tag:theconversation.com,2011:/africa/topics/nuclear-physics-8971/articlesNuclear physics – The Conversation2023-07-20T20:04:01Ztag:theconversation.com,2011:article/2084752023-07-20T20:04:01Z2023-07-20T20:04:01ZCurious Kids: what does a nuclear bomb actually do?<figure><img src="https://images.theconversation.com/files/537993/original/file-20230718-17-19622i.jpeg?ixlib=rb-1.1.0&rect=107%2C161%2C11874%2C7814&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><blockquote>
<p>I would like to know what a nuclear bomb actually does – Rafael, age 11, Melbourne</p>
</blockquote>
<p>Hi Rafael! </p>
<p>A nuclear bomb, like any bomb, makes an explosion by releasing an enormous amount of energy at once. Nuclear bombs just use a different process from other bombs. </p>
<p>You may have heard of atoms. These are the super-tiny particles that make up matter – which in turn makes everything around us (and us). </p>
<p>Nuclear bombs work by changing the cores of atoms to turn them into other types of atoms. This process releases a lot of heat energy, which quickly gets converted into a big wave of pressure: an explosion! </p>
<h2>What are nuclei?</h2>
<p>Nuclear bombs release much more energy than normal bombs that use chemicals such as TNT. This is because the cores of atoms are held together very strongly. But before I get into that, let me explain some of the basics.</p>
<p>Atoms themselves are made up of even smaller particles called protons, neutrons and electrons. A cloud of electrons surrounds a tiny inner core made of protons and neutrons. This core is called the nucleus, and more than one nucleus are called nuclei.</p>
<figure class="align-center ">
<img alt="Diagram of an atom, showing electrons surrounding a core of protons and neutrons." src="https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534738/original/file-20230629-15-jbymfg.png?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">
<figcaption>
<span class="caption">An atom is made up of electrons surrounding a central core of protons and neutrons. The core is about one-hundred thousand times smaller than the atom.</span>
<span class="attribution"><span class="source">AG Caesar/Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>Chemical reactions happen when electrons are rearranged, whereas nuclear reactions happen when protons and neutrons inside the nucleus are rearranged. </p>
<p>There are two types of nuclear bombs. In the case of “fission” bombs, nuclei that have a lot of protons and neutrons – such as those in a very dense metal called uranium – are split apart.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537983/original/file-20230718-29-c9r54d.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"></a>
<figcaption>
<span class="caption">Uranium is a chemical element with the atomic number 92. It has 92 protons and electrons.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>In another type of nuclear bomb called a “fusion” bomb, two very small nuclei – such as the cores of two hydrogen atoms – are stuck together. </p>
<p>But fission bombs are simpler and more common, so let’s talk about those. </p>
<h2>Chain reactions</h2>
<p>Some nuclei don’t take very much energy at all to split apart, such as those in some types of uranium or plutonium atoms (plutonium is another dense metal which has 94 protons in its nuclei). </p>
<p>These nuclei will sometimes fission even when they’re just sitting around. When a nucleus fissions, it turns into two smaller nuclei and spits out a few neutrons. </p>
<p>However, one nucleus doing this isn’t a big deal. To make an explosion, you need to have a certain amount of uranium together in one spot.</p>
<p>For instance, a fission bomb would usually use a very purified sphere of uranium weighing about 52kg. Even this would have to use certain types of uranium in which the atoms have a specific number of neutrons. </p>
<p>If you have enough of these atoms together in one spot, the neutrons that are spit out during fission will hit other nuclei, which then also fission and spit out more neutrons – and so it continues in a chain reaction that sets off a massive explosion.</p>
<figure class="align-center ">
<img alt="Diagram of one atom fissioning, showing two smaller nuclei and three neutrons, which cause two more nuclei to fission producing neutrons in a chain reaction" src="https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=518&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=518&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=518&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=651&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=651&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534739/original/file-20230629-19-gpdggj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=651&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A nuclear chain reaction happens when one nucleus fissions, releasing neutrons which cause another nucleus to fission, and so on.</span>
<span class="attribution"><span class="source">Adapted from MikeRun/Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>An unexploded fission bomb will usually be holding separate pieces of uranium (or plutonium) that are too small to start the chain reaction on their own. A chemical explosive is used to smash the pieces together – triggering the chain reaction that sets the bomb off.</p>
<figure class="align-center ">
<img alt="Two different types of fission bombs -- one where two small pieces of uranium are pushed together by a chemical explosive, and another where plutonium is compressed by a chemical explosive." src="https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=655&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=655&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=655&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=823&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=823&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534740/original/file-20230629-25-6pa2c7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=823&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fission bombs work by taking pieces of uranium or plutonium that are too small to make a chain reaction on their own, and using a chemical explosive to push them together until a chain reaction starts.</span>
<span class="attribution"><span class="source">Adapted from Fastfission/Wikimedia Commons</span></span>
</figcaption>
</figure>
<h2>Fallout</h2>
<p>After fission happens, the two smaller nuclei that are left over are radioactive. Having enough of them in one spot can be very harmful to human health. </p>
<p>These leftovers after a nuclear explosion are called “fallout”. Besides the huge size of the explosion itself, the fallout in particular is what makes nuclear bombs more dangerous than other bombs. The technology used to make nuclear weapons is some of the most secret information in the world.</p>
<p>Nuclear bombs have only ever been used twice. Both of these bombs were detonated during World War II, by the United States against Japan. People around the world are working hard to make sure they are never used again.</p><img src="https://counter.theconversation.com/content/208475/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kaitlin Cook receives funding from the Australian Research Council. </span></em></p>A nuclear bomb is a bomb that makes explosions by changing the nucleus of an atom in a way that releases a lot of energy.Kaitlin Cook, DECRA Fellow, Department of Nuclear Physics and Accelerator Applications, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1964752022-12-14T01:03:03Z2022-12-14T01:03:03ZWhy fusion ignition is being hailed as a major breakthrough in fusion – a nuclear physicist explains<figure><img src="https://images.theconversation.com/files/500838/original/file-20221213-20406-ts9sxm.jpg?ixlib=rb-1.1.0&rect=106%2C121%2C3260%2C2549&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The target chamber at the National Ignition Facility has been the site of a number of breakthroughs in fusion physics.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/departmentofenergy/17974887118/">U.S. Department of Energy/Lawrence Livermore National Laboratory</a></span></figcaption></figure><p><em>American scientists have announced what they have called a major breakthrough in a long-elusive goal of creating energy from nuclear fusion.</em></p>
<p><em>The U.S. Department of Energy said on Dec. 13, 2022, that for the first time – and after several decades of trying – scientists have managed to get more energy out of the process than they had to put in.</em></p>
<p><em>But just how significant is the development? And how far off is the long-sought dream of fusion providing abundant, clean energy? <a href="https://scholar.google.com/citations?user=impfKfgAAAAJ&hl=en&oi=ao">Carolyn Kuranz</a>, an associate professor of nuclear engineering at the University of Michigan who has worked at the facility that just broke the fusion record, helps explain this new result.</em></p>
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<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/us/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<figure class="align-right ">
<img alt="An image of the Sun." src="https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500839/original/file-20221213-22736-wtuffc.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">
<figcaption>
<span class="caption">Fusion is the same process that powers the Sun.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Solar_prominence_from_STEREO_spacecraft_September_29,_2008.jpg#/media/File:Solar_prominence_from_STEREO_spacecraft_September_29,_2008.jpg">NASA/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>What happened in the fusion chamber?</h2>
<p>Fusion is a nuclear reaction that combines two atoms to create one or more new atoms with slightly less total mass. The difference in mass is released as energy, as described by Einstein’s famous equation, E = mc<sup>2</sup> , where energy equals mass times the speed of light squared. Since the speed of light is enormous, converting just a tiny amount of mass into energy – like what happens in fusion – produces a similarly enormous amount of energy. </p>
<p>Researchers at the U.S. Government’s <a href="https://lasers.llnl.gov/">National Ignition Facility</a> in California have demonstrated, for the first time, what is known as “fusion ignition.” Ignition is when a fusion reaction produces more energy than is being put into the reaction from an outside source and becomes self-sustaining.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gold and plastic canister." src="https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=639&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=639&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=639&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=803&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=803&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500841/original/file-20221213-24014-83uis7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=803&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 fuel is held in a tiny canister designed to keep the reaction as free from contaminants as possible.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/departmentofenergy/9571677088/">U.S. Department of Energy/Lawrence Livermore National Laboratory</a></span>
</figcaption>
</figure>
<p>The technique used at the National Ignition Facility involved shooting 192 lasers at a <a href="https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition">0.04 inch (1 mm) pellet of fuel</a> made of deuterium and tritium – two versions of the element hydrogen with extra neutrons – placed in a gold canister. When the lasers hit the canister, they produce X-rays that heat and compress the fuel pellet to about 20 times the density of lead and to more than 5 million degrees Fahrenheit (3 million Celsius) – about 100 times hotter than the surface of the Sun. If you can maintain these conditions for a long enough time, the <a href="https://doi.org/10.1038/s41567-021-01485-9">fuel will fuse and release energy</a>.</p>
<p>The fuel and canister get vaporized within a few billionths of a second during the experiment. Researchers then hope their equipment survived the heat and accurately measured the energy released by the fusion reaction.</p>
<h2>So what did they accomplish?</h2>
<p>To assess the success of a fusion experiment, physicists look at the ratio between the energy released from the process of fusion and the amount of energy within the lasers. This ratio is <a href="https://nap.nationalacademies.org/catalog/5730/review-of-the-department-of-energys-inertial-confinement-fusion-program">called gain</a>.</p>
<p>Anything above a gain of 1 means that the fusion process released more energy than the lasers delivered.</p>
<p>On Dec. 5, 2022, the National Ignition Facility shot a pellet of fuel with 2 million joules of laser energy – about the amount of power it takes to run a hair dryer for 15 minutes – all contained within a few billionths of a second. This triggered a fusion reaction that <a href="https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition">released 3 million joules</a>. That is a gain of about 1.5, smashing the previous record of a gain of <a href="https://www.science.org/content/article/explosive-new-result-laser-powered-fusion-effort-nears-ignition">0.7 achieved by the facility in August 2021</a>.</p>
<h2>How big a deal is this result?</h2>
<p>Fusion energy has been the “holy grail” of energy production for <a href="https://www.nature.com/articles/239139a0">nearly half a century</a>. While a gain of 1.5 is, I believe, a truly historic scientific breakthrough, there is still a long way to go before fusion is a viable energy source. </p>
<p>While the laser energy of 2 million joules was less than the fusion yield of 3 million joules, it took the facility nearly <a href="https://www.wired.com/story/the-real-fusion-energy-breakthrough-is-still-decades-away/">300 million joules to produce the lasers</a> used in this experiment. This result has shown that fusion ignition is possible, but it will take a lot of work to improve the efficiency to the point where fusion can provide a net positive energy return when taking into consideration the entire end-to-end system, not just a single interaction between the lasers and the fuel. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hallway full of pipes, tubes and electronics." src="https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500845/original/file-20221213-22773-ts9sxm.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">Machinery used to create the powerful lasers, like these pre-amplifiers, currently requires a lot more energy than the lasers themselves produce.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Preamplifier_at_the_National_Ignition_Facility.jpg#/media/File:Preamplifier_at_the_National_Ignition_Facility.jpg">Lawrence Livermore National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>What needs to be improved?</h2>
<p>There are a number of pieces of the fusion puzzle that scientists have been steadily improving for decades to produce this result, and further work can make this process more efficient. </p>
<p>First, lasers were only <a href="https://press.uchicago.edu/Misc/Chicago/284158_townes.html">invented in 1960</a>. When the U.S. government <a href="https://lasers.llnl.gov/about/nif-construction">completed construction of the National Ignition Facility in 2009</a>, it was the most powerful laser facility in the world, able to deliver <a href="https://www.llnl.gov/news/national-ignition-facility-achieves-unprecedented-1-megajoule-laser-shot">1 million joules of energy to a target</a>. The 2 million joules it produces today is 50 times more energetic than the <a href="https://www.lle.rochester.edu/index.php/omega-laser-facility-2/">next most powerful laser on Earth</a>. More powerful lasers and less energy-intensive ways to produce those powerful lasers could greatly improve the overall efficiency of the system.</p>
<p>Fusion conditions are <a href="https://doi.org/10.1063/1.4865400">very challenging to sustain</a>, and any <a href="https://doi.org/10.1088/1361-6587/ab49f4">small imperfection in the capsule or fuel</a> can increase the energy requirement and decrease efficiency. Scientists have made a lot of progress to <a href="https://www.nature.com/articles/s41586-021-04281-w">more efficiently transfer energy from the laser to the canister</a> and the <a href="https://doi.org/10.1088/1741-4326/ac108d">X-ray radiation from the canister to the fuel capsule</a>, but currently only about <a href="https://doi.org/10.1088/1741-4326/ac108d">10% to 30%</a> of the total laser energy is transferred to the canister and to the fuel.</p>
<p>Finally, while one part of the fuel, deuterium, is naturally <a href="https://doi.org/10.1016/j.fusengdes.2010.11.040">abundant in sea water, tritium is much rarer</a>. Fusion itself actually produces <a href="https://irp.fas.org/agency/dod/jason/tritium.pdf">tritium</a>, so researchers are hoping to develop ways of harvesting this tritium directly. In the meantime, there are <a href="https://www.energy.gov/nnsa/articles/nnsa-achieves-record-number-tritium-extraction-operations">other methods available to produce the needed fuel</a>.</p>
<p>These and other scientific, technological and engineering hurdles will need to be overcome before fusion will produce electricity for your home. Work will also need to be done to bring the cost of a fusion power plant well down from the <a href="https://lasers.llnl.gov/about/faqs#nif_cost">US$3.5 billion of the National Ignition Facility</a>. These steps will require significant investment from both the federal government and private industry. </p>
<p>It’s worth noting that there is a global race around fusion, with many other labs around the world <a href="https://theconversation.com/nuclear-fusion-hit-a-milestone-thanks-to-better-reactor-walls-this-engineering-advance-is-building-toward-reactors-of-the-future-178870">pursuing different techniques</a>. But with the new result from the National Ignition Facility, the world has, for the first time, seen evidence that the <a href="https://nap.nationalacademies.org/catalog/25991/bringing-fusion-to-the-us-grid">dream of fusion is achievable</a>.</p><img src="https://counter.theconversation.com/content/196475/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carolyn Kuranz receives funding from the National Nuclear Security Administration and Lawrence Livermore National Laboratory. She serves on a review board for Lawrence Livermore National Laboratory. She is a member of the Fusion Energy Science Advisory Committee. </span></em></p>The promise of abundant, clean energy powered by nuclear fusion is one big step closer thanks to a new experiment. The results are a historic scientific milestone, but energy production remains a ways off.Carolyn Kuranz, Associate Professor of Nuclear Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1857542022-11-14T22:12:12Z2022-11-14T22:12:12ZPowerful linear accelerator begins smashing atoms – 2 scientists on the team explain how it could reveal rare forms of matter<figure><img src="https://images.theconversation.com/files/484140/original/file-20220912-16-rp5qhi.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3000%2C1199&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A new particle accelerator at Michigan State University is set to discover thousands of never-before-seen isotopes. </span> <span class="attribution"><span class="source">Facility for Rare Isotope Beams</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Just a few hundred feet from where we are sitting is a large metal chamber devoid of air and draped with the wires needed to control the instruments inside. A beam of particles passes through the interior of the chamber silently at around half the speed of light until it smashes into a solid piece of material, resulting in a burst of rare isotopes.</p>
<p>This is all taking place in the <a href="https://frib.msu.edu/">Facility for Rare Isotope Beams</a>, or FRIB, which is operated by Michigan State University for the U.S. Department of Energy Office of Science. Starting in May 2022, national and international teams of scientists converged at Michigan State University and began running scientific experiments at FRIB with the goal of creating, isolating and studying new isotopes. The experiments promised to provide new insights into the fundamental nature of the universe.</p>
<p>We are two professors in <a href="https://www.chemistry.msu.edu/faculty-research/faculty-members/liddick-sean.aspx">nuclear chemistry</a> and <a href="https://scholar.google.com/citations?user=vlmJRrsAAAAJ&hl=en&oi=sra">nuclear physics</a> who study rare isotopes. Isotopes are, in a sense, different flavors of an element with the same number of protons in their nucleus but different numbers of neutrons. </p>
<p>The accelerator at FRIB started working at low power, but when it finishes ramping up to full strength, it will be the most powerful heavy-ion accelerator on Earth. By accelerating heavy ions – electrically charged atoms of elements – FRIB will allow scientists like us to create and study thousands of never-before-seen isotopes. A community of roughly <a href="https://fribusers.org/">1,600 nuclear scientists from all over the world</a> has been waiting for a decade to begin doing science enabled by the new particle accelerator.</p>
<p>The <a href="https://newscenter.lbl.gov/2022/11/14/frib-experiment-pushes-elements-to-the-limit/">first experiments at FRIB</a> were completed over the summer of 2022. Even though the facility is currently running at only a fraction of its full power, multiple scientific collaborations working at FRIB have already produced and <a href="https://doi.org/10.1103/PhysRevLett.129.212501">detected about 100 rare isotopes</a>. These early results are helping researchers learn about some of the rarest physics in the universe.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/yGHuZnfnUtI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Rare isotopes are radioactive and decay over time as they emit radiation – visible here as the streaks coming from the small piece of uranium in the center.</span></figcaption>
