tag:theconversation.com,2011:/id/topics/curious-kids-36782/articles
Curious Kids – The Conversation
2024-03-28T05:45:33Z
tag:theconversation.com,2011:article/224740
2024-03-28T05:45:33Z
2024-03-28T05:45:33Z
Curious Kids: what did people use before toothpaste was invented?
<figure><img src="https://images.theconversation.com/files/583065/original/file-20240320-28-zza8cd.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/little-asian-cute-girl-brush-teeth-612960914">Casezy idea/Shutterstock</a></span></figcaption></figure><blockquote>
<p>How does toothpaste work? What did people use before toothpaste was invented? – Amelia, age 7, Meanjin (Brisbane)</p>
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<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Thanks for your great questions, Amelia. </p>
<p>I’m a dentist, so I know a bit about how toothpaste works and what we used before it was invented.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-cats-and-dogs-lose-baby-teeth-like-people-do-98380">Curious Kids: Do cats and dogs lose baby teeth like people do?</a>
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</em>
</p>
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<h2>How does toothpaste work?</h2>
<p>Toothpaste makes your mouth smell fresh and feel clean. If you brush your teeth two times a day, toothpaste also helps protect your teeth from forming holes or cavities. Let’s look at these benefits one at a time.</p>
<p><strong>That fresh feeling</strong></p>
<p>Some <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7245492/">toothpaste ingredients</a> mix with your spit (or saliva) to make a soapy sudsy foam. The sudsy foam turns into slimy slop that you spit out.</p>
<p>Many toothpastes also have a slight sandy feeling to scrub stains off your teeth. This also helps remove the sticky, soft, white globs that grow on your teeth called plaque (pronounced plark). </p>
<p>Plaque is made from sticky bits of food and bacteria (tiny bugs). The bacteria in your plaque live, grow and multiply in your mouth. Some bacteria – such as <a href="https://www.ingentaconnect.com/content/aapd/pd/2021/00000043/00000001/art00002"><em>Streptococcus mutans</em></a> (pronounced strep-toe-cock-us mew-tans) – love to digest the sugary food you eat. Other bacteria in your plaque burp rotten-egg gases that make your breath smell. </p>
<p>No wonder we want to get rid of plaque with gassy bacteria.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/iAQUCF9n3HU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What is plaque?</span></figcaption>
</figure>
<p><strong>Prevents cavities</strong></p>
<p>Even worse, plaque bacteria poo out diarrhoea (pronounced die-ree-a). That diarrhoea is “acidic”, meaning it can dissolve your teeth to form holes. So we brush our teeth twice a day to get rid of as much bacteria and their diarrhoea as we can.</p>
<p>There are lots of special ingredients in toothpastes to prevent holes from forming that include:</p>
<ul>
<li><p><a href="https://www.tandfonline.com/doi/abs/10.1080/19424396.2003.12224154">xylitol</a> (pronounced zy-lee-toll). When bacteria in your plaque eat this, they get constipated and poo less acid</p></li>
<li><p><a href="https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD007868.pub3/full">fluoride</a> (pronounced floor-ride). Your teeth have tiny gaps on the surface that are so small you can only see them with a microscope. Fluoride fills these gaps to make your teeth strong. This is how fluoride protects against nasty bacteria poo from dissolving your teeth.</p></li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-is-inside-teeth-187258">Curious Kids: what is inside teeth?</a>
</strong>
</em>
</p>
<hr>
<h2>What did people use in the olden days?</h2>
<p>People who lived a long time ago didn’t know much about <em>Streptococcus mutans</em> and bacteria poo. They thought getting holes in teeth was part of growing up. They were wrong. But they tried to make their teeth look whiter by using tooth powders.</p>
<p>People in ancient Egypt, China and India used their fingers to rub <a href="https://mansapublishers.com/index.php/jofr/article/view/1834/1444">tooth powders</a> on their teeth.</p>
<p>The first tooth powders were made of crushed animal bones, ox hooves, and egg, snail and oyster shells. Later, people added crushed charcoal (the black stuff you get when you burn bones or wood), powdered tree bark and flavouring herbs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Snail on green leaves" src="https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/583315/original/file-20240321-16-u9l7da.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">People used to crush snail shells and rub the powder on their teeth.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/snail-muller-gliding-on-wet-leaves-1341770150">Zebra-Studio/Shutterstock</a></span>
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<p>The ancient Romans cleaned their teeth with toothpaste made with <a href="https://mansapublishers.com/index.php/jofr/article/view/1834/1444">pee</a>. </p>
<p>Thank goodness things have changed.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-did-people-clean-their-teeth-in-the-olden-days-119588">How did people clean their teeth in the olden days?</a>
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</em>
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<h2>Thank your lucky stars</h2>
<p>The next time you brush your teeth, think of all those people in the olden days. They made tooth powders with bones and shells, and toothpaste with pee. </p>
<p>Luckily, we now have toothpastes that leave a better taste in your mouth and stop holes forming in your teeth. </p>
<p>But when you brush your teeth, remember to spit out the toothpaste. Don’t rinse it away with water. We want to keep a bit in your mouth to protect your teeth from that nasty bacteria poo. </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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/224740/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Arosha Weerakoon's PhD research on the effect of ageing on mineral and collagen in teeth was funded by Colgate. She is also an Advocate for Oral Health with Colgate. Arosha is a practice owner and works as a general dentist.. </span></em></p>
People once used tooth powders made from crushed bone or shells to whiten their teeth. Others rinsed their mouth out with pee. Yuck!
Arosha Weerakoon, Senior Lecturer and General Dentist, School of Dentistry, The University of Queensland
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/224507
2024-03-25T23:54:53Z
2024-03-25T23:54:53Z
Curious Kids: how is eye colour made? And why are they different colours?
<figure><img src="https://images.theconversation.com/files/582452/original/file-20240318-27766-2yz46i.jpeg?ixlib=rb-1.1.0&rect=8%2C8%2C5982%2C3979&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://images.pexels.com/photos/4039320/pexels-photo-4039320.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=1">Pexels/Nóra Zahradník</a></span></figcaption></figure><p><strong>“How is eye colour made? And why are they different colours?” – Jane, age 12, from Pascoe Vale South</strong></p>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Jane, </p>
<p>Eyes are so fascinating and I’m glad you asked this question!</p>
<p>When we talk about eye colour, we’re talking about the iris or coloured area around the dark dot (pupil) in the centre of the eye. Like our fingerprints, iris colours are <a href="https://www.sciencedirect.com/topics/computer-science/iris-recognition">unique to each person</a>. </p>
<p>The most common eye colour is brown, then blue, and less often green or hazel. Pigment means a substance that adds colour. The amazing thing is the human body only makes brown iris pigment (melanin) but not blue, green or hazel iris pigments. So how come everyone doesn’t have brown irises?</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-are-the-main-factors-in-forming-someones-personality-222264">Curious Kids: what are the main factors in forming someone's personality?</a>
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<hr>
<h2>‘What colour are your eyes?’</h2>
<p>Iris colours can be brown, blue or green, or mixtures such as brown-yellow, greenish brown or blue-brown. The word “iris” comes from the <a href="https://www.researchgate.net/publication/370608432_On_the_etymology_of_the_word_iris_from_the_name_of_a_God_to_the_eye">Greek word</a> meaning “rainbow”. In ancient Greek stories, a goddess <a href="https://www.britannica.com/topic/Iris-Greek-mythology">called Iris</a> carries messages across a rainbow bridge between Earth and the supernatural world.</p>
<p>Genetics – how physical traits and characteristics pass from one generation to the next – play a part in determining eye colour. In many cases, <a href="https://www.nature.com/articles/s41433-021-01749-x">the genes that produce brown eyes</a> are dominant, but how eye colour genes are passed on is complex. This can mean if one biological parent has brown eyes and another has blue eyes, their child is more likely to have brown eyes. But not always. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-we-see-different-colours-when-we-close-our-eyes-154378">Curious Kids: why do we see different colours when we close our eyes?</a>
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</em>
</p>
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<h2>But what about all the other colours?</h2>
<p>So what is the iris made of? <a href="https://www.nei.nih.gov/sites/default/files/2019-06/parts-of-the-eye.pdf">Our iris is inside the eye</a>, behind a clear layer called the cornea. It’s circular and very thin (less than half a millimetre) and shaped like a donut with a hole in the middle for our pupil. The iris contains many cells, special muscles, blood vessels and nerves, surrounded by a gel material with millions of tiny crisscrossed fibres. </p>
<p>Iris pigment cells – melanocytes – contain pigment particles (melanosomes). Pigment cell numbers for all iris colours are about the same. But pigment particles inside the cells are different. For example, a blue iris does not have as many pigment particles as a brown iris. </p>
<p>The other iris cells make the tiny fibres and gel material in the iris, and other cells help protect the iris from damage. Special iris muscles with thin stretchy fibres can bunch up or relax the iris to control our pupil size in bright or dim light. </p>
<p>The back of the iris has a dark brown surface because of cells filled with brown pigment. This back surface pigment helps our vision as it stops light scattering through the iris. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="close ups of four eye irises, showing different colours and patterns" src="https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=200&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=200&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=200&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=251&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=251&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582453/original/file-20240318-18-7mjf76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=251&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Iris colours and patterns are unique to each person, like fingerprints.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-eye-iris-on-black-background-2320170915">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-people-colour-blind-107599">Curious Kids: why are people colour blind?</a>
</strong>
</em>
</p>
<hr>
<p>White or visible light contains a rainbow spectrum of colours from blue to red. As light passes through the iris, the blue light scatters much more than other colours. So blue light bounces back, and this means that if there are fewer pigment particles, we see a blue iris.</p>
<p>Other colours in light, especially red, scatter less and get into the iris between the tiny fibres, gel and cells. Green, hazel or brown irises have more pigment particles that soak up this light. </p>
<p>So the eye colours we see are a result of the scattering of some light colours more or less than others, brown pigment particles soaking up more of some colours, and the number of pigment particles a person has in their iris. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="young woman smiles and has two different coloured eyes" src="https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582454/original/file-20240318-24-72lms1.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">Some people are born with two different coloured eyes and these don’t change over time.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-portrait-beautiful-young-redhead-model-561622528">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-is-the-sky-blue-and-where-does-it-start-81165">Curious Kids: Why is the sky blue and where does it start?</a>
</strong>
</em>
</p>
<hr>
<h2>Can eye colours change?</h2>
<p>Iris colours can seem to change if different colours are near the eye. For example, different-coloured eye makeup can <a href="https://michaelbach.de/ot/col-context/">“trick” us as to the iris colour we see</a>.</p>
<p>People with little or no iris pigment often have very pale blue irises. These can <a href="https://my.clevelandclinic.org/health/articles/21576-eye-colors">look reddish</a> without the iris pigment to soak up the red light from inside the eye, which then passes through the iris. </p>
<p>Iris colour does not always stay the same during life. Babies born with blue eyes can have brown or hazel eyes by their second birthday because <a href="https://pubmed.ncbi.nlm.nih.gov/31811709/">more dark pigment is made in iris cells after birth</a>. </p>
<p>Iris colour can also change because of <a href="https://www.aao.org/eye-health/tips-prevention/why-are-my-eyes-changing-color#:%7E:text=Injury%20or%20trauma%20to%20the,the%20iris%20can%20be%20seen.">rare diseases or injuries</a>. </p>
<p>Some <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/latanoprost">eye drops to treat eye pressure</a> make more brown pigment in iris cells, and make eyes appear browner. Some people are born with <a href="https://www.webmd.com/eye-health/heterochromia-iridis">one brown eye and one blue eye</a>, but these stay the same with age – although we’re not sure why. </p>
<p>There’s still so much to discover about irises and eye colour!</p><img src="https://counter.theconversation.com/content/224507/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michele Madigan receives funding from Australian Vision Research. </span></em></p>
The most common eye colour is brown, then blue, and less often, green or hazel. But the human body only makes brown iris pigment.
