tag:theconversation.com,2011:/id/topics/wavelength-34505/articlesWavelength – The Conversation2023-07-04T15:11:39Ztag:theconversation.com,2011:article/2086392023-07-04T15:11:39Z2023-07-04T15:11:39ZBiting flies are attracted to blue traps – we used AI to work out why<p>Flies which feast on blood – such as tsetse and horse flies – inflict painful bites and spread debilitating diseases among people and animals alike. So a lot of work has gone into designing the most efficient traps to control the populations of these flies.</p>
<p>Biting fly traps tend to be blue, because decades of field research has shown that such flies find this colour especially attractive. But it’s never been clear why these flies find blue to be so irresistible – especially since blue objects are not a common sight in the natural environment.</p>
<p>Scientists have speculated that blue surfaces might look like <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2003.0121">shaded places</a> to flies since shadows have a blueish tinge. Tsetse flies in particular seek out such shaded spots to rest in, which might explain their attraction to blue traps. </p>
<p>Another possibility is that blue surfaces might <a href="https://resjournals.onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2915.1999.00163.x">lure hungry flies</a> by providing them with the telltale signs they use to distinguish animals against a background of foliage. According to this theory, a fly might mistake a blue trap for an animal it wishes to bite and feed upon. </p>
<figure class="align-left ">
<img alt="A blue canvas, diamond shaped container is suspended from a tree." src="https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A bright blue trap for tsetse flies is suspended from a tree.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bright-blue-trap-dangerous-tsetse-fly-724357057">Fabian Plock/Shutterstock</a></span>
</figcaption>
</figure>
<p>But assessing these possibilities is especially tricky because flies perceive colour differently to people. Humans perceive colour using the responses of three kinds of light-detecting photoreceptor in the retina which are broadly sensitive to blue, green and red wavelengths of light.</p>
<p>But most “higher flies” – such as tsetse and horseflies – have five kinds of photoreceptor sensitive to UV, blue and green wavelengths. So, a blue trap won’t look the same to a fly as it does to the human who designed it.</p>
<h2>From flies to AI…</h2>
<p>In <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2023.0463#d1e1574">our study</a>, we tackled the problem by using artificial intelligence (AI). We used artificial neural networks which are a form of machine learning inspired by the structure of real nervous systems. Artificial neural networks learn by modifying the strengths of connections between a network of artificial neurons.</p>
<p>We fed these networks with the photoreceptor signals that a fly would experience when looking at animals or foliage backgrounds, both in light and in shade. We then trained the networks to distinguish animals from leaves, and shaded from unshaded objects, using only that visual information.</p>
<p>The trained networks would find the most efficient way of processing the visual signals, which we expected to share properties with the mechanisms that have evolved in real flies’ nervous systems. We then investigated whether the artificial neural networks classified blue traps as animals or as shaded surfaces.</p>
<h2>Blueness or brightness?</h2>
<p>After training, our neural networks could easily distinguish animals from leaf backgrounds, and shaded from unshaded stimuli, using the sensory information available to a fly. However, what surprised us was that they solved these problems in completely different ways.</p>
<p>The networks identified shade using brightness and not colour – quite simply, the darker a stimulus appeared, the more likely it was to be classified as shaded. Meanwhile, animals were identified using the relative strength of blue and green photoreceptor signals. Relatively greater blue compared to green signals indicated that a stimulus was probably an animal rather than a leaf, and vice versa.</p>
<p>The implications of this became clear when we fed these networks the visual signals caused by blue traps. The blue traps were never mistaken for shaded surfaces, but they were commonly misclassified as animals.</p>
<figure class="align-center ">
<img alt="A close up of an insect with huge blue/green eyes" src="https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The horse fly (<em>Hybomitra epistates</em>) can inflict painful bites upon people and livestock.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/horse-fly-hybomitra-epistates-portrait-1773555527">Mircea Costina/Shutterstock</a></span>
</figcaption>
</figure>
<p>Of course, artificial neural networks are not real flies, nor exact models of a fly’s nervous system. But they do show us the most efficient way of processing a fly’s visual signals to identify natural stimuli. And we expect evolution to have taken advantage of similar principles in real fly nervous systems.</p>
<p>The best way to identify shade using the visual information a fly has is through brightness and not blueness. Meanwhile, the best way of identifying animals was, somewhat counterintuitively, using blueness. Such a mechanism is very strongly stimulated by blue traps, explaining why they prove such a powerful lure for hungry flies. Further evidence for this idea comes from field studies which show that tsetse landing on coloured traps are <a href="https://resjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3032.1990.tb00519.x">relatively starved</a>.</p>