</figure>
<h2>What is a rare isotope?</h2>
<p>It takes incredibly high amounts of energy to produce most isotopes. In nature, heavy rare isotopes are produced during the cataclysmic deaths of massive stars called <a href="https://physicstoday.scitation.org/doi/10.1063/1.1825268">supernovas</a> or during the <a href="https://doi.org/10.1038/s41586-019-1676-3">merging of two neutron stars</a>.</p>
<p>To the naked eye, two isotopes of any element look and behave the same way – all isotopes of the element mercury would look just like the liquid metal used in old thermometers. However, because the nuclei of isotopes of the same element have different numbers of neutrons, they differ in how long they live, what type of radioactivity they emit and in many other ways.</p>
<p>For example, some isotopes are stable and do not decay or emit radiation, so they are common in the universe. Other isotopes of the very same element can be radioactive so they inevitably decay away as they turn into other elements. Since radioactive isotopes disappear over time, they are relatively rarer. </p>
<p>Not all decay happens at the same rate though. Some radioactive elements – like potassium-40 – emit particles through decay at such a low rate that a small amount of the isotope can <a href="https://www.nndc.bnl.gov/nudat3/">last for billions of years</a>. Other, more highly radioactive isotopes like magnesium-38 exist for only a fraction of a second before decaying away into other elements. Short-lived isotopes, by definition, do not survive long and are rare in the universe. So if you want to study them, you have to make them yourself.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram of a large facility." src="https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=582&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=582&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480464/original/file-20220822-77906-xtxwle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=582&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 Facility for Rare Isotope Beams was designed to allow researchers to create rare isotopes and measure them before they decay.</span>
<span class="attribution"><a class="source" href="https://frib.zenfolio.com/p798584095">Facility for Rare Isotope Beams</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Creating isotopes in a lab</h2>
<p>While only about <a href="https://doi.org/10.1038/nature11188">250 isotopes naturally occur on Earth</a>, theoretical models predict that about <a href="https://doi.org/10.1038/nature11188">7,000 isotopes should exist in nature</a>. Scientists have used particle accelerators to produce around <a href="http://www.nndc.bnl.gov/ensdf/">3,000 of these rare isotopes</a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hallway with dozens of large chambers on either side extending into the distance." src="https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=507&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=507&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480463/original/file-20220822-76734-8linop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=507&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 green-colored chambers use electromagnetic waves to accelerate charged ions to nearly half the speed of light.</span>
<span class="attribution"><a class="source" href="https://frib.zenfolio.com/p798584095">Facility for Rare Isotope Beams</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The FRIB accelerator is 1,600 feet long and made of three segments folded in roughly the shape of a paperclip. Within these segments are numerous, extremely cold vacuum chambers that alternatively pull and push the ions using powerful electromagnetic pulses. FRIB can accelerate any naturally occurring isotope – whether it is as light as oxygen or as heavy as uranium – to approximately <a href="https://frib.msu.edu/science/nuclearphysics/index.html">half the speed of light</a>.</p>
<p>To create radioactive isotopes, you only need to smash this beam of ions into a solid target like a piece of beryllium metal or a rotating disk of carbon.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A complicated machine in a large tube." src="https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480466/original/file-20220822-38135-yurmqa.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">There are many different instruments designed to measure specific attributes of the particles created during experiments at FRIB – like this instrument called FDSi, which is built to measure charged particles, neutrons and photons.</span>
<span class="attribution"><span class="source">Facility for Rare Isotope Beams</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The impact of the ion beam on the fragmentation target <a href="https://doi.org/10.1098/rsta.1998.0260">breaks the nucleus of the stable isotope apart</a> and produces many hundreds of rare isotopes simultaneously. To isolate the interesting or new isotopes from the rest, a separator sits between the target and the sensors. Particles with the right momentum and electrical charge will be passed through the separator while the rest are absorbed. Only a <a href="https://frib.msu.edu/users/instruments/operation.html">subset of the desired isotopes will reach the many instruments</a> built to observe the nature of the particles. </p>
<p>The probability of creating any specific isotope during a single collision can be very small. The odds of creating some of the rarer exotic isotopes can be on the order of <a href="https://doi.org/10.1088/0031-8949/91/5/053003">1 in a quadrillion</a> – roughly the same odds as winning back-to-back Mega Millions jackpots. But the powerful beams of ions used by FRIB contain so many ions and produce so many collisions in a single experiment that the team can reasonably expect to <a href="https://groups.nscl.msu.edu/frib/rates/fribrates.html">find even the rarest of isotopes</a>. According to calculations, FRIB’s accelerator should be able to <a href="https://msu.edu/discoverfrib">produce approximately 80% of all theorized isotopes</a>.</p>
<h2>The first two FRIB scientific experiments</h2>
<p>A multi-institution team led by researchers at Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory (ORNL), University of Tennessee, Knoxville (UTK), Mississippi State University and Florida State University, together with researchers at MSU, began running the first experiment at FRIB on May 9, 2022. The group directed a beam of calcium-48 – a calcium nucleus with 28 neutrons instead of the usual 20 – into a beryllium target at 1 kW of power. Even at one quarter of a percent of the facility’s 400-kW maximum power, approximately 40 different isotopes passed through the separator to the <a href="https://fds.ornl.gov/initiator/">instruments</a>.</p>
<p>The FDSi device recorded the time each ion arrived, what isotope it was and when it decayed away. Using this information, the collaboration deduced the half-lives of the isotopes; the team has already <a href="https://doi.org/10.1103/PhysRevLett.129.212501">reported on five previously unknown half-lives</a>.</p>
<p>The second FRIB experiment began on June 15, 2022, led by a collaboration of researchers from Lawrence Livermore National Laboratory, ORNL, UTK and MSU. The facility accelerated a beam of selenium-82 and used it to produce rare isotopes of the elements scandium, calcium and potassium. These isotopes are commonly found in neutron stars, and the goal of the experiment was to better understand what type of radioactivity these isotopes emit as they decay. Understanding this process could shed light on <a href="https://doi.org/10.1038/nature12757">how neutron stars lose energy</a>.</p>
<p>The first two FRIB experiments were just the tip of the iceberg of this new facility’s capabilities. Over the coming years, FRIB is set to explore four big questions in nuclear physics: First, what are the properties of atomic nuclei with a large difference between the numbers of protons and neutrons? Second, how are elements formed in the cosmos? Third, do physicists understand the fundamental symmetries of the universe, like why there is more matter than antimatter in the universe? Finally, how can the information from rare isotopes be applied in medicine, industry and national security? </p>
<p><em>This story was updated to correctly represent the number of neutrons in the nucleus of calcium-48.</em></p><img src="https://counter.theconversation.com/content/185754/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sean Liddick receives funding from the Department of Energy . </span></em></p><p class="fine-print"><em><span>Artemis Spyrou receives funding from the National Science Foundation in the U.S.</span></em></p>A new particle accelerator has just begun operation. It is the most powerful accelerator of its kind on Earth and will allow physicists to study some of the rarest matter in the universe.Sean Liddick, Associate Professor of Chemistry, Michigan State UniversityArtemis Spyrou, Professor of Nuclear Physics, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1858282022-07-18T12:27:00Z2022-07-18T12:27:00ZWhen did the first fish live on Earth – and how do scientists figure out the timing?<figure><img src="https://images.theconversation.com/files/471719/original/file-20220629-26-9ob4iv.png?ixlib=rb-1.1.0&rect=0%2C0%2C1280%2C1021&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reconstruction of _Haikouichthys ercaicunensis_ based on fossil evidence.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Haikouichthys_3d.png">Talifero/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How do you figure out how long ago fish were created? Hundreds of millions of years is a long time ago. – Josh, age 11, Ephrata, Pennsylvania</strong></p>
</blockquote>
<hr>
<p>The <a href="https://doi.org/10.1038/46965">oldest fossils of animals resembling a fish</a> date back between 518 million and 530 million years ago. Discovered in China and called <em>Haikouichthys</em>, these animals were about an inch long (2.5 cm) and had a <a href="https://doi.org/10.1038/nature01264">head with seven to eight slits at its base that looked like gills</a>. They also had a <a href="https://doi.org/10.1038/nature01264">distinct spine surrounded by muscles</a>. </p>
<p>But there are ways <em>Haikouichthys</em> did not resemble any modern fish. For example, <a href="https://www.science.org/content/article/fossils-give-glimpse-old-mother-lamprey">they didn’t have a jaw</a>. Instead, their mouth was a cone-like opening similar to the ones seen in <a href="https://nhpbs.org/wild/Agnatha.asp">modern hagfish and lampreys</a>. They also <a href="https://doi.org/10.1038/nature01264">appear not to have had side fins</a>.</p>
<p>Even though <a href="https://scholar.google.com/citations?hl=en&user=w4GYLBMAAAAJ">scientists like me</a> weren’t around to see for ourselves what was happening on Earth so long ago, we use geologic clues to figure out what animals lived when. Here’s how we sort out very ancient timelines and even put dates on fossils like <em>Haikouichthys</em>.</p>
<h2>Measuring in the millions</h2>
<p>To figure out how long ago fish first appeared on Earth you need a way to measure really, really long time intervals. Clocks measure short intervals, like seconds, minutes and hours. Calendars measure longer intervals, like days, months and years. What can you use to measure millions of years?</p>
<p><a href="https://cosmosmagazine.com/earth/earth-sciences/what-is-radiometric-dating/">Radiometric dating</a> is the method that scientists use to calculate the passage of time in millions of years. To determine the age of rocks and fossils, scientists measure the type of atoms they are made of. </p>
<p>You might know that atoms are the building blocks of <a href="https://theconversation.com/what-do-molecules-look-like-184892">molecules, which make up everything around you</a> – grass, cement, even air. While most atoms are very stable, <a href="https://kids.britannica.com/kids/article/radioactivity/399579">some, called radioactive atoms, are unstable</a>. Over long periods of time, they spontaneously break down into more stable atoms. </p>
<p>Uranium is one of these radioactive atoms. <a href="https://kids.kiddle.co/Uranium">It breaks down very slowly into lead</a>. Both uranium and lead atoms can be found <a href="https://kids.kiddle.co/Pitchblende">naturally in rocks and minerals</a> in very, very low amounts. </p>
<p>Nuclear physicists have calculated that it would take <a href="https://www.livescience.com/39773-facts-about-uranium.html">700 million years for one pound of uranium</a> to break down into half a pound of lead. This rate of decay occurs at such a predictable rate that scientists can use it to calculate fairly accurately how old rocks and fossils are.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and white photo of man in old style dress sitting in front of an elaborate contraption." src="https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471720/original/file-20220629-22-xaw89m.jpg?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">Ernest Rutherford at McGill University, 1905.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ernest_Rutherford_1905.jpg">Unknown, published in 1939 in 'Rutherford: being the life and letters of the Rt. Hon. Lord Rutherford'/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The idea for radiometric dating first occurred to <a href="https://library.si.edu/digital-library/book/radioactivit00ruth">a New Zealand scientist named Ernest Rutherford</a> in 1904. His idea was to measure the number of uranium atoms and lead atoms in a rock and compare them. He predicted that an older rock would have more lead and less uranium than a younger rock would.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph illustrating how proportion of unstable atoms in a substance decreases while the proportion of stable atoms increases over time." src="https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471722/original/file-20220629-22-7oc2sa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Unstable atoms turn into stable atoms over time at a steady and predictable pace.</span>
<span class="attribution"><a class="source" href="https://oceanexplorer.noaa.gov/edu/learning/player/lesson15/l15_la1.html">NOAA</a></span>
</figcaption>
</figure>
<p>The <a href="https://www.pbs.org/wgbh/aso/databank/entries/do07ra.html">American scientist Bertram Boltwood</a> put Rutherford’s idea to the test, <a href="https://www.lindahall.org/about/news/scientist-of-the-day/bertram-boltwood">measuring the amount of uranium and lead in different rocks</a> collected from all over the world. </p>
<p>Once a rock is formed, no new elements are added to it. So scientists can calculate how much uranium the rock started with by adding what’s left to the amount of lead that’s there now, thanks to the radioactive decay process. Then, because they know exactly how long it takes for uranium to break down into lead, they can figure out the age of the rock. Boltwood proved that Rutherford’s idea worked, establishing the field of radiometric dating in 1907.</p>
<h2>The making of the <em>Haikouichthys</em> fossil</h2>
<p><a href="https://education.nationalgeographic.org/resource/fossil">Fossils are rocks</a>. So scientists can use radiometric dating to estimate how long ago the organisms that left the fossil imprint lived on Earth. </p>
<p>Animals leave fossil imprints only under special circumstances. In order for the <em>Haikouichthys</em> to leave fossils, their dead bodies would have had to sink to the bottom of the water and be covered with sediments before microorganisms could decompose them. Then, minerals in the sediments would have seeped into the <em>Haikouichthys</em> for their remains to become fossilized. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close-up photograph of a Haikouichthys fossil with 'eye' and 'V shaped myomere' labeled." src="https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=273&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=273&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=273&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=343&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=343&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472572/original/file-20220705-4393-thhnx8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=343&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 nearly complete specimen of <em>Haikouichthys</em> with the eye and zigzag-shaped muscle fibers called myomeres visible. This is one of many <em>Haikouichthys</em> fossils discovered in China.</span>
<span class="attribution"><span class="source">Dr. and Prof. Degan Shu, Shannxi Key Laborotory of Early Life and Envionment Department of Geology, Northwest University</span></span>
</figcaption>
</figure>
<p>Radiometric dating of <em>Haikouichthys</em> fossils suggests these animals were <a href="https://doi.org/10.1038/46965">swimming in Earth’s waters between 518 million and 530 million years ago</a> – and possibly longer. </p>
<h2>Earth’s age as a 24-hour day</h2>
<p>Scientists, using radiometric dating, <a href="https://education.nationalgeographic.org/resource/how-did-scientists-calculate-age-earth">estimate the Earth itself is 4.5 billion years old</a>. For a long time on Earth, there was no life at all. Then microorganisms like bacteria showed up. It’s only relatively recently that plants and animals began living on Earth.</p>
<p>In fact, if you think of Earth’s age until now as a 24-hour day, it turns out <em>Haikouichthys</em> lived 2 hours and 45 minutes before the end of the day. <a href="https://australian.museum/learn/science/human-evolution/hominid-and-hominin-whats-the-difference/">Humanlike animals</a> appeared even more recently on Earth – about <a href="https://www.smithsonianmag.com/science-nature/the-human-familys-earliest-ancestors-7372974/">5 million to 7 million years ago </a> – only a few minutes before the end of the hypothetical day. </p>
<p>Whether the <em>Haikouichthys</em> was the first fish or not remains controversial. There are very few other fishlike fossils from the same time period. But paleontologists keep digging. Who knows, maybe in a few years they will discover an even older fishlike animal that will dethrone <em>Haikouichthys</em> as the oldest fishlike creature.</p>
<hr>
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<p class="fine-print"><em><span>Isaac Skromne receives funding from National Science Foundation and National Institute of Health. </span></em></p>A biologist explains how researchers nail down the age of ancient fossils thanks to a physical process called radioactive decay.Isaac Skromne, Assistant Professor of Biology, University of RichmondLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1802312022-05-24T12:27:14Z2022-05-24T12:27:14ZNuclear isomers were discovered 100 years ago, and physicists are still unraveling their mysteries<figure><img src="https://images.theconversation.com/files/464572/original/file-20220520-20-x6afa8.jpg?ixlib=rb-1.1.0&rect=0%2C112%2C7367%2C5395&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Protons and neutrons in an atom's nucleus can be arranged in different configurations, creating nuclear isomers. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/atomic-structure-illustration-royalty-free-image/1339206072?adppopup=true">KTSdesign/SciencePhotoLibrary via Getty Images</a></span></figcaption></figure><p>Nobel laureate Otto Hahn is <a href="https://www.nobelprize.org/prizes/chemistry/1944/hahn/facts/">credited with the discovery of nuclear fission</a>. Fission is one of the most important discoveries of the 20th century, yet Hahn considered something else to be his <a href="https://doi.org/10.1007/978-1-4613-0101-1">best scientific work</a>.</p>
<p>In 1921, he was studying radioactivity at the Kaiser Wilhelm Institute for Chemistry in Berlin, Germany, when he noticed something he could not explain. One of the elements he was working with wasn’t behaving as it <a href="https://doi.org/10.1007/BF01491321">should have</a>. Hahn had unknowingly discovered the first nuclear isomer, an atomic nucleus whose protons and neutrons are arranged differently from the common form of the element, causing it to have unusual properties. It took another 15 years of discoveries in nuclear physics to be able to explain Hahn’s observations. </p>
<p><a href="https://scholar.google.com/citations?user=vlmJRrsAAAAJ&hl=en&oi=ao">We are</a> two <a href="https://www.physics.uoguelph.ca/people/dennis-mucher">professors of</a> nuclear physics who study rare nuclei including nuclear isomers.</p>
<p>The most common place to find isomers is inside stars, where they play a role in the <a href="https://theconversation.com/elements-from-the-stars-the-unexpected-discovery-that-upended-astrophysics-66-years-ago-93916">nuclear reactions that create new elements</a>. In recent years, researchers have begun to explore how isomers can be put to use for the benefit of humanity. They are already <a href="https://www.bnl.gov/newsroom/news.php?a=24796">used in medicine</a> and could one day offer powerful options for energy storage <a href="https://physicsworld.com/a/celebrating-a-century-of-nuclear-isomers">in the form of nuclear batteries</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/yGHuZnfnUtI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows radioactive uranium-238 in a chamber full of mist. The streaks are created as particles are emitted from the radioactive sample and pass through water vapor.</span></figcaption>
</figure>
<h2>On the hunt for radioactive isotopes</h2>
<p>In the early 1900s, scientists were on the hunt for new radioactive elements. An element is considered radioactive if it spontaneously releases particles in a process called <a href="https://www.youtube.com/watch?v=IDkNlU7zKYU">radioactive decay</a>. When this happens, the element is transformed over time into a different element.</p>