Michele Madigan, Associate Professor, Optometry and Vision Science, UNSW Sydney and Clinical Associate Professor, Save Sight Institute, Clinical Ophthalmology, University of Sydney
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/224152
2024-03-25T12:39:22Z
2024-03-25T12:39:22Z
What is dirt? There’s a whole wriggling world alive in the ground beneath our feet, as a soil scientist explains
<figure><img src="https://images.theconversation.com/files/582688/original/file-20240318-24-77z9su.jpg?ixlib=rb-1.1.0&rect=0%2C9%2C3110%2C2057&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dig into soil and you'll find rock dust but also thousands of living species.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/little-childs-hands-digging-in-the-mud-royalty-free-image/619539728">ChristinLola/iStock/Getty Images Plus</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>What is dirt? – Belle and Ryatt, ages 7 and 5, Keystone, South Dakota</strong></p>
</blockquote>
<hr>
<p>When you think about dirt, you’re probably picturing soil. There’s so much more going on under our feet than the rock dust, or “dirt,” that gets on your pants.</p>
<p>When <a href="https://arts-sciences.und.edu/academics/biology/brian-darby/index.html">I began studying soil</a>, I was amazed at how much of it is actually alive. Soil is teeming with life, and not just the earthworms that you see on rainy days.</p>
<p>Keeping this vibrant world healthy is <a href="https://www.youtube.com/watch?v=Qas9tPQKd8w">crucial for food, forests and flowers to grow</a> and for the animals that live in the ground to thrive. Here’s a closer look at what’s down there and how it all works together.</p>
<figure class="align-center ">
<img alt="Cupped hands holds soil against a dark background with a tendril of plant root dangling through the fingers." src="https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582689/original/file-20240318-20-8yglsj.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">Soil is a vibrant ecosystem.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/bokeh-photography-of-person-carrying-soil-jin4W1HqgL4">Gabriel Jimenez via Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The rocky part of soils</h2>
<p>If you scoop up a handful of dry soil, the basic dirt that you feel in your hand is actually very small pieces of <a href="https://passel2.unl.edu/view/lesson/c62dc027ae56/1">weathered rock</a>. These tiny bits eroded from larger rocks over millions of years.</p>
<p>The <a href="https://www.soils4teachers.org/physical-properties/">balance of these particles</a> is important for how well soil can hold water and nutrients that plants need to thrive. </p>
<p>For example, <a href="https://www.masterclass.com/articles/sandy-soil-guide">sandy soil</a> has larger rock grains, so it will be loose and can easily wash away. It won’t hold very much water. <a href="https://www.thespruce.com/understanding-and-improving-clay-soil-2539857">Soil with mostly clay</a> is finer and more compact, making it difficult for plants to access its moisture. In between the two in size is <a href="https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-silt.htm">silt, a mix of rock dust and minerals</a> often found in fertile flood plains.</p>
<p>Some of the most productive soils have a good balance of sand, clay and silt. <a href="https://www.masterclass.com/articles/how-to-create-loam-soil-for-your-garden">That combination</a>, along with the remnants of plants and animals that have died, helps the soil to retain water, allows plants to access that water and minimizes erosion from wind or rain.</p>
<figure class="align-center ">
<img alt="Three tipped over pots spill different types of soil – sandy is heavier grain, clay is finer grain and thicker, and loamy is darker." src="https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581414/original/file-20240312-16-meqnvu.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Loamy soil, ideal for gardens, is a mix of sand, clay and silt.</span>
<span class="attribution"><a class="source" href="https://www.nesdis.noaa.gov/learn-about-soil-types">NOAA</a></span>
</figcaption>
</figure>
<h2>The wriggling, munching parts of soil</h2>
<p>Among all those rock particles is a <a href="https://doi.org/10.3390/app10113717">whole world of living things</a>, each busy doing its job.</p>
<p>To get a sense of just how many creatures are there, picture this: The zoo in Omaha, Nebraska, boasts <a href="https://www.omahazoo.com/">over 1,000 animal species</a>. But if you scooped up a small spoonful of soil in your backyard, it would likely contain <a href="https://www.ceh.ac.uk/our-science/case-studies/case-study-why-do-soil-microbes-matter">at least 10,000 species</a> and around a billion living microscopic cells.</p>
<p>Most of those species are <a href="https://www.westernsydney.edu.au/newscentre/news_centre/story_archive/2018/first_soil_atlas">still largely a mystery</a>. Scientists don’t know much about them or what they do in soil. In fact, most species in soil don’t even have a formal scientific name. But each plays some kind of role in the vast soil ecosystem, including generating the <a href="https://www.aces.edu/blog/topics/farming/essential-plant-elements/">nutrients that plants need to grow</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two centipede-like creatures caught on camera immediately after a rock is lifted." src="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581410/original/file-20240312-20-vn3j2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lifting a rock reveals a symphylan, or garden centipede, left, and a poduromorph, or plump springtail, munching through the soil.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Symphylan_%26_poduromorph_springtail_(3406419924).jpg">Marshal Hedin via Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Imagine a leaf falling from a tree in late autumn.</p>
<p>Inside that leaf are a lot of nutrients that plants need, such as nitrogen, potassium and phosphorus. There is also a lot of <a href="https://scied.ucar.edu/learning-zone/earth-system/biogeochemical-cycles">carbon in that leaf</a>, which holds energy that can be used by other organisms such as bacteria and fungi.</p>
<p>The leaf itself is too large for a plant to take up through its roots, of course. But that leaf can be broken down into smaller and smaller pieces. This process of breaking down plant and animal tissue is <a href="https://youtu.be/IBvKKMzXYtY?feature=shared">known as decomposition</a>.</p>
<p>When the leaf first falls to the ground, <a href="https://doi.org/10.3390%2Finsects11010054">arthropods</a> – such as insects, mites and <a href="https://www.chaosofdelight.org/collembola-springtails">collembolans</a> – break the leaf down into smaller chunks by shredding the tissue. Then, an <a href="https://youtu.be/n3wsUYg3XV0?feature=shared">earthworm might come along</a> and eat one of the smaller chunks and break it down even more in <a href="https://www.pbs.org/video/how-do-worms-turn-garbage-into-compost-jwj6cm/">its digestive tract</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2Pa1FwmKZcQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">PBS explores how earthworms help turn dead plants into fertile soil.</span></figcaption>
</figure>
<p>Now the broken-up leaf is small enough for microbes to come in. <a href="https://ohioline.osu.edu/factsheet/anr-36">Bacteria</a> and <a href="https://ohioline.osu.edu/factsheet/anr-37">fungi secrete enzymes</a> into the soil that further break down organic material into even smaller pieces. If enough microbes are active, eventually this organic material will be broken down enough that it can dissolve in water and be taken up by plants that need it.</p>
<p>To aid in this process, there are many small animals, such as <a href="https://www.canr.msu.edu/news/are_soil_nematodes_beneficial_or_harmful">nematodes</a> and <a href="https://www.livingsoil.net/protozoa">amoebae</a>, that consume bacteria and fungi. There are also predatory nematodes that feed on other nematodes to make sure they don’t become too abundant, so everything remains in balance as much as possible. </p>
<p>It’s quite a complicated food web of interacting species in a delicate balance.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/IBvKKMzXYtY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A time-lapse video filmed about 4 inches underground shows a leaf decomposing over 21 days in July. At the end, radish roots make their way down into the soil. Video by Josh Williams.</span></figcaption>
</figure>
<p>While some fungi and bacteria <a href="https://www.growingagreenerworld.com/bacteria-fungus-and-viruses-an-overview/">can harm plants</a>, there are many species that are considered beneficial. In fact, they <a href="https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soils/soil-health">may be the key</a> to figuring out how to grow enough crops to feed everyone without degrading and overburdening the soil.</p>
<h2>Figuring out your soil type</h2>
<p>Scientists have named <a href="https://www.nrcs.usda.gov/resources/education-and-teaching-materials/soil-facts">over 20,000 different types</a> of unique soils. If you’re curious about the <a href="https://www.nesdis.noaa.gov/learn-about-soil-types">soil and dirt in your area</a>, the University of California, Davis has a <a href="https://casoilresource.lawr.ucdavis.edu/gmap/">website where you can learn</a> more about local soils and their chemical and physical attributes.</p>
<p><a href="https://www.farmers.gov/conservation/soil-health">Caring for soil</a> to promote its living creatures’ benefits and minimize their harm takes work, but it’s essential for keeping the land healthy and growing food for the future.</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/224152/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brian Darby receives funding from the United States Department of Agriculture. </span></em></p>
Rock dust is only part of the story of soil. Living creatures, many of them too tiny to see, keep that soil healthy for growing everything from food to forests.
Brian Darby, Associate Professor of Biology, University of North Dakota
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222847
2024-03-18T12:30:59Z
2024-03-18T12:30:59Z
How do airplanes fly? An aerospace engineer explains the physics of flight
<figure><img src="https://images.theconversation.com/files/578175/original/file-20240227-28-cejldv.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7668%2C4449&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">U.S. airlines carry more than 800 million passengers per year.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/airplane-isolated-on-sky-3d-rendering-royalty-free-image/1147868750?phrase=airplanes">Lasha Kilasonia/iStock via Getty Images Plus</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>How do airplanes fly? – Benson, age 10, Rockford, Michigan</strong></p>
</blockquote>
<hr>
<p>Airplane flight is one of the most significant technological achievements of the 20th century. The <a href="https://airandspace.si.edu/explore/stories/wright-brothers">invention of the airplane</a> allows people to travel from one side of the planet to the other in less than a day, compared with weeks of travel by boat and train.</p>
<p>Understanding precisely why airplanes fly is an ongoing challenge for <a href="https://www.clarkson.edu/people/craig-merrett">aerospace engineers, like me</a>, who study and design airplanes, rockets, satellites, helicopters and space capsules. </p>
<p>Our job is to make sure that flying through the air or in space is safe and reliable, by using tools and ideas from science and mathematics, like computer simulations and experiments. </p>
<p>Because of that work, flying in an airplane is <a href="https://usafacts.org/articles/is-flying-safer-than-driving/">the safest way to travel</a> – safer than cars, buses, trains or boats. But although aerospace engineers design aircraft that are stunningly sophisticated, you might be surprised to learn there are still some details about the physics of flight that we don’t fully understand.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram of an airplane that shows the four forces of flight." src="https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/577439/original/file-20240222-28-v3tjb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&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 forces of weight, thrust, drag and lift act on a plane to keep it aloft and moving.</span>
<span class="attribution"><a class="source" href="https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/airplane-cruise-balanced-forces/">NASA</a></span>
</figcaption>
</figure>
<h2>May the force(s) be with you</h2>
<p>There are <a href="https://www.nasa.gov/stem-content/four-forces-of-flight/#:%7E">four forces</a> that aerospace engineers consider when designing an airplane: weight, thrust, drag and lift. Engineers use these forces to help design the shape of the airplane, the size of the wings, and figure out how many passengers the airplane can carry. </p>
<p>For example, when an airplane takes off, the thrust must be greater than the drag, and the lift must be greater than the weight. If you watch an airplane take off, you’ll see the wings change shape using flaps from the back of the wings. The flaps help make more lift, but they also make more drag, so a powerful engine is necessary to create more thrust. </p>
<p>When the airplane is high enough and is cruising to your destination, lift needs to balance the weight, and the thrust needs to balance the drag. So the pilot pulls the flaps in and can set the engine to produce less power.</p>
<p>That said, let’s define what force means. According to <a href="https://ca.pbslearningmedia.org/resource/4079abf0-7a4b-4f49-80ad-c69cd06a80f9/newtons-second-law-of-motion/">Newton’s Second Law</a>, a force is a mass multiplied by an acceleration, or F = ma. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white historical photograph of the first flight of the Wright brothers." src="https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579678/original/file-20240304-22-jrh9mr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On Dec. 17, 1903, the Wright brothers made their first flight at Kitty Hawk, N.C. Orville Wright is at the controls, while Wilbur looks on.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-flyer-takes-off-from-kill-devil-hill-with-orville-news-photo/517389284?adppopup=true">Bettmann via Getty Images</a></span>
</figcaption>
</figure>
<p>A force that everyone encounters every day is <a href="https://spaceplace.nasa.gov/what-is-gravity/en/#:%7E">the force of gravity</a>, which keeps us on the ground. When you get weighed at the doctor’s office, they’re actually measuring the amount of force that your body applies to the scale. When your weight is given in pounds, that is a measure of force. </p>
<p>While an airplane is flying, gravity is pulling the airplane down. That force is the weight of the airplane. </p>
<p>But its engines push the airplane forward because they create <a href="https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/what-is-thrust/">a force called thrust</a>. The engines pull in air, which has mass, and quickly push that air out of the back of the engine – so there’s a mass multiplied by an acceleration. </p>
<p>According to <a href="https://www.youtube.com/watch?v=a-wh3fJRdjo">Newton’s Third Law</a>, for every action there’s an equal and opposite reaction. When the air rushes out the back of the engines, there is a reaction force that pushes the airplane forward – that’s called thrust.</p>
<p>As the airplane flies through the air, the shape of the airplane pushes air out of the way. Again, by Newton’s Third Law, this air pushes back, <a href="https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/what-is-drag/#:%7E">which leads to drag</a>. </p>
<p>You can experience something similar to drag when swimming. Paddle through a pool, and your arms and feet provide thrust. Stop paddling, and you will keep moving forward because you have mass, but you will slow down. The reason that you slow down is that the water is pushing back on you – that’s drag. </p>
<h2>Understanding lift</h2>
<p><a href="https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/what-is-lift/">Lift</a> is more complicated than the other forces of weight, thrust and drag. It’s created by the wings of an airplane, and the shape of the wing is critical; that shape is <a href="https://howthingsfly.si.edu/media/airfoil#:%7E">known as an airfoil</a>. Basically it means the top and bottom of the wing are curved, although the shapes of the curves can be different from each other. </p>
<p>As air flows around the airfoil, <a href="https://www.youtube.com/watch?v=UO75jDwGCdQ">it creates pressure</a> – a force spread out over a large area. Lower pressure is created on the top of the airfoil compared to the pressure on the bottom. Or to look at it another way, air travels faster over the top of the airfoil than beneath. </p>
<p>Understanding why the pressure and speeds are different on the top and the bottom is <a href="https://airandspace.si.edu/multimedia-gallery/lift-and-copjpg">critical to understand lift</a>. By improving our understanding of lift, engineers can design more fuel-efficient airplanes and give passengers more comfortable flights.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram that shows how the airfoil of a plane works." src="https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579698/original/file-20240304-24-6df49v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Note the airfoil, which is a specific wing shape that helps keep a plane in the air.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/how-airplanes-fly-royalty-free-illustration/1401215523?phrase=airfoil+diagram&adppopup=true">Dimitrios Karamitros/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>The conundrum</h2>
<p>The reason why air moves at different speeds around an airfoil remains mysterious, and <a href="https://www.scientificamerican.com/video/no-one-can-explain-why-planes-stay-in-the-air/">scientists are still investigating</a> this question. </p>
<p>Aerospace engineers have measured these pressures on a wing in both wind tunnel experiments and during flight. We can create models of different wings to predict if they will fly well. We can also change lift by changing a wing’s shape to create airplanes that fly for long distances or fly very fast. </p>
<p>Even though we still don’t fully know why lift happens, aerospace engineers work with mathematical equations that recreate the different speeds on the top and bottom of the airfoil. Those equations describe a process <a href="https://howthingsfly.si.edu/media/circulation-theory-lift">known as circulation</a>. </p>
<p>Circulation provides aerospace engineers with a way to model what happens around a wing even if we do not completely understand why it happens. In other words, through the use of math and science, we are able to build airplanes that are safe and efficient, even if we don’t completely understand the process behind why it works.</p>
<p>Ultimately, if aerospace engineers can figure out why the air flows at different speeds depending on which side of the wing it’s on, we can design airplanes that use less fuel and pollute less.</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/222847/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig Merrett receives funding from the Office of Naval Research and L3Harris. He is affiliated with the American Institute for Aeronautics and Astronautics, and is a licensed professional engineering in Ontario, Canada. Dr. Merrett is an associate professor in the Department of Mechanical and Aerospace Engineering at Clarkson University, Potsdam, NY. </span></em></p>
People have been flying airplanes for well over a century. Engineers know how to balance all the forces at play, but still aren’t exactly sure how some of the physics of flight actually works.
Craig Merrett, Professor of Mechanical and Aerospace Engineering, Clarkson University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222972
2024-03-11T12:25:42Z
2024-03-11T12:25:42Z
Why do trees need sunlight? An environmental scientist explains photosynthesis
<figure><img src="https://images.theconversation.com/files/578432/original/file-20240227-20-s7p24d.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2048%2C1364&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The reason trees need sunlight is the same reason their leaves are green.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/scottb211/10108377914/"> Scottb211/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/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>Why do trees need sunlight? – Tillman, age 9, Asheville, North Carolina</strong></p>
</blockquote>
<hr>
<p>Trees need sunlight for the same reason you need food. The energy from the Sun’s rays is a crucial ingredient in how plants make their own food that helps them power all their cells. Since trees don’t harvest or hunt food, they have to produce their own. The way they make their food is a unique and important chemical process called photosynthesis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="honey-comb pattern of rings each containing many small green spheres" src="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chlorophyll is what makes leaves green.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Plagiomnium_affine_laminazellen.jpeg">Kristian Peters-Fabelfroh/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>What is photosynthesis?</h2>
<p>The cells in plants and all other living things have microscopic components called <a href="https://www.genome.gov/genetics-glossary/Organelle">organelles</a>. One type of organelle in plant cells is the chloroplast, and it contains the <a href="https://www.kidzone.ws/science/lessons/pigments.html">pigment</a> chlorophyll, which is what makes leaves green. When chlorophyll receives sunlight, it starts the <a href="https://education.nationalgeographic.org/resource/photosynthesis">photosynthesis</a> reaction.</p>
<p>The name photosynthesis comes from the ancient Greek words “photo,” which means light, and “synthesis,” which means to make. During this food-making process, plants take carbon dioxide from the air and water from the ground, and with the energy from sunlight, make glucose. Glucose is a very simple type of sugar. Because it is a simple compound, it is simple to make.</p>
<p>Most of the time, photosynthesis occurs in leaves, and leaves take in sunlight to make food. There are some special plants, though, that actually absorb sunlight on their stems. Some of these include cactuses like the balloon-shaped <a href="https://www.gardenia.net/plant/echinocactus-grusonii-golden-barrel-cactus">golden barrel cactus</a>, the spiky <a href="https://huntington.org/educators/learning-resources/spotlight/cylindropuntia-munzii">Munz’s Cholla</a> and the paddle-shaped <a href="https://huntington.org/educators/learning-resources/spotlight/opuntia-ficus-indica">prickly pear</a>. Some plants even have roots that can photosynthesize, like the rare palm <em><a href="https://huntington.org/educators/learning-resources/spotlight/cryosophila-albida">Cryosophila albida</a></em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic diagram of a plant showing sun, soil, roots, leaves and a flower" src="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sunlight gives plants the energy to turn water and carbon dioxide into carbohydrates – the food their cells need to live and grow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Photosynthesis_en.svg">At09kg/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Photosynthesis is billions of years old</h2>
<p>Photosynthesis evolved more than <a href="https://doi.org/10.1104%2Fpp.110.161687">3.5 billion years ago</a>. Initially, only single-celled organisms, kind of like today’s algae, could make sugar this way. Oxygen is a waste product from the photosynthesis process, and over time, these single-celled organisms released enough oxygen to change the Earth’s atmosphere. Ultimately, we and all other animals needed this to happen to be able to live and breathe. </p>
<p>Over time, aquatic plants developed, and gradually plants <a href="https://doi.org/10.1126/science.aat3642">moved to land</a> around 500 million years ago to better access their most vital resource: sunlight. Plants eventually got taller by around <a href="https://doi.org/10.1126/science.aar2986">350 million years ago</a>. This is when the first tree evolved, which grew up to 150 feet tall. These trees looked like the evergreen trees we see today – sort of like pines, firs and spruce. And about 125 million years ago, trees that looked like the maples, oaks and beech trees we see today shared the landscape when <a href="https://new.nsf.gov/news/dinosaur-age-fossils-provide-new-insights-origin">dinosaurs ruled the Earth</a>.</p>
<h2>Not just good for plants</h2>
<p>The Sun provides energy for the Earth. However, we humans are not capable of taking in the sun directly and using it to power our bodies. So how do we make use of the Sun’s energy? Plants do it for us.</p>
<p>Plants take in that energy and make food for us and other animals to eat and oxygen for us to breathe. We wouldn’t exist without plants and photosynthesis.</p>
<p>Like the ancient tiny single-celled organisms from 3.5 billion years ago, some microorganisms today use photosynthesis. Specifically, the algae that you might see living on top of lakes and the ocean do. Chlorophyll is why algae is green. </p>
<p>There are <a href="https://news.asu.edu/20191114-asu-study-shows-some-aquatic-plants-depend-landscape-photosynthesis">aquatic plants</a> that use sunlight to grow. They typically make use of less sunlight because sunlight does not travel well through water.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="yellowish green grass-like plants underwater" src="https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578425/original/file-20240227-30-2rnnkd.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">Some plants can do photosynthesis underwater, where there is less sunlight.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/chesbayprogram/32446887586/">Chesapeake Bay Program/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>In addition, there are a very few animals that can photosynthesize. The <a href="https://doi.org/10.1038/nature.2012.11214">pea aphid</a> uses pigment to harvest sunlight to make energy. The <a href="https://phys.org/news/2011-01-physicists-outer-shell-hornet-harvest.html">Oriental hornet</a> uses a pigment in its exoskeleton to make energy from sunlight. The <a href="https://www.nationalgeographic.com/animals/article/solar-powered-photosynthetic-sea-slugs-in-decline-news">emerald-green sea slug</a> eats algae and then incorporates chlorophyll from the algae into its body to photosynthesize. Because of this strategy, the sea slug can go nine months without eating. </p>
<p>So the answer to this question – why do trees need sunlight – is to make their food. And thanks to trees and other plants turning sunlight into their food, most of the rest of the living things on Earth get to eat, too!</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/222972/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rebekah Stein 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>
Trees – and all plants – harvest sunlight to gain the energy they need to live and grow.