<p>If we can understand the sensory signals and behaviour that cause flies to be caught in traps, we can engineer traps to more efficiently exploit those mechanisms and more effectively control the flies. We’ve already had <a href="https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0007905#:%7E:text=Tsetse%20can%20be%20controlled%20using%20insecticide-treated%20fabric%20targets%2C,these%20fabrics%20to%20be%20more%20attractive%20to%20tsetse.">some success</a> in doing this for tsetse flies.</p>
<p>More effective traps will help minimise the impacts of those flies on health and welfare of people and animals. They could help prevent the damaging effects of biting flies on livestock, help in the fight against dangerous fly-borne diseases such as <a href="https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness)">sleeping sickness</a>, and protect us and animals from fly attacks in general.</p><img src="https://counter.theconversation.com/content/208639/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Santer has received funding from the Knowledge Economy Skills Scholarships program, and from the Centre for International Development Research at Aberystwyth (CIDRA). </span></em></p>New research on what attracts blood-feasting flies to blue objects could help minimise the impacts of those insects on people and animals.Roger Santer, Lecturer in Zoology, Aberystwyth UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1696022021-10-26T12:19:57Z2021-10-26T12:19:57ZType of ultraviolet light most effective at killing coronavirus is also the safest to use around people<figure><img src="https://images.theconversation.com/files/428067/original/file-20211022-9818-i87045.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5779%2C3752&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UV light at most wavelengths can kill COVID–19. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/lamp-for-sterilization-covid-19-prevention-concept-royalty-free-image/1296016011?adppopup=true">andriano_cz/iStock via Getty Images</a></span></figcaption></figure><p>Scientists have long known that ultraviolet light can <a href="https://theconversation.com/ultraviolet-light-can-make-indoor-spaces-safer-during-the-pandemic-if-its-used-the-right-way-141512">kill pathogens on surfaces and in air and water</a>. <a href="https://www.nytimes.com/2020/03/28/travel/coronavirus-hotels-private-jets-virtual-spas.html">UV robots are used to disinfect</a> empty hospital rooms, buses and trains; UV bulbs in HVAC systems eliminate pathogens in building air; and <a href="https://www.nytimes.com/2008/03/02/business/02novel.html">UV lamps kill bugs in drinking water</a>.</p>
<p>Perhaps you have seen UV wands, UV LEDs and UV air purifiers advertised as silver bullets to protect against the coronavirus. While decades of research have looked at the ability of UV light to kill many pathogens, there are no set standards for UV disinfection products with regard to the coronavirus. These products may work to kill SARS-CoV-2, the virus that causes COVID-19, but they also may not. </p>
<p>I am an <a href="https://scholar.google.com/citations?user=uAS7KNUAAAAJ&hl=en&oi=ao">environmental engineer and expert in UV disinfection</a>. In May 2021, my colleagues and I set out to accurately test various UV systems and see <a href="https://doi.org/10.1128/AEM.01532-21">which was the most effective</a> at killing off – or inactivating – SARS-CoV-2.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing UV light breaking down a strand of DNA." src="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=462&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=462&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=462&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&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 UV light enters a cell, it breaks the bonds that hold DNA or RNA together.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:DNA_UV_mutation.svg#/media/File:DNA_UV_mutation.svg">NASA/David Herring via WikimediaCommons</a></span>
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</figure>
<h2>How does UV light kill a virus?</h2>
<p>Light is categorized by wavelength – the distance between peaks of a wave of light – and is measured in nanometers. UV wavelengths range from 100 to 400 nanometers – shorter in wavelength than the violet hues in visible light – and are invisible to the human eye. As wavelength shortens, photons of light contain higher amounts of energy.</p>
<p>Different wavelengths of UV light work better than others for inactivating viruses, and this depends on how well the wavelengths are absorbed by the virus’s DNA or RNA. When UV light gets absorbed, the photons of light transfer their energy to and <a href="https://doi.org/10.1038/s41598-021-93231-7">damage the chemical bonds of the genetic material</a>. The virus is then unable to replicate or cause an infection. Researchers have also shown the proteins that viruses use to attach to a host cell and initiate infection – like the spike proteins on a coronavirus – are also <a href="https://doi.org/10.1021/acs.est.7b04602">vulnerable to UV light</a>.</p>
