tag:theconversation.com,2011:/fr/topics/atoms-2536/articles
Atoms – The Conversation
2023-10-04T01:42:55Z
tag:theconversation.com,2011:article/214907
2023-10-04T01:42:55Z
2023-10-04T01:42:55Z
What is an attosecond? A physical chemist explains the tiny time scale behind Nobel Prize-winning research
<figure><img src="https://images.theconversation.com/files/551866/original/file-20231003-27-fn9thz.jpg?ixlib=rb-1.1.0&rect=10%2C3%2C2295%2C1292&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Work in attosecond physics has led to a better understanding of how electrons move around. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/image-of-an-atomic-structure-consisting-of-protons-royalty-free-image/1337003441?phrase=electron">Oselote/iStock via Getty Images</a></span></figcaption></figure><p>A group of three researchers earned the <a href="https://www.nobelprize.org/uploads/2023/10/popular-physicsprize2023.pdf">2023 Nobel Prize in physics</a> for work that has revolutionized how scientists study the electron – by illuminating molecules with attosecond-long flashes of light. But how long is an attosecond, and what can these infinitesimally short pulses tell researchers about the nature of matter?</p>
<p><a href="https://www.austincollege.edu/aaron-harrison/">I first learned</a> of this area of research as a graduate student in physical chemistry. My doctoral adviser’s group had a project dedicated to studying <a href="http://bromine.cchem.berkeley.edu/atto.htm">chemical reactions with attosecond pulses</a>. Before understanding why attosecond research resulted in the most prestigious award in the sciences, it helps to understand what an attosecond pulse of light is.</p>
<h2>How long is an attosecond?</h2>
<p>“Atto” is the <a href="https://www.nrel.gov/comm-standards/editorial/scientific-notation.html">scientific notation prefix</a> that represents 10<sup>-18</sup>, which is a decimal point followed by 17 zeroes and a 1. So a flash of light lasting an attosecond, or 0.000000000000000001 of a second, is an extremely short pulse of light. </p>
<p>In fact, there are approximately as many attoseconds in one second as there are seconds in the <a href="https://81018.com/universeclock/">age of the universe</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing an attosecond, depicted as an orange collection of hexagons, on the left, with the age of the universe, depicted as a dark vacuum on the right, and a heartbeat, depicted as a human heart, in the middle." src="https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=322&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=322&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551859/original/file-20231003-21-rkpekw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=322&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An attosecond is incredibly small when compared to a second.</span>
<span class="attribution"><a class="source" href="https://www.nobelprize.org/prizes/physics/2023/press-release/">©Johan Jarnestad/The Royal Swedish Academy of Sciences</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Previously, scientists could study the motion of heavier and slower-moving atomic nuclei with <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/femtosecond-laser">femtosecond (10<sup>-15</sup>) light pulses</a>. One thousand attoseconds are in 1 femtosecond. But researchers couldn’t see movement on the electron scale until they could generate attosecond light pulses – electrons move too fast for scientists to parse exactly what they are up to at the femtosecond level.</p>
<h2>Attosecond pulses</h2>
<p>The rearrangement of electrons in atoms and molecules guides a lot of processes in physics, and it underlies practically every part of chemistry. Therefore, researchers have put a lot of effort into figuring out how electrons are moving and rearranging. </p>
<p>However, electrons move around very rapidly in physical and chemical processes, making them difficult to study. To investigate these processes, <a href="https://www.britannica.com/science/spectroscopy">scientists use spectroscopy</a>, a method of examining how matter absorbs or emits light. In order to <a href="https://doi.org/10.1146/annurev-physchem-040215-112025">follow the electrons in real time</a>, researchers need a pulse of light that is shorter than the time it takes for electrons to rearrange. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Vy71bJJ9EnU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Pump-probe spectroscopy is a common technique in physics and chemistry and can be performed with attosecond light pulses.</span></figcaption>
</figure>
<p>As an analogy, imagine a camera that could only take longer exposures, around 1 second long. Things in motion, like a person running toward the camera or a bird flying across the sky, would appear blurry in the photos taken, and it would be difficult to see exactly what was going on. </p>
<p>Then, imagine you use a camera with a 1 millisecond exposure. Now, motions that were previously smeared out would be nicely resolved into clear and precise snapshots. That’s how using the attosecond scale, rather than the femtosecond scale, can illuminate electron behavior. </p>
<h2>Attosecond research</h2>
<p>So what kind of research questions can attosecond pulses help answer?</p>
<p>For one, breaking a chemical bond is a fundamental process in nature where electrons that are shared between two atoms separate out into unbound atoms. The previously shared electrons undergo ultrafast changes during this process, and <a href="https://doi.org/10.1126/science.aax0076">attosecond pulses</a> made it possible for researchers to follow the real-time breaking of a chemical bond. </p>
<p>The <a href="https://doi.org/10.1038/nphys620">ability to generate attosecond pulses</a> – the research for which three researchers earned the <a href="https://www.nobelprize.org/prizes/physics/2023/press-release/">2023 Nobel Prize in physics</a> – first became possible in the early 2000s, and the field has <a href="https://phys.org/news/2010-04-electrons-science-attosecond-scale.html">continued to grow rapidly</a> since. By providing shorter snapshots of atoms and molecules, attosecond spectroscopy has helped researchers understand electron behavior in single molecules, such as how <a href="https://doi.org/10.1038/s41467-022-32313-0">electron charge migrates</a> and how <a href="https://doi.org/10.1063/5.0086775">chemical bonds</a> between atoms break. </p>
<p>On a larger scale, attosecond technology has also been applied to studying how electrons behave in <a href="https://doi.org/10.1126/science.abb0979">liquid water</a> as well as <a href="https://doi.org/10.1038/s42005-021-00635-y">electron transfer in solid-state semiconductors</a>. As researchers continue to improve their ability to produce attosecond light pulses, they’ll gain a deeper understanding of the basic particles that make up matter.</p><img src="https://counter.theconversation.com/content/214907/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aaron W. Harrison 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>
Three scientists won the 2023 Nobel Prize in physics for their work developing methods to shoot laser pulses that only last an attosecond, or a mind-bogglingly tiny fraction of a second.
Aaron W. Harrison, Assistant Professor of Chemistry, Austin College
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/210428
2023-08-04T12:29:16Z
2023-08-04T12:29:16Z
Before he developed the atomic bomb, J. Robert Oppenheimer’s early work revolutionized the field of quantum chemistry – and his theory is still used today
<figure><img src="https://images.theconversation.com/files/541027/original/file-20230803-25-pvmco1.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C2615%2C2031&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">J. Robert Oppenheimer is responsible for a fundamental idea in the field of quantum chemistry. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/87e22879387a45cb8083993acdcbe034?ext=true">AP Photo/John Rooney</a></span></figcaption></figure><p>The release of the film “<a href="https://www.oppenheimermovie.com/">Oppenheimer</a>,” in July 2023, has renewed interest in the enigmatic scientist J. Robert Oppenheimer’s life. While Oppenheimer will always be recognized as the <a href="https://ahf.nuclearmuseum.org/ahf/profile/j-robert-oppenheimer/">father of the atomic bomb</a>, his early contributions to <a href="https://www.livescience.com/33816-quantum-mechanics-explanation.html">quantum mechanics</a> form the bedrock of modern <a href="https://www.sciencedirect.com/topics/chemistry/quantum-chemistry">quantum chemistry</a>. His work still informs how scientists think about the structure of molecules today.</p>
<p>Early on in the film, preeminent scientific figures of the time, including Nobel laureates <a href="https://www.nobelprize.org/prizes/physics/1932/heisenberg/facts/">Werner Heisenberg</a> and <a href="https://www.nobelprize.org/prizes/physics/1939/lawrence/biographical/">Ernest Lawrence</a>, compliment the young Oppenheimer on his groundbreaking work on molecules. As a <a href="https://scholar.google.com/citations?hl=en&pli=1&user=df8z7MQAAAAJ">physical chemist</a>, Oppenheimer’s work on molecular quantum mechanics plays a major role in both my teaching and my research. </p>
<h2>The Born-Oppenheimer approximation</h2>
<p>In 1927, Oppenheimer published a paper called “<a href="https://doi.org/10.1142/9789812795762_0001">On the Quantum Theory of Molecules</a>” with his research adviser <a href="https://www.nobelprize.org/prizes/physics/1954/born/biographical/">Max Born</a>. This paper outlined what is commonly referred to as the Born-Oppenheimer approximation. While the name credits both Oppenheimer and his adviser, most historians recognize that the theory is mostly Oppenheimer’s work.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black-and-white old photo of two men wearing jackets and ties. The one on the right is younger and looking down, in the backround is a blackboard with equations written on it." src="https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541044/original/file-20230803-23-t9qc82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">J. Robert Oppenheimer, on the right, in 1947, speaking to mathematician Oswald Veblen at the Princeton Institute for Advance Study.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/PrincetonOppenheimer1947/cda75d90e0fe4924be9217d9399b34c0/photo?Query=oppenheimer&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=535&currentItemNo=33&vs=true">AP/Anonymous</a></span>
</figcaption>
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<p>The Born-Oppenheimer approximation offers a way to simplify the complex problem of describing molecules at the atomic level.</p>
<p>Imagine you want to calculate the optimum molecular structure, chemical bonding patterns and physical properties of a molecule using <a href="https://www.britannica.com/science/quantum-mechanics-physics">quantum mechanics</a>. You would start by defining the position and motion of all the atomic nuclei and electrons and calculating the important charge attractions and repulsions occurring between these particles in the <a href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Physical_Chemistry_(LibreTexts)/09%3A_Chemical_Bonding_in_Diatomic_Molecules/9.02%3A_The_H_Prototypical_Species">molecule</a>. </p>
<p>Calculating the properties of molecules gets even more complicated at the quantum level, where particles have wavelike properties and scientists can’t pinpoint their exact position. Instead, particles like electrons must be described by a <a href="https://www.britannica.com/science/wave-function">wave function</a>. A wave function describes the electron’s probability of being in a certain region of space. Determining this wave function and the corresponding energies of the molecule is what is known as solving the <a href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Thermodynamics_and_Chemical_Equilibrium_(Ellgen)/18%3A_Quantum_Mechanics_and_Molecular_Energy_Levels/18.04%3A_The_Schrodinger_Equation_for_a_Molecule">molecular Schrödinger equation</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/AR23uxZruhE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Solving the Schrödinger equation lets scientists calculate the properties of a molecule.</span></figcaption>
</figure>
<p>Unfortunately, this equation <a href="https://doi.org/10.1134/S1063779622010038">cannot be solved exactly</a> for even the <a href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Physical_Chemistry_(LibreTexts)/09%3A_Chemical_Bonding_in_Diatomic_Molecules/9.02%3A_The_H_Prototypical_Species">simplest possible molecule, H₂⁺</a>, which consists of three particles: two hydrogen nuclei (or protons) and one electron. </p>
<p>Oppenheimer’s approach provided a means to obtain an approximate solution. He observed that atomic nuclei are significantly heavier than electrons, with a single proton being nearly 2,000 times more massive than an electron. This means nuclei move much slower than electrons, so scientists can think of them as stationary objects while solving the Schrödinger equation solely for the electrons. </p>
<p>This method reduces the complexity of the calculation and enables scientists to <a href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Book%3A_Quantum_States_of_Atoms_and_Molecules_(Zielinksi_et_al)/10%3A_Theories_of_Electronic_Molecular_Structure/10.01%3A_The_Born-Oppenheimer_Approximation">determine the molecule’s wave function</a> with relative ease. </p>
<p>This approximation may seem like a minor adjustment, but the Born-Oppenheimer approximation goes far beyond just simplifying quantum mechanics calculations on molecules. It actually shapes how chemists view molecules and chemical reactions. </p>
<p>When scientists visualize molecules, we usually think of them as a set of fixed nuclei with shared electrons that move between nuclei.
In chemistry class, students typically build “<a href="https://doi.org/10.1021/ed048p407">ball-and-stick</a>” models consisting of rigid nuclei (balls) sharing electrons through a bonding framework (sticks). These models are a direct consequence of the <a href="https://doi.org/10.1007/s002149900049">Born-Oppenheimer approximation</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three images, one on the left showing simple chemistry annotation of a hexagonal benzene ring of C for carbon connected to H for hydrogen. The second image shows the same shape, but with spheres to represent the atoms and sticks to represent bonds." src="https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=184&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=184&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=184&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=231&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=231&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540016/original/file-20230728-24473-tdzlqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=231&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 ball-and-stick model shows nuclei represented by spheres – or balls – with shared electron bonds represented by sticks. This image shows the structure of a benzene molecule.</span>
<span class="attribution"><span class="source">Aaron Harrison</span></span>
</figcaption>
</figure>
<p>The Born-Oppenheimer approximation also influenced how scientists think about chemical reactions. During a chemical reaction, atomic nuclei are not stationary; they rearrange and move. Electron interactions guide the nuclei’s movements by forming an <a href="https://chem.libretexts.org/Courses/University_of_California_Davis/UCD_Chem_107B%3A_Physical_Chemistry_for_Life_Scientists/Chapters/2%3A_Chemical_Kinetics/2.06%3A_Potential_Energy_Surfaces/">energy surface</a>, which the nuclei can move on throughout the reaction. In this way, electrons drive the molecule’s progression through a chemical reaction. Oppenheimer demonstrated that the way electrons behave is the essence of chemistry as a science.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a graph of a chemical reaction, with a molecule arranged one way at the beginning, and another way at the end." src="https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=478&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=478&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540907/original/file-20230802-25-b7ng1i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=478&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Molecules can change structure during a chemical reaction.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Rxn_coordinate_diagram.JPG">Chem540grp1f08/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Computational quantum chemistry</h2>
<p>In the century since the publication of the Born-Oppenheimer approximation, scientists have vastly improved their ability to calculate the chemical structure and reactivity of molecules.</p>
<p>This field, known as computational quantum chemistry, has grown exponentially with the widespread availability of faster, more powerful high-end computational resources. Currently, chemists use computational quantum chemistry for various applications ranging from discovering novel <a href="https://doi.org/10.1016/j.cplett.2021.138723">pharmaceuticals</a> to designing better <a href="https://doi.org/10.1039/D0TC03709E">photovoltaics</a> before ever trying to produce them in the lab. At the core of much of this field of research is the Born-Oppenheimer approximation. </p>
<p>Despite its many uses, the Born-Oppenheimer approximation <a href="https://elliptigon.com/when-born-oppenheimer-fails/">isn’t perfect</a>. For example, the approximation often breaks down in light-driven chemical reactions, such as in the chemical reaction that <a href="https://doi.org/10.1038/nchem.894">allows animals to see light</a>. Chemists are <a href="https://doi.org/10.1098/rsta.2020.0375">investigating workarounds</a> for these cases. Nevertheless, the application of quantum chemistry made possible by the Born-Oppenheimer approximation will continue to expand and improve. </p>
<p>In the future, a new era of <a href="https://www.scientificamerican.com/article/how-quantum-computing-could-remake-chemistry/">quantum computers</a> could make computational quantum chemistry even more robust by performing faster computations on increasingly large molecular systems.</p><img src="https://counter.theconversation.com/content/210428/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aaron W. Harrison 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>
Remember building model molecules with balls and sticks in chemistry class? You have J. Robert Oppenheimer to thank for that, as a quantum chemist explains.
Aaron W. Harrison, Assistant Professor of Chemistry, Austin College
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/185828
2022-07-18T12:27:00Z
2022-07-18T12:27:00Z
When 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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/185828/count.gif" alt="The Conversation" width="1" height="1" />
<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 Richmond
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/184892
2022-07-11T12:30:22Z
2022-07-11T12:30:22Z
What do molecules look like?