<p>At that time, scientists relied on three criteria to discover and describe a new radioactive element. One was to look at chemical properties – how the new element reacts with other substances. They also measured the type and energy of the particles released during the radioactive decay. Finally, they would measure how fast an element decayed. Decay speeds are described using the term half-life, which is the amount of time it takes for half of the initial radioactive element to decay into something else.</p>
<p>By the 1920s, physicists had discovered some radioactive substances with identical chemical properties but different half-lives. These are called isotopes. Isotopes are different versions of the same element that have the same number of protons in their nucleus, but different numbers of neutrons.</p>
<p>Uranium is a radioactive element with many isotopes, two of which occur naturally on Earth. These natural uranium isotopes decay into the element thorium, which in turn decays into protactinium, and each has its own isotopes. Hahn and his colleague <a href="https://theconversation.com/lise-meitner-the-forgotten-woman-of-nuclear-physics-who-deserved-a-nobel-prize-106220">Lise Meitner</a> were the first to discover and identify many different isotopes originating from the decay of the element uranium.</p>
<p>All the isotopes they studied behaved as expected, except for one. This isotope appeared to have the same properties as one of the others, but its half-life was longer. This made no sense, as Hahn and Meitner had placed all the known isotopes of uranium in a neat classification, and there were no empty spaces to accommodate a new isotope. They called this substance “uranium Z.” </p>
<p>The radioactive signal of uranium Z was about <a href="https://doi.org/10.1007/BF01491321">500 times weaker</a> than the radioactivity of the other isotopes in the sample, so Hahn decided to confirm his observations by using more material. He purchased and chemically separated uranium from 220 pounds (100 kilograms) of highly toxic and rare uranium salt. The surprising result of this second, more precise experiment suggested that the mysterious uranium Z, now known as protactinium-234, was an already known isotope, but with a very different half-life. This was the first case of an isotope with two different half-lives. Hahn published his discovery of the <a href="https://doi.org/10.1007/BF01491321">first nuclear isomer</a>, even though he could not fully explain it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the labeled parts of an atom." src="https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/464579/original/file-20220520-24-4pnisz.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">The discovery that the nucleus of an atom is made of both protons and neutrons allowed physicists to explain isotopes as well as uranium Z.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/bohr-atomic-model-of-a-nitrogen-atom-vector-royalty-free-illustration/1300855627?adppopup=true">PANGGABEAN/iStock via Getty Images</a></span>
</figcaption>
</figure>
<h2>Neutrons complete the story</h2>
<p>At the time of Hahn’s experiments in the 1920s, scientists still thought of atoms as a clump of protons surrounded by an equal number of electrons. It wasn’t until 1932 that James Chadwick suggested a third particle – neutrons – were also <a href="https://doi.org/10.1098/rspa.1932.0112">part of the nucleus</a>.</p>
<p>With this new information, physicists were immediately able to explain isotopes – they are nuclei with the same number of protons and different numbers of neutrons. With this knowledge, the scientific community finally had the tools to understand uranium Z. </p>
<p>In 1936 <a href="https://doi.org/10.1007/BF01497732">Carl Friedrich von Weizsäcker proposed</a> that two different substances could have the same number of protons and neutrons in their nuclei but in different arrangements and with different half-lives. The arrangement of protons and neutrons that results in the lowest energy is the most stable material and is called ground state. Arrangements resulting in less stable, higher energies of an isotope are called isomeric states.</p>
<p>At first nuclear isomers were useful in the scientific community only as a means to understand how nuclei behave. But once you understand the properties of an isomer, it’s possible to start asking how they can be used.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person getting an injection of a fluid." src="https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/464581/original/file-20220520-19-ubuap7.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>
<figcaption>
<span class="caption">Technetium-99m is an isomer that is commonly used for diagnosing many diseases, as doctors can easily track its movement through the human body. This photo shows a medical professional injecting technetium-99m into a patient.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Technetium-99m#/media/File:Tc99minjektion.jpg">Bionerd/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Isomers in medicine and astronomy</h2>
<p>Isomers have important applications in medicine and are used in tens of millions of diagnostic procedures annually. Since isomers undergo radioactive decay, special cameras can track them as they move through the body.</p>
<p>For example, technetium-99m is an isomer of technetium-99. As the isomer decays, it emits photons. Using photon detectors, doctors can track how technetium-99m <a href="https://doi.org/10.2967/jnumed.116.187807">moves throughout the body</a> and <a href="https://www.ncbi.nlm.nih.gov/books/NBK559013/">create images</a> of the heart, brain, lungs and other critical organs to help diagnose diseases including cancer. Radioactive elements and isotopes are normally dangerous because they emit charged particles that damage bodily tissues. Isomers like technetium are <a href="https://doi.org/10.4103/0971-6203.94740">safe for medical use</a> because they emit only a single, harmless photon at a time and nothing else as they decay.</p>
<p>Isomers are also important in astronomy and astrophysics. Stars are fueled by the energy released during nuclear reactions. Since isomers are <a href="https://iopscience.iop.org/article/10.3847/1538-4365/abc41d/pdf">present in stars</a>, nuclear reactions are different than if a material were in its ground state. This makes the study of isomers critical for understanding how stars produce all the elements in the universe.</p>
<h2>Isomers in the future</h2>
<p>A century after Hahn first discovered isomers, scientists are still <a href="https://doi.org/10.1038/d41586-022-00711-5">discovering new isomers using powerful research facilities</a> around the world, including the the <a href="https://frib.msu.edu/">Facility for Rare Isotope Beams</a> at Michigan State University. This facility came online in May 2022, and we hope it will unlock more than 1,000 new isotopes and isomers.</p>
<p>Scientists are also investigating whether nuclear isomers could be used to <a href="https://doi.org/10.1038/d41586-019-02664-8">build the world’s most accurate clock</a> or whether isomers may one day be the basis for the next generation of <a href="https://www.semanticscholar.org/paper/Controlled-Extraction-of-Energy-from-Nuclear-Litz-Merkel/7f0f5cb36908e0a890a21d33916f940735bd4152">batteries</a>. More than 100 years after the detection of a small anomaly in uranium salt, scientists are still on the hunt for new isomers and have just begun to reveal the full potential of these fascinating pieces of physics.</p><img src="https://counter.theconversation.com/content/180231/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Artemis Spyrou receives funding from the National Science Foundation in the US </span></em></p><p class="fine-print"><em><span>Dennis Mücher receives funding from the Natural Sciences and Engineering Research Council of Canada and the Social Sciences and Humanities Research Council of Canada.</span></em></p>Nuclear isomers are rare versions of elements with properties that mystified physicists when first discovered. Isomers are now used in medicine and astronomy, and researchers are set to discover thousands more of them.Artemis Spyrou, Professor of Nuclear Physics, Michigan State UniversityDennis Mücher, Associate Professor of Nuclear Physics, University of GuelphLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1788702022-04-04T12:28:52Z2022-04-04T12:28:52ZNuclear fusion hit a milestone thanks to better reactor walls – this engineering advance is building toward reactors of the future<figure><img src="https://images.theconversation.com/files/455627/original/file-20220331-19-f4teht.jpg?ixlib=rb-1.1.0&rect=647%2C535%2C6180%2C4428&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Magnetic fusion reactors contain super hot plasma in a donut-shaped container called a tokamak.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/high-energy-particles-flow-through-a-tokamak-or-royalty-free-image/1092180978?adppopup=true">dani3315/iStock via Getty Images</a></span></figcaption></figure><p>Scientists at a laboratory in England have shattered the record for the amount of energy produced during a controlled, sustained fusion reaction. The production of <a href="https://ccfe.ukaea.uk/fusion-energy-record-demonstrates-powerplant-future/">59 megajoules of energy over five seconds</a> at the Joint European Torus – or JET – experiment in England has been <a href="https://www.bbc.com/news/science-environment-60312633">called “a breakthrough” by some news outlets</a> and caused quite a lot of excitement among physicists. But a common line regarding fusion electricity production is that it is “<a href="https://www.discovermagazine.com/technology/why-nuclear-fusion-is-always-30-years-away">always 20 years away</a>.”</p>
<p>We are a <a href="https://scholar.google.com/citations?user=-d-oklMAAAAJ&hl=en&oi=ao">nuclear physicist</a> and a <a href="https://scholar.google.com/citations?user=Qsmx1roAAAAJ&hl=en&oi=ao">nuclear engineer</a> who study how to develop controlled nuclear fusion for the purpose of generating electricity.</p>
<p>The JET result demonstrates remarkable advancements in the understanding of the physics of fusion. But just as importantly, it shows that the new materials used to construct the inner walls of the fusion reactor worked as intended. The fact that the new wall construction performed as well as it did is what separates these results from previous milestones and elevates magnetic fusion <a href="https://theconversation.com/nuclear-fusion-record-broken-what-will-it-take-to-start-generating-electricity-podcast-177773">from a dream toward a reality</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing two particles fusing together and the resultant products." src="https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=720&fit=crop&dpr=1 600w, https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=720&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=720&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=905&fit=crop&dpr=1 754w, https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=905&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/455632/original/file-20220331-15-lwe1fe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=905&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fusion reactors smash two forms of hydrogen together (top) so that they fuse, producing helium and a high energy neutron (bottom).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Deuterium-tritium_fusion.svg#/media/File:Deuterium-tritium_fusion.svg">Wykis/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>Fusing particles together</h2>
<p>Nuclear fusion is the merging of two atomic nuclei into one compound nucleus. This nucleus then breaks apart and releases energy in the form of new atoms and particles that speed away from the reaction. A fusion power plant would capture the escaping particles and use their energy to generate electricity. </p>
<p>There are a few <a href="https://usfusionenergy.org/approaches-fusion">different ways to safely control fusion on Earth</a>. Our research focuses on the approach taken by JET – using <a href="https://www.iter.org/sci/whatisfusion">powerful magnetic fields to confine atoms</a> until they are heated to a high enough temperature for them to fuse. </p>
<p>The fuel for current and future reactors are two different isotopes of hydrogen – meaning they have the one proton, but different numbers of neutrons – called <a href="https://www.energy.gov/science/doe-explainsdeuterium-tritium-fusion-reactor-fuel">deuterium and tritium</a>. Normal hydrogen has one proton and no neutrons in its nucleus. Deuterium has one proton and one neutron while tritium has one proton and two neutrons. </p>
<p>For a fusion reaction to be successful, the fuel atoms must first become so hot that the electrons break free from the nuclei. This creates plasma – a collection of positive ions and electrons. You then need to keep heating that plasma until it reaches a temperature over 200 million degrees Fahrenheit (100 million Celsius). This plasma must then be kept in a confined space at high densities for a long enough period of time for the <a href="https://www.euro-fusion.org/fusion/fusion-conditions/">fuel atoms to collide into each other and fuse together</a>. </p>
<p>To control fusion on Earth, researchers developed donut-shaped devices – <a href="https://www.iter.org/mach/Tokamak">called tokamaks</a> – which use magnetic fields to contain the plasma. Magnetic field lines wrapping around the inside of the donut act like <a href="https://www.iter.org/mach/Tokamak">train tracks that the ions and electrons follow</a>. By injecting energy into the plasma and heating it up, it is possible to accelerate the fuel particles to such high speeds that when they collide, instead of bouncing off each other, the fuel nuclei fuse together. When this happens, they release energy, <a href="https://www.iter.org/sci/makingitwork">primarily in the form of fast-moving neutrons</a>. </p>
<p>During the fusion process, fuel particles gradually drift away from the hot, dense core and eventually collide with the inner wall of the fusion vessel. To prevent the walls from degrading due to these collisions – which in turn also contaminates the fusion fuel – reactors are built so that they channel the wayward particles toward a heavily armored chamber called the divertor. This pumps out the diverted particles and removes any excess heat to protect the tokamak. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large, complicated machine of pipes and electronics." src="https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/455633/original/file-20220331-15-omia10.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&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 JET magnetic fusion experiment is the largest tokamak in the world.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:The_JET_magnetic_fusion_experiment_in_1991.jpg#/media/File:The_JET_magnetic_fusion_experiment_in_1991.jpg">EFDA JET/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The walls are important</h2>
<p>A major limitation of past reactors has been the fact that divertors can’t survive the constant particle bombardment for more than a few seconds. To make fusion power work commercially, engineers need to build a tokamak vessel that will survive for years of use under the conditions necessary for fusion.</p>
<p>The divertor wall is the first consideration. Though the fuel particles are much cooler when they reach the divertor, they still have enough energy to <a href="https://www.fz-juelich.de/iek/iek-4/EN/Research/01_Plasma-Wall_Interaction/_node.html;jsessionid=EF82D54C35881E2A9BC621B743370E4E">knock atoms loose from the wall material of the divertor when they collide with it</a>. Previously, JET’s divertor had a wall made of graphite, but <a href="https://www.fz-juelich.de/iek/iek-4/EN/Research/03_Plasma-facing_materials/_node.html;jsessionid=EF82D54C35881E2A9BC621B743370E4E">graphite absorbs and traps too much of the fuel for practical use</a>.</p>
<p>Around 2011, engineers at JET upgraded the divertor and inner vessel walls to tungsten. Tungsten was chosen in part because it has the highest melting point of any metal – an extremely important trait when the divertor is likely to experience heat loads nearly <a href="https://www.iter.org/mach/Divertor">10 times higher than the nose cone of a space shuttle</a> reentering the Earth’s atmosphere. The inner vessel wall of the tokamak was upgraded from graphite to beryllium. Beryllium has excellent thermal and mechanical properties for a fusion reactor – it <a href="https://www.iter.org/mach/blanket">absorbs less fuel than graphite but can still withstand the high temperatures</a>. </p>
<p>The energy JET produced was what made the headlines, but we’d argue it is in fact the use of the new wall materials which make the experiment truly impressive because future devices will need these more robust walls to operate at high power for even longer periods of time. JET is a successful proof of concept for how to build the next generation of fusion reactors.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A drawing of a reactor with many rooms surrounding it." src="https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=294&fit=crop&dpr=1 600w, https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=294&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=294&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=369&fit=crop&dpr=1 754w, https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=369&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/455635/original/file-20220331-27-phj55s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=369&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 ITER fusion reactor, seen here in a diagram, is going to incorporate the lessons of JET, but at a much bigger and more powerful scale.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/ITER#/media/File:ITER_Tokamak_and_Plant_Systems_(2016)_(41783636452).jpg">Oak Ridge National Laboratory, ITER Tokamak and Plant Systems/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>The next fusion reactors</h2>
<p>The JET tokamak is the largest and most advanced magnetic fusion reactor currently operating. But the next generation of reactors is already in the works, most notably <a href="https://www.iter.org/">the ITER experiment</a>, set to begin operations in 2027. ITER – which is Latin for “the way” – is under construction in France and funded and directed by an international organization that includes the U.S.</p>
<p>ITER is going to put to use many of the material advances JET showed to be viable. But there are also some key differences. First, ITER is massive. The fusion chamber is <a href="https://www.iter.org/mach/vacuumvessel">37 feet (11.4 meters) tall and 63 feet (19.4 meters) around</a> – more than eight times larger than JET. In addition, ITER will utilize superconducting magnets capable of producing <a href="https://www.iter.org/mach/Magnets">stronger magnetic fields for longer periods of time</a> compared to JET’s magnets. With these upgrades, ITER is expected to smash JET’s fusion records – both for energy output and how long the reaction will run.</p>
<p>ITER is also expected to do something central to the idea of a fusion powerplant: produce more energy than it takes to heat the fuel. Models predict that ITER will produce around 500 megawatts of power continuously for 400 seconds while only consuming 50 MW of energy to heat the fuel. This would mean the reactor <a href="https://www.iter.org/sci/Goals">produced 10 times more energy than it consumed</a> – a huge improvement over JET, which required <a href="https://www.popularmechanics.com/science/energy/a39107836/nuclear-fusion-energy-record/">roughly three times more energy to heat the fuel than it produced</a> for its recent <a href="https://doi.org/10.1038/d41586-022-00391-1">59 megajoule record</a>.</p>
<p>JET’s recent record has shown that years of research in plasma physics and materials science have paid off and brought scientists to the doorstep of harnessing fusion for power generation. ITER will provide an enormous leap forward toward the goal of industrial scale fusion power plants.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/178870/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Donovan has consulted in the past for Commonwealth Fusion Systems. He has been awarded funding for his research from the Office of Science Fusion Energy Sciences Program. He is a member of the American Physical Society and has been an executive committee member for divisions of the American Nuclear Society, the Institute of Electrical and Electronics Engineers, and the University Fusion Association.</span></em></p><p class="fine-print"><em><span>Livia Casali is the U.S. representative of the International Tokamak Activity in support of ITER for SOL and divertor. She is the core-edge Integration Area Leader for the DIII-D tokamak in San Diego, Vice Chair of the Edge Coordinating Committee, Executive member of the Transport Task Force and the U.S. Burning Plasma Organizational Council. Livia Casali is affiliated with the American Physical Society and the Italian Physical Society</span></em></p>In January 2022, the JET fusion experiment produced more power over a longer period of time than any past attempt. Two physicists explain the engineering advancements that made the result possible.David Donovan, Associate Professor of Nuclear Engineering, University of TennesseeLivia Casali, Assistant Professor of Nuclear Engineering, Zinkle Faculty Fellow, University of TennesseeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1546872021-02-10T20:45:08Z2021-02-10T20:45:08ZNew postage stamp honors Chien-Shiung Wu, trailblazing nuclear physicist<figure><img src="https://images.theconversation.com/files/383602/original/file-20210210-17-1ra43r9.jpg?ixlib=rb-1.1.0&rect=62%2C178%2C2915%2C2120&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Chien-Shiung Wu's experiments were instrumental in supporting some of the biggest 20th-century theories in physics.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/physics-professor-dr-chien-shiung-wu-in-a-laboratory-at-news-photo/515185238">Bettmann via Getty Images</a></span></figcaption></figure><figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Forever stamp with portrait of Chien-Shiung Wu." src="https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=944&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=944&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=944&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1187&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1187&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383299/original/file-20210209-23-13scq0b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1187&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 new U.S. postage stamp featuring Wu.</span>