<p>The dose of light matters too. Light can vary in intensity – bright light is more intense, and there is more energy in it than in dim light. Being exposed to a bright light for a short time can produce the same UV dose as being exposed to a dim light for a longer period. You need to know the right dose that can kill coronavirus particles at each UV wavelength.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man with sunburned shoulders sitting on a beach." src="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.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">Sunburns are caused by UV light damaging skin cells.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-with-sun-burnt-shoulders-sitting-on-beach-rear-royalty-free-image/85775471?adppopup=true">Ian Hooton/Science Photo Library via Getty Images</a></span>
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</figure>
<h2>Making ultraviolet lights safe for people</h2>
<p>Traditional UV systems use wavelengths at or around 254 nanometers. At these wavelengths the light is dangerous to human skin and eyes, <a href="https://doi.org/10.1111/php.13402">even at low doses</a>. Sunlight includes UV light near these wavelengths; anyone who has ever gotten a bad sunburn knows just how dangerous UV light can be. </p>
<p>However, recent research has shown that at certain UV wavelengths – specifically below 230 nanometers – the high-energy photons <a href="https://iuva.org/resources/covid-19/Far%20UV-C%20Radiation-%20Current%20State-of%20Knowledge.pdf">are absorbed by the top layers of dead skin cells</a> and don’t penetrate into the active skin layers where damage can occur. Similarly, the <a href="https://doi.org/10.1111/php.13402">tear layer around eyes also blocks out these germicidal UV rays</a>.</p>
<p>This means that at wavelengths of UV light below 230 nanometers, people can move around more freely while the air around them is being disinfected in real time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a lamp above a sample of water containing the coronavirus." src="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=317&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=317&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=317&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=399&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=399&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=399&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers used this setup to test multiple different UV lights at various doses to see what it took to kill SARS-CoV-2.</span>
<span class="attribution"><span class="source">Karl Linden</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Testing different wavelengths</h2>
<p>My colleagues and I tested five commonly used UV wavelengths to see which work best to inactivate SARS-CoV-2. Specifically, we tested how large a dose is needed to <a href="https://doi.org/10.1128/AEM.01532-21">kill 90% to 99.9% of the viral particles present</a>.</p>
<p>We ran these tests in a biosafety level three facility at the <a href="https://environmentalscience.cals.arizona.edu/person/charles-chuck-gerba">University of Arizona</a> that is built to handle lethal pathogens. There we tested numerous lights across the UV spectrum, including UV LEDs that emit light at 270 and 282 nanometers, traditional UV tube lamps at 254 nanometers and a newer technology called an <a href="https://www.ushio.eu/excimer-explained/">excited dimer, or excimer, UV source</a> at 222 nanometers. </p>
<p>To test each device we spiked a sample of water with millions of SARS-CoV-2 viruses and coated a petri dish with a thin layer of this mixture. We then shined UV light on the petri dish until we achieved a specific dose. Finally we examined the viral particles to see if they could still infect human cells in culture. If the viruses could infect the cells, the dose was not high enough. If the viruses did not cause an infection, the UV source at that dose had successfully killed the pathogen. We carefully repeated this process for a range of UV doses using the five different UV devices.</p>
<p>While all of the wavelengths we tested can inactivate SARS-CoV-2 at very low doses, the ones that required the lowest dose were the <a href="https://doi.org/10.1128/AEM.01532-21">systems that emit UV light at a wavelength of 222 nanometers</a>. In our experiment, it took a dose of less than 2 millijoules of energy per square centimeter to kill 99.9% of viral particles. This translates to needing about 20 seconds to disinfect a space receiving a low intensity of short wavelength UV light, similar to that used in our test.</p>
<p>[<em>Get our best science, health and technology stories.</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-best">Sign up for The Conversation’s science newsletter</a>.]</p>
<p>These 222-nanometer systems are almost twice as effective as conventional UV tube lamps, which are often used in ultraviolet disinfecting systems. But importantly, the winning lamp also happens to be the safest for humans, too. At the same UV light intensity it takes to kill 99.9% of SARS-CoV-2 in 20 seconds, a person could be safely exposed to 222-nanometer light for <a href="https://doi.org/10.1111/php.13402">up to one hour and 20 minutes</a>.</p>
<p>What this means is that <a href="https://edenpark.com/">widely available</a> types of <a href="https://www.ushio.com/product/care222-filtered-far-uv-c-excimer-lamp-module/">UV lamp</a> lights can be used to safely knock down levels of the coronavirus with people present.</p>