<figure><img src="https://images.theconversation.com/files/471251/original/file-20220627-20-ydsy5i.jpg?ixlib=rb-1.1.0&rect=2%2C1%2C782%2C774&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A nanographene molecule imaged by noncontact atomic force microscopy.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Hexabenzocoronene_AFM_2.jpg">Patrik Tschudin/gross3HR/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</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>
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<blockquote>
<p><strong>What do molecules look like? – Justice B., age 6, Wimberley, Texas</strong></p>
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<hr>
<p>A molecule is a group of atoms bonded together. Molecules make up nearly everything around you – your skin, your chair, even your food. </p>
<p>They vary in size, but are extremely small. You can’t see an individual molecule with your eyes or even a microscope. They are 100,000 times smaller than the <a href="https://hypertextbook.com/facts/1999/BrianLey.shtml">width of a hair</a>.</p>
<p>The smallest molecule is made of two atoms stuck together, while a <a href="https://doi.org/10.1126/science.270.5244.1905-a">large molecule</a> can be a combination of 100,000 atoms or more. A molecule can be a repeat of the same atom, such as the oxygen molecules we breathe, or can be made up of a variety of atoms, such as a sugar molecule made of carbon, oxygen and hydrogen. </p>
<p>But what do molecules look like? It all begins with their building blocks: atoms. </p>
<h2>Opposites attract</h2>
<p>The <a href="https://education.jlab.org/atomtour/">particles of matter that make up an atom</a> are not all the same. They can have a positive charge, a negative charge or no charge. Scientists call them protons, electrons and neutrons. </p>
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<img src="https://cdn.theconversation.com/static_files/files/2147/A%CC%81tomo_de_Oro.gif?1656372844">
<figcaption> <span class="caption">A gold atom has a dense center made of 79 protons and 118 neutrons, with a more-spread-out cloud of 79 electrons around it. Illustration created by Galarza Creador.</span></figcaption>
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<p>Neutrons with no charge and protons with a positive charge form the heavy center of the atom. The negatively charged electrons surround this small center.</p>
<p>As atoms approach each other to potentially join and make molecules, the negative electrons in one atom are attracted to the positive protons in the other, and vice versa. Both atoms adjust themselves accordingly.</p>
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<a href="https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a round single atom, top. Below are two atoms stretched into oval shapes, with the positive part of one drawn to the negative part of the other." src="https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=270&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=270&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=270&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471509/original/file-20220629-17-tyb14b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=340&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 an atom is alone, the negative electrons surrounding its center are symmetric. As two atoms approach, the negative electrons of one atom move toward the positive center of the other atom.</span>
<span class="attribution"><span class="source">Christine Helms</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>You can compare it to trying to choose a seat in a classroom. There are some rules. For example, you have to stay in the classroom and you cannot sit on top of someone. Following those rules, you might try to sit next to your friends and far from your enemies. Finding the perfect position so everyone in the class is happy is similar to finding the perfect position for the atoms in a molecule. Sometimes, atoms cannot find a happy arrangement and no molecule is formed.</p>
<h2>Seeing the unseeable</h2>
<p>If molecules are too small to see with your eyes or even a powerful microscope, how do scientists see them? The answer is they have developed special tools to do it.</p>
<p>One tool uses X-rays, which you might know about since doctors use them to see bones in the body. <a href="https://theconversation.com/curious-kids-how-do-x-rays-see-inside-you-85895">X-rays are a type of light that human eyes can’t see</a>, <a href="https://www.amnh.org/research/natural-science-collections-conservation/general-conservation/preventive-conservation/light-ultraviolet-and-infrared">like ultraviolet or infrared light</a>. </p>
<p>When scientists <a href="https://www.sciencemuseum.org.uk/objects-and-stories/chemistry/x-ray-crystallography-revealing-our-molecular-world">shoot X-rays at molecules</a>, some bounce off. Scientists can record these rebounding X-rays and use their patterns to figure out what individual molecules look like. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A scattering of black dots on a white background." src="https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471249/original/file-20220627-22-lv4r5v.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"></a>
<figcaption>
<span class="caption">X-rays that bounce off the atoms in a protein molecule form the black dots in the above image. The location of these dots tells scientists how the atoms are arranged in the molecule.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lysozym_diffraction.png">Del45/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In 1912, one of the <a href="https://doi.org/10.1038/491186a">first molecules seen this way was salt</a> (NaCl) – the molecule that makes up the ingredient we all know and love on french fries.</p>
<p>Scientists have invented other methods to see molecules, too. Similar to how the electrons change their behavior as two atoms come close together, the center of the atom can also change its behavior. A technique called <a href="https://www.jeol.co.jp/en/products/nmr/basics.html">nuclear magnetic resonance</a> detects those changes to the center of the atom and uses them as clues to determine what atoms are close by. </p>
<p>An <a href="https://www.parksystems.com/medias/nano-academy/how-afm-works">atomic force microscope</a> works like a flimsy diving board that shakes when you walk and jump on it. But this diving board is extremely small, so small that a negative charge on the end of it will bend it toward the positive center of an atom. Moving this diving board around and watching how it bends can show the location of atoms in a molecule.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8gCf1sEn0UU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">An animation showing how an atomic force microscope works.</span></figcaption>
</figure>
<p>One more technique scientists have developed to see molecules is called <a href="https://cryoem.slac.stanford.edu/what-is-cryo-em">cyro-electron microscopy</a>. First, scientists freeze molecules to a temperature much colder than snow or ice. Then they shoot electrons at the molecule and collect those that pass through to make an image. <a href="https://theconversation.com/chilled-proteins-and-3-d-images-the-cryo-electron-microscopy-technology-that-just-won-a-nobel-prize-85229">This technique won</a> the <a href="https://www.nobelprize.org/prizes/chemistry/2017/press-release/">Nobel Prize in Chemistry in 2017</a>. </p>
<h2>All shapes and sizes</h2>
<p>So what do molecules look like? They are a grouping of atoms, with the center containing most of the material, while the rest is largely empty space. Each atom has a specific position where it is happy, much like the students in that classroom. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Side by side diagram of a flat molecule and a round molecule." src="https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=315&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=315&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=315&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=396&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=396&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471674/original/file-20220629-21-45b5zt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=396&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Diagrams of the atoms making up the molecules benzene, left, and fullerene, right.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Buckminsterfullerene-perspective-3D-balls.png">Jynto (left) Benjah-bmm27 (right)/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Every molecule is different – some are really different. For example, benzene is flat like a pancake, while fullerene is round like a ball. <a href="http://www.chemspider.com/Chemical-Structure.10338857.html">Penguinone</a> can be drawn to look like a penguin, while other molecules appear to look completely random. But the positions of atoms in a molecule are never random. </p>
<p>While scientists know what a lot of molecules look like, there are some we’re still trying to figure out. Knowing these answers can lead to inventions of new materials and <a href="https://www.mdpi.com/1422-0067/20/11/2783/htm">medicines</a>. </p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/184892/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christine Helms 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>
A physicist explains how atoms arrange themselves into molecules – and how scientists are able to image these tiny bits of matter that make up everything around you.
Christine Helms, Associate Professor of Physics, University of Richmond
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/180231
2022-05-24T12:27:14Z
2022-05-24T12:27:14Z
Nuclear 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 University
Dennis Mücher, Associate Professor of Nuclear Physics, University of Guelph
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/154687
2021-02-10T20:45:08Z
2021-02-10T20:45:08Z
New 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 - Newark
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/132827
2020-06-22T12:16:50Z
2020-06-22T12:16:50Z
What is the slowest thing on Earth?
<figure><img src="https://images.theconversation.com/files/342474/original/file-20200617-94049-47hnes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lasers create colorful light shows at concerts, are used by doctors in surgeries – and are used in scientific laboratories.</span> <span class="attribution"><span class="source">EyeWolf/Getty Images</span></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>What is the slowest thing on Earth? – Jiwon, Brookline, Massachusetts</strong></p>
</blockquote>
<hr>
<p>In the words of the infamous villain, <a href="https://www.imdb.com/title/tt0118655/">Dr. Evil</a>: “Lasers.” </p>
<p>Lasers focus a narrow, directed beam of light on a specific spot, making them a great tool for cutting, burning, welding – or in the case of Dr. Evil, shooting enemies from atop a shark. These activities all produce or require heat. Laser beams travel at the speed of light, more than 670 million miles per hour, making them the fastest thing in the universe.</p>
<p>So how does a laser produce the slowest thing on Earth? </p>
<p>First, it’s important to understand the relationship between an object’s temperature and its speed. The hotter something is, the more energy it has and the faster it moves. Even things that appear to be perfectly still – say, a pen or your notebook – are not. On a microscopic level, the particles they’re made of are moving rapidly. This is even true of living beings.</p>
<p>Let’s use the sloth as an example. If you zoom in on the molecules that make up this famously slow animal’s body, you’ll see them behaving like kids jumping around inside a bounce house. Why? About <a href="https://doi.org/10.2307/1379840">70% of this creature’s body is made up of water</a> and those water molecules are bouncing around at <a href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Map%3A_Physical_Chemistry_(McQuarrie_and_Simon)/18%3A_Partition_Functions_and_Ideal_Gases/18.11%3A_The_Equipartition_Principle">hundreds of miles per hour</a>.</p>
<h2>Laser cooling</h2>
<p>So it might seem surprising that I use bright, intense lasers to cool things down in my lab experiments. <a href="https://scholar.google.com/citations?user=rm6lxY0AAAAJ&hl=en&oi=sra">I am a physicist</a> who is interested in how atoms and molecules behave at the very coldest temperatures. It’s a strange world where quantum mechanics rules. In this realm, particles sometimes behave like waves in the ocean, and believe it or not, can sometimes be in two different places at the same time. </p>
<p>To study this extraordinary behavior, I use lasers to produce clouds of frigid atoms that are the coldest things on Earth – which we call <a href="https://www.britannica.com/science/Bose-Einstein-condensate">Bose-Einstein condensates</a>. When you cool a bunch of atoms down to almost absolute zero, the coldest possible temperature, atoms start to obey quantum mechanics and behave in surprising ways. </p>
<p>Studying ultra-cold atom clouds might provide clues about how other weird materials, <a href="https://theconversation.com/physicists-hunt-for-room-temperature-superconductors-that-could-revolutionize-the-worlds-energy-system-80707">like superconductors</a>, work. Superconductors carry electricity much better than existing materials, so well that they may someday be used to build super high-speed trains.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/340717/original/file-20200609-21208-18v2oum.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In 1995, researchers cooled atoms lower than ever before and created a new state of matter that had been predicted by Albert Einstein. This graphic shows snapshots as the atoms condensed from more spread-out red, yellow and green areas into very dense blue and white areas.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Quantum_Physics;_Bose_Einstein_condensate_(5940505475).jpg#/media/File:Quantum_Physics;_Bose_Einstein_condensate_(5940505475).jpg">NIST/JILA/CU-Boulder</a></span>
</figcaption>
</figure>
<h2>Creating the slowest thing on Earth</h2>
<p>So how exactly do lasers chill out a cloud of atoms? In the lab, we start by shining lasers at atoms of a silvery-white metal called ytterbium. These atoms, which are really hot, are held inside a 1-foot-wide chamber. But after a few seconds under the laser beam, they cool off, slow down and become trapped together in the center of the chamber. </p>
<p>How does this happen? All light, including a laser, is made up of photons, which are packets of energy that are constantly moving. When we shine a laser into our chamber, the atoms collide with streams of photons in the beam and slow down and get colder – like what would happen if you tried running really fast against a strong wind.</p>
<p>These little collisions bring the temperature of the atom cloud down to just a few millionths of a degree above absolute zero. That’s 459 degrees below 0 degrees Fahrenheit.</p>
<p>But that’s still not enough to give this cloud the prize for being the slowest thing on Earth. It takes one last step to make it just a little colder, a technique we physicists call “<a href="https://www.sciencedirect.com/science/article/pii/S1049250X08601019">evaporative cooling</a>.” </p>
<p>First, we capture all the atoms, sometimes using a magnetic field made by running electricity through a wound-up wire. This creates an invisible well that holds the atoms: Picture marbles sitting at the bottom of a bowl. Then we lower the sides of this bowl-shaped force field by decreasing the electric current that runs through the wire. That allows the faster, warmer atoms to zoom out of the “bowl” and escape the trap. </p>
<p>Only the slower atoms are left behind – and they are truly beyond freezing: one-tenth of one-millionth of a degree above absolute zero. The atoms in this cloud move in slow motion: If they traveled in a straight line instead of bouncing around, it would take them an entire hour to travel across a room. For comparison, the molecules in your body could dash across that room in just a fraction of a second.</p>
<p>The atoms in our frigid atom cloud quite literally move at less than a snail’s pace – and that cloud is the slowest thing on Earth.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/132827/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katie McCormick 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>
Physicists can use bright, hot lasers to slow atoms down so much that they measure -459 degrees Fahrenheit.
Katie McCormick, Postdoctoral Scholar of Physics, University of Washington
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/130087
2020-05-14T12:04:36Z
2020-05-14T12:04:36Z
A new type of chemical bond: The charge-shift bond
<figure><img src="https://images.theconversation.com/files/318398/original/file-20200303-66099-zi9ikj.jpg?ixlib=rb-1.1.0&rect=28%2C18%2C3054%2C1960&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A universe of chemical equations.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/science-old-chemistry-laboratory-seamless-pattern-276554942">Nikolayenko Yekaterina/Shutterstock.com</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=171&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=171&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=171&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=215&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=215&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287050/original/file-20190806-84240-i26yzq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=215&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>The Abstract features interesting research and the people behind it.</em></p>
<hr>
<p><a href="https://www.researchgate.net/profile/John_Galbraith">John Morrison Galbraith</a> is an associate professor of chemistry at Marist College who studies chemical bonding, which is the process that holds atoms together to make molecules. </p>
<p><strong>What have you discovered?</strong></p>
<p>Did you take a chemistry course in high school? Did you think it was a boring static field filled with established facts that were determined a long time ago? I’ve done research that shows that the most fundamental of these established “facts,” the nature of the chemical bond, is now being questioned.</p>
<p>You have likely heard of covalent bonds, where electrons are shared between atoms, and ionic bonds, where electrons are completely transferred from one atom to another. But you probably don’t know about a third type of bond, discovered in the early 1990s by <a href="http://yfaat.ch.huji.ac.il/sason/sason.php">Sason Shaik</a> and <a href="http://pagesperso.lcp.u-psud.fr/hiberty/">Philippe Hiberty</a>: <a href="https://doi.org/10.1002/anie.201910085">the charge-shift bond</a>. I began working with them soon after. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=534&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=534&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=534&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=672&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=672&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334505/original/file-20200512-82388-pcsd25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=672&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The three types of chemical bonds. Red indicates electron-rich areas and blue indicates electron-deficient areas. (Top) the covalent bond in the hydrogen molecule showing electron build up in the bonding region between two indivual hydrogen atoms.</span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334506/original/file-20200512-82388-1u9m9z6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The ionic bond in sodium chloride (table salt) showing electron transfer to the chlorine side (right).</span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334507/original/file-20200512-82370-1hqwkkd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The charge-shift bond of the fluorine molecule showing electron depletion in the bonding region.</span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p><strong>What makes a charge-shift bond different?</strong></p>
<p>In charge-shift bonds, electrons are both shared and transferred at the same time. </p>
<p>That might sound a little crazy, but think of it like this: You know those movable walkways at airports? Suppose that for over 100 years, people thought that the only way to get from one point to another was to either stand on the moving walkway or walk alongside it. </p>
<p>Now suppose that someone realized that there is a third way to move: You can stand on the walkway and walk at the same time. The speed at which you move through the airport is not due to standing or walking, but a combination of both. </p>
<p><a href="https://doi.org/10.1038/nchem.327">Along with Shaik, Hiberty</a> and a handful of others around the world, <a href="https://doi.org/10.1021/jp049632o">I</a> <a href="https://doi.org/10.1021/acs.jpca.7b02988">have helped</a> show that charge-shift bonding is a broad phenomenon that happens between a variety of elements from across the periodic table. </p>
<p><strong>What inspired this discovery?</strong></p>
<p>Shaik and Hiberty were calculating the energy required to break a series of bonds using a method called valence bond theory. Chemistry is all about pattern recognition, and all of the bonds they studied fit a well-established pattern, except the bond between two fluorine atoms. Traditionally thought of as a purely covalent bond, this molecule didn’t behave like any other covalent bond. By trying to understand why, Shaik and Hiberty uncovered something completely unique. </p>
<p><strong>Why is it important?</strong></p>
<p>This is the first major change in the way chemists think about bonding in more than 100 years. Chemical bonding is at the heart of chemistry, so changing the way chemists think about bonding will change the entire field. </p>
<p><strong>How are charge-shift bonds applied in the real world?</strong></p>
<p>Synthetic <a href="https://www.ted.com/talks/cathy_mulzer_the_incredible_chemistry_powering_your_smartphone">materials</a> such as <a href="https://cen.acs.org/materials/2-d-materials/Method-irons-2-D-materials/96/i49">computer chips</a>, <a href="https://cen.acs.org/articles/88/i16/Plastic-Logic-Links-Germanys-Merck.html">plastics</a>, <a href="http://cenblog.org/just-another-electron-pusher/2011/09/the-science-of-beauty-cosmetic-chemistry/">cosmetics</a>, <a href="https://cen.acs.org/articles/93/web/2015/03/Motion-Powered-Fabric-Charge-Small.html">textiles</a> and <a href="https://cen.acs.org/articles/93/i43/Revolution-Medicines.html">medicines</a> come from making and breaking chemical bonds. </p>
<p>Therefore, insight into chemical bonding can inspire new materials with properties we have yet to imagine. We are already seeing chemists exploit the properties of charge-shift bonds to speed up chemical reactions and to understand the properties of industrial solvents.</p>
<p><strong>What is the coolest element of your new research?</strong></p>
<p>Chemistry is alive and constantly changing – that’s what first attracted me to the field. Charge-shift bonding challenges something so fundamental to the field that it is largely taken for granted. </p>
<p>The drama of sweeping theory change is in full effect here: The concept was introduced many years ago but not rapidly accepted; over time, diligent work by a handful of believers provided more support for the idea; and now it is gaining <a href="https://www.chemistryworld.com/features/what-is-a-bond/6983.article">widespread acceptance</a> due to verification through alternative <a href="https://doi.org/10.1021/ja053130m">experimental</a> and <a href="https://doi.org/10.1021/acs.jctc.6b00571">theoretical</a> means. </p>
<p>I also find it fascinating that most chemical processes can now be reliably modeled on a computer. I always liked chemistry for the knowledge it provided about how things work on the atomic scale. However, I never felt comfortable playing with beakers and hazardous chemicals. While chemistry is still a predominantly experimental science, today computers can direct those experiments while also providing a place for an experimentally challenged chemist such as myself.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p><img src="https://counter.theconversation.com/content/130087/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cottrell College Science Award for $35,718: Marist College, May 2006 - May 2008.