<span class="attribution"><a class="source" href="https://about.usps.com/newsroom/national-releases/2021/0201ma-nuclear-physicist-chien-shiung-wu-to-be-honored-on-forever-stamp.htm">U.S. Postal Service</a></span>
</figcaption>
</figure>
<p>On Feb. 11, 2021, the sixth <a href="https://www.un.org/en/observances/women-and-girls-in-science-day">International Day of Women and Girls in Science</a>, the U.S. Postal Service issued <a href="https://store.usps.com/store/product/buy-stamps/chien-shiung-wu-S_480204">a new Forever stamp to honor</a> Chien-Shiung Wu, one of the most influential nuclear physicists of the 20th century.</p>
<p>A Chinese American woman, Wu performed experiments that tested the fundamental laws of physics. In a male-dominated field, she won many honors and awards, including the <a href="https://www.nsf.gov/news/special_reports/medalofscience50/wu.jsp">National Medal of Science</a> (1975), the inaugural <a href="https://wolffund.org.il/2018/12/09/chien-shiung-wu/">Wolf Prize in Physics</a> (1978) and honorary degrees from universities around the world. </p>
<p>In China, where I grew up, Wu is an icon who is sometimes called the “Chinese Marie Curie.” I first read about Wu’s extraordinary story in my physics textbook, when I was a teenager in high school. Chien-Shiung Wu became a scientific role model for me, inspiring me to <a href="https://scholar.google.com/citations?user=-x2wJigAAAAJ&hl=en&oi=ao">pursue an academic career in physics</a> and follow her path to the U.S.</p>
<h2>From China to the US, to pursue physics</h2>
<p>In 1912, <a href="https://www.biography.com/scientist/chien-shiung-wu">Wu was born in Liuhe</a> in Jiangsu province, a town about 40 miles north of Shanghai. Although it was uncommon in China for girls to attend school at that time, her father founded a school for girls where she received her elementary education.</p>
<p>In 1930, Wu attended National Central University in Nanjing to study mathematics. But the revolutionary triumphs of late 19th-century modern physics – such as the <a href="http://www.pbs.org/wgbh/aso/databank/entries/dp13at.html">discoveries of atomic structure</a> and <a href="https://theconversation.com/on-the-120th-anniversary-of-the-x-ray-a-look-at-how-it-changed-our-view-of-the-world-50154">of X-rays</a> – attracted Wu’s attention. She changed her major to physics and graduated at the top of her class in 1934.</p>
<p>Encouraged by her college advisor and financially supported by her uncle, Wu booked the month-long steamship trip to the United States in 1936 to pursue her doctoral education. She arrived in San Francisco, where she met her future husband, <a href="https://www.nytimes.com/2003/02/23/world/luke-yuan-90-senior-physicist-at-brookhaven.html">Luke Chia-Liu Yuan</a>, another physicist, when he showed her around the Radiation Laboratory at the University of California, Berkeley. Scientists at the lab had only <a href="https://www2.lbl.gov/Science-Articles/Archive/early-years.html">recently invented the cyclotron</a>, the most advanced instrument for accelerating charged particles in a spiral trajectory.</p>
<p>Enticed by the atomic nuclei research being done in the lab, Wu abandoned her original plan to attend the University of Michigan and successfully enrolled in the physics doctoral program at Berkeley.</p>
<p>In her graduate research, Wu worked closely with nuclear scientist <a href="https://www.nobelprize.org/prizes/physics/1939/lawrence/biographical/">Ernest Lawrence</a>, who had won the Nobel Prize in Physics in 1939, and <a href="https://www.nobelprize.org/prizes/physics/1959/segre/biographical/">Emillo Segrè</a>, who went on to win the Nobel Prize in Physics in 1959. She studied the <a href="https://doi.org/10.1103/PhysRev.59.481">electromagnetic radiation produced when charged particles decelerate</a>, as well as <a href="https://doi.org/10.1103/PhysRev.67.142">radioactive isotopes of xenon generated by splitting uranium atoms</a> via nuclear fission. In June 1940, Wu completed her Ph.D. with honors.</p>
<p>After a short period of postdoctoral research still at the Radiation Laboratory, Wu moved to the East Coast, where she taught at Smith College and then Princeton University.</p>
<h2>Experimental work in radioactive decay</h2>
<p>In 1944, Wu became a research scientist at Columbia University, where she joined <a href="https://www.energy.gov/sites/prod/files/The%20Manhattan%20Project.pdf">the Manhattan Project</a>, the top-secret U.S. effort to turn basic research in physics into a new kind of weapon, the atomic bomb. As a team member, Wu helped develop the process for separating uranium atoms into the charged uranium-235 and uranium-238 isotopes using gaseous diffusion. This work eventually led to enriched uranium, a critical component for nuclear reactions.</p>
<p>After World War II, Wu remained at Columbia and focused her research on the radioactive process of <a href="https://www2.lbl.gov/abc/wallchart/chapters/03/2.html">beta decay</a>. She investigated beta particles: fast-moving electrons or positrons emitted from an atomic nucleus in the radioactive decay process.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Beta particles leave one atom and transform it into another" src="https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=655&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=655&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=655&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=823&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=823&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383606/original/file-20210210-13-1geajf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=823&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Beta decay describes the process when a fast-moving electron or positron leaves an atom’s nucleus, leaving behind a different kind of atom.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/beta-plus-and-beta-minus-decay-royalty-free-illustration/1195604225?adppopup=true">ttsz/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>In the mid-1950s, Wu performed a famous experiment to test the <a href="https://physics.aps.org/story/v22/st19">law of parity conservation</a>. This was a widely accepted but unproven principle implying that a physical process and its mirror reflection are identical. As proposed by theoretical physicists <a href="https://www.nobelprize.org/prizes/physics/1957/yang/biographical/">Chen Ning Yang</a> and <a href="https://www.nobelprize.org/prizes/physics/1957/lee/biographical/">Tsung-Dao Lee</a>, Wu designed an experiment to see if reality matched the theory.</p>
<p>Observing the beta decay of cobalt-60 atoms, Wu measured the radiation intensity as a function of the radiation direction. To increase the accuracy of her experimental measurements, Wu figured out techniques to get her cobalt-60 atoms all spinning in the same direction. She observed that more particles flew off in the direction opposite to the direction the nuclei were spinning. The law of parity conservation predicted that the atoms would emit beta particles in symmetrical ways. But Wu’s observations meant the “law” did not hold and she had discovered parity nonconservation.</p>
<p>This breakthrough achievement helped Wu’s theoretical colleagues win the <a href="https://www.nobelprize.org/prizes/physics/1957/summary/">1957 Nobel Prize in Physics</a>, but unfortunately, the Nobel Committee <a href="https://physicsworld.com/a/overlooked-for-the-nobel-chien-shiung-wu/">overlooked Wu’s experimental contribution</a>. </p>
<p>In addition to her famous parity law research, Wu carried out <a href="https://doi.org/10.1142/S0217751X15300501">a series of important experiments</a> in nuclear physics and quantum physics. In 1949, she experimentally verified <a href="https://www.nobelprize.org/prizes/physics/1938/fermi/biographical/">Enrico Fermi</a>’s theory of beta decay, <a href="https://doi.org/10.1103/PhysRev.75.1107.2">correcting the discrepancies</a> between the theory and previous inaccurate experimental results and <a href="https://doi.org/10.1103/PhysRevLett.10.253">developing a universal version of his theory</a>. She also <a href="https://doi.org/10.1103/PhysRev.77.136">proved the quantum phenomenon</a> relevant to a pair of <a href="https://www.nist.gov/itl/entangled-photon-pair-sources">entangled photons</a>.</p>
<p>In 1958, Wu was the first Chinese-American <a href="http://www.nasonline.org/member-directory/deceased-members/48916.html">elected to the National Academy of Sciences</a>. In 1967, she served as the first female <a href="https://aps.org/about/governance/presidents.cfm">president of the American Physical Society</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Wu stands with other honorary degree recipients in academic gowns." src="https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383605/original/file-20210210-13-1tao3qm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Wu received many accolades, including an honorary doctorate at Harvard in 1974.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/six-of-the-seven-honorary-degree-recipients-at-harvard-news-photo/515112302">Bettmann via Getty Images</a></span>
</figcaption>
</figure>
<p>After her retirement in 1981, Wu dedicated herself to public educational programs in both the United States and China, giving numerous lectures and working to inspire younger generations to pursue science, technology, engineering and math education. She died in 1997. </p>
<p>Wu’s legacy continues with the issuing of her postage stamp. She joined a short list of physicists featured on U.S. stamps, including Albert Einstein, Richard Feynman and Maria Goeppert-Mayer.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/154687/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Xuejian Wu 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>Chinese American physicist Wu worked on the Manhattan Project and performed groundbreaking experiments throughout her long career.Xuejian Wu, Assistant Professor of Physics, Rutgers University - NewarkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1279872019-12-10T00:04:01Z2019-12-10T00:04:01ZThe X17 factor: a particle new to physics might solve the dark matter mystery<figure><img src="https://images.theconversation.com/files/304869/original/file-20191203-67011-f5wdzi.jpg?ixlib=rb-1.1.0&rect=0%2C13%2C4551%2C4579&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anomalies in nuclear physics experiments may show signs of a new force.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>A team of scientists in Hungary recently <a href="https://arxiv.org/abs/1910.10459">published a paper</a> that hints at the existence of a previously unknown subatomic particle. The team first <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.042501">reported</a> finding traces of the particle in 2016, and they now report more traces in a different experiment.</p>
<p>If the results are confirmed, the so-called X17 particle could help to explain dark matter, the mysterious substance scientists believe accounts for more than 80% of the mass in the universe. It may be the carrier of a “fifth force” beyond the four accounted for in the standard model of physics (gravity, electromagnetism, the weak nuclear force and the strong nuclear force). </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-astronomers-believe-in-dark-matter-122864">Why do astronomers believe in dark matter?</a>
</strong>
</em>
</p>
<hr>
<h2>Smashing atoms</h2>
<p>Most researchers who hunt for new particles use enormous accelerators that smash subatomic particles together at high speed and look at what comes out of the explosion. The biggest of these accelerators is the Large Hadron Collider in Europe, where the Higgs boson – a particle scientists had been hunting for decades – was discovered in 2012.</p>
<p>Attila J. Krasznahorkay and his colleagues at ATOMKI (the Institute of Nuclear Research in Debrecen, Hungary) have taken a different approach, conducting smaller experiments that fire the subatomic particles called protons at the nuclei of different atoms.</p>
<p>In 2016, they looked at pairs of electrons and positrons (the antimatter version of electrons) produced when beryllium-8 nuclei went from a high energy state to a low energy state.</p>
<p>They found a deviation from what they expected to see when there was a large angle between the electrons and positrons. This anomaly could be best be explained if the nucleus emitted an unknown particle which later “split” into an electron and a positron. </p>
<p>This particle would have to be a boson, which is the kind of particle that carries force, and its mass would be around 17 million electron volts. That’s about as heavy as 34 electrons, which is fairly lightweight for a particle like this. (The Higgs boson, for example, is more than 10,000 times heavier.) </p>
<p>Because of its mass, Krasznahorkay and his team called the hypothetical particle X17. Now they have observed some strange behaviour in helium-4 nuclei which can also be explained by the presence of X17. </p>
<p>This latest anomaly is statistically significant – a seven sigma confidence level, which means there is only a very tiny possibility the result occurred by chance. This is well beyond the usual five-sigma standard for a new discovery, so the result would seem to suggest there is some new physics here. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/304866/original/file-20191203-66986-1ygqhma.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">The new research is led by Attila Krasznahorkay (right).</span>
<span class="attribution"><span class="source">Attila Krasznahorkay</span></span>
</figcaption>
</figure>
<h2>Checking and double checking</h2>
<p>However, the new announcement and the one in 2016 have been met with scepticism by the physics community – the kind of scepticism that did not exist when two teams simultaneously announced the discovery of the Higgs boson in 2012. </p>
<p>So why is it so hard for physicists to believe a new lightweight boson like this could exist? </p>
<p>First, experiments of this sort are difficult, and so is the analysis of the data. Signals can appear and disappear. Back in 2004, for example, the group in Debrecen found <a href="https://arxiv.org/abs/hep-ph/0511049">evidence</a> they interpreted as the possible existence of an even lighter boson, but when they repeated the experiment the signal was gone.</p>
<p>Second, one needs to make sure the very existence of X17 is compatible with the results from other experiments. In this case, both the 2016 result with beryllium and the new result with helium can be explained by the existence of X17 but an independent check from an independent group is still necessary. </p>
<p>Krasznahorkay and his group first reported weak evidence (at a three-sigma level) for a new boson in 2012 at <a href="http://inspirehep.net/record/1235778">a workshop</a> in Italy. </p>
<p>Since then the team has repeated the experiment using upgraded equipment and successfully reproduced the beryllium-8 results, which is reassuring, as are the new results in helium-4. These new results were presented at the <a href="http://hias.anu.edu.au/2019/">HIAS 2019</a> symposium at the Australian National University in Canberra. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-standard-model-of-particle-physics-2539">Explainer: Standard Model of Particle Physics</a>
</strong>
</em>
</p>
<hr>
<h2>What does this have to do with dark matter?</h2>
<p>Scientists believe that most of the matter in the universe is invisible to us. So-called dark matter would only interact with normal matter very weakly. We can infer that it exists from its gravitational effects on distant stars and galaxies, but it has never been detected in the lab. </p>
<p>So where does X17 come in?</p>
<p>In 2003, in one of us (Boehm) showed that a particle like X17 could exist, in <a href="https://arxiv.org/abs/hep-ph/0305261">work co-authored with Pierre Fayet</a> and <a href="https://arxiv.org/abs/astro-ph/0208458">alone</a>. It would carry force between dark matter particles in much the same way photons, or particles of light, do for ordinary matter.</p>
<p>In one of the scenarios I proposed, lightweight dark matter particles could sometimes produce pairs of electrons and positrons in a way that is similar to what Krasznahorkay’s team has seen. </p>
<p>This scenario has led to many searches in low-energy experiments, which have ruled out a lot of possibilities. However, X17 has not yet been ruled out – in which case the Debrecen group might have indeed discovered how dark matter particles communicate with our world. </p>
<h2>More evidence required</h2>
<p>While the results from Debrecen are very interesting, the physics community will not be convinced a new particle has indeed been found until there is independent confirmation. </p>
<p>So we can expect many experiments around the world that are looking for a new lightweight boson to start hunting for evidence of X17 and its interaction with pairs of electrons and positrons.</p>
<p>If confirmation arrives, the next discovery might be the dark matter particles themselves.</p><img src="https://counter.theconversation.com/content/127987/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>A recent experiment with atomic nuclei is hard to square with our current understanding of physics.Celine Boehm, Head of School for Physics, University of SydneyTibor Kibedi, Senior Fellow in Nuclear Physics, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1062202019-02-07T12:28:21Z2019-02-07T12:28:21ZLise Meitner – the forgotten woman of nuclear physics who deserved a Nobel Prize<figure><img src="https://images.theconversation.com/files/257317/original/file-20190205-86205-ff9763.jpg?ixlib=rb-1.1.0&rect=40%2C4%2C1556%2C1171&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lise Meitner was left off the publication that eventually led to a Nobel Prize for her colleague.</span> </figcaption></figure><p><a href="http://www.atomicarchive.com/Fission/Fission1.shtml">Nuclear fission</a> – the physical process by which very large atoms like uranium split into pairs of smaller atoms – is what makes <a href="https://www.atomicheritage.org/history/science-behind-atom-bomb">nuclear bombs</a> and <a href="http://www.world-nuclear.org/information-library/current-and-future-generation/outline-history-of-nuclear-energy.aspx">nuclear power plants</a> possible. But for many years, physicists believed it energetically impossible for atoms as large as uranium (atomic mass = 235 or 238) to be split into two.</p>
<p>That all changed on Feb. 11, 1939, with a <a href="https://www.nature.com/articles/143239a0">letter to the editor</a> of Nature – a premier international scientific journal – that described exactly how such a thing could occur and even named it fission. In that letter, physicist Lise Meitner, with the assistance of her young nephew <a href="http://www.atomicarchive.com/Bios/Frisch.shtml">Otto Frisch</a>, provided a physical explanation of how nuclear fission could happen.</p>
<p>It was a massive leap forward in nuclear physics, but today Lise Meitner remains obscure and largely forgotten. She was excluded from the victory celebration because she was a Jewish woman. Her story is a sad one.</p>
<h2>What happens when you split an atom</h2>
<p>Meitner based her fission argument on the “<a href="https://socratic.org/questions/how-does-the-liquid-drop-model-account-for-nuclear-fission">liquid droplet model</a>” of nuclear structure – a model that likened the forces that hold the atomic nucleus together to the surface tension that gives a water droplet its structure.</p>
<p>She noted that the surface tension of an atomic nucleus weakens as the charge of the nucleus increases, and could even approach zero tension if the nuclear charge was very high, as is the case for uranium (charge = 92+). The lack of sufficient nuclear surface tension would then allow the nucleus to split into two fragments when struck by a <a href="https://sciencenotes.org/neutron-definition-chemistry/">neutron</a> – a chargeless subatomic particle – with each fragment carrying away very high levels of kinetic energy. Meisner remarked: “The whole ‘fission’ process can thus be described in an essentially classical [physics] way.” Just that simple, right?</p>
<p>Meitner went further to explain how her scientific colleagues had gotten it wrong. When scientists bombarded uranium with neutrons, they believed the uranium nucleus, rather than splitting, captured some neutrons. These captured neutrons were then converted into positively charged protons and thus transformed the uranium into the incrementally larger elements on the <a href="https://www.livescience.com/25300-periodic-table.html">periodic table of elements</a> – the so-called “<a href="https://www.britannica.com/science/transuranium-element">transuranium</a>,” or beyond uranium, elements.</p>
<p>Some people were skeptical that neutron bombardment could produce transuranium elements, including <a href="https://www.atomicheritage.org/profile/irene-joliot-curie">Irene Joliot-Curie</a> – Marie Curie’s daughter – and Meitner. Joliot-Curie had found that one of these new alleged transuranium elements actually behaved chemically just like <a href="https://www.livescience.com/39623-facts-about-radium.html">radium</a>, the element her mother had discovered. Joliot-Curie suggested that it might be just radium (atomic mass = 226) – an element somewhat smaller than uranium – that was coming from the neutron-bombarded uranium.</p>