Rebekah Stein, Assistant Professor of Environmental Science, Quinnipiac University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/213208
2024-03-04T13:35:40Z
2024-03-04T13:35:40Z
Why do bees have queens? 2 biologists explain this insect’s social structure – and why some bees don’t have a queen at all
<figure><img src="https://images.theconversation.com/files/578405/original/file-20240227-30-jjne39.jpg?ixlib=rb-1.1.0&rect=9%2C0%2C3019%2C1971&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The queen, on the right with a larger, darker body, is bigger than the worker bees in the colony and lives several times longer.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/bees-from-a-bee-colony-with-a-queen-are-seen-on-a-honeycomb-news-photo/1233050929">Jens Kalaene/picture alliance 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>Why do bees have queens? – Rhylie, age 8, Rosburg, Washington</strong></p>
</blockquote>
<hr>
<p>When you think “bee,” you likely picture one species that lives all over the world: the <a href="https://www.natgeokids.com/au/discover/animals/insects/honey-bees/">honey bee</a>. And honey bees have queens, a female who lays essentially all of the eggs for the colony.</p>
<p>But most bees don’t have queens. With about <a href="https://www.usgs.gov/faqs/how-many-species-native-bees-are-united-states#:%7E">20,000 species of bees worldwide</a> – that’s about 2 trillion bees – the majority of them don’t even live in groups. They do just fine <a href="https://tpwd.texas.gov/huntwild/wild/wildlife_diversity/nongame/native-pollinators/solitary-social.phtml#:%7E">without queens or colonies</a>. </p>
<p>Instead, a single female lays eggs in a simple nest, either inside a plant stem or an underground tunnel. She provides each egg with a ball of pollen mixed with nectar that she collected from flowers, and she leaves the eggs to hatch and develop on their own. She doesn’t have anyone to help with this process. </p>
<p>These bee species, often spectacularly beautiful, are <a href="https://www.fs.usda.gov/wildflowers/pollinators/animals/bees.shtml">important pollinators of many crops and plants</a>, though most people aren’t even aware of them. </p>
<p>Since lots of bees successfully live without a queen, what is it that queens provide for the bee species that do have them? <a href="https://scholar.google.com/citations?user=KF4sBDIAAAAJ&hl=en&oi=ao">We are behavioral ecologists</a> <a href="https://scholar.google.com/citations?user=r9Wuv18AAAAJ&hl=en&oi=ao">who study social insects</a>, and this question is at the heart of our research. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="handful of bees flying toward a busy hive" src="https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578406/original/file-20240227-26-jefrkz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A bee colony may have many thousands of workers who support the single queen.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/bees-flying-royalty-free-image/172457089">bo1982/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>A queen, workers and drones</h2>
<p>Along with honey bees, two other kinds of bees also have queens: <a href="https://www.treehugger.com/bumblebee-facts-5119379">bumble bees</a>, which are found on all continents except Australia and Antarctica, and <a href="https://beeswiki.com/stingless-bees/">stingless bees</a>, which are found primarily in tropical areas. </p>
<p>One honey bee colony – also called a hive – may have <a href="https://www.buzzaboutbees.net/honey-bee-facts.html">more than 50,000 bees</a>, while bumble bee colonies usually have just a few hundred bees. Stingless bee colonies are often small, but some are as large as the biggest honey bee hives. </p>
<p>These bees’ social structures have two more things in common besides the egg-laying queen: the female workers who care for the colony, and the males, <a href="https://www.buzzaboutbees.net/dronebee.html">sometimes called “drones</a>.” </p>
<p>Notice the males are not included in the “worker” group. Males generally don’t help collect nectar or pollen, protect and maintain the hive, or care for the young larvae. The females do all of those jobs. </p>
<p>Instead, the males have one task: to find and then mate with a female who may become a future queen. After building their strength, males leave the hive to join thousands of other drones to wait for new queens that are also looking for mates. If males are lucky enough to mate, they die soon afterward. In contrast, females typically mate with many different males before starting their lives as egg-laying queens. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/9ePic3dtykk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Female worker bees do pretty much all the work.</span></figcaption>
</figure>
<h2>The isolated queen</h2>
<p>Maybe you imagine a queen as the one in charge, ordering everyone around. But that’s a case of language being misleading. Unlike human queens who lead their people, bee queens don’t rule over their workers. </p>
<p>Instead, particularly for honey bees, the queen is rather isolated from what’s happening in the hive. Remember, she just lays eggs, up to 2,000 in a day. The workers surround and take care of her while managing the colony. The queen bee might <a href="https://www.buzzaboutbees.net/how-long-do-bees-live.html">live for a few years</a>, much longer than female worker bees and drones.</p>
<p>Other animals also live in social groups with a division of labor between those who reproduce and those who maintain the colony. <a href="https://www.natgeokids.com/uk/discover/animals/insects/ant-facts/">Ants</a>, <a href="https://kids.britannica.com/kids/article/termite/353849#:%7E">termites</a> and <a href="https://kids.britannica.com/kids/article/wasp/353914#:%7E">some wasps</a> – like yellow jackets and hornets – have a similar kind of colony structure. So does the <a href="https://nationalzoo.si.edu/animals/naked-mole-rat">naked mole rat</a>. Why did these groups evolve to have queens? </p>
<h2>Family ties</h2>
<p>One way for an organism to pass on genes is by having offspring. </p>
<p>Another way is to help close relatives, who are likely to share many of your same genes, to produce more offspring than they would if they were on their own. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="dozens of hexagonal cells, each containing a tiny white egg or slightly larger white worm" src="https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578408/original/file-20240227-28-3bsd6f.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"></a>
<figcaption>
<span class="caption">Honey bee eggs and larvae develop one to a cell.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/honey-bee-eggs-and-larva-in-comb-with-black-royalty-free-image/1455295651">Megan Kobe/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>This option is pretty much what happens in a bee colony. Those thousands of female worker bees may not themselves reproduce, but the queen is their mother. They help her produce another generation of siblings who will one day be their sisters. In this way, the female worker bees are passing their genes on to the next generation, just not directly. </p>
<p>Something else to consider: A honey bee hive is a <a href="https://www.beebasket.in/stories/nature/hive-architecture-the-engineering-marvel-of-beehives/#:%7E">wonderfully complex structure</a>. The layers of wax combs built to store honey and raise offspring are a marvel of architecture and require a large workforce for construction, ongoing repairs and protection from intruders or predators. </p>
<p>So you might ask: Which came first? Social groups with queens and workers producing large numbers of related offspring that required more elaborate nest structures? Or did the complex nest arise first, which led to greater success for groups that evolved to divide tasks among queens and workers? </p>
<p>These are fascinating questions that biologists have been exploring for decades. But both of these factors – the division of labor and the complex hive structures – help explain why there are bees with queens. </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/213208/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>
A queen’s main job in the hive is to lay eggs and pass genes on to offspring. But many bee species do just fine without queens or big colonies.
Phil Starks, Associate Professor of Biology, Tufts University
Aviva Liebert, Professor of Biology, Framingham State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222264
2024-03-01T00:39:18Z
2024-03-01T00:39:18Z
Curious Kids: what are the main factors in forming someone’s personality?
<figure><img src="https://images.theconversation.com/files/577829/original/file-20240226-24-q8fp4p.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C7348%2C4891&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/casual-children-cheerful-cute-friends-kids-499922971">Rawpixel.com/Shutterstock</a></span></figcaption></figure><p><strong>“What are the main factors in forming someone’s personality?” – Emma, age 10, from Shanghai</strong></p>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hello Emma, and thank you for this very interesting question!</p>
<p>Let’s start by exploring what we mean by personality. Have you noticed no two people are completely alike? We all see, experience, and understand the world in different ways. </p>
<p>For example, some people love spending time with friends and being the centre of attention, whereas other people are more shy and enjoy having time to themselves. </p>
<p>Your unique personality is shaped by your genes as well as various influences in your environment. And your personality plays an important role in how you interact with the world.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-did-the-first-person-evolve-142735">Curious Kids: how did the first person evolve?</a>
</strong>
</em>
</p>
<hr>
<h2>The big five</h2>
<p>Did you know there are scientists who spend time researching personality? Their research is concerned with describing the ways <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev.psych.093008.100507">people differ from each other</a>, and understanding how these differences could be important for other parts of life such as our health and how well we do in school or at work.</p>
<p>There are many different perspectives on personality. A widely accepted viewpoint based on <a href="https://www.sciencedirect.com/science/article/abs/pii/S0092656620301367?via%3Dihub">a lot of research</a> is called the five factor model or the “big five”. According to this theory, a great deal of a person’s personality can be summarised in terms of where they sit on five dimensions, called traits:</p>
<ol>
<li><p>the <strong>introversion-extraversion</strong> trait refers to how much someone is outgoing and social (extroverted) or prefers being with smaller groups of friends or focusing on their own thoughts (introverted)</p></li>
<li><p><strong>agreeableness</strong> captures how much someone tends to be cooperative and helps others</p></li>
<li><p><strong>openness to experience</strong> refers to how much a person is creative and enjoys experiencing new things</p></li>
<li><p><strong>neuroticism</strong> describes a person’s tendency to experience negative feelings, like worrying about things that could go wrong</p></li>
<li><p><strong>conscientiousness</strong> encompasses how much a person is organised, responsible, and dedicated to things that are important to them, like schoolwork or training for a sports team. </p></li>
</ol>
<p>A person can have high, low, or moderate levels of each of these traits. And understanding whether someone has higher or lower levels of the big five can tell us a lot about how we might expect them to behave in different situations.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-does-our-dna-relate-to-our-personality-and-appearance-168489">Curious Kids: how does our DNA relate to our personality and appearance?</a>
</strong>
</em>
</p>
<hr>
<h2>So what shapes our personalities?</h2>
<p>A number of factors shape <a href="https://www.annualreviews.org/doi/10.1146/annurev-psych-010418-103244">our personalities</a>, including our genes and social environment. </p>
<p>Our bodies are made up of many very small structures called cells. Within these cells are genes. We inherit genes from our parents, and they carry the information needed to make our bodies and personalities. So, your personality may be a bit like your parents’ personalities. For example, if you’re an outgoing sort of person who loves to meet new people, perhaps one or both of your parents are very social too.</p>
<figure class="align-center ">
<img alt="A mother getting her son ready, fastening his backpack." src="https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/577830/original/file-20240226-16-1uvanq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Our personalities are influenced by the genes we get from our parents.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mother-dressing-her-child-getting-ready-2012433464">KieferPix/Shutterstock</a></span>
</figcaption>
</figure>
<p>Personalities are also affected by our environment, such as our experiences and our relationships with family and friends. For example, <a href="https://www.sciencedirect.com/science/article/pii/S0165178102001282">some research has shown</a> our relationships with our parents can influence our personality. If we have loving and warm relationships, we may be more agreeable and open. But if our relationships are hurtful or stressful, this may increase our neuroticism. </p>
<p><a href="https://bpspsychub.onlinelibrary.wiley.com/doi/full/10.1111/bjdp.12102">Another study</a> showed that, over time, young children who were more physically active were less introverted (less shy) and less likely to get very upset when things don’t go their way, compared to children who were less physically active. Although we don’t know why this is for sure, one possible explanation is that playing sport leads to reduced shyness because it introduces children to different people.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-some-people-worry-more-than-others-119874">Curious Kids: why do some people worry more than others?</a>
</strong>
</em>
</p>
<hr>
<p>While we’re learning more about personality development all the time, research in this area presents quite a few challenges. Many different biological, cultural and environmental influences shape our development, and these factors can interact with each other <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-psych-010213-115100">in complex ways</a>. </p>
<h2>Is our personality fixed once we become adults?</h2>
<p>Although we develop most of our personality when we are young, and people’s personalities tend to become more stable as they get older, it is possible for aspects of a person’s personality to change, even when they are fully grown. </p>
<p>A good example of this can be seen among people who seek treatment for conditions like anxiety or depression. People who respond well to working with a psychologist can show <a href="https://onlinelibrary.wiley.com/doi/10.1002/cpp.2541">decreases in neuroticism</a>, indicating they become less likely to worry a lot or feel strong negative feelings when something stressful happens.</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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/222264/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim Windsor receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Natalie Goulter receives funding from the National Health and Medical Research Council. </span></em></p>
Personality is shaped by our genes and various influences in our social environments, and it plays an important role in how we interact with the world.