Merk AAAS Undergraduate Science Research Program Award: Marist College, Summer 2004 - Summer 2005.</span></em></p>
The laws and principles of chemistry seem pretty set in stone. But as a chemist explains, the field is always evolving, including such fundamental principles as what is a chemical bond.
John Morrison Galbraith, Associate Professor of Chemistry, Marist College
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/137467
2020-05-04T12:10:06Z
2020-05-04T12:10:06Z
Will scientists ever be able to shrink and grow stuff?
<figure><img src="https://images.theconversation.com/files/332037/original/file-20200501-42956-8faz6q.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7403%2C6738&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It would be fun to be able to shrink people and objects, but it's something we can only imagine.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/father-holding-superhero-son-flying-on-paper-royalty-free-image/912523752?adppopup=true">Jasmin Merdan/Moment via Getty Images</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">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<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>Will we ever be able to shrink and grow stuff? – Luke, Brookline, Massachusetts</strong></p>
</blockquote>
<hr>
<p>Maybe you’ve seen “<a href="https://www.imdb.com/title/tt0478970/">Ant Man</a>” or “<a href="https://www.imdb.com/title/tt4154796/">Avengers: Endgame</a>,” where people can grow to the size of buildings or shrink down to the “Quantum Realm” and travel through time.</p>
<p>This sounds fun, but unfortunately it can’t happen in real life. To see why, let’s look at how things are put together. </p>
<p>Everything we know of in the universe is made of the same things: atoms. They work similarly to <a href="https://en.wikipedia.org/wiki/Tinkertoy">Tinkertoys</a>, where blocks are connected by rods to make things.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=492&fit=crop&dpr=1 600w, https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=492&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=492&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=618&fit=crop&dpr=1 754w, https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=618&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/332039/original/file-20200501-42956-1yeyf0m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=618&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A cartoon of atoms arranged in a cube, zoomed in 20 million times.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Alpha_po_lattice.jpg">Cadmium/Wikimedia</a></span>
</figcaption>
</figure>
<p>The simplest forms objects take are crystals. You see crystals in your life all the time, from table salt to metals. These crystals are bunches of atoms connected in repeating shapes, like cubes or hexagons. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/331161/original/file-20200428-110738-hc4tq4.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 actual image of a crystal in a hexagonal pattern, taken with a very powerful microscope called a scanning tunneling microscope.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Silicium-atomes.png">Guillaume Baffou/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>If you wanted to grow or shrink something like a crystal, an ant or a person, you’d need to change the distance between the atoms. To shrink something, the distance must get smaller. To grow something, the distance must get larger.</p>
<p>The problem is that the rods connecting the atoms really act like tiny springs: they don’t want to be pushed together, or pulled apart. They want to stay at the same length. This length is so tiny that you could fit a thousand of them inside the width of a single human hair. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=526&fit=crop&dpr=1 754w, https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=526&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/331564/original/file-20200429-51485-1l534n9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=526&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Atoms don’t like to be too close or too far apart.</span>
<span class="attribution"><span class="source">Viviana Rappoccio</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>How much these tiny springs resist pushing or pulling is determined by the electric force, which is a constant of nature. As far as scientists know, the electric force has the same strength everywhere in the universe, for all time. To grow or shrink something, we would have to change the strength of the electric force, which is not possible to the best of our knowledge. </p>
<p>There are a few things in the world that do shrink or grow, but the way they do so is not by shrinking or growing at the atomic level. Usually it involves adding or removing water or something else. Grapes shrink into raisins when they lose water, and sponges expand when they soak up water. </p>
<p>Many cultures throughout history have removed water from the bodies of people who have died, which is <a href="https://www.natgeokids.com/au/discover/history/egypt/how-to-make-a-mummy/">how mummies are made</a>. However, they don’t really shrink all that much. There are also ways to grow or shrink microscopic things like nano-structures by pushing or pulling their atoms together a little bit, but we can’t do the same thing to people, or ants. Sorry, “<a href="https://marvelcinematicuniverse.fandom.com/wiki/Ant-thony">Ant-thony</a>.” </p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/137467/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Salvatore Rappoccio receives funding from the National Science Foundation. </span></em></p>
The movies make it seem like someday we’ll be able to make people and objects grow really big or shrink really small. Whether this will be possible comes down to the smallest of things.
Salvatore Rappoccio, Associate Professor of Physics, University at Buffalo
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/118686
2019-07-09T04:06:42Z
2019-07-09T04:06:42Z
Curious Kids: how does electricity work?
<figure><img src="https://images.theconversation.com/files/282629/original/file-20190704-126340-4zn4a7.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C5129%2C2899&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/77667666@N07/9978795445/in/photolist-gcMWek-pez8WG-L8A5bm-21nigrt-jwk5Ag-dQLt9k-HYoZ2G-23H5Los-pNhV1r-bfuidK-2f6rxmy-92eZzU-5hBxBP-4xMK-DPKH4F-8aN1y4-zKnB7i-58z7y6-4Ucg3d-TrETdG-SycDQ1-ehp14h-qDVqv6-pwEVEt-hCptd1-cbHBBj-92D4mM-iZfPTy-oTxWMm-pqPCHB-7LQ9Db-pHonEm-4AtMPi-dqSYHm-91cVDh-oaoazR-8CQ7eQ-iCkFLY-Bsc8iu-4tyJ5J-7nGoAe-8s9aVu-58yf37-mSxAbX-aVgCr4-aqcUu6-4nRVbY-nFDyeS-Hh6rFj-8u7YXG">Flickr/Tsvetan Bondzhov</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
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<p><strong>How does electricity work? - Edie, age 5.</strong></p>
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<p>Electricity is all around us. Maybe some of the toys you play with run on batteries, which have electricity stored in them. You or your parents are reading this article on a computer, phone or tablet, all of which use electricity. The light bulbs, the television, the traffic lights, cars, aeroplanes – they all run on electricity. Electricity is exciting and important, so I am glad you asked this excellent question.</p>
<h2>Everything is made from atoms</h2>
<p>Everything is made from little tiny things called atoms. They are so small we cannot see them. They are much smaller than chickpeas, rice, ants, and ant eggs. </p>
<p>Because atoms are so small, we need a lot of them to make things. For example, a grain of rice has billions and billions and billions of atoms. Those atoms make up the rice, in the way LEGO pieces make up a LEGO car or house. They atoms click together and hold onto each other.</p>
<p>Even though an atom is extremely small, it is also made from even smaller things.</p>
<p>One of the things that make up the atom is called an “electron”. Electrons have many jobs. Some electrons help the atoms hold onto each other. Scientists call these electrons the “bonding electrons”. Bond means to stick together. </p>
<p>Other electrons just keep running around in the atoms. They are free electrons and they’re always on the move. Sometimes, they can move from one atom to another. </p>
<p>Electricity happens when electrons move from one atom to another. </p>
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<h2>Electricity in the power cable</h2>
<p>So, the story so far: we know there are billions and billions and billions of atoms. There are also billions and billions and billions of electrons in everything around you. A leaf, a plastic cup, your pet - they all have electrons. Some things, like metals, have more free electrons than other things. A plastic cup, for example, doesn’t have as many free electrons.</p>
<p>You probably have a lot of power cables at home. They might be plugged into the TV or computer or a phone charger. Power cables have a <em>huge</em> number of free electrons.</p>
<p>When the free electrons in a power cable move from one atom to another, almost all in the same direction, you get something called an “electric current” running through the power cable.</p>
<p>How do we push the electrons through the cable? Adults do that by plugging the cable into a wall socket.</p>
<p><img width="100%" src="https://media.giphy.com/media/3ohrygAnH3QLVxC3Pq/giphy.gif"></p>
<p>Remember, electricity can be very dangerous and can even kill people, so it’s important that kids just let adults handle the cables and wall sockets.</p>
<p>The socket makes a thing called “voltage”, which is like an invisible force that pushes all the electrons in the same direction down the cable.</p>
<p>Once the cable is plugged into the socket, the socket pushes the electrons inside the cable, like cars moving down lots of lanes in a highway. The electrons inside the cable then keep pushing each other forward (and sometimes back and forth depending on the type of electricity). This creates an electric current inside the cable.</p>
<p>The cables have a kind of jacket (which we call “insulation”) on the outside to keep the electrons moving along the metal safely. These jackets make it safe for us to use electricity by keeping them in the metal.</p>
<h2>But where does electricity come from?</h2>
<p>Electricity comes from power stations - great, big places that can make electricity in different ways. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282195/original/file-20190702-126396-ji9kjz.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">
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<span class="caption">Solar panels on this roof create energy.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/photos/solar-roof-solar-energy-2666770/">RoyBuri/ Pixabay</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>One way is by burning coal. But this way is bad for our environment. Some power stations use the light from the Sun to make electricity, using large solar panels. Or they might use wind, or water to make electricity. These methods are not as bad for our environment. </p>
<p>If you’re interested in learning more about how electricity is made, check out this Curious Kids article over <a href="https://theconversation.com/curious-kids-why-do-we-not-use-the-magnetic-energy-the-earth-provides-to-create-electricity-113205">here</a>. </p>
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<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=754&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>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em> <em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/118686/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sherif A. Tawfik Abbas 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>
Electricity happens when electrons move from one atom to another.
Sherif A. Tawfik Abbas, Research Fellow, RMIT University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/104885
2019-04-25T21:51:09Z
2019-04-25T21:51:09Z
Remote connections? Detangling entanglement in quantum physics
<figure><img src="https://images.theconversation.com/files/268922/original/file-20190412-44818-j8cj8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Entanglement is a "quantum correlation" between the properties of particles.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><a href="https://quantum-journal.org/papers/q-2018-08-06-79/">Quantum computers</a>, <a href="https://www.technologyreview.com/s/613079/theres-a-new-way-to-break-quantum-cryptography/">quantum cryptography</a> and <a href="https://www.forbes.com/sites/arthurherman/2019/03/12/the-quantum-revolution-is-coming-ready-or-not/#13f06520265a">quantum (insert name here)</a> are often in the news these days. Articles about them inevitably refer to <em>entanglement</em>, a property of quantum physics that makes all these magical devices possible. </p>
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<p>
<em>
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Read more:
<a href="https://theconversation.com/seven-common-myths-about-quantum-physics-115029">Seven common myths about quantum physics</a>
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</em>
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<p>Einstein called entanglement “<a href="https://www.sciencemag.org/news/2018/04/einstein-s-spooky-action-distance-spotted-objects-almost-big-enough-see">spooky action at a distance</a>,” a name that has stuck and become <a href="https://books.google.com/ngrams/graph?content=spooky+action+at+a+distance&year_start=1947&year_end=2008">increasingly popular</a>. Beyond just building better <a href="https://www.technologyreview.com/s/612844/what-is-quantum-computing/">quantum computers</a>, understanding and harnessing entanglement is also useful in other ways.</p>
<p>For example, it can be used to make more accurate measurements of <a href="https://theconversation.com/new-detections-of-gravitational-waves-brings-the-number-to-11-so-far-107962">gravitational waves</a>, and to better understand the properties of <a href="https://theconversation.com/how-quantum-materials-may-soon-make-star-trek-technology-reality-86378">exotic materials</a>. It also subtly shows up in other places: I have been studying how atoms bumping into each other become entangled, to understand how this affects the accuracy of atomic clocks.</p>
<p>But what <em>is</em> entanglement? Is there some way to understand this “spooky” phenomenon? I will try to explain it by bringing together two notions from physics: conservation laws and quantum superpositions.</p>
<h2>Conservation laws</h2>
<p><a href="https://www.britannica.com/science/conservation-law">Conservation laws</a> are some of the deepest and most pervasive concepts in all of physics. The law of conservation of energy states that the total amount of energy in an isolated system remains fixed (although it can be converted from electrical energy to mechanical energy to heat, and so on). This law underlies the workings of all of our machines, whether they are steam engines or electric cars. Conservation laws are a kind of accounting statement: you can exchange bits of energy around, but the total amount has to stay the same.</p>
<p><a href="https://www.grc.nasa.gov/www/k-12/airplane/conmo.html">Conservation of momentum</a> (momentum being mass times velocity) is the reason why, when two ice skaters with different masses push off from each other, the lighter one moves away faster than the heavier. This law also underlies the famous dictum that “every action has an equal and opposite reaction.” Conservation of <em>angular</em> momentum is why — going back to ice skaters again — a whirling <a href="https://youtu.be/FmnkQ2ytlO8?t=44">figure skater can spin faster</a> by drawing her arms closer to her body. </p>
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<a href="https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/268923/original/file-20190412-44781-1i5p684.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">France’s Gabriella Papadakis and Guillaume Cizeron demonstrate the effects of conservation laws during the 2019 ISU European Figure Skating Championships in Belarus.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>These conservation laws have been experimentally verified to work across an extraordinary range of scales in the universe, from <a href="https://doi.org/10.1103/PhysRevD.74.104013">black holes in distant galaxies</a> all the way down to the tiniest <a href="http://www.edmcubed.com">spinning electrons</a>. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-new-discovery-of-gravitational-waves-has-black-holes-in-a-spin-78262">A new discovery of gravitational waves has black holes in a spin</a>
</strong>
</em>
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<h2>Quantum addition</h2>
<p>Picture yourself on a nice hike through the woods. You come to a fork in the trail, but you find yourself struggling to decide whether to go left or right. The path to the left looks dark and gloomy but is reputed to lead to some nice views, while the one to the right looks sunny but steep. You finally decide to go right, <a href="https://www.poets.org/poetsorg/poem/road-not-taken">wistfully wondering about the road not taken</a>. In a quantum world, you could have chosen both. </p>
<p>For systems described by quantum mechanics (that is, things that are sufficiently well isolated from heat and external disturbances), the rules are more interesting. Like a spinning top, an electron for example can be in a state where it spins clockwise, or in another state where it spins anticlockwise. Unlike a spinning top though, it can also be in a state that is <em>[clockwise spinning] + [anticlockwise spinning]</em>.</p>
<p><em>The states of quantum systems can be added together and subtracted from each other</em>. Mathematically, the rules for combining quantum states can be described in the same way as the rules for <a href="https://www.youtube.com/watch?v=8QihetGj3pg">adding and subtracting vectors</a>. The word for such a combination of quantum states is a <em>superposition</em>. This is really what is behind strange quantum effects that you may have heard about, such as the double-slit experiment, or particle-wave duality. </p>
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<figcaption><span class="caption">PBS Studios: The Double-Slit Experiment.</span></figcaption>
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<p>Say you decide to force an electron in the <em>[clockwise spinning] + [anticlockwise spinning]</em> superposition state to yield a definite answer. Then the electron randomly ends up either in the <em>[clockwise spinning]</em> state or in the <em>[anticlockwise spinning]</em> state. The odds of one outcome versus the other are easy to calculate (with a <a href="http://www.feynmanlectures.caltech.edu/III_toc.html">good physics book</a> at hand). The intrinsic randomness of this process may bother you if your worldview requires the universe to behave in a <a href="http://www.hawking.org.uk/does-god-play-dice.html">completely predictable</a> way, but … <em>c'est la</em> (experimentally tested) <em>vie</em>.</p>
<h2>Conservation laws and quantum mechanics</h2>
<p>Let’s put these two ideas together now, and apply the law of conservation of energy to a pair of quantum particles.</p>
<p>Imagine a pair of quantum particles (say atoms) that start off with a total of 100 units of energy. You and your friend separate the pair, taking one each. You find that yours has 40 units of energy. Using the law of conservation of energy, you deduce that the one your friend has must have 60 units of energy. As soon as you know the energy of your atom, you immediately also know the energy of your friend’s atom. You would know this even if your friend never revealed any information to you. And you would know this even if your friend was off on the other side of the galaxy at the time you measured the energy of your atom. Nothing spooky about it (once you realize this is just correlation, not causation).</p>
<p>But the quantum states of a pair of atoms can be more interesting. The energy of the pair can be partitioned in many possible ways (consistent with energy conservation, of course). The combined state of the pair of atoms can be in a superposition, for example: </p>
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<p>[your atom: 60 units; friend’s atom: 40 units] + [your atom: 70 units; friend’s atom: 30 units]. </p>
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<p>This is an <em>entangled state</em> of the two atoms. Neither your atom, nor your friend’s, has a definite energy in this superposition. Nevertheless, the properties of the two atoms are correlated because of conservation of energy: their energies always add up to 100 units.</p>
<p>For example, if you measure your atom and find it in a state with 70 units of energy, you can be certain that your friend’s atom has 30 units of energy. You would know this even if your friend never revealed any information to you. And thanks to energy conservation, you would know this even if your friend was off on the other side of the galaxy. </p>
<p>Nothing spooky about it.</p><img src="https://counter.theconversation.com/content/104885/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amar Vutha receives funding from NSERC and the Branco Weiss Fellowship. </span></em></p>
Entanglement is the mysterious relationship between two connected atoms. This relationship is the basis of quantum physics, but what is it exactly?