<p>Meitner had an alternative explanation. She thought that, rather than radium, the element in question might actually be <a href="https://www.livescience.com/37581-barium.html">barium</a> – an element with a chemistry very similar to radium. The issue of radium versus barium was very important to Meitner because barium (atomic mass = 139) was a possible fission product according to her split uranium theory, but radium was not – it was too big (atomic mass = 226).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=366&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=366&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=366&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=460&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=460&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257322/original/file-20190205-86198-76178y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=460&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When a neutron bombards a uranium atom, the uranium nucleus splits into two different smaller nuclei.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Kernspaltung.svg">Stefan-Xp/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Meitner urged her chemist colleague <a href="https://www.atomicheritage.org/profile/otto-hahn">Otto Hahn</a> to try to further purify the uranium bombardment samples and assess whether they were, in fact, made up of radium or its chemical cousin barium. Hahn complied, and he found that Meitner was correct: the element in the sample was indeed barium, not radium. Hahn’s finding suggested that the uranium nucleus had split into pieces – becoming two different elements with smaller nuclei – just as Meitner had suspected.</p>
<h2>As a Jewish woman, Meitner was left behind</h2>
<p>Meitner should have been the hero of the day, and the physicists and chemists should have jointly published their findings and waited to receive the world’s accolades for their discovery of nuclear fission. But unfortunately, that’s not what happened.</p>
<p>Meitner had two difficulties: She was a Jew living as an exile in Sweden because of the Jewish persecution going on in Nazi Germany, and she was a woman. She might have overcome either one of these obstacles to scientific success, but both proved insurmountable.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=793&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=793&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=793&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=996&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=996&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257308/original/file-20190205-86195-ggd0rl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=996&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lise Meitner and Otto Hahn in Berlin, 1913.</span>
</figcaption>
</figure>
<p>Meitner had been working as Hahn’s academic equal when they were on the faculty of the Kaiser Wilhelm Institute in Berlin together. By all accounts they were close colleagues and friends for many years. When the Nazis took over, however, Meitner was forced to leave Germany. She took a position in Stockholm, and continued to work on nuclear issues with Hahn and his junior colleague Fritz Strassmann through regular correspondence. This working relationship, though not ideal, was still highly productive. The barium discovery was the latest fruit of that collaboration. </p>
<p>Yet when it came time to publish, Hahn knew that including a Jewish woman on the paper would cost him his career in Germany. So he <a href="https://doi.org/10.1007/BF01488241">published without her</a>, falsely claiming that the discovery was based solely on insights gleaned from his own chemical purification work, and that any physical insight contributed by Meitner played an insignificant role. All this despite the fact he wouldn’t have even thought to isolate barium from his samples had Meitner not directed him to do so.</p>
<p>Hahn had trouble explaining his own findings, though. In his paper, he put forth no plausible mechanism as to how uranium atoms had split into barium atoms. But Meitner had the explanation. So a few weeks later, Meitner wrote her famous fission letter to the editor, ironically explaining the mechanism of “Hahn’s discovery.”</p>
<p>Even that didn’t help her situation. The Nobel Committee awarded the <a href="https://www.nobelprize.org/prizes/chemistry/1944/summary/">1944 Nobel Prize in Chemistry</a> “for the discovery of the fission of heavy nuclei” to Hahn alone. Paradoxically, the word “fission” never appeared in Hahn’s original publication, as Meitner had been the first to coin the term in the letter published afterward. </p>
<p>A controversy has raged about the discovery of nuclear fission ever since, with <a href="https://www.ucpress.edu/book/9780520208605/lise-meitner">critics claiming</a> it represents one of the worst examples of blatant racism and sexism by the Nobel committee. Unlike another prominent female nuclear physicist whose career preceded her – <a href="https://www.nobelprize.org/prizes/chemistry/1911/marie-curie/facts/">Marie Curie</a> – Meitner’s contributions to nuclear physics were never recognized by the Nobel committee. She has been totally left out in the cold, and remains unknown to most of the public.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257320/original/file-20190205-86198-1nmuux6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Meitner received the Enrico Fermi Award in 1966. Her nephew Otto Frisch is on the left.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/iaea_imagebank/4311592724">IAEA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>After the war, Meitner remained in Stockholm and became a Swedish citizen. Later in life, she decided to let bygones be bygones. She reconnected with Hahn, and the two octogenarians resumed their friendship. Although the Nobel committee never acknowledged its mistake, the slight to Meitner was partly mitigated in 1966 when the U.S. Department of Energy jointly awarded her, Hahn and Strassmann its prestigious <a href="https://science.energy.gov/fermi/">Enrico Fermi Award</a> “for pioneering research in the naturally occurring radioactivities and extensive experimental studies leading to the discovery of fission.” The two-decade late recognition came just in time for Meitner. She and Hahn died within months of each other in 1968; they were both 89 years old.</p><img src="https://counter.theconversation.com/content/106220/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Timothy J. Jorgensen 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>Left off publications due to Nazi prejudice, this Jewish woman lost her rightful place in the scientific pantheon as the discoverer of nuclear fission.Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/861772018-12-07T11:39:53Z2018-12-07T11:39:53ZHunting for rare isotopes: The mysterious radioactive atomic nuclei that will be in tomorrow’s technology<figure><img src="https://images.theconversation.com/files/249379/original/file-20181206-128202-1d16zby.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers have identified 3,000 radioactive isotopes – and predict 4,000 more are out there.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/high-energy-particles-collision-abstract-illustration-539127385">GiroScience/Shutterstock.com</a></span></figcaption></figure><p>When you hear the term “radioactive” you likely think “bad news,” maybe along the lines of fallout from an atomic bomb.</p>
<p>But radioactive materials are actually used in a wide range of beneficial applications. In medicine, they routinely help diagnose and treat disease. Irradiation helps keep a number of foods free from insects and invasive pests. Archaeologists use them to figure out how old an artifact might be. And the list goes on.</p>
<p>So what is radioactivity?</p>
<p>It’s the spontaneous emission of radiation when an atom’s dense center – called its nucleus – transforms into a different one. Whether in the form of particles or electromagnetic waves called gamma rays, radiation transfers energy away from the atomic nucleus.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249353/original/file-20181206-128193-1ucj6s2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&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 nuclear chart showing the 250 or so stable isotopes in pink, the around 3,000 known rare isotopes in green and the approximately 4,000 predicted isotopes in grey.</span>
<span class="attribution"><span class="source">Erin O'Donnell, Michigan State University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Through experiments, nuclear physicists have seen about 3,000 different kinds of nuclei to date. Current theories, though, predict the existence of about 4,000 more that have never yet been observed. Around the world, thousands of scientists, <a href="https://www.artemisspyrou.com">including me</a>, continue to study these tiny constituents of matter, while governments spend billions of dollars on building powerful new machines that will produce more and more exotic nuclei – and maybe eventually more technologies that will further improve modern life. </p>
<h2>The birth of nuclear physics</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=714&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=714&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=714&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=898&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=898&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249330/original/file-20181206-128193-1qr8qdq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=898&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Henri Becquerel, 1904.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Becquerel,_Henri_(1852-1908).jpg">Library of Congress</a></span>
</figcaption>
</figure>
<p>French physicist <a href="https://www.nobelprize.org/prizes/physics/1903/becquerel/biographical/">Henri Becquerel</a> discovered natural radioactivity in 1896. He was trying to study how uranium salts phosphoresce – that is, emit light – when they’re exposed to sunlight. Becquerel placed a uranium sample on a photographic plate covered with opaque paper and left it in direct sunlight. The plate got foggy, which he concluded was due to sun exposure.</p>
<p>Thanks to a few days of cloudy weather, though, Becquerel left his whole setup in a dark drawer. Surprisingly, the photographic plate still fogged up, even in the absence of light. Sunlight had nothing to do with his previous observation. It was the natural radioactivity of the uranium samples that had this effect. As the uranium nuclei decayed – that is, transformed into different nuclei – they spontaneously emitted lightwaves that registered on the photographic plates.</p>
<p>Becquerel’s discovery ushered in a new era of physics and launched the field of nuclear science. For this work, he won the Nobel Prize in 1903.</p>
<p>Since then, nuclear scientists have unraveled a lot of the inner workings of the atomic nucleus, and have harnessed its amazing energy both for good and unfortunately not so good uses. Nuclear physics discoveries have given us ways to look inside our bodies noninvasively, ways to create energy without air pollution, and ways to study our history and our environment.</p>
<h2>On the atomic level</h2>
<p>The known atomic nuclei belong to 118 different elements, some of them naturally occurring and some of them human-made. For every element on the periodic table there are many different “isotopes,” from the Greek word “ισότοπο,” which means “same place,” implying the same place on the periodic table of the elements.</p>
<p>To be the same element, two isotopes must have the same number of protons – the positively charged subatomic particle. It’s their number of neutrons – subatomic particles with no charge at all – that can vary significantly.</p>
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<figcaption>
<span class="caption">The periodic table lists all the elements based on their number of protons. Isotopes of an element have the same number of protons – for Beryllium it’s four – but various numbers of neutrons.</span>
<span class="attribution"><span class="source">Artemis Spyrou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>For example, gold is element 79 on the periodic table, and all isotopes of gold will have the same metallic, yellowish appearance. However, there are 40 known isotopes of gold that have been discovered, and another roughly 20 are theorized to exist. Only one of these isotopes is the “stable,” or naturally occurring, form of gold you might be wearing on your ring finger right now. The rest are radioactive isotopes, also known as “rare isotopes.”</p>
<p>Rare isotopes each have unique properties: They live for different amounts of time, from a fraction of a second to a few billion years, and they release different types of radiation and different amounts of energy.</p>
<p>For example, modern smoke detectors <a href="https://www3.epa.gov/radtown/americium-smoke-detectors.html">use the isotope Americium-241</a>, which emits a type of radiation called alpha particles that have a very short range. The radioactivity can’t travel more than a couple of inches in air. Americium-241 lives for a few hundred years.</p>
<p>On the other hand, the isotope Fluorine-18, which is commonly used in medical PET scans, lives for only about 100 minutes – long enough to complete the scan, but short enough to avoid irradiating the healthy body unnecessarily for an extended period. The secondary electromagnetic radiation that comes from Fluorine-18 is in the form of long-range gamma rays, which allows it to travel out of the body and into the PET cameras. </p>
<p>These different nuclear properties make each rare isotope unique, and nuclear physicists have to design specialized experiments to study each one of them separately.</p>
<h2>Hunting for more</h2>
<p>Current nuclear science research strives to develop new techniques for discovering new isotopes, understanding their properties, and eventually producing and harvesting them efficiently.</p>
<p>Producing rare isotopes <a href="https://www.youtube.com/watch?v=EPG919lJK8s&t=57s">is not an easy task</a>; it requires large machines that will make nuclei travel, and collide with each other, at speeds close to the speed of light. During these collisions nuclei can fuse together, or they can break each other apart, producing new nuclei, potentially with previously unseen combinations of protons and neutrons.</p>
<p>Nuclear physicists have dedicated equipment - detectors - that can observe these newly formed nuclei and the radiation they emit, and study their properties. For example, at the <a href="https://www.nscl.msu.edu">National Superconducting Cyclotron Laboratory</a> <a href="https://scholar.google.com/citations?user=MFjq3JsAAAAJ&hl=en&oi=ao">where I work</a>, my group has developed an extremely efficient gamma ray detector we called SuN.</p>
<figure class="align-right zoomable">
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<figcaption>
<span class="caption">The SuN detector at the National Superconducting Cyclotron Laboratory measures gamma rays and helps researchers study the properties of rare isotopes.</span>
<span class="attribution"><span class="source">Artemis Spyrou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The majority of the known isotopes emit gamma radiation when they decay. We want to know how much energy is released in this process, how many different gamma rays are emitted and how the energy is shared between them, and how long it takes for the decay to take place. SuN can answer these questions about whichever isotope we are investigating.</p>
<p>In a typical experiment, we implant a beam of rare isotopes at the center of SuN. The rare isotopes will decay of their own accord after a short amount of time, roughly one second or less, and emit their characteristic radiation. SuN detects these emitted gamma rays. It’s our job as nuclear experimentalists to put together the puzzle of how those gamma rays were emitted and what they tell us about the properties of the new isotope.</p>
<p>These kinds of production and detection techniques are complex and costly, and therefore there are only a handful of rare isotope laboratories in the world that can produce and study the most exotic nuclear species.</p>
<p>It’s impossible to predict which new discoveries in basic research will have an impact on people’s lives. Who could have known 100 years ago, when the electron was discovered, that for a few decades almost every house in the developed world would have an electron machine – otherwise known as a <a href="https://electronics.howstuffworks.com/tv3.htm">cathode-ray tube</a> – to watch television? And who could have guessed that the discovery of radioactivity would eventually lead to <a href="https://rps.nasa.gov/power-and-thermal-systems/power-systems/current/">space exploration powered by radioactive decays</a>?</p>
<p>In the same way, we cannot predict which rare isotope discoveries will be the game-changers, but with more than half of the predicted isotopes still unexplored, to me the possibilities feel endless.</p><img src="https://counter.theconversation.com/content/86177/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Artemis Spyrou receives funding from the National Science Foundation and the Department of Energy/National Nuclear Security Administration. </span></em></p>Alongside their famous dangers, radioactive materials have many beneficial uses. With as many more predicted as have already been discovered, nuclear physicists are searching for more isotopes.Artemis Spyrou, Associate Professor of Nuclear Physics, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1072872018-12-03T10:07:22Z2018-12-03T10:07:22ZHow African researchers are adding to deeper knowledge about neutrons<figure><img src="https://images.theconversation.com/files/246993/original/file-20181123-149317-wz6cty.png?ixlib=rb-1.1.0&rect=7%2C159%2C961%2C566&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">iThemba LABS provides support for research and training to all universities.</span> <span class="attribution"><span class="source">iThemba LABS</span></span></figcaption></figure><p>Matter is all around us. As <a href="https://www.independent.co.uk/news/science/what-the-human-body-is-made-of-a7173301.html">human beings</a>, we’re made of it. Matter is the “stuff” that makes up the physical world as we know it; a collection of atoms made up of particles called protons, electrons and neutrons.</p>
<p>Part of <a href="https://www.researchgate.net/profile/Ntombizikhona_Beaulah_Ndlovu">my work</a>, as a post-doctoral researcher at <a href="http://tlabs.ac.za">iThemba LABS</a> (Laboratory for Accelerator Based Sciences) in Cape Town, South Africa, focuses on neutrons. These are subatomic particles that can penetrate through matter, which means they can be harnessed for all sorts of important work. </p>
<p>For example, high-energy neutrons may be used <a href="https://radiationoncology.uw.edu/radiation-treatment/treatment-options/neutron-beam-therapy/">to destroy tough tumours</a> that can’t be killed by the usual x-rays that are available in hospitals.</p>
<p>Neutrons can have negative effects, too. People who work with nuclear fission reactors, particle accelerators and fast neutron generators, for instance, get exposed to high-energy neutrons. Research has shown that this <a href="http://www.who.int/topics/radiation_ionizing/en/">can be harmful</a>: when neutrons interact with human beings, chromosomes in the blood can be damaged. In <a href="https://www.ncbi.nlm.nih.gov/books/NBK218707/">really severe cases</a>, cells can become deformed; this can cause cancer and impair organ function.</p>
<p>There are facilities around the world where scientists can access neutrons for their work. But these are either slow neutrons or neutrons that come with a combination of all possible energies. In those cases, scientists can’t tell exactly which neutrons – slow or fast – had an effect on their samples.</p>
<p>There are only two facilities in the world where researchers can access fast neutrons of almost a single energy, which are necessary to develop and test new theories. One is Osaka University’s <a href="https://www.rcnp.osaka-u.ac.jp/index_en.html">Centre for Nuclear Physics</a> in Japan. The other is iThemba LABS. Researchers from around the world, and from the rest of Africa, use the Cape Town facility to conduct research that has global implications.</p>
<p>It’s important to keep studying neutrons to understand both their harmful properties and the ways they can be used for good. </p>
<h2>What we’ve learned</h2>
<p>Some of the most crucial work that’s being done to fill in our knowledge gaps and find new uses for neutrons is happening on the African continent.</p>
<p>For example, some of this research is being used in outer space. Neutrons are found naturally in outer space, so satellites are installed with devices called detectors to track how many neutrons they’re being exposed to. And also to figure out at what point that exposure becomes dangerous. These detectors can be adjusted and tested at iThemba LABS to ensure they’re accurate.</p>
<p>And next time you board a flight, it’s possible that your plane’s electronic components were also tested in our labs. By exposing such components to neutrons before they are installed and put to use in the real world, scientists are able to ensure that aircraft can safely withstand the amount of neutrons that will bombard them in the atmosphere.</p>
<p>It’s also at facilities like ours and Osaka University’s that research has started slowly unpacking the effect of neutrons on human health. </p>
<p>Scientists at these labs are also responsible for figuring out what kind of materials efficiently shield people from neutron radiation. </p>
<h2>Room to grow</h2>
<p>But there’s much more to be done in understanding neutrons, and particularly creating more space for Africa’s neutron science community to come and conduct research that’s relevant for the continent. More and more countries in Africa are investing in nuclear technology, and so having a facility relatively close to them is really important.</p>