<h2>Better use of existing tech</h2>
<p>Many places or organizations – ranging from the <a href="https://www.defense.gov/News/Feature-Stories/Story/Article/2309289/air-guard-wing-receives-dods-first-uv-light-disinfectant-system/">U.S. Air Force</a> to the <a href="https://www.spaceneedle.com/elevatingclean">Space Needle in Seattle</a> to <a href="https://www.boeing.com/confident-travel/research/CAP-3_Disinfection_with_Far-UV.html">Boeing</a> – are already using or investigating ways to use UV light in the 222 nanometer range to protect public health. </p>
<p>I believe that our findings are important because they quantify the exact doses needed to achieve various levels of SARS-CoV-2 control, whether that be killing 90% or 99.9% of viral particles. </p>
<p>Imagine coffee shops, grocery stores, school classrooms, restaurants and concert venues now made safe by this technology. And this is not a solution for just SARS-CoV-2. These technologies could help protect human health in public spaces in future times of crisis, but also during times of relative normalcy, by reducing exposure to everyday viral and bacterial threats.</p><img src="https://counter.theconversation.com/content/169602/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karl Linden advises various companies promoting the use of UV light for disinfection. He receives funding from federal agencies and industry to conduct research in his role as a professor at the University of Colorado Boulder. He is affiliated with the International Ultraviolet Association. </span></em></p>UV lights come in a variety of different wavelengths, but not all are equally effective at disinfection. Researchers tested a number of commercially available lights to find the best.Karl Linden, Professor of Environmental Engineering and the Mortenson Professor in Sustainable Development, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/828312018-01-09T19:37:46Z2018-01-09T19:37:46ZCurious Kids: Why can some cups go in the microwave and some not?<figure><img src="https://images.theconversation.com/files/198472/original/file-20171211-27714-uyn8cp.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The short answer is that it depends on the material the cups and plates are made of, and even what shape they are.</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Why can some cups go in the microwave and some not? What happens if you put the wrong cup or plate in the microwave? – Edie, age 8, Melbourne.</strong> </p>
</blockquote>
<hr>
<p>Good question, Edie! </p>
<p>The short answer is that it depends on the material the cups and plates are made of, and even what shape they are. </p>
<p>Microwave ovens heat up the food from the inside – using what scientists call “microwaves”. </p>
<h2>What are microwaves?</h2>
<p>Microwaves are a kind of electromagnetic radiation – just like sunlight, radio waves, and x-rays (like the ones they use to take photos of bones in hospitals).</p>
<p>When you put your food in a microwave oven, the microwaves make the water molecules in the food vibrate or jiggle around really fast. This is how the food heats up. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-if-a-huge-huntsman-spider-is-sucked-into-a-vacuum-cleaner-can-it-crawl-out-later-77390">Curious Kids: If a huge huntsman spider is sucked into a vacuum cleaner, can it crawl out later?</a>
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</em>
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<h2>Why are metals dangerous?</h2>
<p>Putting metal in the microwave oven is generally a bad idea. In metals, the electrons – the tiny, negatively charged parts of the atoms – are free to move around. This is why metals conduct electricity, meaning they can carry electricity from one point to another. </p>
<p>The microwaves push and pull the electrons around. With metallic objects that have sharp edges or tips – like aluminium foil or forks – the electrons can build up on the tips. This can lead to sparks and fire. </p>
<p>Other metallic objects may not spark but they can get very hot. That can also lead to a fire depending on what else is inside the microwave.</p>
<p><img width="100%" src="https://media.giphy.com/media/l3mZsuP4R5wPRJnUc/giphy.gif"></p>
<h2>What materials are microwave safe?</h2>
<p>Materials like plastic, glass or ceramics are usually safe to use in the microwave because they don’t contain water and the electrons aren’t free to move around. But we still need to be careful: some plastic containers are too thin and can melt or release plastic into the food. </p>
<p>The bottom line is: it’s hard to tell exactly how something will behave inside a microwave without testing, so the rule of thumb is to only use containers that have been tested and are known to be microwave-safe.</p>
<h2>What about the metal grate on the inside of the microwave door?</h2>