Amar Vutha, Assistant Professor of Physics, University of Toronto
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/111889
2019-02-19T12:25:43Z
2019-02-19T12:25:43Z
Curious Kids: how does heat travel through space if space is a vacuum?
<figure><img src="https://images.theconversation.com/files/259706/original/file-20190219-43284-gey5nt.jpg?ixlib=rb-1.1.0&rect=171%2C0%2C1731%2C1080&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Venus feels the sun's heat – but how?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/gsfc/7158852717/sizes/l">NASA, SDO, AIA/Flickr. </a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: you or an adult can send them – along with your name, age and town or city where you live – to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our best.</em></p>
<hr>
<blockquote>
<p><strong>How does heat travel through space if space is a vacuum? – Katerina, age ten, Norwich, UK.</strong></p>
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<p>What a great question!</p>
<p>First off, to understand what heat is, you need to know that everything you can touch or see is made up of tiny building blocks called atoms. Atoms are so small that you can’t even see them (except with some <a href="https://motherboard.vice.com/en_us/article/8qxe7z/this-microscope-can-see-down-to-individual-atoms">very special equipment</a>) – yet they make up all the matter in the universe. </p>
<p>If something is hot, it means that its atoms have lots of energy and are bouncing around. If something is cold, its atoms have much less energy and they stay quite still. </p>
<p>It’s true that space is a vacuum, which means that there isn’t much matter floating around out there. Space isn’t a perfect vacuum though. Even if we ignore the big stuff like stars, planets and comets, space is not completely empty. </p>
<p>In fact, the sun is constantly blowing matter, known as the <a href="https://theconversation.com/the-scorching-winds-on-the-surface-of-the-sun-and-how-were-forecasting-them-44098">solar wind</a>, out into our solar system. This is part of what causes the beautiful light display we call the aurora.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-causes-the-northern-lights-111573">Curious Kids: what causes the northern lights?</a>
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<p>But the solar wind isn’t very dense - it has much, much fewer atoms in it than air, for example. This means it can’t carry much heat in it and so it can’t explain how the warmth from the sun reaches Earth. </p>
<p>There are three ways heat can be shared: conduction, convection and radiation. Let’s think about each of these in turn, to discover which one allows heat to travel through space. </p>
<h2>Conduction</h2>
<p>Conduction is what scientists call the transfer of heat through touching. If you touch something warm, heat goes from it to you. If you touch something cold, heat goes from you to it. </p>
<p>Some materials, such as metals, are good conductors. Other materials, such as glass, are poor conductors, and are called insulators.</p>
<p>Heat can also be conducted in more than one step. For example, if you hold a metal spoon in a mug of hot tea, heat will be transferred from the tea to the spoon, and then from the spoon to your hand. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/259704/original/file-20190219-43261-egp8pc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">From tea to you.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/z4Vc76nPVU4">Rawpixel/Unsplash.</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
</figcaption>
</figure>
<p>But we’re not touching the sun (and that’s a good thing too - its surface temperature is over 5,000°C!) and space is a vacuum so there isn’t anything to act as a spoon and conduct the heat. So we can rule out conduction.</p>
<h2>Convection</h2>
<p>Convection is the transfer of heat through the flow of fluids. Both liquids and gases can convect heat. Atoms will flow away from hot regions toward cooler regions, carrying their heat and energy with them. </p>
<p>If you’ve ever been in a bath that has started to go cold, and then turn the hot tap on, you’ll feel the hot water convect from the tap further into the bath. </p>
<p>The hot atoms will then bump into colder atoms, sharing their heat through conduction, until the bath becomes an even temperature. </p>
<p>But because space is a vacuum, there are no liquids or gases to convect heat away from the sun, all the way to Earth. So we can rule out convection.</p>
<h2>Radiation</h2>
<p>Hot bodies of matter such as the sun – and even our own human bodies – give off heat. As the matter’s atoms move and vibrate they give off, or “radiate”, electromagnetic energy – this is called “thermal radiation”. </p>
<p>Electromagnetic energy comes in a range, or spectrum, of types - some of these we can see: they make up the rainbow of “visible light”. Other types that we cannot see exist too, such as the infrared energy our hot bodies radiate and microwave energy we use to cook food.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/259699/original/file-20190219-43284-1xk777n.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">
<figcaption>
<span class="caption">A thermal camera lets you ‘see’ heat, by picking up thermal radiation.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/recording-thermal-camera-people-walking-city-530560630?src=nekPl8osuLlV0eLasLYuXA-3-13">Shutterstock.</a></span>
</figcaption>
</figure>
<p>Unlike conduction and convection, radiation does not need matter to transfer heat. Energy is radiated from the sun, through the vacuum of space at the speed of light. When this energy arrives at Earth, some of it is transferred to the gases in our atmosphere. </p>
<p>Some of it passes through and heats up the atoms on the earth’s surface. Some will even be <a href="https://theconversation.com/how-do-the-chemicals-in-sunscreen-protect-our-skin-from-damage-74355">absorbed by your skin</a>.</p>
<p>The ground soaks up the energy from the sun’s radiation, and this causes it to give off heat, too. Some of this heat is conducted – like when the hot sand on the beach burns your feet in the summer. Some is convected through <a href="https://theconversation.com/seven-spectacular-weather-events-and-what-causes-them-50488">wind and ocean currents</a>, and some of it is radiated back into the <a href="https://theconversation.com/paris-climate-summit-primer-what-are-greenhouse-gases-50947">atmosphere</a>, or even outer space.</p>
<hr>
<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-what-makes-a-shooting-star-fall-111068?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What makes a shooting star fall? - Katelyn, age seven, Adelaide, Australia.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-what-causes-the-northern-lights-111573?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What causes the northern lights? – Ffion, age 6.75, Pembrokeshire, UK.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-how-is-water-made-109434?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How is water made? – Clara, age eight, Canberra, Australia</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/111889/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Case receives funding from the Science and Technology Facilities Council.</span></em></p>
There are three ways heat can be shared: conduction, convection and radiation. Find out which one lets heat travel through space.
Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/106220
2019-02-07T12:28:21Z
2019-02-07T12:28:21Z
Lise 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 University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/86177
2018-12-07T11:39:53Z
2018-12-07T11:39:53Z
Hunting 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>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249332/original/file-20181206-128196-1lo06wp.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">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">
<a href="https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=561&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=561&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=561&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=705&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=705&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249321/original/file-20181206-128202-nxvd3q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=705&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 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 University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/104838
2018-10-22T19:13:46Z
2018-10-22T19:13:46Z
A day to celebrate chemistry’s favorite unit — the mole. But what’s a mole?
<figure><img src="https://images.theconversation.com/files/240889/original/file-20181016-165888-1rbw6m2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mole Day is an unofficial holiday celebrated among chemists on Oct. 23, between 6:02 a.m. and 6:02 p.m. The time and date are derived from Avogadro's number.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/reminder-mole-day-calendar-unofficial-holiday-639554344">Ekaterina_Minaeva/Shutterstock.com</a></span></figcaption></figure><p>On Oct. 23, between 6:02 a.m. and 6:02 p.m., chemists celebrate Mole Day. Mole Day is not a day to celebrate those furry little creatures that live in the ground. Rather, it is a day to celebrate a very important idea in the sub-microscopic world. </p>
<p>In chemistry, the mole is a unit used to talk about atoms. It is similar to other units we use everyday. For example, you might walk into the local doughnut shop and order a dozen doughnuts. In doing so, you know that you will get 12 of these snacks and the clerk knows to give you 12. The dozen unit is simply for convenience in discussing a quantity. </p>
<p>We apply the same idea to discuss quantities of atoms. Why do we not simply talk about dozens of atoms? The reason is because atoms are so small that it doesn’t make sense to do so. Imagine a single grain of table salt. That tiny crystal contains over 1,000,000,000,000,000,000 (one quintillion) atoms. Rather than discussing such a large number of atoms, we can talk more conveniently through the mole unit. A mole of something contains 602,000,000,000,000,000,000,000 or 6.02 x 10²³ of that thing. </p>
<p>So rather than talking about over 1,000,000,000,000,000,000 atoms in the grain of salt, we can express the quantity as around 0.000002 moles of atoms, which is much more convenient.</p>
<p>The number 6.02 x 10²³ is also called Avogadro’s number. Amedeo Avogadro was an Italian physicist. In 1811, he proposed that equal volumes of any gas at the same temperature and pressure contain the same number of atoms (or molecules). The number is named after him to honor his work. Because Oct. 23 is abbreviated as 10/23, chemists use this date to celebrate Mole Day. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/241541/original/file-20181021-105748-xmwdoy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Amedeo Avogadro predicted that equal volumes of different gases would contain the same number of molecules.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/avogadros-hypothesis-balloons-340098266?src=sZ9AiRkhU9H5_ym02VaO2g-1-1">magnetix / Shuterstock.com</a></span>
</figcaption>
</figure>
<h2>How much space does a mole occupy?</h2>
<p>Now just how many is 6.02 x 10²³? How long do you think it would take you to count to a mole? One day? One week? One year? Go ahead, start counting. It would take you around 20,000,000,000,000,000 years. As you can see, very large quantities of atoms take up very little space which gives us an idea of just how tiny they are. Here is another example: One mole of water with all 6.02 x 10²³ molecules of H₂O occupies slightly more than a tablespoon. </p>
<p>So how do those tiny atoms come together to make up the stuff in the world around us? Even though atoms are so small, there is a lot of action going on. Each atom is made up of even smaller particles called electrons. The way those electrons place themselves around the atom lead to properties we can experience and observe. In a metal, the tiny atoms are swimming in a sea of electrons which gives them the ability to conduct heat and electricity. </p>
<p>How about water? The electrons in a molecule of water are arranged so that each water molecule is extremely attracted to the one next to it. Because of this they naturally arrange themselves at the atomic level in ways that have big consequences in the world around us. When water freezes, the molecules arrange in a way that creates a lattice that causes ice to float in liquid water. Why is that so important? Because ice floats, a pond or lake will freeze at the top, but below the entire aquatic ecosystem is able to survive. This is an amazing phenomenon of water. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/241542/original/file-20181021-105773-g2nxfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Atoms are made up of even smaller particles called protons, neutrons and electrons. The arrangement of these particles gives each substance specific properties.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/simplest-atomic-model-hydrogen-carbon-oxygen-1022007508?src=q1VjPFk6YNxYoapF9IhEbA-1-31">Nasky / Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Small atoms with big consequences</h2>
<p>Many other substances adopt their own unique properties due to arrangement of electrons. The propane gas that we use to fuel a gas grill is a gas at room temperature because the molecules are weakly attracted to each other. Unlike water, they don’t really want to be next to each other at all. Consequently, the space between them results in a gaseous state. </p>
<p>Another important gas is oxygen. We need oxygen to live out our lives. Close your eyes and take a deep breath. As you do that, the molecules are whizzing through your nose, into your lungs where about 0.001 moles of oxygen are absorbed into your blood. Those molecules are responsible for helping each cell in your body produce energy so that your eyes can see the words on this page and your brain can think about what they mean, all while keeping your heart beating.</p>
<p>So, if you ever feel like you’re too insignificant to make a difference, just remember that even the smallest of things matter in the grand scheme of things. </p>
<p>Happy Mole Day!</p><img src="https://counter.theconversation.com/content/104838/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 organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Chemists sure know how to party. And here is the proof. On October 23rd they celebrate their hallowed unit: the mole. Find out what that’s all about.
Tara S. Carpenter, Senior Lecturer and General Chemistry Coordinator, University of Maryland, Baltimore County
Gabriella Balaa, Assistant researcher, University of Maryland, Baltimore County
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/100490
2018-08-02T09:59:01Z
2018-08-02T09:59:01Z
Curious Kids: what is fire?