<p>As a national facility of South Africa’s National Research Foundation, one of the mandates of iThemba LABS is also to provide support for research and training to all universities. Scientists working at iThemba LABS provide supervision to MSc and PhD postgraduate students, as well as providing in-service training. Postgraduates from countries outside South Africa can also come and learn more, then go back to their own countries and share that knowledge.</p>
<p>All of this has prompted iThemba LABS to develop and grow its neutron beam facility. To do this, it is working with the University of Cape Town in South Africa, Germany’s Physikalisch-Technische Bundesanstalt, the Institute de Radioprotection et Sûreté Nucléaire in France and the National Physical Laboratory (from the United Kingdom). Over the next two or three years, there will be big changes – and this will allow for even more neutron research to emerge from the African continent.</p><img src="https://counter.theconversation.com/content/107287/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ntombizikhona Beaulah Ndlovu works for iThemba LABS (Laboratory for Accelerator Based Sciences - NRF (National Research Foundation). </span></em></p>Neutrons can penetrate through matter, which means they can be harnessed for all sorts of important work.Ntombizikhona Beaulah Ndlovu, Postdoctoral research fellow, iThemba LABSLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/939162018-05-02T10:40:36Z2018-05-02T10:40:36ZElements from the stars: The unexpected discovery that upended astrophysics 66 years ago<figure><img src="https://images.theconversation.com/files/217062/original/file-20180501-135840-1g8smw7.png?ixlib=rb-1.1.0&rect=0%2C97%2C952%2C793&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">New heavy nuclei are constantly generated in stars and other astronomical bodies.</span> <span class="attribution"><span class="source">Erin O’Donnell</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Nearly 70 years ago, astronomer Paul Merrill was watching the sky through a telescope at <a href="https://www.mtwilson.edu/">Mount Wilson Observatory</a> in Pasadena, California. As he observed the light coming from a distant star, he saw signatures of the element technetium.</p>
<p>This was completely unexpected. Technetium has no stable forms – it’s what physicists call an <a href="https://en.wikipedia.org/wiki/Synthetic_element">“artificial” element</a>. As Merrill himself put it with a bit of understatement, “<a href="https://doi.org/10.1126/science.115.2992.479">It is surprising to find an unstable element in the stars</a>.”</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=799&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=799&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=799&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1004&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1004&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217074/original/file-20180501-135803-wsicre.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1004&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Paul W. Merrill standing at the spectrograph mounted on the 60-inch telescope at Mount Wilson Observatory.</span>
<span class="attribution"><a class="source" href="http://hdl.huntington.org/cdm/singleitem/collection/p15150coll2/id/1584/rec/11">Observatories of the Carnegie Institution for Science Collection at the Huntington Library, San Marino, California</a></span>
</figcaption>
</figure>
<p>Any technetium present when the star formed should have transformed itself into a different element, such as ruthenium or molybdenum, a very long time ago. As an artificial element, someone must have recently created the technetium Merrill spotted. But who or what could have done that in this star?</p>
<p>On May 2, 1952, Merrill reported his <a href="https://doi.org/10.1126/science.115.2992.479">discovery in the journal Science</a>. Among the three interpretations offered by Merrill was the answer: Stars create heavy elements! Not only had Merrill explained a puzzling observation, he had also opened the door to understand our cosmic origins. Not many discoveries in science completely change our view of the world – but this one did. The newly revealed picture of the universe was simply mind-blowing, and the repercussions of this discovery are still driving nuclear science research today.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=520&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=520&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217099/original/file-20180501-135848-hyzcan.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=520&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Technetium nuclei are transformed into Ruthenium or Molybdenum within a few million years – so if you spot them now, they can’t be left from the Big Bang billions of years ago.</span>
<span class="attribution"><span class="source">Erin O’Donnell, Michigan State University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Where do elements come from?</h2>
<p>In the early 1950s, it was still unclear how the elements that make up our universe, our solar system, even our human bodies, were created. Initially, the most popular scenario was that they were all made in the Big Bang.</p>
<p>First alternative scenarios were developed by renowned scientists of the time, like <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1967/bethe-facts.html">Hans Bethe</a> (Nobel Prize in Physics, 1967), <a href="https://www.atomicheritage.org/profile/carl-friedrich-von-weizs%C3%A4cker">Carl Friedrich von Weizsäcker</a> (Max-Plank Medal, 1957), and <a href="https://www.britannica.com/biography/Fred-Hoyle">Fred Hoyle</a> (Royal Medal, 1974). But no one really had come up with a convincing theory for the origin of the elements – until Paul Merrill’s observation. </p>
<p>Merrill’s discovery marked the birth of a completely new field: stellar nucleosynthesis. It’s the study of how the elements, or more accurately their atomic nuclei, are synthesized in stars. It didn’t take long for scientists to start trying to figure out exactly what the process of element synthesis in stars entailed. This is where nuclear physics had to come into play, to help explain Merrill’s amazing observation.</p>
<h2>Fusing nuclei in the heart of a star</h2>
<p>Brick by brick, element by element, nuclear processes in stars take the abundant hydrogen atoms and build heavier elements, from helium and carbon all the way to technetium and beyond. </p>
<p>Four prominent nuclear (astro)physicists of the time worked together, and in 1957 published the “<a href="https://journals.aps.org/rmp/pdf/10.1103/RevModPhys.29.547">Synthesis of the Elements in Stars</a>”: <a href="https://www.britannica.com/biography/Margaret-Burbidge">Margaret Burbidge</a> (Albert Einstein World Award of Science, 1988), <a href="http://www.phys-astro.sonoma.edu/brucemedalists/burbidgeg/index.html">Geoffrey Burbidge</a> (Bruce Medal, 1999), <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1983/fowler-facts.html">William Fowler</a> (Nobel Prize in Physics, 1983), and <a href="https://www.britannica.com/biography/Fred-Hoyle">Fred Hoyle</a> (Royal Medal, 1974). The publication, known as B2FH, still remains a reference for describing astrophysical processes in stars. <a href="http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/cameron-a-g-w.pdf">Al Cameron</a> (Hans Bethe Prize, 2006) in the same year independently arrived at the same theory in his paper “<a href="https://doi.org/10.1086/127051">Nuclear Reactions in Stars and Nucleogenesis</a>.”</p>
<p>Here’s the story they put together.</p>
<p>Stars are heavy. You’d think they would completely collapse in upon themselves because of their own gravity – but they don’t. What prevents this collapse is nuclear fusion reactions happening at the star’s center.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=855&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=855&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=855&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1074&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1074&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217106/original/file-20180501-135810-6g81mr.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1074&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When atomic nuclei collide, they sometimes fuse, forming new elements.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:FusionintheSun.svg">Borb</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Within a star are billions and billions of atoms. They’re zooming all around, sometimes colliding with one another. Initially the star is too cold, and when atoms’ nuclei collide they simply bounce off each other. As the star compresses because of its gravity, though, the temperature at its center increases. In such hot conditions, now when nuclei run into each other they have enough energy to merge together. This is what physicists call a <a href="https://en.wikipedia.org/wiki/Nuclear_fusion">nuclear fusion reaction</a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=642&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=642&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=642&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=807&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=807&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217066/original/file-20180501-135817-rqu0m6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=807&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fusion reactions happen in different parts of a star. Technetium is created in the shell.</span>
<span class="attribution"><a class="source" href="http://www.eso.org/public/images/eso0729a/">ESO</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>These nuclear reactions serve two purposes.</p>
<p>First, they release energy that heats the star, providing the outward pressure that prevents its gravitational collapse and keeps the star in balance for billions of years. Second, they <a href="http://www.jinaweb.org/movies/pp_chain.html">fuse light elements into heavier ones</a>. And slowly, starting with hydrogen and helium, stars will make the technetium that Merrill observed, the calcium in our bones and the gold in our jewelry.</p>
<p>Many different nuclear reactions are responsible for making all this happen. And they’re extremely difficult to study in the laboratory because nuclei are hard to fuse. That’s why, for more than six decades, <a href="https://doi.org/10.1007/s00016-018-0216-0">nuclear physicists have continued to work</a> to get a handle on the nuclear reactions that drive the stars.</p>
<h2>Astrophysicists still untangling element origins</h2>
<p>Today there are many more ways to observe the signatures of element creation throughout the universe.</p>
<p>Very old stars record the composition of the universe way back at the time of their formation. As more and more stars of varying ages are found, their compositions begin to tell the <a href="https://doi.org/10.1063/PT.3.3815">story of element synthesis in our galaxy</a>, from its formation shortly after the Big Bang to today.</p>
<p>And the more researchers learn, the more complex the picture gets. In the last decade, observations provided evidence for a much broader range of element-creating processes than anticipated. For some of these processes, we do not even know yet in what kind of stars or stellar explosions they occur. But astrophysicists think all these stellar events have contributed their characteristic mix of elements into the swirling dust cloud that ultimately became our solar system.</p>
<p>The most recent example comes from a <a href="https://theconversation.com/cosmic-alchemy-colliding-neutron-stars-show-us-how-the-universe-creates-gold-86104">neutron-star merger event</a> tracked <a href="https://theconversation.com/ligo-announcement-vaults-astronomy-out-of-its-silent-movie-era-into-the-talkies-85727">by gravitational and electromagnetic observatories</a> around the world. This observation demonstrates that even merging neutron stars make a large contribution to the production of heavy elements in the universe – in this case the so-called Lanthanides that include elements such as Terbium, Neodynium and the Dysprosium used in cellphones. And just like at the time of Merrill’s discovery, nuclear scientists around the world are scrambling, working overtime at their accelerators, to figure out what nuclear reactions could possibly explain all these new observations.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=380&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=380&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=380&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=477&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=477&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217108/original/file-20180501-135825-hhntgj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=477&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Modern nucleosynthesis experiments, like those of the authors, are run on nuclear physics equipment including particle accelerators.</span>
<span class="attribution"><a class="source" href="http://nscl.msu.edu/">National Superconducting Cyclotron Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Discoveries that change our view of the world don’t happen every day. But when they do, they can provide more questions than answers. It takes a lot of additional work to find all the pieces of the new scientific jigsaw puzzle, put them together step by step and eventually arrive at a new understanding. Advanced astronomical observations with modern telescopes continue to reveal more and more secrets hidden in distant stars. State-of-the-art accelerator facilities study the nuclear reactions that create elements in stars. And sophisticated computer models put it all together, trying to recreate the parts of the universe we see, while reaching out toward the ones that are still hiding until the next major discovery.</p><img src="https://counter.theconversation.com/content/93916/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Artemis Spyrou receives funding from the National Science Foundation and the Department of Energy/National Nuclear Security Administration. </span></em></p><p class="fine-print"><em><span>Hendrik Schatz receives funding from National Science Foundation and Department of Energy Office of Science.</span></em></p>People long assumed all the elements we see now were created during the Big Bang. But on May 2, 1952, an astronomer reported spotting new elements coming from an old star and changed our origin story.Artemis Spyrou, Associate Professor of Nuclear Physics, Michigan State UniversityHendrik Schatz, University Distinguished Professor of Nuclear Astrophysics, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/871542017-11-30T18:07:28Z2017-11-30T18:07:28ZAtomic age began 75 years ago with the first controlled nuclear chain reaction<figure><img src="https://images.theconversation.com/files/197029/original/file-20171129-12027-8o9l1v.jpg?ixlib=rb-1.1.0&rect=67%2C323%2C2806%2C1980&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">For the first time, human beings harnessed the power of atomic fission.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Atomic_Man_-_panoramio.jpg">Keith Ruffles</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Over Christmas vacation in 1938, physicists <a href="https://www.atomicheritage.org/profile/lise-meitner">Lise Meitner</a> and <a href="https://www.atomicheritage.org/profile/otto-frisch">Otto Frisch</a> received puzzling scientific news in a private letter from nuclear chemist <a href="https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1944/">Otto Hahn</a>. When bombarding uranium with neutrons, Hahn had made some surprising observations that went against everything known at the time about the dense cores of atoms – their nuclei. </p>
<p>Meitner and Frisch were able to provide an explanation for what he saw that would revolutionize the field of nuclear physics: A uranium nucleus could split in half – or fission, as they called it – producing two new nuclei, called fission fragments. More importantly, this fission process releases huge amounts of energy. This finding at the dawn of World War II was the start of a scientific and military race to understand and use this new atomic source of power.</p>
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<span class="caption">Leo Szilard lectures on the fission process.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/argonne/9623642054">Argonne National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
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</figure>
<p>The <a href="https://doi.org/10.1038/143239a0">release of these findings</a> to the academic community immediately inspired many nuclear scientists to investigate the nuclear fission process further. Physicist <a href="https://www.atomicheritage.org/profile/leo-szilard">Leo Szilard</a> made an important realization: if fission emits neutrons, and neutrons can induce fission, then neutrons from the fission of one nucleus could cause the fission of another nucleus. It could all cascade in a self-sustained “chain” process.</p>
<p>Thus began the quest to experimentally prove that a nuclear chain reaction was possible – and 75 years ago, researchers at the University of Chicago succeeded, opening the door to what would become the nuclear era.</p>
<h2>Harnessing fission</h2>
<p>As part of the <a href="https://www.energy.gov/management/office-management/operational-management/history/manhattan-project">Manhattan Project</a> effort to build an atomic bomb during World War II, Szilard worked together with <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1938/">physicist Enrico Fermi</a> and other colleagues at the University of Chicago to create the world’s first experimental nuclear reactor.</p>
<p>For a sustained, controlled chain reaction, each fission must induce just one additional fission. Any more, and there’d be an explosion. Any fewer and the reaction would peter out.</p>
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<figcaption>
<span class="caption">Nobel Prize winner Enrico Fermi led the project.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/argonne/5039457612">Argonne National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
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</figure>
<p>In earlier studies, Fermi had found that uranium nuclei would absorb neutrons more easily if the neutrons were moving relatively slowly. But neutrons emitted from the fission of uranium are fast. So for the Chicago experiment, the physicists used graphite to slow down the emitted neutrons, via multiple scattering processes. The idea was to increase the neutrons’ chances of being absorbed by another uranium nucleus.</p>
<p>To make sure they could safely control the chain reaction, the team rigged together what they called “control rods.” These were simply sheets of the element cadmium, an excellent neutron absorber. The physicists interspersed control rods through the uranium-graphite pile. At every step of the process Fermi calculated the expected neutron emission, and slowly removed a control rod to confirm his expectations. As a safety mechanism, the cadmium control rods could quickly be inserted if something started going wrong, to shut down the chain reaction.</p>
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<figcaption>
<span class="caption">Chicago Pile 1, erected in 1942 in the stands of an athletic field at the University of Chicago.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/argonne/12371772445">Argonne National Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
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<p>They called this <a href="https://en.wikipedia.org/wiki/Chicago_Pile-1">20x6x25-foot setup</a> <a href="https://www.uchicago.edu/features/how_the_first_chain_reaction_changed_science/">Chicago Pile Number One</a>, or CP-1 for short – and it was here they obtained world’s the first controlled nuclear chain reaction on December 2, 1942. A single random neutron was enough to start the chain reaction process once the physicists assembled CP-1. The first neutron would induce fission on a uranium nucleus, emitting a set of new neutrons. These secondary neutrons hit carbon nuclei in the graphite and slowed down. Then they’d run into other uranium nuclei and induce a second round of fission reactions, emit even more neutrons, and on and on. The cadmium control rods made sure the process wouldn’t continue indefinitely, because Fermi and his team could choose exactly how and where to insert them to control the chain reaction.</p>
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<figcaption>
<span class="caption">A nuclear chain reaction. Green arrows show the split of a uranium nucleus in two fission fragments, emitting new neutrons. Some of these neutrons can induce new fission reactions (black arrows). Some of the neutrons may be lost in other processes (blue arrows). Red arrows show the delayed neutrons that come later from the radioactive fission fragments and that can induce new fission reactions.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Nuclear_fission_chain_reaction.svg">MikeRun modified by Erin O’Donnell, MSU</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>Controlling the chain reaction was extremely important: If the balance between produced and absorbed neutrons was not exactly right, then the chain reactions either would not proceed at all, or in the other much more dangerous extreme, the chain reactions would multiply rapidly with the release of enormous amounts of energy.</p>
<p>Sometimes, a few seconds after the fission occurs in a nuclear chain reaction, additional neutrons are released. Fission fragments are typically radioactive, and can emit different types of radiation, among them neutrons. Right away, Enrico Fermi, Leo Szilard, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1963/wigner-facts.html">Eugene Wigner</a> and others recognized the importance of these so-called “delayed neutrons” in controlling the chain reaction.</p>