<p>You’re right! There is a metal grate on the inside of the metal door, with tiny holes in it. I’ll explain why it’s there and why that metal grate doesn’t cause sparks or fire. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183701/original/file-20170829-23262-18ap31t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There is a metal grate on the inside of the microwave door.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/david55king/2168539444/in/photolist-4iCke7-4UZCcC-nw5eXn-7JCjGq-7uC4v8-4f65N4-4UZBJY-bUDDeo-dQKTC6-3pCvgL-a4twUJ-9qJ1yc-5AcfTd-8Yu6SJ-indRF-agK3GR-f9nh3Z-8b82ds-qGej85-95bFQF-dD7wZD-6eFdQ4-6jpPMv-8YuTzy-cht11A-9iCJBh-8Yop38-owRDm-dzERHs-4Hs7sD-8eiRQG-4Ut6u2-4UVt8p-8AHe9z-7AkpHi-nAGJ7M-qNFinB-StSst-aseJX7-4xBjka-2VynCp-hkSoZS-fHUQCV-59TbCN-7v59aA-cv66bq-xAk2n-4UVq4T-6CCQiE-6dYRiE">Flickr/David King</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Electromagnetic radiation – like sunlight, x-rays and microwaves – all differ in their “wavelengths”. Like waves on the ocean, this is the distance between the peaks of the waves. </p>
<p>Sunlight and microwaves only differ by how far apart are the peaks of the wave. For light, this distance between peaks, that we call the “wavelength”, is very tiny – a thousand times smaller than the width of a hair.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-is-it-safe-to-microwave-your-food-66776">Health check: is it safe to microwave your food?</a>
</strong>
</em>
</p>
<hr>
<p>In a typical microwave oven, the wavelength is much larger – about 12cm. This is why they have small holes (of about 1mm) on a metal plate in the door. </p>
<p>The wavelength of light is smaller than the holes and it can get out (so we can see inside), but the wavelength of the microwaves is too big for the hole and they bounce off the metal plate. The microwaves cannot escape.</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
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<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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<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 city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/82831/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eric Cavalcanti 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>Have you ever been told not to put metal in the microwave? Edie, age 8, wants to know why.Eric Cavalcanti, Senior Lecturer, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/742492017-03-15T00:01:27Z2017-03-15T00:01:27ZHot food, fast: The home microwave oven turns 50<figure><img src="https://images.theconversation.com/files/160772/original/image-20170314-10741-13z767t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It will be quick and it will be hot.</span> <span class="attribution"><a class="source" href="https://amana.com/content.jsp?pageName=amana-brand-history">1967 promotional image for the Amana Radarange</a></span></figcaption></figure><p>The year 2017 marks the 50th anniversary of the home microwave oven. The ovens were first sold for home use by Amana corporation in 1967, but they had actually been used for commercial food preparation since the 1950s. It wasn’t until 1967, however, that technology miniaturization and cost reductions in manufacturing made the ovens small enough and cheap enough (<a href="http://spectrum.ieee.org/geek-life/history/a-brief-history-of-the-microwave-oven">a still steep US$495</a>; US$3,575 in 2017 dollars) for use in the kitchens of the American middle class. Now, it would be <a href="http://escholarship.org/uc/item/3s29h7wd">hard to find a U.S. home without a microwave</a>.</p>
<p>Amana, a subsidiary of Raytheon corporation, actually called their first model the “<a href="https://www.wired.com/2010/10/1025home-microwave-ovens/">Radarange</a>” – a contraction of radar and range (as in stove). What do microwave ovens have to do with radar? </p>
<p>Radar is an acronym for “radio detection and ranging.” Developed prior to World War II, the technology is based on the principle that <a href="http://science.howstuffworks.com/radar.htm">radio waves can bounce off the surfaces of large objects</a>. So if you point a radio wave beam in a certain direction, some of the radio waves will come bouncing back to you, if they encounter an obstruction in their path.</p>
<p>By measuring the bounced-back radio waves, distant objects or objects hidden from view by clouds or fog can be detected. Radar can detect planes and ships, but early on it was also found that rainstorms caused interference with radar detection. It wasn’t long before the presence of such interference was actually utilized to track the movement of rainstorms across the landscape, and the age of modern <a href="http://ethw.org/Radar_and_Weather_Forecasting">radar-based weather forecasting</a> began.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=594&fit=crop&dpr=1 600w, https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=594&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=594&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/160770/original/image-20170314-10755-mjkqk3.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">Original cavity magnetron as used to develop radar.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Original_cavity_magnetron,_1940_(9663811280).jpg">Mrjohncummings</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>At the heart of radar technology is the “<a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/magnetron.html">magnetron</a>,” the device that produces the radio waves. During World War II, the American military couldn’t get enough magnetrons to satisfy their radar needs. So <a href="http://www.famousinventors.org/percy-spencer">Percy Spencer</a>, an engineer at Raytheon, was tasked with ramping up magnetron production. He soon redesigned the magnetron so that its components could be punched out from sheet metal – like sugar cookies are cut from dough – rather than each part needing to be individually machined. This allowed mass production of magnetrons, raising wartime production from just 17 to 2,600 per day.</p>