<figure><img src="https://images.theconversation.com/files/230070/original/file-20180731-136679-4urkrl.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/jameswest/5079424994/sizes/l">Westy48/Flickr.</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children of all ages. The Conversation is asking young people to send in questions they’d like an expert to answer. All questions are welcome: find details on how to enter at the bottom.</em> </p>
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<p><strong>What is fire? – Lyra, age seven, Oxford, UK</strong></p>
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<p>Thanks for the question, Lyra. Basically, fire is light and heat that comes from a special kind of chemical reaction, which humans figured out how to make hundreds of thousands of years ago. </p>
<p>To understand how that reaction works, there are a few things that we need to learn about the world around us. Everything that you see and touch is made up of tiny things called atoms. You can think of atoms as really, really small bits of Lego – so small you can’t even see them. </p>
<p>Atoms join together to form molecules, and molecules join together to form the objects we can see and feel in everyday life. For example, wood is mainly made of a type of molecule called <a href="http://www.bbc.co.uk/guides/z2d2gdm">cellulose</a> and each molecule of cellulose is made of atoms called carbon, oxygen and hydrogen.</p>
<p>Now, to see how the chemical reaction works, let’s imagine that you’re living in a cave <a href="https://www.history.com/news/human-ancestors-tamed-fire-earlier-than-thought">400,000 years ago</a>, and that you’re one of the very first people to use fire. </p>
<p>You’re hungry and you want to cook an animal that you caught earlier in the day. On your way back to the cave, you collected some twigs and sticks for your fire. But there’s two other things you need before you can light the fire. You need oxygen – but luckily there’s plenty of that in the air (though you wouldn’t have known about it at the time). And you’ll need some heat to start things burning.</p>
<p>Of course, matches haven’t been invented yet, so instead you quickly rub two sticks together. The rubbing causes friction, which heats up the sticks – like when you rub your hands together fast to warm them up. This heat causes all the molecules in the wood to jiggle around. </p>
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<img alt="" src="https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/230072/original/file-20180731-136670-1pc4i5.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">
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<span class="caption">Where there’s smoke…</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/traditional-way-starting-fire-seen-namibia-603688799?src=kYWAB-T379wXBY8sCVHjvQ-2-46">Shutterstock.</a></span>
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<p>When a part of a stick gets hot enough, the molecules are moving about so much they start to break apart. This is when you start to see smoke. The smoke is all those broken up molecules escaping from the wood as gases.</p>
<p>But you haven’t made fire yet – you need things to get even hotter! So you keep rubbing the sticks together really hard. Eventually, the gas molecules from the wood get so hot they bash into oxygen in the air and join together. When they do that, they make new molecules called water and carbon dioxide. At the same time, they also make heat and light. Well done, you’ve made a flame! You can stop rubbing the sticks together now. </p>
<p>As you put more twigs on your small fire, the heat carries on breaking down the molecules in the wood, and making more gases. These gases catch fire as well. But something else needs to happen before your fire can really grow. When the gases leave the wood you get left with charcoal. Then, as your fire gets even hotter, the charcoal also starts to combine with more oxygen, making even more heat and light. Now things are hot enough to start cooking.</p>
<p>You make your meal, and after a while you run out of fuel for your fire. All the wood and charcoal burns away leaving ash. This is the stuff in the wood that doesn’t burn. Without the light and heat from the fire, there’s nothing to do but go to sleep – but at least you’re not hungry anymore. </p>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
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<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.</em></p>
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<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-how-do-sim-cards-make-a-phone-work-96273?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How do SIM cards make a phone work? – Leo, age 5, Sydney</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-whats-it-like-to-be-a-fighter-pilot-100563?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What’s it like to be a fighter pilot? – Torben, age eight, Sussex, UK</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-if-an-insect-is-flying-in-a-car-while-it-is-moving-does-the-insect-have-to-move-at-the-same-speed-98833?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">If an insect is flying in a car while it is moving, does the insect have to move at the same speed? – Sarah, age 12, Strathfield, Australia</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/100490/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Lorch 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>
Put simply, it’s the outcome of a chemical reaction, which humans learned how to make some 400,000 years ago.
Mark Lorch, Professor of Science Communication and Chemistry, University of Hull
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/85808
2017-10-25T13:34:11Z
2017-10-25T13:34:11Z
Dark matter: The mystery substance physics still can’t identify that makes up the majority of our universe
<figure><img src="https://images.theconversation.com/files/191475/original/file-20171023-1695-1xeghxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Map of all matter – most of which is invisible dark matter – between Earth and the edge of the observable universe.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/planck/multimedia/pia16875.html#.We5FQkzMzdc">ESA/NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The past few decades have ushered in an amazing era in the science of cosmology. A diverse array of high-precision measurements has allowed us to reconstruct our universe’s history in remarkable detail.</p>
<p>And when we compare different measurements – of the <a href="http://earthsky.org/space/video-hubble-constant-rate-expansion-universe">expansion rate of the universe</a>, the patterns of light released in the <a href="http://planck.cf.ac.uk/science/cmb">formation of the first atoms</a>, the <a href="https://www.e-education.psu.edu/astro801/content/l10_p6.html">distributions in space of galaxies and galaxy clusters</a> and the <a href="http://w.astro.berkeley.edu/%7Emwhite/darkmatter/bbn.html">abundances of various chemical species</a> – we find that they all tell the same story, and all support the same series of events.</p>
<p>This line of research has, frankly, been more successful than I think we had any right to have hoped. We know more about the origin and history of our universe today than almost anyone a few decades ago would have guessed that we would learn in such a short time.</p>
<p>But despite these very considerable successes, there remains much more to be learned. And in some ways, the discoveries made in recent decades have raised as many new questions as they have answered.</p>
<p>One of the most vexing gets at the heart of what our universe is actually made of. Cosmological observations have determined the <a href="https://doi.org/10.1051/0004-6361/201525830">average density of matter in our universe</a> to very high precision. But this density turns out to be much greater than can be accounted for with ordinary atoms.</p>
<p>After decades of measurements and debate, we are now confident that the overwhelming majority of our universe’s matter – about 84 percent – is not made up of atoms, or of any other known substance. Although we can feel the gravitational pull of this other matter, and clearly tell that it’s there, we simply do not know what it is. This mysterious stuff is invisible, or at least nearly so. For lack of a better name, we call it “dark matter.” But naming something is very different from understanding it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&rect=79%2C517%2C2119%2C1562&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&rect=79%2C517%2C2119%2C1562&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Astronomers map dark matter indirectly, via its gravitational pull on other objects.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/hubble/science/dark-matter-map.html">NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>For almost as long as we’ve known that dark matter exists, physicists and astronomers have been devising ways to try to learn what it’s made of. They’ve built <a href="https://pandax.sjtu.edu.cn/">ultra-sensitive detectors</a>, <a href="http://lux.brown.edu/LUX_dark_matter/Home.html">deployed in</a> <a href="http://www.xenon1t.org/">deep underground mines</a>, in an effort to measure the gentle impacts of individual dark matter particles colliding with atoms.</p>
<p>They’ve built exotic telescopes – sensitive not to optical light but <a href="https://fermi.gsfc.nasa.gov/">to less familiar gamma rays</a>, <a href="http://www.ams02.org/">cosmic rays</a> and <a href="http://icecube.wisc.edu/">neutrinos</a> – to search for the high-energy radiation that is thought to be generated through the interactions of dark matter particles.</p>
<p>And we have searched for signs of dark matter using incredible machines which accelerate beams of particles – typically protons or electrons – up to the highest speeds possible, and then smash them into one another in an effort to <a href="http://www.tedxnaperville.com/talks/dan-hooper/">convert their energy into matter</a>. The idea is these collisions could create new and exotic substances, perhaps including the kinds of particles that make up the dark matter of our universe.</p>
<p>As recently as a decade ago, most cosmologists – including myself – were reasonably confident that we would soon begin to solve the puzzle of dark matter. After all, there was an ambitious experimental program on the horizon, which we anticipated would enable us to identify the nature of this substance and to begin to measure its properties. This program included the world’s most powerful particle accelerator – <a href="https://home.cern/topics/large-hadron-collider">the Large Hadron Collider</a> – as well as an array of other new experiments and powerful telescopes.</p>
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<a href="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Experiments at CERN are trying to zero in on dark matter – but so far no dice.</span>
<span class="attribution"><a class="source" href="http://cds.cern.ch/record/2229237">CERN</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>But things did not play out the way that we expected them to. Although these experiments and observations have been carried out as well as or better than we could have hoped, the discoveries did not come.</p>
<p>Over the past 15 years, for example, experiments designed to detect individual particles of dark matter have become a million times more sensitive, and yet no signs of these elusive particles have appeared. And although the Large Hadron Collider has by all technical standards performed beautifully, with the exception of the <a href="https://home.cern/topics/higgs-boson">Higgs boson</a>, no new particles or other phenomena have been discovered.</p>
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<a href="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=902&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=902&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=902&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At Fermilab, the Cryogenic Dark Matter Search uses towers of disks made from silicon and germanium to search for particle interactions from dark matter.</span>
<span class="attribution"><a class="source" href="http://vms.fnal.gov/asset/detail?recid=1783766">Reidar Hahn/Fermilab</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>The stubborn elusiveness of dark matter has left many scientists both surprised and confused. We had what seemed like very good reasons to expect particles of dark matter to be discovered by now. And yet the hunt continues, and the mystery deepens.</p>
<p>In many ways, we have only more open questions now than we did a decade or two ago. And at times, it can seem that the more precisely we measure our universe, the less we understand it. Throughout the second half of the 20th century, theoretical particle physicists were often very successful at predicting the kinds of particles that would be discovered as accelerators became increasingly powerful. It was a truly impressive run.</p>
<p>But our prescience seems to have come to an end – the long-predicted particles associated with our favorite and most well-motivated theories have stubbornly refused to appear. Perhaps the discoveries of such particles are right around the corner, and our confidence will soon be restored. But right now, there seems to be little support for such optimism.</p>
<p>In response, droves of physicists are going back to their chalkboards, revisiting and revising their assumptions. With bruised egos and a bit more humility, we are desperately attempting to find a new way to make sense of our world.</p><img src="https://counter.theconversation.com/content/85808/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Hooper 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>
Cosmologists are heading back to their chalkboards as the experiments designed to figure out what this unknown 84 percent of our universe actually is come up empty.
Dan Hooper, Associate Scientist in Theoretical Astrophysics at Fermi National Accelerator Laboratory and Associate Professor of Astronomy and Astrophysics, University of Chicago
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/84562
2017-09-27T23:37:05Z
2017-09-27T23:37:05Z
Why Canada must not be shut out of the neutron technology it invented
<figure><img src="https://images.theconversation.com/files/187641/original/file-20170926-10570-ss0751.jpg?ixlib=rb-1.1.0&rect=23%2C28%2C3194%2C1965&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Chalk River Laboratories in 2012. Canada's role as a world leader in neutron-scattering is at risk because of a failure to invest in infrastructure renewal at the facility.</span> <span class="attribution"><span class="source">THE CANADIAN PRESS/Sean Kilpatrick</span></span></figcaption></figure><p>In the 1950s, physicists at Canada’s Chalk River Laboratories, led by <a href="https://cns-snc.ca/media/history/pioneers/b_brockhouse/bbrockhouse.html">Bertram Brockhouse,</a> developed an important new method that revealed the positions of
atoms and how they move in materials.</p>
<p>With his colleagues, Brockhouse – who would later share a Nobel Prize in Physics for his work – helped create a technique called neutron scattering, and specifically gave birth to <a href="http://www.spectroscopyonline.com/neutron-spectroscopy">neutron spectroscopy.</a></p>
<p>By directing a beam of neutrons at a sample material and measuring how the neutrons ricocheted off the atoms, and how they slowed down and sped up in the process, Brockhouse made it possible to look into materials and understand their atomic architecture and dynamics.</p>
<p>These pioneering neutron-scattering developments, first established at Chalk River’s National Research Universal (NRU) reactor in eastern Ontario and further developed at the McMaster Nuclear Reactor in Hamilton, Ont., were a creation of basic science. </p>
<p>What motivated Brockhouse (who joined the faculty at McMaster University in 1962) and his contemporaries was to understand the possibilities of neutron beam technology.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=725&fit=crop&dpr=1 600w, https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=725&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=725&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=911&fit=crop&dpr=1 754w, https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=911&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/187643/original/file-20170926-10570-1ttfe5s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=911&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bertram Brockhouse won the Nobel Prize for Physics in 1994 for his neutron-scattering discoveries at Chalk River.</span>
<span class="attribution"><span class="source">Creative Commons</span></span>
</figcaption>
</figure>
<p>Today, neutron-scattering is recognized as an essential tool for understanding the structure and dynamics of materials, part of a suite of complementary techniques including <a href="http://photon-science.desy.de/research/students__teaching/primers/synchrotron_radiation/index_eng.html">synchrotron radiation</a> and <a href="https://www.jic.ac.uk/microscopy/intro_EM.html">electron microscopy</a>.</p>
<p>Some 60 years later, the discovery made by scientists at the Chalk River Laboratories is producing major scientific advances and delivering huge economic benefits all over the world.</p>
<p>Canada’s scientific and economic competitors, including the United States, the European Union, Japan, Australia and China, have developed and are making new investments in stand-alone neutron-scattering facilities. They do so frequently with the assistance of the Canadians who still know the technology best.</p>
<p>They are investing billions of dollars to access the information that neutron scattering alone can provide. That will allow them to understand, develop and perfect materials, from superconductors (materials with no electrical resistance) to auto parts, towards improving the quality of life for people everywhere.</p>
<p>Neutron scattering played an important part, for example, in the 1988 discovery of a scientific curiosity called <a href="https://arxiv.org/pdf/1412.7691.pdf">giant magnetoresistance</a>. By 1994, that basic science discovery, later recognized with the 2007 Nobel Prize in Physics, had become the platform of choice for data storage in our computers, tablets and cellphones.</p>
<h2>Future in doubt in Canada</h2>
<p>While neutron scattering continues to grow in importance and Canada enjoys international recognition as its ancestral home, its future here in Canada is nonetheless very much in doubt.</p>
<p>The NRU reactor at Chalk River, where the bulk of Canada’s neutron-scattering work has traditionally been done, <a href="http://ottawacitizen.com/news/politics/historic-nru-reactor-to-close-in-2018">is set to close in March</a>. There’s no foreseeable replacement. </p>
<p>Besides the issue of the cost to operate the NRU reactor as a source of neutron beams — the stated reason for closing the reactor — an underlying truth is that scientific infrastructure requires investment to keep it current.</p>
<p>And the neutron-scattering infrastructure at Chalk River has receded from the forefront for some time due to a lack of consistent renewal. </p>
<p>Canadian scientists have coped by expanding their access to newer, foreign neutron facilities, but there is little doubt that our wonderful legacy in this science, one that brought the Nobel Prize to Canada, has been hollowed out over time.</p>
<p>While neutron scattering is itself more important than ever, the generation of Canadian scientists who inherited and maintained the legacy of neutron scattering has less reason to stay here.</p>
<p>We invented this game, and now we’re on the sidelines.</p>
<h2>A realistic alternative</h2>
<p>McMaster University and the University of Saskatchewan have formed the <a href="http://cins.ca/2017/02/27/canadian-neutron-initiative-goes-public/">Canadian Neutron Initiative</a> because we believe there is both a strong reason to maintain Canada’s proud place in this important field and a practical alternative to make it happen.</p>
<p>Today, the federal government spends more than $100 million annually to operate the NRU reactor at Chalk River. For about a fifth of that cost, we propose that Canada invest strategically in the neutron facilities of our international partners and in exploiting the neutron-scattering capabilities of the <a href="https://mnr.mcmaster.ca/index.php/about">McMaster Nuclear Reactor.</a></p>
<p>This would guarantee Canadian scientists access to neutron-scattering infrastructure to keep our country at the forefront of this key scientific capability until the federal government can consider the larger possibility of building a stand-alone neutron-scattering facility.</p>
<p>Although it started operating in 1959, the McMaster Nuclear Reactor is expected to remain viable for many years, in part due to the fact that it’s a relatively low-power reactor.</p>
<p>Today, McMaster is building a new $9 million facility that will tap neutron beams from its reactor to re-establish some of the work that will be lost at Chalk River. </p>
<h2>Time to increase science spending</h2>
<p>This will not only generate unique and exciting science, but it will also help us buy time during the five to 10 years it would take for Canada to fully establish foreign partnerships and consider a stand-alone neutron source that would compete globally. </p>
<p>And the McMaster Nuclear Reactor has capacity for even greater neutron innovation.</p>
<p>Canada already punches above its weight in international science, but its spending on science is well below its weight. The Canadian Neutron Initiative is proposing an investment that will pay off.</p>
<p>The ability to perform materials research with neutron beams is something that Canadian industrial, government and academic researchers absolutely require to be competitive, and we need it now. </p>
<p>Unless this type of initiative is successful, Canada won’t be.</p><img src="https://counter.theconversation.com/content/84562/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span><a href="mailto:gaulin@mcmaster.ca">gaulin@mcmaster.ca</a> receives funding from NSERC, CFI, ORF. </span></em></p><p class="fine-print"><em><span>John Root is the Executive Director of the Sylvia Fedoruk Canadian Centre for Nuclear Innovation, a wholly owned subsidiary of the University of Saskatchewan, funded by Innovation Saskatchewan, an agency of the Province of Saskatchewan, for a mandate from 2012-2019. John Root is also the Director of the Canadian Neutron Beam Centre, which, prior to 2012, was 35% supported by an NSERC Major Resource Support grant administered by McGill University, to maintain facilities in a state of readiness for access by academic researchers. </span></em></p>
Canada is a world leader in the field of neutron scattering, winning a Nobel Prize in 1994 for its invention. But the looming shutdown of facilities at Chalk River puts us on the sidelines.