<p>If they weren’t taken into account, these additional neutrons would induce more fission reactions than anticipated. As a result, the nuclear chain reaction in their Chicago experiment could have spiraled out of control, with potentially devastating results. More importantly, however, this time delay between the fission and the release of more neutrons allows some time for human beings to react and make adjustments, controlling the power of the chain reaction so it doesn’t proceed too fast.</p>
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<figcaption>
<span class="caption">Nuclear power plants operate in 30 countries today.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Plant-Vogtle/05d857a8e2c640adacf01d8e0dcf77ca/1/0">AP Photo/John Bazemore</a></span>
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<p>The events of December 2, 1942 marked a huge milestone. Figuring out how to create and control the nuclear chain reaction was the foundation for the 448 nuclear reactors producing energy worldwide today. At present, 30 countries include nuclear reactors in their power portfolio. Within these countries, <a href="https://www.iaea.org/PRIS/CountryStatistics/CountryDetails.aspx?current=US">nuclear energy contributes on average 24 percent</a> of their total electrical power, ranging as high as <a href="https://www.iaea.org/PRIS/CountryStatistics/CountryDetails.aspx?current=FR">72 percent in France</a>.</p>
<p>CP-1’s success was also essential for the continuation of the Manhattan Project and the creation of the <a href="https://www.atomicheritage.org/history/bombings-hiroshima-and-nagasaki-1945">two atomic bombs used during World War II</a>.</p>
<h2>Physicists’ remaining questions</h2>
<p>The quest to understand delayed neutron emission and nuclear fission continues in modern nuclear physics laboratories. The race today is not for building atomic bombs or even nuclear reactors; it’s for understanding of basic properties of nuclei through close collaboration between experiment and theory. </p>
<p>Researchers have observed fission experimentally only for a small number of <a href="http://edtech2.boisestate.edu/lindabennett1/502/atoms_isotopes.html">isotopes</a> – the various versions of an element based on how many neutrons each has – and the details of this complex process are not yet well-understood. State-of-the-art theoretical models try to explain the observed fission properties, like how much energy is released, the number of neutrons emitted and the masses of the fission fragments.</p>
<p>Delayed neutron emission happens only for nuclei that are not naturally occurring, and these nuclei live for only a short amount of time. While experiments have revealed some of the nuclei that emit delayed neutrons, we are not yet able to reliably predict which isotopes should have this property. We also don’t know exact probabilities for delayed neutron emission or the amount of energy released – properties that are very important for understanding the details of energy production in nuclear reactors.</p>
<p>In addition, researchers are trying to <a href="https://science.energy.gov/ascr/highlights/2015/ascr-2015-08-a/">predict new nuclei where nuclear fission might be possible</a>. They’re building new experiments and powerful new facilities which will provide access to nuclei that have never before been studied, in an attempt to measure all these properties directly. Together, the new experimental and theoretical studies will give us a much better understanding of nuclear fission, which can help improve the performance and safety of nuclear reactors.</p>
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<figcaption>
<span class="caption">Artist’s rendition of two merging neutron stars, another situation where fission occurs.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/12740">NASA's Goddard Space Flight Center/CI Lab</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>Both fission and delayed neutron emission are processes that also happen within stars. The <a href="https://theconversation.com/cosmic-alchemy-colliding-neutron-stars-show-us-how-the-universe-creates-gold-86104">creation of heavy elements, like silver and gold</a>, in particular can depend on the fission and delayed neutron emission properties of exotic nuclei. Fission breaks the heaviest elements and replaces them with lighter ones (fission fragments), completely changing the element composition of a star. Delayed neutron emission adds more neutrons to the stellar environment, that can then induce new nuclear reactions. For example, nuclear properties played a vital role in the <a href="https://theconversation.com/why-astrophysicists-are-over-the-moon-about-observing-merging-neutron-stars-84957">neutron-star merger event</a> that was recently discovered by <a href="https://theconversation.com/ligo-announcement-vaults-astronomy-out-of-its-silent-movie-era-into-the-talkies-85727">gravitational-wave and electromagnetic observatories around the world</a>.</p>
<p>The science has come a long way since Szilard’s vision and Fermi’s proof of a controlled nuclear chain reaction. At the same time, new questions have emerged, and there’s still a lot to learn about the basic nuclear properties that drive the chain reaction and its impact on energy production here on Earth and elsewhere in our universe.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/GDUncuEErzQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How the Atomic Age began at UChicago.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/87154/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Artemis Spyrou receives funding from the National Science Foundation and the Department of Energy/National Nuclear Security Administration.</span></em></p><p class="fine-print"><em><span>Wolfgang Mittig receives funding from NSF.</span></em></p>By figuring out fission, physicists were able to split uranium atoms and release massive amounts of energy. This Manhattan Project work paved the way both for atomic bombs and nuclear power reactors.Artemis Spyrou, Associate Professor of Nuclear Astrophysics, Michigan State UniversityWolfgang Mittig, Professor of Physics, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/879462017-11-22T18:01:37Z2017-11-22T18:01:37ZThunderstorms create radioactivity, scientists discover<figure><img src="https://images.theconversation.com/files/195818/original/file-20171122-6072-skhc5p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Maxime Raynal/wikipedia</span></span></figcaption></figure><p>Thunder and lightning have sparked awe and fear in humans since time immemorial. In both modern and ancient cultures, these natural phenomena are often thought to be governed by some of the most important and powerful gods – <a href="http://www.sanatansociety.org/hindu_gods_and_goddesses/indra.htm#.WhVO8bSFhmA">Indra in Hinduism</a>, <a href="https://www.greekmythology.com/Olympians/Zeus/zeus.html">Zeus in Greek mythology</a> and <a href="https://www.ancient.eu/Thor/">Thor in Norse mythology</a>. </p>
<p>We know that thunderstorms can trigger a number of remarkable effects, most commonly power cuts, hailstorms and pets hiding under beds. But it turns out we still have things to learn about them. A new study, <a href="http://nature.com/articles/doi:10.1038/nature24630">published in Nature</a>, has now shown that thunderstorms can also produce radioactivity by triggering nuclear reactions in the atmosphere. </p>
<p>This may sound like the plot of a blockbuster science fiction disaster. But in reality, it’s nothing to worry about. Since the early 20th century, scientists have been aware of <a href="https://theconversation.com/explainer-how-much-radiation-is-harmful-to-health-17906">ionising radiation</a> – particles and electromagnetic waves that can damage cells – raining down into the Earth’s atmosphere from space. This radiation can react with atoms or molecules, carrying enough energy to liberate electrons from either atoms or molecules. It therefore leaves behind an “ion” with a positive electrical charge.</p>
<p>Just over a century ago, the Austrian physicist <a href="https://en.wikipedia.org/wiki/Victor_Francis_Hess">Victor Hess</a> made measurements of ionisation in a hot-air balloon five kilometres above the Earth’s surface. He noted that the ionisation rate increased rapidly with height, the opposite of what might be expected if the source of the ionising radiation was coming from the ground. Hess therefore concluded that there must be a source of radiation with very high penetrating power located above the atmosphere. He was named co-recipient of the <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1936/">Nobel Prize in Physics in 1936</a> for his discovery, later dubbed “cosmic rays”.</p>
<p>We now know that cosmic rays are made up of charged particles: primarily, electrons, atomic nuclei and protons – the latter make up the nucleus along with neutrons. Some originate from the sun, while others come from the <a href="https://theconversation.com/an-extragalactic-mystery-where-do-high-energy-cosmic-rays-come-from-6623">distant explosions of dead stars</a> in our galaxy, known as supernovas. When these cosmic rays enter the Earth’s atmosphere, they interact with atoms and molecules to produce a shower of <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">subatomic particles</a>. Among these are neutrons, which have no electric charge.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=573&fit=crop&dpr=1 754w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=573&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=573&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A simulation of a cosmic ray shower formed when a proton hits the atmosphere about 20km above the ground.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>It is these neutrons that <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">make radiocarbon dating possible</a>. Most carbon atoms have six protons and either six or seven neutrons in their nuclei (dubbed “isotopes <sup>12</sup>C and <sup>13</sup>C” respectively). However, neutrons produced by cosmic rays can react with atmospheric nitrogen to create <sup>14</sup>C, a heavy and unstable isotope of carbon that, over time, will “radioactively decay” (split up while emitting radiation) back into nitrogen. </p>
<p>In nature, <sup>14</sup>C is incredibly rare and makes up only about one in a trillion carbon atoms. But, apart from its weight and radioactive properties, 14C is basically identical to the more common carbon isotopes. It oxidises to form carbon dioxide and enters the food chain as plants absorb the radioactive CO<sub>2</sub>. </p>
<p>The ratio of <sup>12</sup>C to <sup>14</sup>C in a given organism will start to change when that organism dies and ceases to ingest carbon. The <sup>14</sup>C already in its system then starts to decay. It’s a slow process since <sup>14</sup>C has a radioactive half-life of 5,730 years, but it is predictable, meaning that organic samples can be dated by measuring the ratio of <sup>12</sup>C to <sup>14</sup>C still remaining.</p>
<p>In this way, cosmic rays are responsible for nuclear reactions in the Earth’s atmosphere. Until today, we thought it was the only natural channel producing radioactive elements such as <sup>14</sup>C. The word “nuclear”, so sinister when partnered with “bomb” or “waste”, simply refers to the changes that are brought about in an atomic nucleus. </p>
<h2>Chasing neutrons</h2>
<p>Almost 100 years ago, the renowned Scottish physicist and meteorologist <a href="https://en.wikipedia.org/wiki/Charles_Thomson_Rees_Wilson">Charles Wilson</a> proposed that thunderstorms could also trigger nuclear reactions in the atmosphere. Wilson, who undertook fieldwork at the isolated meteorological observatory on the summit of Ben Nevis, Britain’s highest mountain, was fascinated by thundercloud formation and atmospheric electricity. However, his suggestion predated the discovery of the neutron – one of the tell-tale products of nuclear reactions – by seven years, so his proposal could not be tested.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.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">
<figcaption>
<span class="caption">Lightning over the St Lawrence River on a stormy night in Quebec in 2010.</span>
<span class="attribution"><span class="source">Jp Marquis/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Since Wilson’s time, there have been many studies that have claimed to have detected thunderstorm-produced neutrons, but <a href="https://www.nature.com/articles/313773a0">none have proven to be definitive</a>. Others have searched for energetic electomagnetic radiation (X-rays and gamma-rays) that accompanies the avalanche of high-energy electrons that we know is produced by lightning in thunderclouds. Calculations show that these electrons and gamma-rays can knock neutrons out of nitrogen and oxygen in the atmosphere. But although the X-ray and gamma-rays have been observed, there has never been a direct observation of the consequent nuclear reactions taking place in a thunderstorm.</p>
<p>The new study uses a different approach. Instead of searching for the elusive neutrons, the authors rely on other byproducts of the nuclear reactions. If electrons and gamma-rays cause unstable isotopes of nitrogen and oxygen to be formed by nuclear reactions following a lightning stroke, these should decay after a few minutes to form stable isotopes of carbon and nitrogen. </p>
<p>Crucially, this decay produces a particle known as a “positron”, the “<a href="https://theconversation.com/explainer-what-is-antimatter-53414">antimatter</a>” version of the electron. All particles have antimatter versions of themselves – these have the same mass but the opposite charge. When antimatter and matter come in contact, they annihilate in a flash of energy. This is the energy the researchers looked for. Using radiation detectors looking over the Sea of Japan, they observed the unambiguous gamma ray fingerprints of positron-electron annihilation taking place immediately after lightning strikes in low winter thunderclouds. This is clear evidence of nuclear reactions taking place in thunderclouds.</p>
<p>These results are important as they demonstrate a previously unknown source of isotopes in the Earth’s atmosphere. These include <sup>13</sup>C, <sup>14</sup>C and <sup>15</sup>N but future studies may also reveal others, such as isotopes of hydrogen, helium and beryllium. </p>
<p>The findings also have implications for astronomers and planetary scientists.
Other planets within our solar system have thunderstorms in their atmospheres that might contribute to the composition of their atmospheres. One of these planets is Jupiter, which is fittingly also the god of thunder in ancient Roman mythology.</p><img src="https://counter.theconversation.com/content/87946/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Wild receives funding from the Science and Technology Facilities Council (STFC) and the Natural Environment Research Council (NERC). He is a Fellow of the Royal Astronomical Society and a member of the American Geophysical Union. He is currently the Chairman of the STFC Astronomy Grants Panel. </span></em></p>Scientists have finally been able to prove that thunder and lightning drive nuclear reactions.Jim Wild, Professor of Space Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/652842016-09-20T18:13:30Z2016-09-20T18:13:30ZAfrica’s universities can shrug off history and stage science revolutions<figure><img src="https://images.theconversation.com/files/138073/original/image-20160916-6342-1c5hkqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The sky is the limit for African science when universities work together.</span> <span class="attribution"><span class="source">Mohamed Nureldin Abdallah/Reuters</span></span></figcaption></figure><p><em>South Africa’s <a href="https://www.uwc.ac.za/Pages/default.aspx">University of the Western Cape (UWC)</a> has been ranked <a href="http://www.timeslive.co.za/scitech/2016/09/07/Sky-science-sees-University-of-the-Western-Cape-beat-big-names-in-Nature-ranking">number one</a> for Physical Science in Africa by top journal <a href="http://www.nature.com/nature/index.html">Nature</a>. Nico Orce, an associate professor with UWC’s nuclear physics and nuclear astrophysics group, tells The Conversation Africa what lessons there are for other universities on the continent – and why there’s more work to be done.</em></p>
<p><strong>UWC still serves a historically disadvantaged community and is less well-funded than many previously white universities in South Africa. Against this backdrop, what did it take for you, your colleagues and your students to get this far?</strong></p>
<p>Being ranked number one on the continent is strongly linked to the <a href="https://www.ska.ac.za">Square Kilometre Array (SKA)</a> telescope being built in South Africa. A number of UWC’s scientists are very involved in this project. </p>
<p>Smart strategic planning and a real push for funding helped to stimulate the physical sciences at UWC. That energy attracted more and more talented researchers, including post-doctoral candidates. This is a crucial way to speed up transformation: bringing in highly skilled researchers from all over the country and the world to train a new generation of local scientists.</p>
<p><strong>The sciences have had a good year at UWC. Your group is also about to become the first from an African institution to <a href="http://www.netwerk24.com/ZA/Tygerburger/Nuus/uwc-students-on-the-way-to-cern-20160830-2">lead an experiment at CERN</a>, the <a href="https://home.cern/about">European Organisation for Nuclear Research</a>. How did that happen?</strong></p>
<p>When I was finishing my degree in Fundamental Physics back in Spain I convinced some of my friends to attend a summer school at CERN. We asked the professor in charge of international exchange programmes to sign our applications. He told us with malicious pleasure that, “Only the crème de la crème goes to CERN – students from Harvard, Oxford or Cambridge. You come from the University of Granada. I cannot believe you even thought of it.” He wouldn’t sign it, so there went our slight chance of working at CERN.</p>
<p>Since then, I promised myself that one day I would go to CERN through the big door and open it up to the ones behind me: young hopeful students.</p>
<p>That promise came to fruition in September 2013 when our group’s proposal to run an experiment at CERN was approved. Our work, which will finally be conducted in November 2016, involves measuring the nuclear shapes of very rare nuclei. Some of our postgraduates have already received training, and did so well that they were awarded a prestigious CERN fellowship.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138236/original/image-20160919-11108-es00iq.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">UWC students (bottom from left to right) Kenzo Abrahams, Makabata Mokgolobotho and Craig Mehl. They are with CERN employees, including (back, second from left) Professor Maria Garcia Borge.</span>
<span class="attribution"><span class="source">Supplied</span></span>
</figcaption>
</figure>
<p>This experiment will open the doors of CERN to all African institutions. We walked through first. Now others will be able to follow.</p>
<p><strong>Enrolling more women students, as well as those who are not white and those from poor backgrounds, is a huge imperative for South African universities. Are you getting that right in the Physics department?</strong></p>
<p>One of the Physics and Astronomy Department’s highest priorities is to attract and enthuse South African students. We have strong outreach programmes to achieve this. One that I like very much is when we give talks to high school students; those in Grades 10, 11 and 12 who are close to finishing school. Our staff members and postgraduates present examples of the work we do.</p>
<p>It’s especially amazing when one of our postgraduates returns to their own school. You should have heard the eruption when one postgraduate, Sivuyile Xabanisa, told kids at his Khayelitsha high school that he was studying the oldest stars in the universe – and going to Oxford University as part of his training.</p>
<p>We also invite high school groups to events organised at the university. In 2013 <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/2012/haroche-facts.html">Serge Haroche</a> visited our Science Research Open Day. He was the 2012 Nobel Laureate in Physics. The auditorium practically shook with excitement when he handed over a new microscope to pupils from a high school in Wallacedene, a poor area quite close to UWC.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-ipl6CLiLnc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Nobel Laureate Serge Haroche visits the University of the Western Cape.</span></figcaption>
</figure>
<p>Another really valuable initiative has been the MaNus/MatSci programme for Nuclear Science and Material Science. In the same way that the SKA is driving strong growth in astronomy, this Honours and Masters programme is attracting growing numbers of future nuclear physicists. It trains about 25 South African students each year, most of them black and from poor backgrounds. These students are drawn from historically disadvantaged institutions like the universities of Fort Hare, Venda, Limpopo and the North West – and from UWC’s undergraduate programmes.</p>
<p>All of this work and outreach has produced impressive results. Today there are more than 100 postgraduate students in the Physics and Astronomy Department. Most of them are black South Africans from historically disadvantaged backgrounds. </p>
<p><strong>What are the lessons other African institutions’ science faculties and individual departments can learn from UWC’s recent successes?</strong></p>
<p>We need to break history to change things dramatically. And we must do it the South African, or African way – using our own strengths and methods, not adopting European approaches.</p>
<p>Universities need to work harder to make sure women and all races are equally represented in their science classrooms. At UWC we’ve got a number of postgraduate women students who are doing great science, winning awards and raising the bar for everyone. Having women there makes other women realise the door is open for them. In the same way, having postgraduates like Sivuyile Xabanisa visiting schools in poorer communities makes pupils realise they also have a place in science labs. Role models are so important.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138237/original/image-20160919-11090-sfbdlu.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>