<p>One day, while Spencer was working with a live magnetron, he noticed that a candy bar in his pocket had started to melt. Suspecting that the radio waves from the magnetron were the cause, he decided to try an experiment with an egg. He took a raw egg and pointed the radar beam at it. The egg exploded from rapid heating. Another experiment with corn kernels showed that radio waves could quickly make popcorn. This was a remarkably lucky find. <a href="https://www.aps.org/publications/apsnews/201510/physicshistory.cfm">Raytheon soon filed for a patent</a> on the use of radar technology for cooking, and the Radarange was born.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/mr7dvUxeFgQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Amana Radarange commercial from 1976.</span></figcaption>
</figure>
<p>As time passed and other companies got into the business, the trademarked Radarange gave way to more generic terminology and people started calling them “microwave ovens,” or even just “microwaves.” Why microwaves? Because the radio waves that are used for cooking have relatively short wavelengths. While the radio waves used for telecommunications can be as long as a football field, the ovens rely on <a href="https://public.nrao.edu/types-of-radio-waves">radio waves with wavelengths measured in inches</a> (or centimeters); so they are considered “micro” (Latin for small), as far as radio waves go.</p>
<p>Microwaves are able to heat food but not the paper plate holding it because the frequency of the microwaves is set such that they specifically agitate water molecules, causing them to vibrate rapidly. It is this vibration that causes the heat production. No water, no heat. So objects that don’t contain water, like a paper plate or ceramic dish, are not heated by microwaves. All the heating takes place in the food itself, not its container.</p>
<p>Microwaves have never completely replaced conventional ovens, despite their rapid speed of cooking, nor will they ever. <a href="http://www.msn.com/en-us/foodanddrink/quickandeasy/best-and-worst-foods-to-microwave/ss-BBr7BXD#image=1">Fast heating is not useful for certain types of cooking</a> like bread-baking, where slow heating is required for the yeast to make the dough rise; and a microwaved steak is no taste match for a broiled one. Nevertheless, as the fast-paced American lifestyle becomes increasingly dependent upon processed foods, reheating is sometimes the only “cooking” that’s required to make a meal. Microwave ovens’ uniform and rapid heating make them ideal for this purpose.</p>
<p>Over the years, there have been many myths associated with microwave cooking. But the truth is that, no, they <a href="http://www.health.harvard.edu/staying-healthy/microwave-cooking-and-nutrition">don’t destroy the food’s nutrients</a>. And, as I explain in my book “<a href="http://press.princeton.edu/titles/10691.html">Strange Glow: The Story of Radiation</a>,” you don’t get cancer from either cooking with a microwave oven or eating microwaved food. In fact, the <a href="http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=1030.10">leakage standards for modern microwave ovens</a> are so stringent that your candy bar is safe from melting, even if you tape it to the outside of the oven’s door. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/jWOxnpmw7Dk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What’s the deal with metal in the microwave?</span></figcaption>
</figure>
<p>Nevertheless, you should be careful about <a href="http://www.health.harvard.edu/staying-healthy/microwaving-food-in-plastic-dangerous-or-not">microwaving food in plastic containers</a>, because some chemicals from the plastic can leach into the food. And, yes, you <a href="http://mentalfloss.com/article/32032/why-cant-you-put-metal-microwave">shouldn’t put any metal in the microwave</a>, because metallic objects with pointed edges can interact with the microwaves from the magnetron in a way that can cause electrical sparking (<a href="https://www.corrosionpedia.com/definition/1482/arcing-corrosion">arcing</a>) and consequently damage the oven or cause a fire.</p>
<p>The microwave oven has definitely transformed the way most of us cook. So let’s all celebrate the 50th anniversary of the home microwave and the many hours of kitchen drudgery it has saved us from. But if you want to mark the date with an anniversary cake, best not to cook it in your microwave – you’d likely end up with just a very hot and unappetizing bowl of sweet mush.</p><img src="https://counter.theconversation.com/content/74249/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>It’s been five decades of microwave popcorn and piping hot leftovers in home kitchens. A serendipitous discovery helped engineers harness radar to create this now ubiquitous timesaving appliance.Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/706362016-12-20T20:15:26Z2016-12-20T20:15:26ZWhy you can’t fry eggs (or testicles) with a cellphone<figure><img src="https://images.theconversation.com/files/151083/original/image-20161220-26741-nmhzbw.jpg?ixlib=rb-1.1.0&rect=721%2C0%2C3197%2C1982&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pocket your phone without worry.