Tim Windsor, Professor, Director, Generations Research Initiative, College of Education, Psychology and Social Work, Flinders University
Natalie Goulter, Lecturer, College of Education, Psychology and Social Work, Flinders University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222851
2024-02-26T13:38:23Z
2024-02-26T13:38:23Z
How is snow made? An atmospheric scientist describes the journey of frozen ice crystals from clouds to the ground
<figure><img src="https://images.theconversation.com/files/576863/original/file-20240220-22-v6kq2o.jpg?ixlib=rb-1.1.0&rect=22%2C5%2C3764%2C2055&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some parts of the U.S. see well over 100 inches (2.5 meters) of snow per year.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/downhill-sledging-royalty-free-image/488074477?phrase=sledding+in+snow">Edoardo Frola/Moment Open 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>How is snow made? – Tenley, age 7, Rockford, Michigan</strong></p>
</blockquote>
<hr>
<p>The thought of snow can conjure up images of powdery slopes, days out of school or hours of shoveling. For millions of people, it’s an inevitable part of life – but you may rarely stop to think about what made the snow.</p>
<p>As a <a href="https://www.eaps.purdue.edu/people/profile/ablanch.html">professor of atmospheric and planetary sciences</a>, <a href="https://scholar.google.com/citations?user=xClwTzUAAAAJ&hl=en&oi=ao">I’ve studied how ice crystals floating</a> in the sky become the snow that coats the ground.</p>
<p>It all starts in the clouds.</p>
<p>Clouds form when air near the Earth’s surface rises. This happens when sunlight warms the ground and the air closest to it, just like the Sun can warm your face on a cold winter day. </p>
<p>As the slightly warmer air rises, it cools – and the water vapor in that rising air condenses to form liquid water or water ice. From that, <a href="https://climatekids.nasa.gov/cloud-formation/#:%7E">a cloud is born</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Cf6El0mI1fM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You need just two things for snow to form.</span></figcaption>
</figure>
<h2>Endless pathways</h2>
<p>When temperatures are well below freezing on the ground, the clouds are primarily made of water in the form of ice. Under 32 degrees Fahrenheit – that’s zero degrees Celsius – the frozen water molecules arrange themselves into a hexagonal, or six-sided, crystalline shape. As ice crystals grow and clump together, they become too heavy to stay aloft. With the help of gravity, they begin to fall back down through and eventually out of the cloud.</p>
<p>What these ice crystals look like once they reach land depends on the temperature and humidity of the atmosphere. As the humidity – or the amount of water vapor in the cloud – increases, some of the ice crystals will grow intricate arms at their six corners. That branching process creates what we think of as the <a href="https://www.timeforkids.com/g2/snowflake-science-g2-5-plus/?rl=en-500">characteristic shapes of snowflakes</a>. </p>
<p>No two ice crystals take the same path through a cloud. Instead, every ice crystal experiences different temperatures and humidities as it travels through the cloud, whether going up or down. The ever-changing conditions, combined with the infinite number of paths the crystals could take, result in a unique growth history and crystalline shape for each and every snowflake. This is why you’ve likely heard the saying, “<a href="https://www.willyswilderness.org/post/no-two-snowflakes-are-alike-it-s-actually-true">No two snowflakes are exactly alike</a>.” </p>
<p>Many times, these differences are visible to the naked eye; sometimes a microscope is required to tell them apart. Either way, scientists who study clouds and snow can examine a snowflake and ultimately understand the path it took through the cloud to land on your hand. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Snow crystals attached to a window." src="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=636&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=636&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=636&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=799&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=799&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=799&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It takes approximately one hour for a snowflake to reach the ground.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/snowflakes-royalty-free-image/158720307?phrase=snowflakes">LiLi/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Liquid water as glue</h2>
<p>When snow falls from the sky, you don’t usually see individual ice crystals, but rather clumps of <a href="https://scied.ucar.edu/learning-zone/storms/snowflakes">crystals stuck together</a>. One way ice crystals aggregate is through what’s called mechanical interlocking. When ice crystals bump into each other, crystals with intricate branches and arms intertwine and stick to others. </p>
<p>This mechanism is the main sticking process in cooler, drier conditions – what people call a “<a href="https://compuweather.com/the-important-difference-between-wet-snow-and-dry-snow/">dry snow</a>.” The result is a snow perfect for skiing, and easily picked up by the wind, but that won’t hold together when formed into a snowball. </p>
<p>The second way to stick ice crystals together is to warm them up a bit. When ice crystals fall through a region of cloud or atmosphere where the temperature is slightly above freezing, the edges of the crystals start to melt. Just a tiny bit of liquid water allows ice crystals that bump into each other to stick together very efficiently, almost like glue. </p>
<p>The result? Large clumps of ice crystals falling from the sky, what we call a “<a href="https://www.acurite.com/blog/types-of-snow.html">wet snow</a>” – less than ideal for hitting the slopes but perfect for building a snowman. </p>
<p>Snow formed in clouds typically reaches the ground only in winter. But almost all clouds, no matter the time of year or location, <a href="https://scijinks.gov/clouds/">contain some ice</a>. This is true even for clouds in warm tropical regions, because the atmosphere above us is much colder and can reach temperatures below freezing even on the warmest of days. In fact, scientists who study weather discovered that clouds containing ice produce more rain than those that don’t contain any ice at all.</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/222851/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexandria Johnson receives funding from NASA. </span></em></p>
There are an infinite number of paths an ice crystal can take before you touch it.
Alexandria Johnson, Professor of Atmospheric and Planetary Sciences, Purdue University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/218330
2024-02-19T13:36:56Z
2024-02-19T13:36:56Z
Why does a leap year have 366 days?
<figure><img src="https://images.theconversation.com/files/575717/original/file-20240214-24-h6q6if.jpg?ixlib=rb-1.1.0&rect=38%2C23%2C5137%2C3422&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Leap Day is coming.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/calendar-on-february-29-on-a-leap-year-leap-day-royalty-free-image/1196849410">Marvin Samuel Tolentino Pineda/iStock, 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>Why does a leap year have 366 days? Does the Earth move slower every four years? – Aarush, age 8, Milpitas, California</p>
</blockquote>
<hr>
<p>You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun. </p>
<p>After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28.</p>
<p>The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calendar was getting out of sync with the seasons, so they began adding an extra month, <a href="https://www.britannica.com/science/Roman-republican-calendar">which they called Mercedonius</a>, every two years to catch up with the missing days.</p>
<p>In the year 45 B.C.E., Roman emperor Julius Caesar introduced a solar calendar, based on one developed in Egypt. Every four years, February received an extra day to keep the calendar in line with the Earth’s journey around the Sun. In honor of Caesar, this system is still known as the Julian calendar.</p>
<p>But that wasn’t the last tweak. As time went on, people realized that the Earth’s journey wasn’t exactly 365.25 days – it <a href="https://airandspace.si.edu/stories/editorial/science-leap-year">actually took 365.24219 days</a>, which is about 11 minutes less. So adding a whole day every four years was actually a little more correction than was needed. </p>
<p>In 1582, Pope Gregory XIII signed an order that made a small adjustment. There would still be a leap year every four years, except in “century” years – years divisible by 100, like 1700 or 2100 – unless they were also divisible by 400. It might sound a bit like a puzzle, but this adjustment made the calendar <a href="https://airandspace.si.edu/stories/editorial/science-leap-year">even more accurate</a> – and from that point on, it was known as the Gregorian calendar.</p>
<h2>What if we didn’t have leap years?</h2>
<p>If the calendar didn’t make that small correction every four years, it would gradually fall out of alignment with the seasons. Over centuries, this could lead to the <a href="https://www.britannica.com/story/whats-the-difference-between-a-solstice-and-an-equinox">solstices and equinoxes</a> occurring at different times than expected. Winter weather might develop in what the calendar showed as summer, and farmers could become confused about when to plant their seeds.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YTOr8_ILqGw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Without leap years, our calendar would gradually become disconnected from the seasons.</span></figcaption>
</figure>
<p>Other calendars around the world have their own ways of keeping time. The Jewish calendar, which is regulated by <a href="https://www.britannica.com/topic/Jewish-religious-year">both the Moon and the Sun</a>, is like a big puzzle with a 19-year cycle. Every now and then, it adds a leap month to make sure that special celebrations happen at just the right time. </p>
<p>The <a href="https://ing.org/resources/for-all-groups/calendar-of-important-islamic-dates/">Islamic calendar</a> is even more unusual. It follows the <a href="https://spaceplace.nasa.gov/moon-phases/en/">phases of the Moon</a> and doesn’t add extra days. Since a lunar year is only about 355 days long, key dates on the Islamic calendar move 10 to 11 days earlier each year on the solar calendar. </p>
<p>For example, Ramadan, the <a href="https://ing.org/resources/for-all-groups/calendar-of-important-islamic-dates/">Islamic month of fasting</a>, falls in the ninth month of the Islamic calendar. In 2024, it will run from March 11 to April 9; in 2025, it will occur from March 1-29; and in 2026, it will be celebrated from Feb. 18 to March 19.</p>
<h2>Learning from the planets</h2>
<p>Astronomy originated as a way to make sense of our daily lives, linking the events around us to celestial phenomena. The concept of leap years exemplifies how, from early ages, humans found order in conditions that seemed chaotic. </p>
<p>Simple, unsophisticated but effective tools, born from creative ideas of ancient astronomers and visionaries, provided the first glimpses into understanding the nature that envelops us. Some <a href="https://www.britannica.com/science/astronomy/History-of-astronomy">ancient methods</a>, such as <a href="https://sci.esa.int/web/gaia/-/53196-the-oldest-sky-maps">astrometry and lists of astronomical objects</a>, persist even today, revealing the timeless essence of our quest to understand nature. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photograph of an intricate schematic guide to the night sky." src="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=356&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=356&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=356&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=447&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=447&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575719/original/file-20240214-30-of8z7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=447&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ancient Egyptians were dedicated astronomers. This section from the ceiling of the tomb of Senenmut, a high court official in Egypt, was drawn sometime circa 1479–1458 B.C.E. It shows constellations, protective gods and 24 segmented wheels for the hours of the day and the months of the year.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Senenmut-Grab.JPG">NebMaatRa/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>People who do research in physics and astronomy, the <a href="https://scholar.google.com/citations?user=t4L_D18AAAAJ&hl=en">field that I study</a>, are inherently curious about the workings of the universe and our origins. This work is exciting, and also extremely humbling; it constantly shows that in the grand scheme, our lives occupy a mere second in the vast expanse of space and time – even in leap years when we add that extra day.</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/218330/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bhagya Subrayan 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>
Humans have synced their calendars to the sun and moon for centuries, but every so often, these systems need a little correction.
Bhagya Subrayan, PhD Student in Physics and Astronomy, Purdue University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/221677
2024-02-12T13:24:56Z
2024-02-12T13:24:56Z
Can anyone make a citizen’s arrest? The history and legalities of catching criminals yourself
<figure><img src="https://images.theconversation.com/files/574490/original/file-20240208-28-q5mmu6.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4600%2C2452&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Can you detain someone you just saw break the law?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-mugging-woman-in-street-royalty-free-image/BC3542-001">Alan Thornton/The Image Bank 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>Can anyone make a citizen’s arrest, even me? – Henry, age 12, Winter Hill, Massachusetts</strong></p>
</blockquote>
<hr>
<p>What does Spider-Man do when he sees someone commit a crime and there are no police officers around to help? He swings in, wraps the wrongdoer in his web and leaves them hanging from a telephone pole until the cops take over. </p>
<p>But is he allowed to do that? Are you?</p>
<h2>Seizing criminals</h2>
<p>Until about 200 years ago, uniformed police officers and police departments as we know them today <a href="https://time.com/4779112/police-history-origins/">didn’t exist in the United States</a>. It was up to the citizens to arrest criminals.</p>
<p>In 1285, England introduced what we now know as “citizen’s arrests” in a law called <a href="https://study.sagepub.com/rowe3e/student-resources/chapter-3/the-statute-of-winchester">the Statute of Winchester</a>. It allowed any person to arrest – in other words, capture – lawbreakers. This concept spread throughout the English colonies, which ultimately became their own countries, including Australia, Canada and the United States. Other <a href="https://en.wikipedia.org/wiki/Citizen%27s_arrest">countries have adopted similar rules</a>.</p>
<p>In the United States, citizen’s arrests have a pretty dark history. Originally, <a href="https://www.fastcompany.com/90528764/the-troubling-history-of-citizens-arrests-from-slave-patrols-to-ahmaud-arbery-to-ice">only white men could make citizen’s arrests</a>. By the mid-1600s, many militias and city watchmen, especially in the South, used that power to <a href="https://www.fastcompany.com/90528764/the-troubling-history-of-citizens-arrests-from-slave-patrols-to-ahmaud-arbery-to-ice">intimidate and terrorize enslaved and free Black communities</a>.</p>
<p>This practice continued <a href="https://racism.org/articles/law-and-justice/criminal-justice-and-racism/134-police-brutality-and-lynchings/9617-a-legacy">through the Civil War</a>, <a href="https://historynewsnetwork.org/article/175619">the Jim Crow era and even into the 1900s</a>, with vigilantes – people who appoint themselves to catch and punish others – engaging in heinous abuses, <a href="https://theconversation.com/lynching-memorial-shows-women-were-victims-too-95029">including lynchings</a>. Just recently, in 2020, Ahmaud Arbery, a Black man who was jogging around his Georgia neighborhood, <a href="https://theconversation.com/jury-finds-3-georgia-men-guilty-of-ahmaud-arbery-murder-3-essential-reads-172493">was shot and killed</a> by a group of white men who accosted him because they wrongly thought he had committed a crime.</p>
<p>Despite this history, most states still have citizen’s arrest <a href="https://www.washingtonpost.com/nation/2021/11/05/ahmaud-arbery-citizens-arrest-vigilante/">laws on the books</a>.</p>
<h2>Making a legal citizen’s arrest</h2>
<p>Arrest literally means “to stop.” If someone wants to leave, you usually can’t stop them – that could be considered false imprisonment or even kidnapping. Citizen’s arrest laws are an exception to that general rule; they allow everyday people to make an arrest.</p>
<p>When the police make an arrest, they typically handcuff the subject and take them in a secure transport vehicle to a booking facility, such as the county jail. When Spidey webs a wrongdoer, he can’t just take them back to Aunt May’s apartment. Making a citizen’s arrest means holding the lawbreaker in place until the police arrive and take over.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A blurry, dark black-and-white picture of a figure holding what could be a knife, or something else entirely" src="https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574491/original/file-20240208-24-qtcx1d.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">You’d better be sure about what you think you saw.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-holding-knife-in-kitchen-rear-view-silhouette-royalty-free-image/588312130">Glasshouse Images/The Image Bank via Getty Images</a></span>
</figcaption>
</figure>
<p>When can someone make a citizen’s arrest? The rules are a bit different in every state, which can make things confusing. You can ask a librarian to help you find information about the law in your state, but here are some common requirements to get you started:</p>
<p><strong>Who can make a citizen’s arrest?</strong> Although some state laws use the word “<a href="https://www.scstatehouse.gov/code/t17c013.php">citizen</a>,” most states allow any “<a href="https://statutes.capitol.texas.gov/Docs/CR/htm/CR.14.htm">person</a>” or any “<a href="https://www.revisor.mn.gov/statutes/cite/629.37">private person</a>” – as opposed to a public employee such as a police officer – to make a citizen’s arrest. Despite the name, you usually don’t have to be a citizen. And most states don’t require any minimum age, so it looks like high school student Peter Parker, Spider-Man’s alter ego, is good to go.</p>
<p><strong>Did you see it, and how serious is it?</strong> Most states allow you to make a citizen’s arrest for a minor crime – those <a href="https://www.britannica.com/topic/crime-law/Classification-of-crimes">categorized as a misdemeanor</a> – only if you actually saw the person commit the crime. Some states allow a citizen’s arrest for a minor crime only if it is considered a “breach of peace,” meaning the crime is likely to disturb other people, such as fighting in public. For felonies, a more serious category of crime, the law usually allows you to make a citizen’s arrest even if you didn’t see the person commit the crime.</p>
<p><strong>You’d better be sure!</strong> In most states, citizen’s arrest laws apply only if the person actually committed a crime. If you make a mistake by making a citizen’s arrest of someone who didn’t actually commit a crime, the <a href="https://www.findlaw.com/injury/torts-and-personal-injuries/false-imprisonment.html">person you arrested can sue you</a>. You might even get <a href="https://www.law.cornell.edu/wex/false_imprisonment">arrested</a> yourself!</p>
<p>This is different from when police arrest someone. Law enforcement officers need “<a href="https://www.law.cornell.edu/wex/probable_cause">probable cause</a>,” which is the legal standard for how sure you need to be that a person committed a crime before arresting them. As long as an officer meets the probable cause standard, they won’t get in trouble, even if they’re ultimately mistaken about the person committing a crime.</p>
<p><strong>Try not to rough anyone up.</strong> Someone making a citizen’s arrest is usually allowed to use a reasonable amount of physical force to ensure that the lawbreaker stops committing the crime and can’t leave. But that doesn’t mean you can do anything you want. The type and amount of force you use must be <a href="https://nyupress.org/9781479814657/evaluating-police-uses-of-force/">closely related</a> to whether the other person is trying to get away and, if so, what they’re doing.</p>
<p><strong>Just because you can doesn’t mean you should.</strong> Making a citizen’s arrest is no joke. There’s the danger of making a mistake about what the person did and whether it was a crime. After all, most people don’t know exactly what the law allows or prohibits, so it’s easy to get something wrong.</p>
<p>And there’s the danger of getting hurt. Most people aren’t trained or equipped to arrest someone safely, and they rarely have backup available like the police do. If you see a crime occur, it’s better to call the police and be a good witness than it is to try to make a citizen’s arrest yourself. </p>
<p>So, what do you think: Is Spider-Man allowed to make a citizen’s arrest? And if he is, does that make him a hero or a vigilante?</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/221677/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>
Stopping someone against their will can be false imprisonment or even kidnapping. There are laws that determine who is acting as a hero and who is acting as a vigilante.