Bruce Gaulin, McMaster University
John Root, Executive Director of the Sylvia Fedoruk Canadian Centre for Nuclear Innovation, University of Saskatchewan
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/83744
2017-09-10T23:12:11Z
2017-09-10T23:12:11Z
Science lesson: How anesthetics work, and why xenon’s perfect
<figure><img src="https://images.theconversation.com/files/185278/original/file-20170908-32313-1n0er7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">General anesthetics affect cellular proteins to knock us out. Some do so better than others, especially the noble gas Xenon. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Common wisdom maintains that, because of the myriad effects on the brain, how anesthetic drugs work at the molecular level <a href="http://io9.gizmodo.com/how-does-anesthesia-work-doctors-arent-sure-and-her-1592809615">is a mystery.</a></p>
<p>On the contrary. As a longtime pharmacology researcher, I believe there’s a sufficient body of evidence to certify it’s not so mysterious after all.</p>
<p>First, some information —and a bit of a history lesson — on anesthetics for all the armchair scientists and doctors among us.</p>
<p>General anesthetics are so called because the administered drug is transported via the blood throughout the body, including the brain — the intended target.</p>
<p>The first general anesthetic used clinically was <a href="https://eic.rsc.org/feature/nitrous-oxide-are-you-having-a-laugh/2020202.article">nitrous oxide,</a> a gas synthesized in a research lab in 1772. It’s still known as laughing gas, and in later years, because it could not silence the brain sufficiently, it was useful only for minor surgery.</p>
<p>By the 1800s, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1279690/">William T.G. Morton</a> (1819-1868), a young Boston dentist, was on the hunt for a better anesthetic than nitrous oxide, commonly used then by dentists. </p>
<p>Ether was a liquid compound produced by distilling ethanol and sulfuric acid. It was just a curiosity at the time. But Morton left a bottle of ether open in his living room and passed out. In 1846, he gave the first public demonstration of ether’s effects on a patient undergoing major surgery.</p>
<h2>How it works</h2>
<p>How do general anesthetics like ether work to subdue brain function?</p>
<p>Most are inhaled and administered from pressure tanks. Ether, as a liquid, emits vapours that are inhaled. Another extremely potent liquid anesthetic is propofol, administered intravenously. It was identified <a href="http://www.telegraph.co.uk/culture/music/michael-jackson/10272782/Michael-Jackson-sought-propofol-long-before-death-says-doctor.html">as a major contributor</a> to pop icon Michael Jackson’s death. </p>
<p>Some barbiturates given via IV are useful general anesthetics. Alcohol is another, but it’s too toxic for clinical use.</p>
<p>The process of anesthesia is commonly divided into four stages. </p>
<h2>The four phases of unconsciousness</h2>
<p>Stage 1 is known as induction, the period between the administration of anesthetic and loss of consciousness. </p>
<p>Stage 2 is the excitement stage, the period following loss of consciousness and marked by excited and delirious activity.</p>
<p>Stage 3 is surgical anesthesia. Skeletal muscles relax, vomiting stops if present, respiratory depression and eye movements stop. The patient is ready for surgery. </p>
<p>Stage 4 is overdose, involving severe depression of vital organs that can be lethal. </p>
<h2>Works in worms like it works in humans</h2>
<p>The various compounds that produce anesthesia in human beings do so in all animals, including invertebrates. The response of the earthworm, C. elegans, to the steady administration of anesthetic elicits a progressive depression of function similar to how it works in humans. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185346/original/file-20170909-32313-xxqknn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Earthworms respond just as humans do to anesthetic, becoming slow and uncoordinated before finally passing out.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>There is an initial phase of increased locomotion, followed by uncoordination, and finally immobility. Motion returns quickly when the administration of the anesthetic stops. This shows that optimal nerve cell architecture developed early in the evolution of life on Earth.</p>
<p>But now let’s do a deep dive into what happens at the molecular level. How does the anesthetic molecule obstruct vital molecules or molecule assemblies essential for cell function in order to bring about unconsciousness?</p>
<p>A prevalent <a href="https://paulingblog.wordpress.com/2009/06/04/the-meyer-overton-theory-of-anesthesia/">lipid (fat) theory of anesthetic action</a> had been based on the fact that all anesthetics are “hydrophobic” chemical compounds, meaning they mix with oil but not water. Presumably, they impair brain cell (neuron) function and bring about unconsciousness by dissolving into the fatty cell membranes, thereby disrupting normal cell activity.</p>
<p>I doubted this theory.</p>
<h2>Proteins are critical to understanding anesthesia</h2>
<p>And so 35 years ago, I made the observation that the molecular weights of the different anesthetics were no more than about 350 <a href="https://sizes.com/units/dalton.htm">Daltons,</a> comparable in size to the smaller messenger molecules that activate the utilitarian proteins in cells. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185345/original/file-20170909-27562-3artt6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An artist’s rendering of human cells. Anesthetics do their work when their molecules penetrate the cavity in a cell’s protein, which in turn sets off a neural process that results in sedation.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Functional, vital proteins are the cell’s workhorses. They include receptors that serve to communicate to the cell signals from hormones and other regulators that induce changes in cell activity in a variety of ways, and ion channels that constantly monitor and control the cells’ levels of sodium, potassium and calcium, a process particularly vital for brain cell function.</p>
<p>The proteins are spherical and contain at their cores a cavity lined with hydrophobic parts (those that mix with oil, not water) of the surrounding <a href="http://study.com/academy/lesson/what-are-amino-acids-definition-structure-quiz.html">constituent amino acids</a>, and they accommodate small <a href="https://www.neurogistics.com/the-science/what-are-neurotransmitters">so-called regulator molecules.</a></p>
<p>The cavities are about the same size for all these proteins, but differ from one another only by the types of constituent amino acids both lining and around the cavity.</p>
<h2>Cavity penetration sets off chain of events</h2>
<p>An estimated volume for the cavity reported for one particular type of protein ranged from 853 to 1,566 cubic <a href="http://whatis.techtarget.com/definition/angstrom-angstrom-unit">Angstroms.</a> By way of comparison, the volume of an occupant of the cavity, the epilepsy drug diphenylhydantoin (brand name Dilantin, used to control seizures) was reported as 693 cubic Angstroms — small enough to occupy the cavity, as all anesthetics are.</p>
<p>The penetration into the cavity by the regulator molecule causes the protein to activate an intracellular process, or the opening of an ion channel that, as mentioned, controls the brain cell’s levels of sodium, potassium and calcium. The anesthetic molecule displaces the regulator, normal cell activity ceases and unconsciousness results.</p>
<p><em>Is There a General Anesthesia Receptor?</em> That’s the title of <a href="https://www.ncbi.nlm.nih.gov/pubmed/6263435">a paper I published in 1982.</a> The answer is: Yes, there is a general anesthesia receptor. It’s the crucial central cavity in all vital cell proteins. </p>
<p>The many cellular vital proteins and their small regulator molecules constitute a biological lock-and-key, each lock with its own special key. The anesthetic molecule occupies all locks, thereby obstructing all keys. </p>
<p>Today, it’s generally accepted that proteins are the targets of general anesthetics and that the lipid theory is ancient history.</p>
<h2>So what’s the perfect anesthetic?</h2>
<p>The diverse molecular structures of anesthetics are reflected in their different repertoires of interactions with numerous protein cavities and other cellular entities. That means each anesthetic is unique in how it precisely sedates patients, and has unique side effects.</p>
<p>The ideal anesthetic would have these major characteristics: chemical stability, low flammability, lack of irritation to airway passages, low blood:gas solubility to allow for patients to be sedated and brought out of sedation quickly, minimal cardiovascular and respiratory side effects, minimal effect on brain blood flow and low interactions with other administered drugs.</p>
<p>In the operating room, the agent that ticks all those boxes is the gaseous xenon atom.</p>
<p>Xenon is one of the mono-atomic rare, “noble” gases present in trace amounts in the atmosphere. The others are helium, neon, argon, krypton and radon. They are inert, meaning they have extremely low chemical reactivity.</p>
<p>Xenon’s sole interaction with biological tissue is the occupation of protein cavities. </p>
<p>The xenon atom is like a smooth, round billiard ball and has no exchangeable electrons and no appendages, i.e. additional atoms, to engage other cellular entities. In contrast, other anesthetics are comprised of multiple atoms, all of which express reactive electrons, a feature that accounts for many of their side effects. The xenon atom literally just rolls into a protein.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=604&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=604&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185382/original/file-20170910-32284-f12igi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=604&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The structure of a brain neuron. Anesthetics diffuse into the cell body to inhibit vital proteins, thereby silencing both the transmitting and receiving neurons.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>The gas is unique. Side effects are almost non-existent. </p>
<p>Inhaled, blood-borne xenon permeates body tissues harmlessly until it engages a protein pocket, where it becomes entrapped. The amino acids lining the cavity then form a tight bond with xenon.</p>
<h2>Xenon: A noble gas, a noble anesthetic</h2>
<p>As a result, xenon shuts out the physiological activator molecule, leading to the shutdown of the vital protein and, thus, impairment of cell function. All of that amounts to a safely and efficiently unconscious patient.</p>
<p>So why isn’t xenon the anesthetic of choice for surgery in general? </p>
<p>A chief factor is <a href="https://www.ncbi.nlm.nih.gov/pubmed/10526826">its steep pricetag.</a> There have been attempts to overcome that hurdle by, for example, installing devices to recover the exhaled xenon in the operating room atmosphere after it’s been administered to a patient; xenon recycling, so to speak. </p>
<p>That’s a challenge. The next formidable challenge in our understanding of anesthetics is figuring out which vital proteins in which brain neurons — among the billions of neurons — are silenced in turn with progressively deeper anesthesia. </p>
<p>But, optimistically, that can be the subject of a future science lesson.</p><img src="https://counter.theconversation.com/content/83744/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frank LaBella during his career has received research funds and salary support from several government and public granting bodies.</span></em></p>
How do anesthetics work, and what makes for an ideal anesthetic? It’s not as mysterious as once believed, and there’s a gas that ticks all the boxes for a perfect anesthetic: xenon.
Frank LaBella, Professor Emeritus, Department of Pharmacology and Therapeutics, University of Manitoba
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/82601
2017-08-24T14:06:12Z
2017-08-24T14:06:12Z
How to store data on magnets the size of a single atom
<figure><img src="https://images.theconversation.com/files/183289/original/file-20170824-25612-fy7mwk.png?ixlib=rb-1.1.0&rect=24%2C247%2C1193%2C845&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Magnetism is useful in many ways, and the magnetic memory effect appears even at the atomic level.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PSM_V83_D111_Force_flow_of_a_magnetized_steel_sphere.png">Popular Science Monthly</a></span></figcaption></figure><p>There is an adage that says that data will expand to fill all available capacity. Perhaps ten or 20 years ago, it was common to stockpile software programs, MP3 music, films and other files, which may have taken years to collect. In the days when hard disk drives offered a few tens of gigabytes of storage, running out of space was almost inevitable.</p>
<p>Now that we have fast broadband internet and think nothing of downloading a 4.7 gigabyte DVD, we can amass data even more quickly. Estimates of the total amount of data held worldwide are to rise from <a href="https://www.emc.com/leadership/digital-universe/2014iview/executive-summary.htm">4.4 trillion gigabytes in 2013 to 44 trillion gigabytes by 2020</a>. This means that we are generating an average of 15m gigabytes per day. Even though hard disk drives are now measured in thousands of gigabytes rather than tens, we still have a storage problem.</p>
<p>Research and development is focused on developing new means of data storage that are more dense and so can store greater amounts of data, and do so in a more energy efficient way. Sometimes this involves updating established techniques: recently IBM announced a <a href="https://www.theverge.com/2017/8/2/16074568/ibm-330-terabytes-record-uncompressed-data-cartridge-cartridge-tape">new magnetic tape technology</a> that can store 25 gigabytes per square inch, a new world record for the 60-year-old technology. While current magnetic or solid-state consumer hard drives are more dense at around <a href="http://www.computerworld.com/article/3030642/data-storage/flash-memorys-density-surpasses-hard-drives-for-first-time.html">200 gigabytes per square inch</a>, magnetic tapes are still frequently used for data back-up. </p>
<p>However, the cutting edge of data storage research is working at the level of individual atoms and molecules, representing the ultimate limit of technological miniaturisation. </p>
<h2>The quest for atomic magnets</h2>
<p>Current magnetic data storage technologies – those used in traditional hard disks with spinning platters, the standard until a few years ago and still common today – are built using “top-down” methods. This involves making thin layers from a large piece of ferromagnetic material, each containing the many <a href="https://www.nde-ed.org/EducationResources/HighSchool/Magnetism/magneticdomain.htm">magnetic domains</a> that are used to hold data. Each of these magnetic domains is made of a large collection of magnetised atoms, whose magnetic polarity is set by the hard disk’s read/write head to represent data as either a binary one or zero.</p>
<p>An alternative “bottom-up” method would involve constructing storage devices by placing individual atoms or molecules one by one, each capable of storing a single bit of information. Magnetic domains retain their magnetic memory due to communication between groups of neighbouring magnetised atoms.</p>
<p>Single-atom or single-molecule magnets on the other hand do not require this communication with their neighbours to retain their magnetic memory. Instead, the memory effect arises from quantum mechanics. So because atoms or molecules are much, much smaller than the magnetic domains currently used, and can be used individually rather than in groups, they can be packed more closely together which could result in an enormous increase in data density.</p>
<p>Working with atoms and molecules like this is not science fiction. Magnetic memory effects in single-molecule magnets (SMMs) were <a href="http://dx.doi.org/10.1038/365141a0">first demonstrated in 1993</a>, and <a href="http://dx.doi.org/10.1126/science.aad9898">similar effects for single-atom magnets</a> were shown in 2016. </p>
<h2>Raising the temperature</h2>
<p>The main problem standing in the way of moving these technologies out of the lab and into the mainstream is that they do not yet work at ambient temperatures. Both single atoms and SMMs require cooling with liquid helium (at a temperature of –269°C), an expensive and limited resource. So research effort over the last 25 years has concentrated on raising the temperature at which <a href="https://www.doitpoms.ac.uk/tlplib/ferromagnetic/hysteresis.php">magnetic hysteresis</a> – a demonstration of the magnetic memory effect – can be observed. An important target is –196°C, because this is the temperature that can be achieved with liquid nitrogen, which is abundant and cheap.</p>
<p>It took 18 years for the first substantive step towards raising the temperature in which magnetic memory is possible in SMMs – an increase of 10°C <a href="http://dx.doi.org/10.1021/ja206286h">achieved by researchers in California</a>. But now our research team at the University of Manchester’s School of Chemistry have <a href="http://dx.doi.org/10.1038/nature23447">achieved magnetic hysteresis in a SMM at –213 °C</a> using a new molecule based on the rare earth element dysprosocenium, as reported in a letter to the journal Nature. With a leap of 56°C, this is only 17°C away from the temperature of liquid nitrogen.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2laKpYWIa5I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Future uses</h2>
<p>There are other challenges, however. In order to practically store individual bits of data, molecules must be fixed to surfaces. This has been <a href="http://dx.doi.org/10.1038/nmat2374">demonstrated with SMMs in the past</a>, but not for this latest generation of high-temperature SMMs. On the other hand, <a href="http://dx.doi.org/10.1126/science.aad9898">magnetic memory in single atoms</a> has already been demonstrated on a surface.</p>
<p>The ultimate test is demonstration of writing and non-destructively reading data in single atoms or molecules. This was achieved for the first time in 2017 by a group of researchers at IBM who demonstrated the <a href="http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/single-atom-serves-as-worlds-smallest-magnet-and-data-storage-device">world’s smallest magnetic memory storage device</a>, built around a <a href="http://dx.doi.org/10.1038/nature21371">single atom</a>.</p>
<p>But regardless of whether single-atom or single-molecule storage devices ever become truly practical, the advancements in fundamental science being made along this path are phenomenal. The synthetic chemistry techniques developed by groups working on SMMs now allow us to design molecules with customised magnetic properties, which will have applications in quantum computing and even magnetic resonance imaging.</p><img src="https://counter.theconversation.com/content/82601/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Nicholas Chilton receives funding from the EPSRC, the Ramsay Memorial Trust and the University of Manchester.</span></em></p>
Work to develop a single-atom magnet that works at room temperature has just taken a big leap forward.