<figcaption>
<span class="caption">UWC’s Dr Nico Orce with pupils from Khayelitsha’s Zola High School.</span>
<span class="attribution"><span class="source">Supplied</span></span>
</figcaption>
</figure>
<p>Ultimately, UWC wants to be number one for physical science not just in Africa but in the world. To do that, we cannot constantly fight among ourselves as individual researchers or with other institutions on the continent. The only competition we need is the healthy sort that improves everyone’s performance. </p>
<p>Collaboration is really crucial. UWC applied for about R30 million from country’s the National Research Foundation and its Department of Science and Technology to build a new detector system called <a href="https://www.uwc.ac.za/Faculties/NS/NuclearPhysics/Pages/Gamka.aspx">GAMKA</a>.</p>
<p>The construction will happen at iThemba LABS in Cape Town and involves a consortium of both wealthy and less well resourced universities. We’ll all have to work closely together, with the same aim, to be successful. That’s the key to making African science soar: knowing that if you try to do it alone, you won’t have all the skills or equipment. Together we can lead science worldwide through work done right here on the continent.</p><img src="https://counter.theconversation.com/content/65284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nico Orce receives funding from the National Research Foundation (NRF), the South African-CERN Collaboration (Department of Science and Technology) and the University of the Western Cape.</span></em></p>Collaboration is one of the keys to making African science soar: when the continent’s universities work together, they can produce amazing results.Nico Orce, Associate Professor in the Department of Nuclear Physics and Nuclear Astrophysics, University of the Western CapeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/570442016-04-15T02:00:40Z2016-04-15T02:00:40ZAustralia’s waterbirds are disappearing – but nuclear physics can help save them<figure><img src="https://images.theconversation.com/files/118236/original/image-20160412-21989-1nowvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Straw-necked ibis gather to breed. </span> <span class="attribution"><span class="source">Kate Brandis</span>, <span class="license">Author provided</span></span></figcaption></figure><p>When wetlands flood they become full of life. They are spectacularly beautiful and noisy. There is nothing quite like the sound of a wetland when thousands of birds come together to take advantage of the newly created habitat.</p>
<p>Ibis, spoonbills, egrets, herons, cormorants and pelicans all congregate in large numbers, tens to hundreds of thousands, to breed when wetland conditions are good. These gatherings of birds are spectacular, but a mystery remains: where do they come from, and where do they go?</p>
<p>These questions aren’t trivial. <a href="https://www.ecosystem.unsw.edu.au/content/rivers-and-wetlands/waterbirds/eastern-australian-waterbird-survey">Over the past 30 years waterbird populations have declined</a> as opportunities for breeding have disappeared, mainly <a href="http://www.sciencedirect.com/science/article/pii/S0006320708000451">due to water resource development</a>. </p>
<p>Worldwide, wetlands have been lost or are under threat from water resource development, agricultural development and climate change. In Australia we have <a href="http://link.springer.com/article/10.1023%2FA%3A1008495619951#page-1">lost an estimated 50% of wetlands since European settlement</a>. </p>
<p>The loss of wetlands has serious implications for wildlife. Many species are wetland-dependent throughout their lives while others, such as some species of waterbirds, rely on wetlands as places to breed.</p>
<p>Knowing which wetlands waterbirds use when they aren’t breeding will help us figure out which places we need to protect. So the Centre for Ecosystem Science, UNSW and the Australian Nuclear Science Technology Organisation have developed a new technique to analyse Australian bird feathers using nuclear physics. </p>
<p>Now we want you to <a href="http://feathermap.ansto.gov.au/">send us waterbird feathers</a> so we can build an Australia-wide map of where our waterbirds go. </p>
<h2>High-tech tracking</h2>
<p>Traditional tracking methods such as leg banding and satellite trackers have had limited success and can be expensive. So we looked for a cheaper and more effective method. And what could be easier than collecting bird feathers? </p>
<p>Feathers are made of keratin (the same material as human hair and nails) and as they grow record the diet of the bird in chemical elements. Once fully grown, feathers are inert – they no longer change. </p>
<p>Chemical elements (carbon, nitrogen, hydrogen, oxygen) exist in a number of different forms known as isotopes. Some isotopes of some elements are radioactive, but many elements have stable, non-radioactive isotopes. The relative proportion of different isotopes can be <a href="http://www.pnas.org/content/95/26/15436.full">explicitly linked to a specific location</a>, as has been done for monarch butterflies in North America.</p>
<p>To test whether this could be applied to Australian wetlands and waterbirds I did a pilot study in 2010-11. Widespread flooding in the Murray-Darling Basin resulted in colonial waterbirds breeding at a number of wetlands including the Gwydir wetlands, Macquarie Marshes and Lowbidgee wetlands. These three wetlands are geographically distinct, spread across the Basin from north to south. </p>
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<p>We used feathers from chicks and juveniles, because they are eating food from only the wetland where they were hatched and so provide a unique signature for that wetland. </p>
<p>We tested the feathers using two techniques: one to look at the elemental composition of feathers, and the other to measure the amount of two particular isotopes, carbon-13 and nitrogen-15.</p>
<p>Results from these analyses showed that we were able to distinguish between the three wetland sites based on the elemental composition of the feather and the isotopic composition. </p>
<p>Either technique showed the ability to distinguish between wetland sites. Combined, they should be able to provide greater spatial accuracy in identifying the wetland at which the feather was grown. With the knowledge that wetlands have their own unique elemental and isotopic signature, we are expanding the study nationally. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.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">Sunset at an ibis colony.</span>
<span class="attribution"><span class="source">Kate Brandis</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Building a ‘feather map’</h2>
<p>The Feather Map of Australia is a citizen science project that aims to map the signatures for as many wetlands across Australia as possible. To do this we have asked interested members of the public to collect feathers from their local wetlands and contribute them for analyses. </p>
<p>Once analysed, we will have an isotopic map of wetlands against which we can track waterbird movements. Feathers collected from chicks and birds that don’t move large distances will provide us with a signature for that particular wetland. We can then analyse the feathers of birds that do travel long distances and match the signature in their feathers against those of wetlands, telling us where these birds have been. </p>
<p>The signature will not tell us all the movements a bird has made, but it will tell us where it was when it grew the feather. And this will also give us information about the health of the wetland based on what food the bird has eaten and how long it took to grow the feather.</p>
<p>Knowing the movements of waterbirds helps identify wetlands that are important waterbird habitats. This knowledge can be used to provide information to policymakers and land and water managers for improved water delivery, wetland management and decision-making, and ultimately protect wetlands and waterbirds. </p>
<p><em>Read more on how to <a href="http://feathermap.ansto.gov.au/GetInvolved/index.htm">send feathers to scientists</a> and help build the Feather Map of Australia.</em></p><img src="https://counter.theconversation.com/content/57044/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kate Brandis receives funding from Australia Nuclear Science Technology Organistion and the UNSW.</span></em></p>Bird feathers can tell us a lot about their owners and the places they visit.Kate Brandis, Joint Research Fellow, Centre for Ecosystem Science, UNSW and Australia Nuclear Science Technology Organisation, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/457902015-08-07T16:27:03Z2015-08-07T16:27:03ZWhat has nuclear physics ever given us?<figure><img src="https://images.theconversation.com/files/91172/original/image-20150807-27590-1vvbaay.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/75001512@N00/3242522688/in/photostream/">Joel Kramer</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>This year marks the 103rd anniversary of the birth of nuclear physics, when Ernest Rutherford, Hans Geiger and Ernest Marsden’s experiments at the University of Manchester led them to conclude that atoms consist of tiny, positively-charged nuclei orbited by negatively-charged electrons.</p>
<p>This year is also the 70th anniversary of the first nuclear bomb, dropped on Hiroshima. Though their discoveries led to the harnessing of nuclear energy as a weapon, it should not be forgotten that the purpose of Rutherford, Geiger and Marsden’s experiments, as with much of scientific research, was simply to understand nature. And in this they succeeded, handing us an understanding that has changed forever how we see the fabric of the world, and one which had led to much good, too.</p>
<h2>Nuclear physics, a window on the world</h2>
<p>So much science and technology has followed from the nuclear model of the atom. It spurred Danish physicist <a href="http://www.britannica.com/biography/Niels-Bohr">Niels Bohr</a> to develop the nascent quantum theory into a fully-fledged quantum mechanics that could describe the way atoms worked. That in turn has paved the way for so much of modern technology, not the least of which of course is the silicon chip and computerisation. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91173/original/image-20150807-27582-tukotb.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">Of particle accelerators, big…</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:View_inside_detector_at_the_CMS_cavern_LHC_CERN.jpg">Tighef</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Rutherford’s experiments fired the nuclei of helium atoms at other nuclei, making use of the fact that radioactive decay generates fast <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html">alpha particles</a> to emerge from the nucleus. </p>
<p>To provide much more control, particle accelerators were developed in order to fire the basic building blocks of matter such as alpha particles, protons, or electrons at other objects. They didn’t know it at the time, but this set in motion the entire field of research now known as particle physics. The grandchildren of those first accelerators are devices such as the CERN Large Hadron Collider, at which the Higgs boson was discovered last year, inching us closer to understanding the universe. </p>
<h2>Nuclear understanding permeates everything</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91174/original/image-20150807-27590-1s6fm9t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">…and small particle accelerators too.</span>
<span class="attribution"><span class="source">TV by Sergio Stakhnyk/shutterstock.com</span></span>
</figcaption>
</figure>
<p>A century is a long time in science, and things move quickly. It wasn’t long ago that we all had particle accelerators in our homes – the cathode ray tubes in our televisions. These have been superseded by LCD, LED and plasma displays, which are founded on our development of <a href="https://theconversation.com/the-future-is-bright-the-future-is-quantum-dot-televisions-35765">quantum technologies</a>.<br>
Perhaps the most prevalent application of particle accelerators today is in hospitals in the form of radiotherapy machines for the treatment of cancer. </p>
<p>In addition, Nuclear physics is the key to more or less all diagnostic imaging such as such X-ray, PET, CT, MRI, NMR, SPECT and other techniques that allow us to look inside the body without resorting to the knife. </p>
<p>If you’ve ever benefitted from one of these, thanks are due to many people, not least the nuclear physics pioneers who just wondered “what is this stuff?” and “what if…?”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91177/original/image-20150807-27612-7h8cmh.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">Nuclear science gives us a different view.</span>
<span class="attribution"><span class="source">scan by T-Photo/shutterstock.com</span></span>
</figcaption>
</figure>
<h2>From power stations to carbon dating</h2>
<p>The Hiroshima and Nagasaki bombs, those most infamous uses of nuclear physics, shocked the world 70 years ago. Nuclear processes are extremely energetic and can be manipulated to generate devastating explosive power. Yet the atomic bombs of World War II pale in comparison to the destructive force of modern thermonuclear weapons, which mimic the nuclear reactions taking place in the stars.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=534&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=534&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91176/original/image-20150807-27573-zak3g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=534&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Nuclear power comes in all shapes.</span>
<span class="attribution"><a class="source" href="http://www.geograph.org.uk/photo/1396226">Dave Croker</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Less well-known are the applications of nuclear physics in earth sciences. It’s our grasp of nuclear physics that helps us understand the Earth’s historical temperature record, through studying the ratio of oxygen isotopes in ice cores from Greenland and the Antarctic. Isotope tracking helps us understand the flow of ocean currents, the nature of aquifers in parts of the world where water is scarce, the migration of long-dead human populations, and the geological evolution of the earth as well as what is happening in stars. </p>
<p>It’s hard to disentangle one field of scientific research and place it in isolation. The words we use to isolate one from another are only to help humans categorise them – nature does not see it that way. Nuclear physics is so closely interwoven with so much of science and technology, and the social, cultural impact it has had in the last century, that it is interwoven with everything we know and use – we should be thankful for it, not fear it.</p><img src="https://counter.theconversation.com/content/45790/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Stevenson receives funding from the UK Science and Technology Facilities Council. He is a member of the Green Party.</span></em></p>It’s not just about weapons, nuclear science has changed practically everything around us – for the better.Paul Stevenson, Reader, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/230592014-02-25T12:52:01Z2014-02-25T12:52:01ZWhat Cold War nuclear weapons can tell us about art fraud<figure><img src="https://images.theconversation.com/files/42195/original/f78fjbdv-1392984994.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">'Nope, definitely not a Caravaggio.'</span> <span class="attribution"><a class="source" href="http://www.flickr.com/photos/30835738@N03/7936190234/sizes/l/">International Campaign to Abolish Nuclear Weapons</a></span></figcaption></figure><p>The identification of fakes and forgeries is a basic issue that has always raised controversy. This is unsurprising, of course – the enormous sums garnered by top paintings would turn to dust as soon as a question as to their authenticity arose.</p>
<p>To determine whether a painting is original or not, the expertise of critics and art historians is of course central. They are the only ones who know all the details about the technique of a painter, his or her way of drawing, the colours they used and the typical ideas and subjects represented. </p>
<p>But often forgeries are so good that this kind of analysis reaches an insurmountable wall. And here, science plays a major role.</p>
<p>Nuclear techniques such as <a href="http://www.oxford-instruments.com/businesses/industrial-products/industrial-analysis/xrf">X-ray Fluorescence</a> and <a href="http://www.mrsec.harvard.edu/cams/PIXE.html">Particle Induced X-ray Emission</a> allow us to analyse and reconstruct the exact composition of pigments used by the artist. </p>
<p>These methods are non-destructive and non-invasive, and have almost become a routine tool to help art historians and restorers. Analysis of the different pigments used may reveal that one or more are anachronistic to the alleged date of painting. This would suggest that the artwork may be a fake if the investigated areas have not been previously subjected to pictorial retouching. </p>
<p>But often it is necessary to date a painting with much more accuracy, something only possible with <a href="http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm">radiocarbon dating</a>, using an instrument known as <a href="http://www.ph.surrey.ac.uk/partphys/chapter4/ElectroAcc.html">electrostatic accelerator</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Tandem electrostatic accelerator installed at INFN-LABEC, Florence.</span>
</figcaption>
</figure>
<p>The potential of this is maximised if dating something from the past 70 years or so. This is because there has been an enormous variation in carbon concentration in the atmosphere during this time. Since 1955, the <sup>14</sup>C concentration in the atmosphere started to increase dramatically as a consequence of the many nuclear weapon tests performed in air during the Cold War. </p>
<p>The effect was so significant that the concentration of the substance almost doubled in less than ten years, reaching its maximum in 1963-1965. Then, the <a href="http://www.history.com/this-day-in-history/nuclear-test-ban-treaty-signed">Nuclear Ban Treaty</a> signed in 1963 stopped all the nuclear experiments except those performed underground. The <sup>14</sup>C concentration then started to decrease. </p>
<p>Nowadays, the concentration has almost come back to the typical amount seen in the years before 1955. We usually refer to this trend of radiocarbon concentration as the “Bomb Peak”. All living organisms from 1955 time will have had a <sup>14</sup>C content higher than all the organisms that lived before. So a cotton plant that grew in that period will have had a higher <sup>14</sup>C content than one that didn’t.</p>
<p>And so, if we measure the amount of radiocarbon in a canvas made from that cotton plant we can easily conclude that the canvas was manufactured after 1955. At the Istituto Nazionale di Fisica Nucleare (INFN), we exploited this idea to <a href="http://www.infn.it/comunicazione/index.php?option=com_content&view=article&id=388:physicists-at-the-infn-resolve-the-enigma-of-a-painting-by-leger&catid=38&Itemid=862&lang=it">finally solve an enigma</a> that had remained unresolved for more than 30 years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=758&fit=crop&dpr=1 600w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=758&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=758&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=953&fit=crop&dpr=1 754w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=953&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=953&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The painting thought to belong to the series Contrastes de Formes by F. Léger.</span>
<span class="attribution"><span class="source">Guggenheim Venice</span></span>
</figcaption>
</figure>
<p>In the late 1960s, Peggy Guggenheim bought a painting on canvas that was supposed to be part of the series <a href="http://www.guggenheim.org/new-york/collections/collection-online/artwork/2437">Contrastes de Formes</a>, painted in the period 1913-14 by the French artist <a href="http://www.britannica.com/EBchecked/topic/334999/Fernand-Leger">Fernand Léger</a>. But after some years, the art critic Douglas Cooper questioned the authenticity of the painting. So, even though the artwork was still in the <a href="http://www.guggenheim-venice.it/inglese/default.html">Peggy Guggenheim Collection</a> in Venice, it was never shown to the public. </p>
<p>Thanks to the collaboration with the Guggenheim Museum we dated a small canvas sample taken from the excess fabric around the frame. We measured the radiocarbon concentration, comparing it to the Bomb Peak trend. The result was conclusive: the canvas – or, the cotton plants used to make it – had a high radiocarbon concentration and was dated to 1959 or 1962, at least four years after the death of Léger. </p>
<p>So, nuclear physics proved that the painting was not authentic, nor was it a later copy by Léger himself, as some had suggested. The result of the radiocarbon measurement was unquestionable. This was the first time that the Bomb Peak has been used to discover a forgery of a modern artwork. </p><img src="https://counter.theconversation.com/content/23059/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mariaelena Fedi 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 identification of fakes and forgeries is a basic issue that has always raised controversy. This is unsurprising, of course – the enormous sums garnered by top paintings would turn to dust as soon as…Mariaelena Fedi, Researcher, Italian Institute for Nuclear PhysicsLicensed as Creative Commons – attribution, no derivatives.