Seth W. Stoughton, Professor of Law, University of South Carolina
Caroline McAtee, Law Student at the University of South Carolina School of Law, Research Assistant for the Excellence in Policing and Public Safety Program, University of South Carolina
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222863
2024-02-12T04:57:01Z
2024-02-12T04:57:01Z
Curious Kids: why do we shiver when we feel cold?
<figure><img src="https://images.theconversation.com/files/574832/original/file-20240212-26-pv68gh.jpg?ixlib=rb-1.1.0&rect=33%2C0%2C3748%2C2496&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sad-froze-teenage-caucasian-girl-shivering-2017458494">Georgy Dzyura/Shutterstock</a></span></figcaption></figure><blockquote>
<p><strong>“Why do we shiver when we feel cold?” – Syeda, age 10, from Karachi</strong></p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>What a cool question, Syeda!</p>
<p>Our bodies like to be nice and warm, usually <a href="https://www.ncbi.nlm.nih.gov/books/NBK331/">around 37°C</a>. This allows our internal functions to work at their best. But our bodies are constantly losing heat to the outside air.</p>
<p>When it’s cold outside, or if we jump into a cold swimming pool, or even if the air-conditioning is a bit strong, our body temperature can lower, sometimes to levels that are uncomfortable.</p>
<p>If our body temperature drops too low, our heart, nervous system and other organs are not able to work <a href="https://www.cdc.gov/niosh/topics/coldstress/coldrelatedillnesses.html">normally</a>. If it falls to extremely low temperatures, called hypothermia, this can cause some organs to <a href="https://www.mayoclinic.org/diseases-conditions/hypothermia/symptoms-causes/syc-20352682">completely fail</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-are-my-hands-and-feet-always-cold-and-when-should-i-be-worried-184154">Why are my hands and feet always cold? And when should I be worried?</a>
</strong>
</em>
</p>
<hr>
<p>Luckily, our bodies have their own internal heaters to protect us against small changes in temperature. This is mostly thanks to the actions of our muscles, through a process called <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">thermoregulation</a>. It’s this process that leads our bodies to shiver when we’re chilly.</p>
<h2>Muscles are our bodies’ personal heaters</h2>
<p>When our muscles twitch, they generate <a href="https://www.ted.com/talks/christian_moro_the_surprising_reason_our_muscles_get_tired">movement</a>. This is called “muscle contraction”, and can involve the muscles tightening and shortening. </p>
<p>Muscle contractions help us walk around, smile, lift heavy objects and high-five each other.</p>
<p>Moving our muscles also generates a bit of <a href="https://www.britannica.com/science/excretion/Types-of-waste-metabolic-and-nonmetabolic">heat</a>. With many <a href="https://www.youtube.com/watch?v=ZqwGTso2Wmc">muscles moving</a> most of the time, this helps our bodies stay nice and warm.</p>
<figure class="align-center ">
<img alt="A woman shivering." src="https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574266/original/file-20240208-24-1hlrj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We’ll often hunch our necks, tense up, and rub our shoulders when cold. Shivering usually follows to help warm us up.</span>
<span class="attribution"><span class="source">Christian Moro</span></span>
</figcaption>
</figure>
<p>The more our muscles move, the more heat they generate. This is why you might feel hot and bothered after running around or playing sports.</p>
<p>On the other hand, when we stop moving our muscles, we start to cool down. This is one of the reasons we cover up with bedsheets at night.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-women-might-feel-the-cold-more-than-men-heres-why-184329">Yes, women might 'feel the cold' more than men. Here's why</a>
</strong>
</em>
</p>
<hr>
<h2>What about the shiver?</h2>
<p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3167123/">Shivering</a> is the rapid contractions of our muscles over and over. This doesn’t generate any significant movement, but instead releases heat that helps to warm us up.</p>
<p>Most of the time we don’t have control over when our brain tells our muscles to shiver. We have special sensors throughout our <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">body</a> that pick up when our system is cold, and our brain then responds by telling the muscles to start shivering.</p>
<p>And we aren’t the only ones who shiver! All <a href="https://www.khanacademy.org/science/ap-biology/ecology-ap/energy-flow-through-ecosystems/a/animal-temperature-regulation-strategies">mammals</a> have the ability to shiver, so your pet cat or dog might shiver when they’re cold too. Even <a href="https://www.fws.gov/story/how-do-birds-keep-warm-winter">birds</a> shiver.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-if-our-bodies-are-happy-at-37-why-do-we-feel-so-unhappy-when-its-too-hot-outside-159134">Curious Kids: if our bodies are happy at 37℃, why do we feel so unhappy when it's too hot outside?</a>
</strong>
</em>
</p>
<hr>
<p>When it’s a chilly day outside, you might also notice you get <a href="https://www.health.harvard.edu/blog/wondering-about-goosebumps-of-course-you-are-2020080320688">goosebumps</a>. Goosebumps happen when tiny muscles connected to the hair follicles (from which our hair grows) tighten. This causes the little hairs on our arms to stand up, helping to trap in warm air and slow down body heat loss to the outside.</p>
<h2>How can you ‘chill out’ your shiver?</h2>
<p>Thermoregulation is key to maintaining a nice, consistent body temperature, which keeps our internal organs happy.</p>
<p>While shivering can help us warm up, it’s best to make sure you wear the right clothes if you’re going to be out in the cold.</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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/222863/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Shivering actually helps warm our bodies up.
Charlotte Phelps, Senior Teaching Fellow, Medical Program, Bond University
Christian Moro, Associate Professor of Science & Medicine, Bond University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/221678
2024-02-06T16:01:53Z
2024-02-06T16:01:53Z
Curious Kids: why do you get interest payments when you have a bank account?
<figure><img src="https://images.theconversation.com/files/572800/original/file-20240201-21-e9sm7x.jpg?ixlib=rb-1.1.0&rect=27%2C0%2C6079%2C3442&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/preteen-girl-using-credit-bank-card-2248721489">Andrii Iemelianenko/Shutterstock</a></span></figcaption></figure><p><strong>Why do you get money back when you have a bank account? – Grace, aged nine, Belfast, Northern Ireland</strong></p>
<p>A bank is a place where people go to either borrow money or save the extra money they have. If you’ve got money to save, there’s a reason why it’s better to put it in a bank account than to keep it in a money box under your bed. In a bank account, your money will increase, because the bank will add what’s <a href="https://www.halifax.co.uk/savings/help-guidance/saving-explained/what-are-interest-rates.html#:%7E:text=Basically%2C%20it%20is%20how%20much,annual%20percentage%20of%20the%20loan.">known as interest</a> to it. </p>
<p>When you put your money in a bank, the bank gets to use your money. It might lend it to other people or businesses who need it. This doesn’t mean your money is gone: when you want to take it out of the bank, they will pay it back to you. The interest your bank pays you is a reward for letting it use your money. </p>
<p>So, let’s say you put a £100 deposit in a bank, and the bank promised to give you 5% interest every year as a reward. At the end of the year the bank would pay you £5 reward and so now the total amount you have in the bank is £105. </p>
<p>If you don’t take any money out, the following year you would get 5% on £105. At the end of that year, you’d have £110.25. You’re earning interest on your interest as well as the amount you put in the bank. This is called <a href="https://www.bbc.co.uk/bitesize/guides/z37pqhv/revision/3">compound interest</a>. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.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/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>This is how money in a bank account keeps on growing every year. It’s like a snowball effect – the more money you have, the more interest you get, and the more your money grows. This is one way people can make their savings grow over time, and it’s a neat way to encourage people to save their money in the bank.</p>
<h2>Borrowing and lending</h2>
<p>You may wonder where the bank gets the extra money to reward you for letting it use your money. People may need to borrow money from a bank to buy a house or a car and businesses may want to borrow to invest in machinery or equipment – and banks <a href="https://www.bbc.co.uk/bitesize/guides/z9b6nbk/revision/4">charge interest</a> to those it lends money to. </p>
<p>When households and businesses borrow money, they have to pay back the whole amount – plus a little extra. So, the money that the borrowers pay back to the banks in interest is the same money that the bank uses to pay you and other savers. </p>
<figure class="align-center ">
<img alt="Mother and child at ATM" src="https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/572806/original/file-20240201-27-4gipkc.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">It’s a good idea to keep your savings in a bank account.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mother-daughter-withdrawing-money-form-cash-737201143">LumineImages/Shutterstock</a></span>
</figcaption>
</figure>
<p>The bank has to decide how much interest it should pay those who save with the bank, and how much it should charge those who borrow from it. The bank is a business, and it needs to make profits, so it charges a higher interest to those who borrow money compared to the interest it pays to people who save with it. </p>
<p>For example a bank may want to charge a person who wants to borrow money to buy a house a 6% interest rate, while paying only 4% interest to a person who saves their money with the bank. This means there’s money left over. The bank uses the extra money to pay to keep itself running, and whatever is left the bank keeps as profits. </p>
<p>Banks play an important role in our financial system by acting as a middle man between savers and borrowers. The interest rates charged to borrowers and paid to lenders form the foundation of a bank’s operations.</p><img src="https://counter.theconversation.com/content/221678/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shampa Roy-Mukherjee does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
The interest your bank pays you is a reward for letting it use your money.
Shampa Roy-Mukherjee, Vice Dean and Associate Professor in Economics, University of East London
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/219169
2024-02-05T13:30:00Z
2024-02-05T13:30:00Z
Why do people and animals need to breathe? A biologist explains why you need a constant source of oxygen
<figure><img src="https://images.theconversation.com/files/567973/original/file-20240104-26-jrvms0.jpg?ixlib=rb-1.1.0&rect=419%2C364%2C3255%2C2085&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Your blood's natural limit to how much oxygen it can hold means you can't stockpile it.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/girl-swimming-in-idyllic-caribbean-sea-take-a-royalty-free-image/1394071551">Lisa520/E+ 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>Why do humans and animals have to breathe? – Tennessee, age 7, Hartford, Kentucky</strong></p>
</blockquote>
<hr>
<p>You need to breathe for the same reason you need to eat: It helps you make the energy your body requires. </p>
<p>You probably already know that food is fuel for your body. When you eat, food gets broken down in your stomach and <a href="https://www.vattenhallen.lu.se/english/experiences/from-mouth-to-rectum/">enters your bloodstream</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A plastic object on a stand that is tube shaped with part of it cut off showing an interior space with fuzzy looking walls with dividers." src="https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=801&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=801&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=801&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1006&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1006&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568258/original/file-20240108-16-q7f3ve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1006&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 plastic model of a mitochondrion.</span>
<span class="attribution"><a class="source" href="https://coimages.sciencemuseumgroup.org.uk/images/24/460/large_2010_0084__0001_.jpg">Science Museum Group Collection © The Board of Trustees of the Science Museum</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>From there, it gets delivered to your cells. Inside your cells are even <a href="https://collection.sciencemuseumgroup.org.uk/objects/co505977/plastic-organelle-model-of-a-mitochondrion-from-a-cell-model-representation">tinier structures called mitochondria</a>, which are the engines that power your entire body. Your mitochondria use the nutrients from food as fuel. But to turn it into energy, they need one more ingredient – oxygen.</p>
<p><a href="https://scholar.google.com/citations?hl=en&user=tuuK7xcAAAAJ">I am a biologist who studies</a> animals and plants. All living things need oxygen, except for <a href="https://en.wikipedia.org/wiki/Obligate_anaerobe">some bacteria</a> and <a href="https://www.doi.org/10.1186/1741-7007-8-30">a few tiny animals</a> that don’t. You might be surprised to learn how many ways there are to get oxygen – breathing is only one of them.</p>
<h2>Lungs and their linings</h2>
<p>When you breathe in, your lungs temporarily trap oxygen, allowing it to pass through very <a href="https://www.britannica.com/science/pulmonary-alveolus">thin surfaces in your lungs</a> into your bloodstream. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A central tube comes down, which then branches and rebranches over and over." src="https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=603&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=603&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=603&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=758&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=758&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567972/original/file-20240104-19-n4vt7u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=758&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 CT scan of healthy lungs.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/healthy-lungs-ct-scan-royalty-free-image/1786377109">RAJAAISYA/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<p>Because you need a lot of oxygen, your lungs need a lot of surface area to do their job. They achieve this by having millions of <a href="https://upload.wikimedia.org/wikipedia/commons/b/bb/Lung_structure_normal.jpg">little air sacs</a> lined with tiny blood vessels called capillaries.</p>
<p>If you could somehow flatten out all the capillary surface area in your lungs, it would more than cover the floor of <a href="https://seatingchartmaker.app/articles/average-classroom-size-square-feet/#classroom-size-by-us-state">an average classroom</a> – around <a href="https://www.sciencedirect.com/topics/engineering/pulmonary-capillary">1,350 square feet (125 square meters)</a>. </p>
<h2>Getting enough oxygen</h2>
<p>If breathing is kind of like eating, why can’t you just take three breaths a day?</p>
<p>One reason is that <a href="https://climate.nasa.gov/news/2915/the-atmosphere-getting-a-handle-on-carbon-dioxide/">air on Earth</a> is only 21% oxygen – the rest is mostly nitrogen. That means you need to take five breaths just to get the equivalent of one complete lungful of oxygen. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration depicting the tunnel-like inside of a blood vessel, with vaguely donut-shaped spheres flowing through it." src="https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567971/original/file-20240104-14-2jppnf.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">Your blood can carry only so much oxygen.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/3d-render-of-red-blood-cells-or-corpuscle-flowing-royalty-free-image/1144992100">libre de droit/iStock via Getty Images</a></span>
</figcaption>
</figure>
<p>Also, when you take a breath, only some of the oxygen makes it into your bloodstream. Even though people and many animals make specialized <a href="https://teachchemistry.org/chemmatters/february-2010/the-many-colors-of-blood">proteins to grab and carry oxygen</a>, there’s a limit to how much they can hold at once. To keep your body’s oxygen levels high enough to power all your cells, you need to keep breathing.</p>
<p>Of course, once you breathe in, you also have to breathe out. The gas you breathe out is called <a href="https://learningzone.oumnh.ox.ac.uk/respiration">carbon dioxide</a>. You can think of it as the exhaust from your mitochondria engines, the leftovers once the mitochondria burn oxygen and nutrients to release energy.</p>
<h2>Other animals and plants</h2>
<p>Most living things get oxygen without lungs. </p>
<p>Many aquatic animals use gills, which are sort of like lungs turned inside out. Instead of a bunch of capillaries wrapped around air sacs, <a href="https://theconversation.com/curious-kids-how-do-gills-work-150375">gills are a bunch of capillaries</a> sticking out into the water. Just like in your lungs, the blood vessels take in oxygen from the water and release carbon dioxide.</p>
<p>Insects take in oxygen through a network of little <a href="https://askabiologist.asu.edu/how-insects-breathe">air tubes just under their skin</a>, sort of like the chimneys of a building. This system works because insects are small, so the tubes are already close enough to their cells to give them oxygen. When large insects need extra energy, they <a href="https://askabiologist.asu.edu/how-insects-breathe">pump air through the tubes</a> with their muscles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A microscopic photo showing a green mouth shape." src="https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=507&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=507&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=507&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=637&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=637&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567945/original/file-20240104-28-4qdii8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=637&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 close-up look at the underside of this tomato leaf shows where the air goes in and out.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/8/85/Tomato_leaf_stomate_cropped_and_scaled.jpg">Vojtěch Dostál</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Plants have <a href="https://www.rhs.org.uk/advice/understanding-plants/how-plants-breathe">little holes in their leaves called stomata</a>. They open and close to let in air when plants need it. Plant roots need oxygen, too, which they usually get from the soil.</p>
<p>You may have heard that plants are the opposite of people: They <a href="https://www.britannica.com/story/do-plants-emit-oxygen-and-carbon-dioxide-at-night">breathe in carbon dioxide and breathe out oxygen</a>. That’s true because carbon dioxide is a crucial ingredient in <a href="https://www.britannica.com/science/photosynthesis">photosynthesis</a> – the process plants use to make their own sugar fuel – and oxygen is a byproduct. But plants’ mitochondria also need oxygen to make energy, just like yours do.</p>
<p>Even though most animals and plants don’t breathe in and out the way people do, they all have ways of getting enough oxygen. Learning how organisms solve the same problem in different ways is one of my favorite things about biology.</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/219169/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christina S. Baer 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>
Inhaling air is how you get the oxygen your body needs to turn your food into energy. Other living things use different strategies.