Nicholas Chilton, Research Fellow - School of Chemistry, University of Manchester
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/81122
2017-07-24T08:06:31Z
2017-07-24T08:06:31Z
Booze in space: how the universe is absolutely drowning in the hard stuff
<figure><img src="https://images.theconversation.com/files/179195/original/file-20170721-18128-14pw7he.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mine's a Star-opramen. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/retro-astronaut-mug-beer-pop-art-486571996?src=GRArIRYoATk-qqeZn7VeGg-1-7">Studioloks</a></span></figcaption></figure><p>A cold beer on a hot day or a whisky nightcap beside a coal fire. A well earned glass can loosen your thinking until you feel able to pierce the mysteries of life, death, love and identity. In moments like these, alcohol and the cosmic can seem intimately entwined. </p>
<p>So perhaps it should come as no surprise that the universe is awash with alcohol. In the gas that occupies the space between the stars, the hard stuff is almost all-pervasive. What is it doing there? Is it time to send out some big rockets to start collecting it?</p>
<p>The chemical elements around us reflect the history of the universe and the stars within it. Shortly after the Big Bang, protons were formed throughout the expanding, cooling universe. Protons are the nuclei of hydrogen atoms and building blocks for the nuclei of all the other elements. </p>
<p>These have mostly been manufactured since the Big Bang through nuclear reactions in the hot dense cores of stars. Heavier elements such as lead or gold are only fabricated in rare massive stars or incredibly explosive events. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=835&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=835&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=835&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1050&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1050&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1050&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ethanol molecule.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Ethanol-3D-balls.png#/media/File:Ethanol-3D-balls.png">Wikimedia</a></span>
</figcaption>
</figure>
<p>Lighter ones such as carbon and oxygen are synthesised in the life cycles of very many ordinary stars – including our own sun eventually. Like hydrogen, they are among the most common in the universe. In the vast spaces between the stars, <a href="https://ay201b.wordpress.com/2011/04/12/course-notes/">typically</a> 88% of atoms are hydrogen, 10% are helium and the remaining 2% are chiefly carbon and oxygen.</p>
<p>Which is great news for booze enthusiasts. Each molecule of ethanol, the alcohol that gives us so much pleasure, includes nine atoms: two carbon, one oxygen and six hydrogen. Hence the chemical symbol C₂H₆O. It’s as if the universe turned itself into a monumental distillery on purpose. </p>
<h2>Interstellar intoxication</h2>
<p>The spaces between stars are known as the interstellar medium. The famous Orion Nebula is perhaps the best known example. It is the closest region of star formation to Earth and visible to the naked eye – albeit still more than 1,300 light years away. </p>
<p>Yet while we tend to focus on the colourful parts of nebulae like Orion where stars are emerging, this is not where the alcohol is coming from. Emerging stars produce intense ultraviolet radiation, which destroys nearby molecules and makes it harder for new substances to form. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=587&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=587&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=587&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=737&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=737&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=737&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Orion Nebula.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Orion_Nebula#/media/File:Orion_Nebula_-_Hubble_2006_mosaic_18000.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>Instead you need to look to the parts of the interstellar medium that appear to astronomers as dark and cloudy, and only dimly illuminated by distant stars. The gas in these spaces is <a href="http://casswww.ucsd.edu/archive/public/tutorial/ISM.html">extremely cold</a>, slightly less than -260°C, or about 10°C above absolute zero. This makes it very sluggish. </p>
<p>It is also fantastically widely dispersed. At sea level on Earth, by my calculations there are roughly 3x10<sup>25</sup> molecules per cubic metre of air – that’s a three followed by 25 zeros, an enormously huge number. At passenger jet altitude, circa 36,000ft, the density of molecules is about a third of this value – say 1x10<sup>25</sup>. We would struggle to breathe outside the aircraft, but that’s still quite a lot of gas in absolute terms. </p>
<p>Now compare this to the dark parts of the interstellar medium, where there are typically 100,000,000,000 particles per cubic metre, or 1x10<sup>11</sup>, and often much less than even that. These atoms seldom come close enough to interact. Yet when they do, they can form molecules less prone to being blown apart by further high-speed collisions than when the same thing happens on Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.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">The proof is out there.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/very-bright-white-star-named-procyon-412689028?src=sMN_naWxfUHYuErfk0iKOQ-2-44">Tragoolchitr Jittasaiyapan</a></span>
</figcaption>
</figure>
<p>If an atom of carbon meets an atom of hydrogen, for instance, they can stick together as a molecule called <a href="https://link.springer.com/referenceworkentry/10.1007%2F978-3-642-11274-4_1807">methylidyne</a> (chemical symbol CH). Methylidyne is highly reactive and so is quickly destroyed on Earth, but it is common in the interstellar medium. </p>
<p>Simple molecules like these are more free to encounter other molecules and atoms and slowly build up more complex substances. Sometimes molecules will be destroyed by ultraviolet light from distant stars, but this light can also turn particles into slightly different versions of themselves called <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/bonding/ionic_bondingrev1.shtml">ions</a>, thereby slowly expanding the range of molecules that can form. </p>
<h2>Soot and fire water</h2>
<p>To make a nine-atom molecule such as ethanol in these cool and tenuous conditions might still take an extremely long time – certainly much longer than the seven days you might ferment home brew in the attic, let alone the time it takes to walk to the liquor store. </p>
<p>But there is help at hand from other simple organic molecules, which start sticking together to form grains of dust, something like soot. On the surfaces of these grains, chemical reactions take place much more rapidly because the molecules get held in proximity to them. </p>
<p>It is therefore cool sooty regions, the potential stellar birthplaces of the future, that encourage complex molecules to appear more quickly. We can tell from the distinctive spectrum lines of different particles in these regions that there is water, carbon dioxide, methane and ammonia – but also plenty of ethanol. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=693&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=693&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=693&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=871&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=871&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=871&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Room for more!</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/almost-empty-beer-glass-isolated-on-453410167?src=zWSyEpcHcissj_TKI0sNcA-1-76">Africa Studio</a></span>
</figcaption>
</figure>
<p>Now when I say plenty, you have to bear in mind the vastness of the universe. And we are still only <a href="http://adsabs.harvard.edu/doi/10.1086/168830">talking about</a> roughly one in every 10m atoms and molecules. Suppose you could travel through interstellar space holding a pint glass, scooping up only alcohol as you moved. To collect enough for a pint of beer you would have to travel about half a million light years – much further than the size of our Milky Way. </p>
<p>In short, there are mind-bogglingly vast quantities of alcohol in outer space. But since it is dispersed over truly enormous distances, the drinks companies can rest easy. It will be a cold day on the sun before we figure out how to collect any of it, I’m sorry to say.</p><img src="https://counter.theconversation.com/content/81122/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander MacKinnon 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>
It’s like one great big distillery up there.
Alexander MacKinnon, Senior Lecturer, Astrophysics, University of Glasgow
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/80430
2017-07-17T13:34:37Z
2017-07-17T13:34:37Z
How giant atoms may help catch gravitational waves from the Big Bang
<figure><img src="https://images.theconversation.com/files/176885/original/file-20170705-30047-1sugg2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some of the earliest known galaxies in the universe, seen by the Hubble Space Telescope.</span> <span class="attribution"><span class="source">NASA/ESA</span></span></figcaption></figure><p>There was a lot of excitement last year when the LIGO collaboration <a href="https://theconversation.com/explainer-gravitational-waves-and-why-their-discovery-is-such-a-big-deal-53239">detected gravitational waves</a>, which are ripples in the fabric of space itself. And it’s no wonder – it was one of the most important discoveries of the century. By measuring gravitational waves from intense astrophysical processes like merging black holes, the experiment opens up a completely new way of observing and understanding the universe.</p>
<p>But there are limits to what LIGO can do. While gravitational waves exist with a big variety of frequencies, LIGO can only detect those within a certain range. In particular, there’s no way of measuring the type of high frequency gravitational waves that were <a href="https://theconversation.com/gravitational-waves-offer-glimpse-into-the-past-but-will-we-ever-catch-ripples-from-the-big-bang-54855">generated in the Big Bang</a> itself. Catching such waves would revolutionise cosmology, giving us crucial information about how the universe came to be. <a href="https://arxiv.org/abs/1702.03905">Our research</a> presents a model that may one day enable this.</p>
<p>In the theory of general relativity developed by Einstein, the mass of an object curves space and time – the more mass, the more curvature. This is similar to how a person stretches the fabric of a trampoline when stepping on it. If the person starts moving up and down, this would generate undulations in the fabric that will move outwards from the position of the person. The speed at which the person is jumping will determine the frequency of the generated ripples in the fabric.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108310/original/image-20160115-7368-1hr8sts.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Trampolines: fun and educational.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/en/trampoline-children-playing-infant-241899/">cotrim/pixabay</a></span>
</figcaption>
</figure>
<p>An important trace of the Big Bang is the Cosmic Microwave Background. This is the radiation left over from the birth of the universe, created about 300,000 years after the Big Bang. But the birth of our universe also created gravitational waves – and these would have originated just a fraction of a second after the event. Because these gravitational waves contain invaluable information about the origin of the universe, there is a lot of interest in detecting them. The waves with the highest frequencies may have originated during phase transitions of the primitive universe or by vibrations and snapping of cosmic strings. </p>
<h2>An instant flash of brightness</h2>
<p>Our research team, from the universities of Aberdeen and Leeds, think that atoms may have an edge in detecting elusive, high-frequency gravitational waves. We have calculated that a group of “highly excited” atoms (<a href="http://www.phys.uconn.edu/%7Ercote/Projects/Rydberg/Rydberg.html">called Rydberg atoms</a> – in which the electrons have been pushed out far away from the <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">atom’s nucleus</a>, making it huge – will emit a bright pulse of light when hit by a gravitational wave.</p>
<p>To make the atoms excited, we shine a light on them. Each of these enlarged atoms is usually very fragile and the slightest perturbation will make them collapse, releasing the absorbed light. However, the interaction with a gravitational wave <a href="https://arxiv.org/abs/1706.01287">may be too weak</a>, and its effect will be masked by the <a href="http://www.mdpi.com/2218-2004/4/4/28">many interactions </a>such as collisions with other atoms or particles.</p>
<p>Rather than analysing the interaction with individual atoms, we model the collective behaviour of a big group of atoms packed together. If the group of atoms is exposed to a common field, like our oscillating gravitational field, this will induce the excited atoms to decay all at the same time. The atoms will then release a large number of photons (light particles), generating an intense pulse of light, dubbed “superradiance”. </p>
<p>As Rydberg atoms subjected to a gravitational wave will superradiate as a result of the interaction, we can guess that a gravitational wave has passed through the atomic ensemble whenever we see a light pulse.</p>
<p>By changing the size of the atoms, we can make them radiate to different frequencies of the gravitational wave. This can be this useful for detection in different ranges. Using the proper kind of atoms, and under ideal conditions, it could be possible to use this technique to measure relic gravitational waves from the birth of the universe. By analysing the signal of the atoms it is possible to determine the properties, and therefore the origin, of the gravitational waves.</p>
<p>There may be some challenges for this experimental technique: the main one is getting the atoms in an highly excited state. Another one is to have enough atoms, as they are so big that they become very hard to contain.</p>
<h2>A theory of everything?</h2>
<p>Beyond the possibility of studying gravitational waves from the birth of the universe, the ultimate goal of the research is to detect gravitational fluctuations of empty space itself – the vacuum. These are extremely faint gravitational variations that occur spontaneously at the smallest scale, popping up out of</p>
<p>Discovering such waves could lead to the unification of <a href="https://theconversation.com/will-we-have-to-rewrite-einsteins-theory-of-general-relativity-50057">general relativity and quantum mechanics</a>, one of the greatest challenges in modern physics. General relativity is unparalleled when it comes to describing the world on a large scale, such as planets and galaxies, while quantum mechanics perfectly describes physics on the smallest scale, such as the atom or even parts of the atom. But working out the gravitational impact of the tiniest of particles will therefore help bridge this divide.</p>
<p>But discovering the waves associated with such quantum fluctuations would require a great number of atoms prepared with an enormous amount of energy, which may not be possible to do in the laboratory. Rather than doing this, it might be possible to use Rydberg atoms in outer space. Enormous clouds of these atoms exist around white dwarfs – stars which have run out of fuel – and inside nebulas with sizes more than four times larger than anything that can be created on Earth. Radiation coming from these sources could contain the signature of the vacuum gravitational fluctuations, waiting to be unveiled.</p><img src="https://counter.theconversation.com/content/80430/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Diego A. Quiñones is a PhD student at the University of Leeds and receives funding from the Mexican Council for Science and Technology CONACYT. </span></em></p>
Atoms blown up in the right way could signal when a gravitational wave is passing through.
Diego A. Quiñones, PhD Candidate in Quantum Information, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/71742
2017-02-16T10:21:29Z
2017-02-16T10:21:29Z
If atoms are mostly empty space, why do objects look and feel solid?
<figure><img src="https://images.theconversation.com/files/155016/original/image-20170131-3253-44rwcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Why can't we see the spaces?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/atom-icon-palm-391318774?src=OYHZAKupXmgo12-TIByVhw-1-76">Shutterstock</a></span></figcaption></figure><p>Chemist John Dalton proposed the theory that <a href="http://www.iun.edu/%7Ecpanhd/C101webnotes/composition/dalton.html">all matter and objects are made up of particles called atoms</a>, and this is still accepted by the scientific community, almost two centuries later. Each of these <a href="http://www.livescience.com/37206-atom-definition.html">atoms</a> is each made up of an incredibly small nucleus and even smaller electrons, which move around at quite a distance from the centre. </p>
<p>If you imagine a table that is a billion times larger, its atoms would be the size of melons. But even so, the nucleus at the centre would still be far too small to see and so would the electrons as they dance around it. So why don’t our fingers just pass through atoms, and why doesn’t light get through the gaps?</p>
<p>To explain why we must look at the electrons. Unfortunately, much of what we are taught at school is simplified – electrons do not orbit the centre of an atom like planets around the sun, like you may have been taught. Instead, think of electrons like a swarm of bees or birds, where the individual motions are too fast to track, but you still see the shape of the overall swarm.</p>
<h2>Electrons ‘dance’</h2>
<p>In fact, electrons dance – there is no better word for it. But it’s not random dancing – it’s more like ballroom dancing, where they move in set patterns, following steps laid down by a mathematical equation named after <a href="http://www.physlink.com/Education/AskExperts/ae329.cfm">Erwin Schrödinger</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155022/original/image-20170131-3288-v3fvjj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Electrons are like a swarm of birds.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/9/94/The_flock_of_starlings_acting_as_a_swarm._-_geograph.org.uk_-_124593.jpg">John Holmes/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>These patterns can vary – some are slow and gentle, like a waltz whereas some are fast and energetic, like a Charleston. Each electron keeps to the same pattern, but once in a while it may change to another, as long as no other electron is doing that pattern already. No two electrons in an atom can do the same step: this rule is called the <a href="http://abyss.uoregon.edu/%7Ejs/glossary/pauli_exclusion_principle.html">Exclusion Principle</a>. </p>
<p>Although electrons never tire, moving up to a faster step does take energy. And when an electron moves down to a slower pattern it loses energy which it gives out. So when energy in the form of light falls on an electron, it can absorb some energy and move up to a higher, faster “dance” pattern. A light beam won’t get far through our table, since the electrons in all the atoms are eager to grab some energy from the light. </p>
<p>After a very short while they lose this gained energy, perhaps as light again. Changes in the patterns of absorbed and reflected light give reflections and colours - so we see the table as solid.</p>
<h2>Resistance when touched</h2>
<p>So why does a table also feel solid? Many websites will tell you that this is due to the repulsion – that two negatively charged things must repel each other. But this is wrong, and shows you should never trust some things on the internet. It feels solid because of the dancing electrons.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/157108/original/image-20170216-12953-1j19cw2.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">
<figcaption>
<span class="caption">The table resistance is strong.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-woman-leaning-on-table-meeting-543916348?src=f0GcHgTOhI_8nwsmejxpww-1-97">Shutterstock</a></span>
</figcaption>
</figure>
<p>If you touch the table, then the electrons from atoms in your fingers become close to the electrons in the table’s atoms. As the electrons in one atom get close enough to the nucleus of the other, the patterns of their dances change. This is because, an electron in a low energy level around one nucleus can’t do the same around the other – that slot’s already taken by one of its own electrons. The newcomer must step into an unoccupied, more energetic role. That energy has to be supplied, not by light this time but by the force from your probing finger.</p>
<p>So pushing just two atoms close to each other takes energy, as all their electrons need to go into unoccupied high-energy states. Trying to push all the table-atoms and finger-atoms together demands an awful lot of energy – more than your muscles can supply. You feel that, as resistance to your finger, which is why and how the table feels solid to your touch.</p><img src="https://counter.theconversation.com/content/71742/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Barlow is affiliated with the Liberal Democrats</span></em></p>
The reason you feel things as solid is all to do with electrons.
