen below.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/63446/original/4m2dmkkr-1414963523.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">Deakin University</span></span>
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<p>The magnetic pulses travel through to the surface of the brain, where they induce electrical current. This electricity causes brain cells to become active, or “fire”. </p>
<p>Following two decades of research, we know now that rTMS can be used to either increase or decrease activity in specific brain regions. This is potentially very useful in the treatment of a number of brain-related conditions, where brain imaging has shown brain regions that are overactive or underactive.</p>
<p>rTMS has been developed as a safe and effective treatment for people who experience depression, but who haven’t benefited from psychological therapies and medication.</p>
<h2>Could rTMS work for ASD?</h2>
<p>Social difficulties are considered by many to be the hallmark of ASD. We know that the brain networks that allow us to understand and interact with other people are affected in ASD.</p>
<p>For example, a brain network that lets us interpret the intentions behind other people’s behaviour is less active in people with ASD. </p>
<p>In ASD, rTMS can then be used to increase activity or “excite” brain cells in this network, which can have lasting effects on brain chemical systems that control brain activity. This can be thought of as a step toward correcting a dysfunctional brain network. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/YXyipFUZTAQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">See how rTMS is used to treat autism.</span></figcaption>
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<p>Our work shows it’s possible to directly affect brain abnormalities in ASD and promote clinical improvements. It is, however, early days for this research, and far more needs to be done before we could consider it a “treatment” for ASD.</p>
<h2>The future of biomedical interventions in ASD</h2>
<p>When it comes to ASD, there will not be a “one size fits all” approach to treatment. Many children will continue to benefit from intensive early intervention programs.</p>
<p>But there is good reason to be cautiously optimistic about the development of biomedical treatment options in ASD, especially when considering the advances being made in genetics and neuroimaging. </p>
<p>The translation from lab to clinic is often a frustrating slow process. Now that we have a number of biomedical candidates for autism treatment, the priority is to evaluate these new treatment possibilities in a timely manner, and attempt to meet the growing needs and expectations of the ASD community. </p>
<p><strong><em>This article is based on a <a href="https://www.science.org.au/events/brain-stimulation-and-autism-spectrum-disorder">public lecture</a> at the Australian Academy of Science on November 5, 2014.</em></strong></p><img src="https://counter.theconversation.com/content/33313/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Enticott receives funding from the National Health and Medical Research Council, the Australian Research Council, and the Brain and Behaviour Research Foundation.</span></em></p>Around 1 in 68 children has an autism spectrum disorder (ASD), according to the US Centres for Disease Control – an extraordinarily high number. Although the prevalence rise is probably due mainly to changes…Peter Enticott, Associate Professor of Psychology (Cognitive Neuroscience) , Deakin UniversityLicensed as Creative Commons – attribution, no derivatives.