Christina S. Baer, Assistant Professor of Biological Sciences, Binghamton University, State University of New York
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/217185
2024-01-29T13:34:21Z
2024-01-29T13:34:21Z
Who created the alphabet? A historian describes the millennia-long story of the ABCs
<figure><img src="https://images.theconversation.com/files/560517/original/file-20231120-20-pxbkgm.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4928%2C3260&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Creating the alphabet took thousands of years.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/english-alphabet-royalty-free-image/498549449?phrase=alphabet">kovalchuk/iStock via Getty Images Plus</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>Who created the alphabet and decided its order? – Priti C., age 12, Mumbai, India</strong></p>
</blockquote>
<hr>
<p>A, B, C, D, E, F, G – makes you want to hum <a href="https://www.youtube.com/watch?v=75p-N9YKqNo">the alphabet song</a>. But there’s no real reason why people should learn these letters in this order. There are plenty of ways we could structure the alphabet; the computer keyboard in front of me provides one alternative. Plenty of other alphabets exist too, as well as languages that don’t use alphabets at all. </p>
<p>So why did we end up with this one – and who’s responsible for it? </p>
<p><a href="https://www.uml.edu/fahss/history/faculty/sancinito-jane.aspx">As a historian</a>, I love “why” questions. I often like them a lot more than “who” questions, because it’s actually really rare for a single person to change the world. Instead, most of history’s biggest innovations come from teamwork, collaboration and groups figuring out how to make life better, easier and more fun. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ZBiuJ40t4rk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A fascinating story on the origins of writing.</span></figcaption>
</figure>
<h2>What is a letter?</h2>
<p>The alphabet is a perfect example of this process. Our ABCs, known as <a href="https://kids.kiddle.co/Latin_alphabet">the Latin alphabet</a>, are the result of millions of people over thousands of years slowly working together and ultimately agreeing on which letters to use and under what circumstances. </p>
<p>To figure out why they settled on the version we have today, you first need to understand what a letter is and what an alphabet is. Then, you can trace your way back to the very first examples of both. </p>
<p>Letters are symbols, just like emojis or crosswalk signs. Letters are shapes that we – the users – associate with a sound in a particular language. </p>
<p>But many letters change sound completely when they appear in a different language. The English “H,” for example, makes a “ha” sound, but the same symbol “H” is pronounced as “en” in Russian; in the Cyrillic alphabet, “H” makes a “n” sound. </p>
<p>Even when the shape and sound of a letter stay the same within a single language, the letters themselves can have different names. In America, “Z” is called “zee,” while in Canada, the United Kingdom and pretty much every other English-speaking country, it is called “zed.” </p>
<p>All this variety is possible because letters, <a href="https://www.pearson.com/languages/community/blogs/2020/06/how-the-english-language-has-changed-over-the-decades.html">like languages, evolve and change over time</a> based on what local people do out of habit or trend or just for the fun of it. </p>
<h2>What is an alphabet?</h2>
<p>An alphabet is a collection of letter-symbols that have been more or less standardized, and which often – though not always – reflect all of the sounds made in a particular language. </p>
<p>Some languages, <a href="https://goeastmandarin.com/chinese-characters-for-kids/">like Chinese</a>, don’t have alphabets at all, using symbols to represent whole words. Others, <a href="https://www.native-languages.org/cherokee_alphabet.htm">like Cherokee</a>, use symbols that represent syllables. </p>
<p>The first alphabet was <a href="https://www.historyforkids.net/ancient-egyptian-alphabet.html">invented in ancient Egypt</a>, more than 5,000 years ago, and was developed to record religious texts. That’s where its name “hieroglyphs,” or “sacred carvings,” comes from. </p>
<p>Hieroglyphs are beautiful and they do a good job recording prayers, but they are difficult to write quickly, because they are so detailed and often take the form of <a href="https://discoveringegypt.com/egyptian-hieroglyphic-writing/egyptian-hieroglyphic-alphabet/">animals, people or day-to-day objects</a>. Over time, people developed simplified forms of each glyph so they could take notes and write informally. </p>
<p>While hieroglyphs were mostly used by priests and elites, common people, including travelers and traders from other places, <a href="https://magazine.krieger.jhu.edu/2021/10/learning-to-write-in-ancient-cultures/#:">learned informal writing</a>. These visitors realized the Egyptians had developed something useful – a way to record sales or send letters that would be clear to those who could read it but mysterious to everyone else. Many people never learned to read at all, because they did not need to or because they were denied access to education.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/gL18gFhRwq4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Once visitors learned hieroglyphs, the world took a major step toward the creation of our alphabet.</span></figcaption>
</figure>
<h2>Vowels, consonants and the letter ‘J’</h2>
<p>The most important traders in this period <a href="https://www.worldhistory.org/phoenicia/">were from Phoenicia</a> – known today as Syria, Lebanon and Israel – and they spread the alphabet to the towns and villages that surrounded the Mediterranean Sea. </p>
<p>The Phoenicians <a href="https://phoenician.org/alphabet/">established alphabetical order</a> to make it easier to learn and share with others. But the Phoenicians and Egyptians used only consonants; eventually, as people began to write more and more, and more words needed to be created to describe different things, <a href="https://teachphonics.blog/2019/10/10/what-are-vowels-and-consonants/">the Greeks adopted vowels</a>. </p>
<p>The Greek alphabet looks a lot like ours, but our letters took their final form in Italy. First the Etruscan people, and then the Romans, adapted Greek letters to fit their language. The Romans spread their language, Latin, and its alphabet all over modern Europe, the Near East and North Africa. The earliest example of the Latin alphabet in use is called <a href="https://kids.kiddle.co/Duenos_inscription">the duenos inscription</a> and comes from the sixth century BCE, 2,500 years ago. </p>
<p>Even then, the alphabet was still incomplete, because Latin didn’t have all the sounds that are common today. The most obvious is the letter “J”; even though the first month of the Roman calendar was January, it was written with an “I,” “ianuarius,” and pronounced with a “ya” sound. The “J” <a href="https://www.dictionary.com/e/j/">came into use during the Renaissance</a> – during the 1500s in Europe – two or three centuries after the “W” was added, during the Middle Ages.</p>
<p>And there’s no reason to think the alphabet might not change again. English, especially, has a habit of borrowing words from other languages, like karaoke from Japanese, cookie from Dutch and avatar from Sanskrit. Maybe, because of this borrowing, we might eventually need to add new symbols to our alphabet. In short, as the world grows more connected, the alphabet may have to adapt. It won’t be the first time.</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/217185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jane Sancinito 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>
Turns out ‘A’ didn’t have to be the first letter in the alphabet, nor ‘Z’ the last.
Jane Sancinito, Assistant Professor of History, UMass Lowell
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/216859
2024-01-22T13:29:39Z
2024-01-22T13:29:39Z
Why do people have different tastes in music? A music education expert explains why some songs are universally liked, while others aren’t
<figure><img src="https://images.theconversation.com/files/566074/original/file-20231215-21-eo0769.jpg?ixlib=rb-1.1.0&rect=19%2C0%2C2121%2C1409&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The types of music you listen to can reflect your personality traits. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/group-of-young-friends-listening-to-music-with-royalty-free-image/1156897122?phrase=listening+to+music&adppopup=true">Smile/Stone 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">
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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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<p><strong>Why do we have a certain taste in music, different than others? – Shirya R., age 11</strong></p>
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<p>When you turn on the radio, you might hear songs you like and other songs you just skip past. But even the songs you don’t like usually have some fans. Maybe you don’t like older music, but your parents or grandparents might love it <a href="https://theconversation.com/why-do-old-people-hate-new-music-123834">because they grew up</a> with it. It’s familiar and comfortable. When you’re older, you’ll likely return to music you love too.</p>
<p>As a <a href="https://scholar.google.com/citations?user=QXuOzQIAAAAJ&hl=en">music education professor</a> who teaches music psychology, I’ve spent a lot of time thinking about music preferences and how music weaves its way through people’s brains.</p>
<p>Some composers produce music with <a href="https://theconversation.com/burt-bacharach-mastered-the-art-of-the-perfect-pop-song-and-that-aint-easy-199660">cross-generational appeal</a>. Look at the song “True Colors,” which artists have remade time and time again. It was originally released in 1986 by <a href="https://www.youtube.com/watch?v=LPn0KFlbqX8">Cyndi Lauper</a>.</p>
<p>Ten years later, Disney World’s Epcot used it as part of a <a href="https://www.youtube.com/watch?v=yUm22pobGU4">pre-show video</a>. Ten years after that, it made its way to our ears again as part of the “Trolls” movie. Now, if you scour the internet, you’ll find lots of covers of this song.</p>
<p>How can this one song appeal to many different people over time, while other songs do not? Why do some people have wildly different tastes in music, even while certain songs can unite people from a variety of backgrounds and generations? </p>
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<figcaption><span class="caption">‘True Colors’ from the movie ‘Trolls,’ starring Justin Timberlake and Anna Kendrick.</span></figcaption>
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<p>Researchers have looked at <a href="https://www.ucf.edu/pegasus/your-brain-on-music/">how music works in the brain</a>. They suggest people like music with unexpected twists and turns, which sometimes cause <a href="https://theconversation.com/why-do-only-some-people-get-skin-orgasms-from-listening-to-music-59719">pleasurable physical reactions</a> <a href="https://doi.org/10.3389/fnins.2020.565815">or chills</a>. This finding suggests that humans have created and listened to music over time <a href="https://doi.org/10.1093/scan/nsw009">because it is pleasurable or rewarding</a>.</p>
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<figcaption><span class="caption">When you listen to music, you might get chills.</span></figcaption>
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<h2>Emotions and personality</h2>
<p>Some researchers suggest people experience emotions through music, or that they choose music based on what they want to feel. A <a href="https://doi.org/10.1037/a0022406">2011 study</a> suggests musical preference may reflect the emotions people feel when listening to music, regardless of the music’s style.</p>
<p>Some people respond to mellow and relaxing music. Others’ emotions are triggered by classical-style music. Still others emotionally react to singer-songwriter music like country, folk and some pop music. Preferences for certain types or styles of music might come from the time and place they’re first heard, or it may simply be specific to each person, regardless of what’s going on around them. </p>
<p>Though people might like certain music at one point in their lives, their music preferences change over time based on their lived experiences. When you’re struggling through a tough time, you might choose music that reflects what you wish was happening and <a href="https://doi.org/10.1007/s10824-022-09454-7">search for happy songs</a>. On the flip side, sometimes people <a href="https://doi.org/10.3389/fnhum.2015.00404">gravitate toward sad songs</a>. People want to move through grief, so they may search for songs that help them make sense of their emotions.</p>
<p>However, people’s choices don’t account for the whole picture. Musical taste goes <a href="https://doi.org/10.3389/fpsyg.2023.1062146">deeper than the music type or genre</a>. People who like pop or rock music don’t all like the same pop or rock music. </p>
<p>Studies on <a href="https://doi.org/10.1177/0956797618761659">personality and social media interaction</a> suggest your musical tastes can tell others what kind of personality you have. If someone knows what kind of music you like, that might tell them something about your personality. </p>
<p>Other <a href="https://doi.org/10.1037/pspp0000397">research suggests</a> your music preferences mirror your unique personality. So, people who already know you may be able to suggest music that you would like to hear.</p>
<p>For example, those who are more open might prefer mellow, sophisticated music like Billie Eilish’s “<a href="https://www.youtube.com/watch?v=cW8VLC9nnTo">What Was I Made For?</a>” or intense music like Imagine Dragons’ “<a href="https://www.youtube.com/watch?v=V5M2WZiAy6k">Natural</a>.”</p>
<p><a href="https://doi.org/10.1037/pspp0000397">The research found</a> extroverts may lean toward contemporary music. Agreeable people prefer unpretentious music, like Garrett Kato & Elina’s “<a href="https://www.youtube.com/watch?v=zgxNu8fBrgw">Never Alone</a>.” Conscientious people lean toward <a href="https://www.youtube.com/watch?v=0o5NTQMzNPo">unpretentious music</a> or intense music like Marshmello’s “<a href="https://www.youtube.com/watch?v=IYfejxVZ7lg">Power</a>.” People who are more anxious might prefer many different types of music.</p>
<p>People may like music by artists they like, rather than how the music sounds. Some prefer music from <a href="https://doi.org/10.1037/pspp0000293">artists who are like them</a>, especially when they can view their profiles on <a href="https://doi.org/10.1177/0956797618761659">social media</a>.</p>
<p>Why does knowing what music others like matter? Knowing about different people’s musical preferences and personalities <a href="https://www.youtube.com/watch?v=evVRxrOo5iw">can bridge gaps between people</a> with different personalities and identities. </p>
<h2>The music people stream</h2>
<p>A <a href="https://doi.org/10.1038/s41562-018-0508-z">study of 765 million songs streamed</a> by people worldwide revealed several reasons people listen to music. People’s preferences tended to change based on the time of day, their age and particular styles of music. Most people listened to more relaxing music at night but more intense music during the day. </p>
<p>Music streamed in Latin America often produced quicker physical and emotional reactions. Music streamed in Asia was usually relaxing. People who stay up later at night listened to less intense music. Depending on where participants lived, the length of the day also played a part in their music listening habits. In short, people’s environments and their individual moods shaped their preferences.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/TOhANADfR04?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Harmony in the Brain: Unraveling the Neuroscience of Music.</span></figcaption>
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<p>So, why do we have different tastes in music? People have complex personalities, and the music they like may be related to this. People’s brains work in unique ways as they process music. Some may have a physical reaction to certain music, while others may not. People may like music because a musician’s views might be like their own views. That said, some songs surprise, intrigue and entertain a wide variety of listeners, which makes them universally liked.</p>
<p>The bottom line? Each person is unique in many ways, and their musical tastes reflect that uniqueness.</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/216859/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jane Kuehne 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>
Lots of factors can influence your music taste, from your age and where you’re from to the personality traits you have.