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic.mhtml?id=533966416">Phone image via www.shutterstock.com.</a></span></figcaption></figure><p>A minor craze in men’s underwear fashions these days seems to be <a href="http://www.nbcnews.com/news/world/boxer-shorts-claim-protect-testicles-cellphone-radiation-n538576">briefs that shield the genitals</a> from cellphone radiation. The sales claim is that these products protect the testicles from the harmful effects of the radio waves emitted by cellphones, and therefore help maintain a robust sperm count and high fertility. These undergarments may shield the testicles from radiation, but do <a href="http://www.newsweek.com/boxer-rebellion-pocketed-cellphone-may-be-behind-your-infertility-287075">male cellphone users really risk infertility</a>?</p>
<p>The notion that electromagnetic radiation in the radio frequency range can cause male sterility, either temporary or permanent, has been around for a long time. As I describe in my book <a href="http://press.princeton.edu/titles/10691.html">“Strange Glow: The Story of Radiation</a>,” during World War II some enlisted men would consistently and inexplicably volunteer for radar duty just prior to their scheduled leave days. It turned out that a rumor had been circulating that exposure to radio waves from the radar equipment produced temporary sterility, which the soldiers saw as an employment benefit.</p>
<p>The military wanted to know whether there was any substance to the sterility rumor. So they asked <a href="https://www.nobelprize.org/nobel_prizes/medicine/laureates/1946/muller-bio.html">Hermann Muller</a> – a geneticist who <a href="https://www.nobelprize.org/nobel_prizes/medicine/laureates/1946/muller-lecture.html">won the Nobel Prize</a> for showing that x-rays could cause sterility and genetic mutations – to evaluate the effects of radio waves in the same fruit fly experimental model he had used to show that x-rays impaired reproduction. </p>
<p>Muller could find no dose of radio waves that produced either sterility or genetic mutations, and concluded that radio waves did not present the same threat to fertility that x-rays did. Radio waves were different. But why? Aren’t both x-rays and radio waves <a href="http://www.livescience.com/38169-electromagnetism.html">electromagnetic radiation</a>?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=326&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=326&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=326&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=410&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=410&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151022/original/image-20161220-26741-1sutwex.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=410&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 electromagnetic spectrum, tiny wavelengths on the left, longer wavelengths on the right.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:EM_Spectrum_Properties_reflected.svg">Inductiveload</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Yes, they are – but they differ in one key factor: They have very different wavelengths. All electromagnetic radiation travels through space as invisible waves of energy. And it’s the specific wavelength of the radiation that determines all of its effects, both physical and biological. The shorter wavelengths carry higher amounts of energy than the longer wavelengths.</p>
<p>X-rays are able to damage cells and tissues precisely because their wavelengths are extremely short – one-millionth the width of a human hair – and thus are highly energetic and very harmful to cells. Radio waves, in contrast, carry little energy because their wavelengths are very long – about the length of a football field. Such long-wavelength radiations have really low energies – too low to damage cells. And it’s this big difference between the wavelengths of x-rays and radio waves that the infertility theorists fail to recognize.</p>
<p>X-rays, and other high-energy waves, produce sterility by killing off the testicular cells that make sperm – the “<a href="https://www.repropedia.org/spermatogonium">spermatogonia</a>.” And x-ray doses must be extremely high to kill enough cells to produce sterility. Still, even when the doses are high, the sterility effect is usually temporary because the surviving spermatogonia are able to <a href="http://doi.org/10.1002/aja.1001180211">spawn replacements</a> for their dead comrades, and sperm counts typically return to their normal levels within a few months.</p>
<p>So, if high doses of highly energetic x-rays are needed to kill enough cells to produce sterility, how can low doses of radio waves with energies too low to kill cells do it? Good question.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/axUBeF-W7II?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Don’t fall for the phone-cooking-egg hoax.</span></figcaption>
</figure>
<p>At this point you may be thinking that you’ve seen videos of <a href="https://www.youtube.com/watch?v=axUBeF-W7II">cellphones cooking eggs</a>. And you’ve even experienced your cellphone getting pretty warm when it’s used heavily. But this doesn’t show that cellphones put out a lot of radiation energy. The cooked egg video is a prank, and the phone gets hot because of the heat generated by the chemical reactions going on within the battery, not from radio waves.</p>