Roger Barlow, Research Professor and Director of the International Institute for Accelerator Applications, University of Huddersfield
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/70868
2017-01-05T20:02:12Z
2017-01-05T20:02:12Z
Giant atoms could help unveil ‘dark matter’ and other cosmic secrets
<figure><img src="https://images.theconversation.com/files/151811/original/image-20170105-18668-ihhz4l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Composite image showing the galaxy cluster 1E 0657-56.</span> <span class="attribution"><span class="source">Chandra X-Ray Observatory/NASA</span></span></figcaption></figure><p>The universe is an astonishingly secretive place. Mysterious substances known as dark matter and dark energy account for some 95% of it. Despite huge effort to find out what they are, we simply don’t know. </p>
<p>We know dark matter exists because of the gravitational pull of galaxy clusters – the matter we can see in a cluster just isn’t enough to hold it together by gravity. So there must be some extra material there, made up by unknown particles that simply aren’t visible to us. <a href="https://theconversation.com/from-machos-to-wimps-meet-the-top-five-candidates-for-dark-matter-51516">Several candidate particles</a> have already been proposed.</p>
<p>Scientists are trying to work out what these unknown particles are by looking at how they affect the ordinary matter we see around us. But so far it has proven difficult, so we know it interacts only weakly with normal matter at best. Now my colleague Benjamin Varcoe and I have come up with a new way to probe dark matter that may just prove successful: <a href="http://www.mdpi.com/2218-2004/4/4/28">by using atoms that have been stretched to be 4,000 times </a> larger than usual. </p>
<h2>Advantageous atoms</h2>
<p>We have come a long way from the Greeks’ vision of atoms as the indivisible components of all matter. The first evidence-based argument for the existence of atoms <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/rocks/atomsrev1.shtml">was presented in the early 1800s by John Dalton</a>. But it wasn’t until the beginning of the 20th century that JJ Thomson and Ernest Rutherford <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/atomstrucrev5.shtml">discovered</a> that atoms consist of electrons and a nucleus. Soon after, <a href="https://en.wikipedia.org/wiki/Erwin_Schr%C3%B6dinger">Erwin Schrödinger</a> described the atom mathematically using what is today called quantum theory. </p>
<p>Modern experiments have been able to <a href="https://theconversation.com/the-2012-nobel-prize-in-physics-explained-10085">trap and manipulate</a> individual atoms with outstanding precision. This knowledge has been used to create new technologies, like lasers and atomic clocks, and future computers may use single atoms as their primary components. </p>
<p>Individual atoms are hard to study and control because they are very sensitive to external perturbations. This sensitivity is usually an inconvenience, but our study suggests that it makes some atoms ideal as probes for the detection of particles that don’t interact strongly with regular matter – such as dark matter.</p>
<p>Our model is based on the fact that weakly interacting particles must bounce from the nucleus of the atom it collides with and exchange a small amount of energy with it – similar to the collision between two pool balls. The energy exchange will produce a sudden displacement of the nucleus that will eventually be felt by the electron. This means the entire energy of the atom changes, which can be analysed to obtain information about the properties of the colliding particle. </p>
<p>However the amount of transferred energy is very small, so a special kind of atom is necessary to make the interaction relevant. We worked out that the so-called “<a href="http://www.phys.uconn.edu/%7Ercote/Projects/Rydberg/Rydberg.html">Rydberg atom</a>” would do the trick. These are atoms with long distances between the electron and the nucleus, meaning they possess high potential energy. Potential energy is a form of stored energy. For example, a ball on a high shelf has potential energy because this could be converted to kinetic energy if it falls off the shelf.</p>
<p>In the lab, it is possible to trap atoms and prepare them in a Rydberg state – making them as big as 4,000 times their original size. This is done by illuminating the atoms with a laser with light at a very specific frequency. </p>
<p>This prepared atom is likely much heavier than the dark matter particles. So rather than a pool ball striking another, a more appropriate description will be a marble hitting a bowling ball. It seems strange that big atoms are more perturbed by collisions than small ones – one may expect the opposite (smaller things are usually more affected when a collision occurs).</p>
<p>The explanation is related to two features of Rydberg atoms: they are highly unstable because of their elevated energy, so minor perturbations would disturb them more. Also, due to their big area, the probability of the atoms interacting with particles is increased, so they will suffer more collisions.</p>
<h2>Spotting the tiniest of particles</h2>
<p><a href="https://theconversation.com/the-search-for-dark-matter-and-dark-energy-just-got-interesting-46422">Current experiments</a> typically look for dark matter particles by trying to detect their scattering off atomic nuclei or electrons on Earth. They do this by looking for light or free electrons in big tanks of liquid noble gases that are generated by energy transfer between the dark matter particle and the atoms of the liquid.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=345&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=345&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=345&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=433&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=433&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151837/original/image-20170105-18668-qjsn3w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=433&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Large Underground Xenon experiment installed 4,850 ft underground inside a 70,000-gallon water tank shield.</span>
<span class="attribution"><span class="source">Gigaparsec at English Wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>But, according to the laws of quantum mechanics, there needs to be a certain a minimum energy transfer for the light to be produced. An analogy would be a particle colliding with a guitar string: it will produce a note that we can hear, but if the particle is too small the string will not vibrate at all. </p>
<p>So the problem with these methods is that the dark matter particle has to be big enough if we are to detect it in this way. However, our calculations show that the Rydberg atoms will be disturbed in a significant way even by low-mass particles – meaning they can be applied to search for candidates of dark matter that other experiments miss. One of such particles is the <a href="https://en.wikipedia.org/wiki/Axion">Axion</a>, a hypothetical particle which is a strong candidate for dark matter.</p>
<p>Experiments would require for the atoms to be treated with extreme care, but they will not require to be done in a deep underground facility like <a href="https://en.wikipedia.org/wiki/XENON">other experiments</a>, as the Rydberg atoms are expected to be less susceptible to cosmic rays compared to dark matter. </p>
<p>We are working to further improve the sensitivity of the system, aiming to extend the range of particles that it may be able to perceive.</p>
<p>Beyond dark matter we are also aiming to one day apply it for the detection of <a href="https://theconversation.com/explainer-gravitational-waves-and-why-their-discovery-is-such-a-big-deal-53239">gravitational waves</a>, the ripples in the fabric of space predicted by Einstein long time ago. These perturbations of the space-time continuum have been <a href="https://theconversation.com/gravitational-waves-found-the-inside-story-54589">recently discovered</a>, but we believe that by using atoms we may be able to detect gravitational waves with a different frequency to the ones already observed.</p><img src="https://counter.theconversation.com/content/70868/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Diego A. Quiñones is a PhD student at the University of Leeds and receives funding from the Mexican Council for Science and Technology CONACYT. </span></em></p>
Atoms manipulated to be 4000 times larger than usual may be the tool dark-matter hunters have been waiting for.
Diego A. Quiñones, PhD Student in Quantum Information, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/67685
2016-10-26T18:02:15Z
2016-10-26T18:02:15Z
Turning diamonds’ defects into long-term 3-D data storage
<figure><img src="https://images.theconversation.com/files/143343/original/image-20161026-11275-1ilzlvw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Diamonds are a data storers' best friend?</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-132329216/stock-photo-3d-abstract-crystal-clear-background-texture.html">Diamond image via www.shutterstock.com</a></span></figcaption></figure><p>With the amount of data storage required for our daily lives growing and growing, and currently available technology being almost saturated, we’re in desparate need of a new method of data storage. The standard magnetic hard disk drive (HDD) – like what’s probably in your laptop computer – has reached its limit, holding a maximum of a few terabytes. Standard optical disk technologies, like compact disc (CD), digital video disc (DVD) and Blu-ray disc, are restricted by their two-dimensional nature – they just store data in one plane – and also by a physical law called the diffraction limit, based on the wavelength of light, that constrains our ability to focus light to a very small volume. </p>
<p>And then there’s the lifetime of the memory itself to consider. HDDs, as we’ve all experienced in our personal lives, may last only a few years before things start to behave strangely or just fail outright. DVDs and similar media are advertised as having a storage lifetime of hundreds of years. In practice this may be cut down to a few decades, assuming the disk is not rewritable. Rewritable disks degrade on each rewrite.</p>
<p>Without better solutions, we face financial and technological catastrophes as our current storage media reach their limits. How can we store large amounts of data in a way that’s secure for a long time and can be reused or recycled?</p>
<p>In our lab, we’re experimenting with a perhaps unexpected memory material you may even be wearing on your ring finger right now: diamond. On the atomic level, these crystals are extremely orderly – but sometimes defects arise. <a href="http://doi.org/10.1126/sciadv.1600911">We’re exploiting these defects as a possible way to store information</a> in three dimensions.</p>
<h2>Focusing on tiny defects</h2>
<p>One approach to improving data storage has been to continue in the direction of optical memory, but extend it to multiple dimensions. Instead of writing the data to a surface, write it to a volume; make your bits three-dimensional. The data are still limited by the physical inability to focus light to a very small space, but you now have access to an additional dimension in which to store the data. Some methods also polarize the light, giving you even more dimensions for data storage. However, most of these methods are not rewritable.</p>
<p>Here’s where the diamonds come in. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=588&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=588&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=588&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=739&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=739&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=739&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 orderly structure of a diamond, but with a vacancy and a nitrogen replacing two of the carbon atoms.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Diamond_Structure.png">Zas2000</a></span>
</figcaption>
</figure>
<p>A diamond is supposed to be a pure well-ordered array of carbon atoms. Under an electron microscope it usually looks like a neatly arranged three-dimensional lattice. But occasionally there is a break in the order and a carbon atom is missing. This is what is known as a vacancy. Even further tainting the diamond, sometimes a nitrogen atom will take the place of a carbon atom. When a vacancy and a nitrogen atom are next to each other, the composite defect is called a nitrogen vacancy, or NV, center. These types of defects are always present to some degree, even in natural diamonds. In large concentrations, NV centers can impart a characteristic red color to the diamond that contains them.</p>
<p>This defect is having a huge impact in physics and chemistry right now. Researchers have used it to detect the <a href="http://doi.org/10.1126/science.aaa2253">unique nuclear magnetic resonance</a> signatures of <a href="http://doi.org/10.1126/science.aad8022">single proteins</a> and are probing it in a variety of <a href="http://doi.org/10.1038/nature15759">cutting-edge quantum mechanical experiments</a>.</p>
<p>Nitrogen vacancy centers have a tendency to trap electrons, but the electron can also be forced out of the defect by a laser pulse. For many researchers, the defects are interesting only when they’re holding on to electrons. So for them, the fact that the defects can release the electrons, too, is a problem.</p>
<p>But in our lab, we instead look at these nitrogen vacancy centers as a potential benefit. We think of each one as a nanoscopic “bit.” If the defect has an extra electron, the bit is a one. If it doesn’t have an extra electron, the bit is a zero. This electron yes/no, on/off, one/zero property opens the door for turning the NV center’s charge state into the basis for using diamonds as a long-term storage medium.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=747&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Starting from a blank ensemble of NV centers in a diamond (1), information can be written (2), erased (3), and rewritten (4).</span>
<span class="attribution"><span class="source">Siddharth Dhomkar and Carlos A. Meriles</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Turning the defect into a benefit</h2>
<p>Previous experiments with this defect have demonstrated some properties that make diamond a good candidate for a memory platform.</p>
<p>First, researchers can selectively change the charge state of an individual defect <a href="http://doi.org/10.1088/1367-2630/15/1/013064">so it either holds an electron or not</a>. We’ve used a green laser pulse to assist in trapping an electron and a high-power red laser pulse to eject an electron from the defect. A low-power red laser pulse can help check if an electron is trapped or not. If left completely in the dark, the defects maintain their charged/discharged status virtually forever. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&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 NV centers can encode data on various levels.</span>
<span class="attribution"><span class="source">Siddharth Dhomkar and Carlos A. Meriles</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our method is still diffraction limited, but is 3-D in the sense that we can charge and discharge the defects at any point inside of the diamond. We also present a sort of fourth dimension. Since the defects are so small and our laser is diffraction limited, we are technically charging and discharging many defects in a single pulse. By varying the duration of the laser pulse in a single region we can control the number of charged NV centers and consequently encode multiple bits of information.</p>
<p>Though one could use natural diamonds for these applications, we use artificially lab-grown diamonds. That way we can efficiently control the concentration of nitrogen vacancy centers in the diamond.</p>
<p>All these improvements add up to about 100 times enhancement in terms of bit density relative to the current DVD technology. That means we can encode all the information from a DVD into a diamond that takes up about one percent of the space.</p>
<h2>Past just charge, to spin as well</h2>
<p>If we could get beyond the diffraction limit of light, we could improve storage capacities even further. We have one novel proposal on this front.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A human cell, imaged on the right with super-resolution microscope.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/zeissmicro/9132340803/">Dr. Muthugapatti Kandasamy</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Nitrogen vacancy centers have also been used in the execution of what is <a href="http://doi.org/10.1038/NPHOTON.2009.2">called super-resolution microscopy</a> to image things that are much smaller than the wavelength of light. However, since the super-resolution technique works on the same principles of charging and discharging the defect, it will cause unintentional alteration in the pattern that one wants to encode. Therefore, we won’t be able to use it as it is for memory storage application and we’d need to back up the already written data somehow during a read or write step.</p>
<p>Here we propose the idea of what we call charge-to-spin conversion; we temporarily encode the charge state of the defect in the spin state of the defect’s host nitrogen nucleus. Spin is a fundamental property of any elementary particle; it’s similar to its charge, and can be imagined as having a very tiny magnet permanently attached it.</p>
<p>While the charges are being adjusted to read/write the information as desired, the previously written information is well protected in the nitrogen spin state. Once the charges have encoded, the information can be back converted from the nitrogen spin to the charge state through another mechanism which we call spin-to-charge conversion.</p>
<p>With these advanced protocols, the storage capacity of a diamond would surpass what existing technologies can achieve. This is just a beginning, but these initial results provide us a potential way of storing huge amount of data in a brand new way. We’re looking forward to transform this beautiful quirk of physics into a vastly useful technology.</p><img src="https://counter.theconversation.com/content/67685/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Support for this work was provided by National Science Foundation.</span></em></p><p class="fine-print"><em><span>The research is funded by the National Science Foundation</span></em></p>
With current modes up against their limits, we need new data storage solutions. Tiny defects in diamonds’ atomic structure might turn them into a new medium for memory.
Siddharth Dhomkar, Postdoctoral Associate in Physics, City College of New York
Jacob Henshaw, Teaching Assistant in Physics, City College of New York
Licensed as Creative Commons – attribution, no derivatives.