Jane Kuehne, Associate Professor of Music Education, Auburn University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/214919
2024-01-15T13:33:10Z
2024-01-15T13:33:10Z
What if every germ hit you at the exact same time? An immunologist explains
<figure><img src="https://images.theconversation.com/files/565348/original/file-20231212-15-ba3kr2.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Your immune system encounters a legion of potential pathogens every day.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-shielding-eyes-by-large-green-coronavirus-royalty-free-image/1250588799">Klaus Vedfelt/DigitalVision 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">
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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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<p><strong>What would happen if all the diseases in the world hit us at the exact same time? – Gabriella, age 12, Irving, Texas</strong></p>
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<p>When I was younger, I would watch “Batman” on my black-and-white television after school. Usually, Batman would face either the Joker, the Penguin, the Puzzler, Catwoman or any one of his usual opponents. However, on some occasions, Batman would have to face them all at the same time.</p>
<p>What would happen if, like Batman, the immune system had to face all of its rivals at once?</p>
<p><a href="https://scholar.google.com/citations?user=6JOQvNwAAAAJ&hl=en">I am an immunologist</a> who teaches the fundamentals of immunology to college undergraduates. My research generally focuses on factors that regulate immune responses and prevent autoimmune diseases – conditions where the immune system attacks your own body. As a scientist studying how we build immunity against pathogens such as the virus that causes COVID-19, understanding how the immune system combats multiple threats at the same time is immensely important to me. </p>
<p>There’s no reason why you can’t come down with strep throat at the same time as when you have a cold. In fact, sometimes fighting off one enemy can leave a hole in your defenses that another opportunistic pathogen can take advantage of.</p>
<h2>BAM! Understanding the rivals</h2>
<p>The first point to consider is what your immune system protects you from. The potential bad guys <a href="https://theconversation.com/immune-cells-that-fight-cancer-become-exhausted-within-hours-of-first-encountering-tumors-new-research-210947">include cancer cells</a> and dangerous microorganisms – including bacteria, viruses, fungi and more – that cause infections. The immune system must also be careful <a href="https://theconversation.com/immune-health-is-all-about-balance-an-immunologist-explains-why-both-too-strong-and-too-weak-an-immune-response-can-lead-to-illness-215217">not to damage</a> healthy cells and beneficial microorganisms that live on and inside you. </p>
<p>You interact with <a href="https://kids.frontiersin.org/articles/10.3389/frym.2022.629355">thousands of microorganisms</a> with every breath of air you take. Is the immune system facing off against all of them? Sort of. </p>
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<a href="https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Microscope images of two T regulatory cells wrapped around an antigen-presenting cell" src="https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/565525/original/file-20231213-27-oegbgf.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>
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<span class="caption">T regulatory cells (red) determine whether an immune response should be mounted.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/SjQFf7">NIAID/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>It takes a <a href="https://theconversation.com/how-does-fever-help-fight-infections-theres-more-to-it-than-even-some-scientists-realize-210240">tremendous amount of energy</a> to fight a battle once a rival gains a foothold within your blood or tissues, so your immune system works to <a href="https://theconversation.com/how-do-viruses-get-into-cells-their-infection-tactics-determine-whether-they-can-jump-species-or-set-off-a-pandemic-216139">prevent it from getting in the body</a> in the first place. Your skin, <a href="https://theconversation.com/why-do-our-noses-get-snotty-when-we-are-sick-a-school-nurse-explains-the-powers-of-mucus-212949">snot</a>, saliva and <a href="https://theconversation.com/can-you-cry-underwater-205464">tears</a> form a critical <a href="https://www.ncbi.nlm.nih.gov/books/NBK279396/">first line of defense</a>. This is why <a href="https://doi.org/10.1089%2Fsur.2013.134">burn victims</a> who lose too much skin often die from overwhelming infection – their defensive barriers are too compromised and pathogens pour in.</p>
<p>The immune system greatly prefers <a href="https://theconversation.com/a-pediatric-nurse-explains-the-science-of-sneezing-160970">catching a microbe in snot</a> and blowing it out of your nose, or giving you time to wash it off the skin of your hands, over having to wage a cellular war. Gathering an army of <a href="https://theconversation.com/coronavirus-b-cells-and-t-cells-explained-141888">immune cells</a> to fight pathogens takes a lot of energy and makes you feel awful. </p>
<p>For example, the immune system <a href="https://theconversation.com/how-does-fever-help-fight-infections-theres-more-to-it-than-even-some-scientists-realize-210240">increases your body temperature</a> to make it an uncomfortable place for microorganisms to live and grow, but that fever can also make you want to lie down for days.</p>
<h2>BOOM! Where are their weaknesses?</h2>
<p>When Batman faced multiple opponents, he would find a weakness shared by all of the opponents and target it to foil their plans. The immune system uses the exact same strategy.</p>
<p>Certain microbes are considered pathogens largely because they are in the wrong place – such as inside your body instead of on your skin – and causing damage. Pathogens have specific parts on their surfaces called <a href="https://doi.org/10.1038/s41392-021-00687-0">pathogen associated molecular patterns, or PAMPs</a>.</p>
<p>Very importantly, your body doesn’t make PAMPS. This means if your immune system comes across a PAMP, it knows it isn’t supposed to be there and will mount an attack. Because the same PAMP is present on many different pathogens, a strategy to combat one PAMP can defeat many pathogens.</p>
<p>There are molecules in cells all over your body that can recognize PAMPS and destroy anything those PAMPS are on. It’s as though your immune system set up booby traps that can only attack your enemies.</p>
<p>Many of those booby traps are <a href="https://doi.org/10.1038/35100529">toll-like receptors</a>. This family of molecules is located on the surface and inside of many of your cells. Once microbes contact these booby traps, they trigger an alarm that warn other cells of potential danger. In technical terms, this alarm is <a href="https://theconversation.com/what-is-inflammation-two-immunologists-explain-how-the-body-responds-to-everything-from-stings-to-vaccination-and-why-it-sometimes-goes-wrong-193503">called inflammation</a>.</p>
<h2>SPLAT! Raising an army of defenders</h2>
<p>Whereas Batman would need to think of a new strategy to combat the Joker, the Penguin and Catwoman, your immune system devised a plan long ago. </p>
<p>When the virus that causes COVID-19 emerged in 2019, it was something people’s immune systems likely had never seen before. However, some people already had immune cells that could target components of the virus. How is that possible?</p>
<p>The immune system makes many immune cells that are specific to antigens, or unique and recognizable parts of cancers and microorganisms, it hasn’t encountered before. This occurs through a process where pieces of your DNA <a href="https://doi.org/10.1038/nri2941">randomly recombine to form</a> unique immune cell receptors. The DNA in each of these immune cells is different from the DNA in any other cell in your body. Researchers believe that each person can generate <a href="https://www.ncbi.nlm.nih.gov/books/NBK27140/">at least a trillion different combinations</a> of immune receptors, which is <a href="https://doi.org/10.1038/nrmicro2644">more than the number of pathogens</a> an average person would ever face in their lifetime overall.</p>
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<figcaption><span class="caption">Your immune system can churn out billions of unique antibodies.</span></figcaption>
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<p>Although the immune system makes a lot of immune cells, most of them aren’t used because you’re not exposed to the antigen they’re made to recognize. However, when an immune cell recognizes an antigen, it rapidly <a href="https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Boundless)/11%3A_Immunology/11.07%3A_Antibodies/11.7C%3A_Clonal_Selection_of_Antibody-Producing_Cells">makes many copies of itself</a>. Since pathogens can also multiply rapidly, clonal selection allows you to rapidly raise an army to fight them.</p>
<p>Usually this strategy works well with <a href="https://theconversation.com/when-covid-19-or-flu-viruses-kill-they-often-have-an-accomplice-bacterial-infections-187056">one or two coinfections</a>, such as if you have the common cold and an eye infection at the same time. But what if you were infected with a trillion pathogens at the same time? It would take a tremendous amount of energy and time to build an appropriate army against each microorganism all at once. Unfortunately, the immune system likely would be overwhelmed by this challenge, and you would probably die. </p>
<p>Fortunately, your immune system – like Batman – usually figures out the best way to shift a battle against rivals to its favor, pulling out a victory in the final minutes of the episode.</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/214919/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joseph Larkin III receives funding from the Grayson Jockey Research Foundation, The National Institutes of Health, and industry. </span></em></p>
Your immune system is often able to fend off pathogens it’s never seen before. But defending your body against all of them all at once is a tough challenge.
Joseph Larkin III, Associate Professor of Microbiology and Cell Science, University of Florida
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/220559
2024-01-11T12:50:07Z
2024-01-11T12:50:07Z
Curious Kids: how much money is there in the world?
<figure><img src="https://images.theconversation.com/files/568279/original/file-20240108-29-9nfec1.jpg?ixlib=rb-1.1.0&rect=7%2C7%2C5128%2C2595&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pound-gbp-coin-gold-money-on-1044478525">Bukhta Yurii/Shutterstock</a></span></figcaption></figure><p><strong>How much money is there in the world? – Tsubamé, aged ten, London</strong></p>
<p>If we want to add up how much money there is in the world, a good place to start would be counting all the notes and coins out there – in people’s wallets and money boxes and in cash machines. </p>
<p>Let’s start with pounds. There is about <a href="https://stats.bis.org/statx/srs/table/T2?c=GB">£84 billion</a> (or 84,000,000,000) of British money out there in coins and notes. There’s also <a href="https://stats.bis.org/statx/srs/table/T2?c=US">US$2,236 billion</a> in US money, <a href="https://stats.bis.org/statx/srs/table/T2?c=XM">€1,578 billion</a> in the money of the European Union and <a href="https://stats.bis.org/statx/srs/table/T2?c=CN">¥9,616 billion</a> in Chinese money – plus money in many other currencies. </p>
<p>As money is not the same in every country, summing up all the coins and notes in the world means that you need to measure how much a US dollar, an Indian rupee, or a Chinese yuan is worth in Great British pounds. If this is done with <a href="https://stats.bis.org/statx/srs/table/CT2">the latest available data</a>, then added up, you will find a total of £6,113 billion. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.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/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>This amount could change very quickly and is probably already outdated at the moment you read this article. </p>
<p>This is partly because countries print more money all the time. But it’s also because the exchange rate – how much a British pound, say, is worth in another currency, like US dollars – is not always the same. <a href="https://www.xe.com/currencyconverter/convert/?Amount=1&From=GBP&To=USD">Today, £1 is worth</a> around US$1.30 – one dollar and 30 cents in US money. Ten years ago, it was much more: <a href="https://www.xe.com/currencycharts/?from=GBP&to=USD&view=10Y">one dollar and 70 cents</a>. </p>
<p>How many US dollars you get for a pound depends on how much people want to use British money. That’s why when some people decide to create their own money, such as cryptocurrencies like bitcoin, they spend so much time <a href="https://theconversation.com/why-sports-sponsorship-is-unlikely-to-save-cryptocurrency-firms-from-crypto-winter-195582">trying to convince others</a> to use it. </p>
<p>But counting coins and notes does not tell us everything about how much money there is in the world. For instance, people have money in their bank accounts that do not correspond to any specific coin. In the UK, around 96% of money exists only in electronic form. When you include that, the total is not £84 billion but <a href="https://stats.bis.org/statx/srs/table/T2?c=GB">£2,223 billion</a>. If you add up again the figures available for the entire world – money in coins and notes, plus electronic money in bank accounts – you get roughly £46,557 billion. </p>
<h2>Wealth – but not money</h2>
<p>What’s more, many things that are worth a lot are not money itself. Very rich people keep only a little part of their fortune in cash. They prefer to also own things like businesses that are likely to make them even richer.</p>
<p>Perhaps a better way to count how much money there is in the world is to look at the value of the things we buy and sell. That is a tricky thing to do, because you don’t want to double count anything. If farmers sell the milk of their cows to a cheese maker, who then sells cheese to a shop, which sells it to people, all the value – the milk, the cheese and the people selling it, is contained in what you pay at the shop: the final sale. </p>
<p>When you sum up all these final sales, you will find that last year, in the entire world, there was around <a href="https://data.worldbank.org/indicator/NY.GDP.MKTP.CD">£79,437 billion</a> worth of value created. </p>
<figure class="align-center ">
<img alt="Diamonds with one held in tweezers" src="https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568282/original/file-20240108-25-lhu7a2.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">Diamonds aren’t money, but they can make you rich.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/brilliant-cut-diamond-held-by-tweezers-1069154252">Bjoern Wylezich/Shutterstock</a></span>
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<p>But there are also a lot of things that have value and are not exchanged. If you own a bag of diamonds and keep it in your bedroom, you are rich. But this is not money. And you are not exchanging it either. So it does not count in any of the numbers I have given you so far.</p>
<p>And sometimes, things that have value cannot easily be turned into money. Imagine that you own a beautiful forest, with a nice clean river to swim in during the summer, and some very rare birds and old trees. And underneath that forest, there is a lot of oil. </p>
<p>By owning this forest, you are very wealthy. Like the diamonds in your bedroom, owning the land and the forest and the oil makes you rich. But once you decide to turn your wealth into a lot of money, you will need to destroy the forest: cut down the trees for wood to sell, and drill into the earth to get the oil out. </p>
<p>People might have enjoyed spending time with friends walking in the forest, or paddling in the rivers. This has value, and it is lost when the forest is gone. And the wealth you held by owning the forest is gone too.</p>
<p>If we want the money we use to still be worth something in the future, we sometimes need to restrain from destroying what we own to get cash today.</p><img src="https://counter.theconversation.com/content/220559/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Renaud Foucart 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>
We can look at the value of the things we buy and sell.