<p>Still you protest: What about those sporadic reports claiming that cellphones suppress sperm counts? For the moment, that’s all they are – sporadic reports, unconfirmed by other investigators. You can find all kinds of random assertions about the effects of radiation on health, both <a href="http://www.orau.org/ptp/collection/quackcures/quackcures.htm">good</a> and <a href="https://www.scribd.com/document/59721111/TOP10-Myths-About-Radiation">bad</a>, most of which imply that there is some type of validated scientific evidence to support the claim. Why not believe all of them?</p>
<p>If we’ve learned anything over the years about scientific evidence, it’s that isolated findings from individual labs, reporting limited experimental data, do not a strong case make. Most of the very limited “scientific” reports of infertility caused by cellphones, often <a href="http://www.ewg.org/cell-phone-radiation-damages-sperm-studies-find">cited by anti-cellphone activists</a>, come from outside the radiation biology community, and are published in lower-tier journals of questionable quality. Few, if any, of these reports make any attempt at actually measuring the radiation doses received from the cellphones (probably because they lack either the expertise or the equipment required to do it).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151040/original/image-20161220-26748-1ive95i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Human sperm, unconcerned by what’s in your pocket.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Sperm_(265_33)_human.jpg">Doc. RNDr. Josef Reischig, CSc.</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>And none actually measure fertility rates – the health endpoint of concern – but rather measure sperm counts and other sperm quality parameters and then infer that there will be an impact on fertility. In fact, sperm counts can vary widely between normally fertile individuals and even within the same individual from day to day. For example, men who frequently ejaculate have lower sperm counts, as you might expect, because they are regularly jettisoning sperm. (Men who ejaculate daily can have <a href="http://doi.org/10.1186/s12958-015-0045-9">sperm counts 50 percent lower</a> than men who don’t.) Perhaps the allegedly lower sperm counts of cellphone users just means that they are having more sex!</p>
<p>But seriously, the point is this: There are so many things that can affect sperm counts in big ways that minor fluctuations in sperm counts have no practical impact on whether a man will produce babies, even if it were true that cellphones can modestly suppress sperm counts.</p>
<p>It is clear that these infertility claims are not the consensus of the mainstream scientific community – a community that demands more rigorous evidence. There are many excellent laboratories around the world that study radiation effects, and it isn’t difficult to study infertility in fruit flies, mice and even people. (It’s fairly easy to find men willing to <a href="https://verdict.justia.com/2012/01/24/men-who-give-it-away">donate sperm samples</a>.) If the sterility story were true, there would be a chorus of well-respected laboratories from around the world singing the cellphone infertility song, not just a few.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=666&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=666&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=666&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=837&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=837&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151036/original/image-20161220-26748-eadyou.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=837&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Guglielmo Marconi, inventor of the radio.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/smithsonian/2551824648">Smithsonian Institution</a></span>
</figcaption>
</figure>
<p>The fact is, the current data suggesting that cellphones cause infertility are too weak to challenge the dogma of over 100 years of commercial experience with radio waves. Radio waves are not unique to cellphones. They have been used for telecommunication ever since <a href="http://www.history.com/this-day-in-history/marconi-sends-first-atlantic-wireless-transmission">Marconi first demonstrated in 1901</a> that they could carry messages across the entire Atlantic Ocean. Early radio workers received massive doses of radio waves, yet there is no indication they had any problems with their fertility. If they didn’t experience fertility problems with their high doses, how can the relatively low doses from cellphones have such an effect? Hard to understand.</p>
<p>Nevertheless, people can spend their money as they please and wear any underwear they want. But if you are still concerned about radio waves affecting your fertility, why not just carry your cellphone in your shirt pocket rather than your pants, and let your testicles be?</p><img src="https://counter.theconversation.com/content/70636/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>Did your holiday gift list include radiation-shielding undies to protect your privates from cellphone radio waves? A radiation expert explains they’re unnecessary – your phone won’t affect your fertility.Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown UniversityLicensed as Creative Commons – attribution, no derivatives.