Renaud Foucart, Senior Lecturer in Economics, Lancaster University Management School, Lancaster University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/209196
2024-01-08T13:36:16Z
2024-01-08T13:36:16Z
What happens to the ocean if we take out all the fish? A marine ecologist explains the complex roles fish play in their ecosystem
<figure><img src="https://images.theconversation.com/files/543088/original/file-20230816-19-h6b36a.jpg?ixlib=rb-1.1.0&rect=6%2C12%2C2038%2C1348&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fish swim in a reef at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/UNBiodiversity/3ead5d56c624402893c0df11ab789657/photo?Query=ocean%20fish&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=262&currentItemNo=31&vs=true">AP Photo/Jacob Asher </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>What would happen to the ocean if we took out all the fish? – Reny, age 12</strong></p>
</blockquote>
<hr>
<p>The ocean is massive and covers most of the surface of our planet. In addition to its size, it’s packed with life, ranging from an astounding diversity of plants, microbes, worms, corals and crabs to squids, whales and, yes, even fish. The ocean is full of fish, so much so that they make up the <a href="https://doi.org/10.1073/pnas.1711842115">second-largest amount of all carbon</a> – the material that makes up living things – in the entire animal kingdom. They’re just behind the group containing insects and crustaceans.</p>
<p>Most people only interact with the ocean from a beach or in a boat, so it can be hard to wrap your head around how many fish there really are. But the ocean is swarming with them, from its surface <a href="https://www.nbcnews.com/news/world/deepest-ever-fish-filmed-japan-scientists-rcna77858">to its depths</a>. </p>
<p>These fish also come in all kinds of shapes and sizes, ranging from the tiny sardines, guppies and blennies that you might <a href="https://www.palmbeachpost.com/story/opinion/columns/guest/2020/01/25/point-of-view-call-for-more-diversity-not-only-more-fish-in-marine-protected-areas/112150854/">see on a coral reef</a> to massive tunas and whale sharks that you might find <a href="https://www.fisheries.noaa.gov/feature-story/surface-slicks-are-pelagic-nurseries-diverse-ocean-fauna">out in the open ocean</a>. </p>
<p>These fish perform all kinds of <a href="https://doi.org/10.1002/ecs2.4288">roles in their ecosystems</a> that support the lives of other organisms around them. If they disappeared one day, the ocean would look very different.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542471/original/file-20230813-127481-q0e3vz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">School of slopehead parrotfish.</span>
<span class="attribution"><span class="source">NOAA, Kevin Lino</span></span>
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</figure>
<p>I’m a <a href="https://koryevans.weebly.com/">scientist who studies fish</a>, their diversity and all the ways they contribute to ocean environments.</p>
<h2>Fish as food</h2>
<p>Fish play important roles as both <a href="https://www.noaa.gov/education/resource-collections/marine-life/aquatic-food-webs">predators and prey</a> in ocean ecosystems. Thousands of species throughout the ocean and terrestrial ecosystems rely on fish for food – <a href="https://www.fisheries.noaa.gov/feature-story/economic-importance-seafood">including people</a>. </p>
<p>In coral reef ecosystems, small fish are eaten by larger fish and other marine animals. This means the little fish form the base of the food web – they provide energy to the bigger fish and other creatures. </p>
<figure class="align-center ">
<img alt="Conceptual food web of a coral reef ecosystem identifying key functional groups." src="https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=569&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=569&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=569&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=715&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=715&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542472/original/file-20230813-197557-ebgabl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=715&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Links between different species of coral reef animals.</span>
<span class="attribution"><span class="source">Global Change Biology, Rogers et al., 2015</span></span>
</figcaption>
</figure>
<p>Outside of the water, many birds, mammals and reptiles eat fish and rely on them as an <a href="https://doi.org/10.1016/S0921-8009(99)00015-4">essential source of protein</a>. </p>
<p>Even land plants can benefit from the presence of fish. On the western coast of the United States, salmon returning to small streams after spending several years at sea function as a conveyor belt of nutrients. The salmon feed not only animals that catch them, like bears, but also the plants that border the streams. Studies have shown that some plants get <a href="https://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=407">70% of their nitrogen</a> from salmon that die on or near the river banks. </p>
<p>Humans also depend on fish as a food source. Fish and other seafood products are an important protein source for <a href="https://www.nature.org/en-us/what-we-do/our-priorities/provide-food-and-water-sustainably/food-and-water-stories/global-fisheries/">nearly 3 billion people</a>. Human populations have been eating and following fish around the world for <a href="https://doi.org/10.1073/pnas.1710186114">thousands of years</a>. </p>
<h2>Fish maintain habitats</h2>
<p>Fish are also more than just food. As fish themselves forage for food, they can create and maintain important <a href="https://doi.org/10.1007/s00338-006-0112-y">habitats for other organisms</a>. In coral reef ecosystems, plant-eating fish control the growth of algae by constantly grazing it down. Without the help of these herbivores, or plant-eating fish, the algae would rapidly grow and smother the coral, effectively killing it. </p>
<p>One type of herbivorous fish, the parrotfish, <a href="https://ocean.si.edu/ocean-life/fish/tough-teeth-and-parrotfish-poop">feeds directly on the corals</a>. At first, this may seem bad for the corals, but the grazing done by parrotfish can actually increase a coral colony’s rate of growth. And <a href="https://ocean.si.edu/ocean-life/fish/tough-teeth-and-parrotfish-poop">the poop</a> – yes, the poop – from parrotfish has been shown to be <a href="https://doi.org/10.1016/j.tim.2022.03.006">particularly nutritious</a> for corals. Parrotfish poop also forms part of the <a href="https://ocean.si.edu/ocean-life/fish/tough-teeth-and-parrotfish-poop">beautiful white sand beaches</a> that you may have enjoyed on a family vacation.</p>
<p>Other fish create habitats for other animals and influence their environment by <a href="https://www.ingentaconnect.com/content/umrsmas/bullmar/1986/00000038/00000001/art00006">disturbing sand</a> while they feed. By moving the sand around, they’re exposing tiny organisms hiding in the sand, which other animals can eat. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_pN5-96nduge?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Some fish sift through sand to find their food. That creates more opportunities for other creatures to find food in the sand.</span></figcaption>
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<p>Despite the fact that many types of fish are confined to the ocean, their presence can be felt across many habitats. They can directly and indirectly affect the lives of the organisms that depend on them for food and shelter. Without fish, Earth would gradually lose its beautiful white sand beaches, the coral reef ecosystems would be overgrown with algae, lots of people would run out of food to eat, and we would lose some of the planet’s most fascinating creatures.</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/209196/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kory Evans receives funding from National Science Foundation. </span></em></p>
There are so many fish in the ocean that if you took them out, important habitats and food sources for many creatures would be lost.
Kory Evans, Assistant Professor of BioSciences, Rice University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/217241
2023-12-18T13:23:27Z
2023-12-18T13:23:27Z
Why are some black holes bigger than others? An astronomer explains how these celestial vacuums grow
<figure><img src="https://images.theconversation.com/files/562536/original/file-20231129-23-ug9ynd.jpg?ixlib=rb-1.1.0&rect=5%2C15%2C3429%2C2863&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Black holes use gravity to pull matter into them. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/HungryBlackHole/4cd9b7c1c318427ba2f3b78c77cfe6de/photo?Query=black%20hole&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=418&currentItemNo=7&vs=true&vs=true">NASA/Chandra X-ray Observatory/M.Weiss via AP</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>Why are there small and big black holes? Also, why are some black holes invisible and others have white outlines? – Sedra and Humaid, Abu Dhabi, United Arab Emirates</strong></p>
</blockquote>
<hr>
<p><a href="https://theconversation.com/the-scariest-things-in-the-universe-are-black-holes-and-here-are-3-reasons-148615">Black holes</a> are dense astronomical objects with gravity so strong that nothing, not even light, can escape. Anything that crosses the boundary of a black hole’s gravitational influence, called the event horizon, will fall into the black hole. Inside this deep, dense pit, it is never to be seen again. </p>
<p>Black holes litter the universe. Some smaller black holes are sprinkled randomly throughout galaxies like our Milky Way. Other gigantic ones, called <a href="https://theconversation.com/supermassive-black-hole-at-the-center-of-our-galaxy-may-have-a-friend-128295">“supermassive” black holes</a>, lie at the centers of galaxies. Those can weigh anywhere between a million to a billion times the mass of our Sun. So you might be wondering: How can astronomers possibly see something so dark and so big?</p>
<p>I am an <a href="https://jackiechampagne.com">astronomer</a> who studies the very first supermassive black holes that formed in our universe. I want to understand how black holes form and what kinds of astrophysical neighborhoods they grow up in.</p>
<h2>Types of black holes</h2>
<p>Let’s talk about how black holes begin their lives. Two famous scientists, <a href="https://www.britannica.com/biography/Albert-Einstein">Albert Einstein</a> and <a href="https://www.britannica.com/biography/Karl-Schwarzschild">Karl Schwarzchild</a>, first pitched the <a href="https://www.astronomy.com/science/a-brief-history-of-black-holes/">idea of a black hole</a>. They thought that when a large star dies, its core might shrink and shrink until it <a href="https://universe.nasa.gov/black-holes/types/">collapses under its own weight</a>. This is what we astronomers call a “<a href="https://www.nasa.gov/image-article/stellar-mass-black-hole/">stellar mass black hole</a>,” which is just another way of saying it’s comparatively very small.</p>
<p>Stellar mass black holes are only a few times bigger than our Sun. Supermassive black holes are more of a mystery, though. They are many millions of times heavier than our Sun, and they are packed into a small area that’s about the size of our solar system. Some scientists think supermassive black holes might form by <a href="https://science.nasa.gov/astrophysics/focus-areas/black-holes/">many stars colliding and collapsing at once</a>, while others think they might have already started growing several billion years ago. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/tMax0KgyZZU?wmode=transparent&start=13" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Stars at the center of the Milky Way are orbiting around an invisible object, a supermassive black hole, like planets orbit around the Sun. Credit: Andrea Ghez/UCLA/W.M. Keck Observatory.</span></figcaption>
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<h2>Growing black holes</h2>
<p>What do black holes look like? Most of the time, they are not actively growing, so they are invisible. But we can tell they’re there because <a href="https://theconversation.com/2020-nobel-prize-in-physics-awarded-for-work-on-black-holes-an-astrophysicist-explains-the-trailblazing-discoveries-147614">stars can still orbit around them</a>, just like Earth around the Sun. </p>
<p>When something is orbiting an invisible object at high speeds, scientists know there <a href="https://theconversation.com/2020-nobel-prize-in-physics-awarded-for-work-on-black-holes-an-astrophysicist-explains-the-trailblazing-discoveries-147614">must be a massive black hole</a> in the middle. This is the case for the closest supermassive black hole to us, which lies at the center of the Milky Way – safely millions of miles away from you.</p>
<p>Meanwhile, when a hungry black hole is eating up gas in a galaxy, it heats that gas up until you can see a <a href="https://universe.nasa.gov/black-holes/anatomy/">glowing ring</a> of X-rays, optical light and infrared light around the black hole. Once it exhausts all of the fuel near the event horizon, the light dies down once again and it becomes invisible. </p>
<h2>Outlines around black holes</h2>
<p>One of the most famous “white outlines” is the <a href="https://cerncourier.com/a/building-gargantua/">image of a black hole</a> from <a href="https://www.imdb.com/title/tt0816692/">the movie “Interstellar</a>.” In that movie, they were trying to show the white-hot, glowing ring of gases that are falling into the actively growing black hole. </p>
<p>In real life, we don’t get such a close-up view. The best image of the ring around a real black hole comes from the <a href="https://eventhorizontelescope.org/">Event Horizon Telescope</a>, showing scientists the supermassive black hole at the center of a <a href="https://science.nasa.gov/resource/first-image-of-a-black-hole/">galaxy called M87</a>. It might look blurry to you, but this doughnut is actually the sharpest image ever taken of something so far away.</p>
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<a href="https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A blurry golden circle against a black background." src="https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=439&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=439&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559440/original/file-20231114-27-fnfqnq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=439&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">The first-ever image of a black hole was taken by the Event Horizon Telescope in 2019. You can see the light as it bends around the intense gravity of the black hole at the center of a galaxy called M87. It might look blurry, but this is the equivalent of being able to read a newspaper on a table in Paris if you were standing in New York.</span>
<span class="attribution"><a class="source" href="https://eventhorizontelescope.org/press-release-april-10-2019-astronomers-capture-first-image-black-hole">Event Horizon Telescope</a></span>
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<p>There are lots of types of black holes out there in the universe. Some are small and invisible, and some grow to gigantic proportions by eating up stuff inside a galaxy and shining bright. But don’t worry, black holes can’t just keep sucking in everything in the universe – eventually there is nothing close enough to the black hole to fall in, and it will become invisible again. So you are safe to keep asking questions about black holes. </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/217241/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaclyn Champagne receives funding from the National Science Foundation and the Space Telescope Science Institute. </span></em></p>
Pictures of black holes have a white outline around them when photographed, due to one of black holes’ unique and key features.
Jaclyn Champagne, JASPER Postdoctoral Researcher, University of Arizona
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/216148
2023-12-11T13:12:05Z
2023-12-11T13:12:05Z
Why do people have wisdom teeth?
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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=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>Why do people have wisdom teeth? – Jack J., age 17, Dedham, Massachusetts</strong></p>
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<p>Wisdom teeth are the third set of molars located at the very back of the mouth. They look just like the first and second molars, but can sometimes be a little smaller. </p>
<p>They are commonly called wisdom teeth because they are the last of the 32 permanent teeth to appear, emerging <a href="https://doi.org/10.1159/000151214">between 17 and 25 years of age</a>, when you are older and wiser.</p>
<p>You might know that <a href="https://doi.org/10.7717/peerj.10367">not everyone grows</a> all four wisdom teeth. You might also know many people get them pulled. So it’s fair to wonder – why do humans even have them? </p>
<p><a href="https://scholar.google.com/citations?hl=en&user=0lZq0kYAAAAJ">We</a> <a href="https://scholar.google.com/citations?hl=en&user=GYMrNdIAAAAJ">study</a> teeth and can tell you the answer has a lot to do with the distant past – and a bit about the present day, too. </p>
<h2>More powerful jaws</h2>
<p>Just like you have many features in common with the people you’re related to, humans share features with their extended family – the primates. <a href="https://doi.org/10.3389/fdmed.2023.1158482">Monkeys, gorillas and chimpanzees</a> all have wisdom teeth. </p>
<p>A few million years ago, early human ancestors had larger jaws and teeth than humans do today. For example, a species called <em>Australopithecus afarensis</em>, <a href="https://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensis">nicknamed Lucy’s species</a> after a <a href="https://www.nature.com/scitable/knowledge/library/lucy-a-marvelous-specimen-135716086/">famous fossil specimen called Lucy</a>, lived roughly 3 million to 4 million years ago. </p>
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<a href="https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A fossilized jaw showing powerful molars and some broken and missing front teeth." src="https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560510/original/file-20231120-21-9261y5.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A fossilized jaw from the extinct human ancestor, <em>Australopithecus afarensis</em>, also known as Lucy’s species.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Australopithecus_afarensis_jaw_-_Fossils_in_the_Arppeanum_-_DSC05509.JPG">Daderot/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
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<p>The jaw and teeth of an <em>Australopithecus afarensis</em> individual were quite a bit <a href="https://doi.org/10.1002/ajpa.21183">larger and thicker</a> than your own. They had three <a href="https://doi.org/10.1007/s12052-010-0249-6">big molar teeth with thick enamel</a>. The fossil skulls of some of these very early humans also show evidence of <a href="https://doi.org/10.1002/ajpa.21183">powerful chewing muscles</a>.</p>
<h2>Changes in diet</h2>
<p>Scientists think more robust jaws and teeth were needed because the foods early human ancestors ate, like raw meat and <a href="https://doi.org/10.1016/j.jhevol.2017.10.013">plants</a>, were much more difficult to chew than food is today. Researchers look at things like <a href="https://doi.org/10.1038/sj.bdj.2014.353">marks and microscopic wear patterns</a> <a href="https://theconversation.com/tooth-be-told-millions-of-years-of-evolutionary-history-mark-those-molars-71428">on fossilized teeth</a> to figure out <a href="https://press.princeton.edu/books/hardcover/9780691160535/evolutions-bite">what extinct ancestors may have eaten</a>. </p>
<p>Today’s food is much softer than it was in the past due to many factors, including <a href="https://doi.org/10.1111/joim.13011">agriculture</a>, <a href="https://doi.org/10.1007/s12110-009-9075-3">cooking</a> and <a href="https://doi.org/10.1038/nplants.2016.194">food storage</a>. Softer, easier-to-chew food means teeth have a less challenging job. As a result, modern human jaws have evolved to be <a href="https://doi.org/10.1038/s41559-019-0865-7">smaller and faces to be flatter</a> than our extinct ancestors’ were, because our meals don’t require the same big, sharp teeth that theirs did. </p>
<p>Given these changes, which took place very slowly over millions of years, the third molars – wisdom teeth – might not be as important now as they once were.</p>
<h2>Missing wisdom teeth</h2>
<p>About <a href="https://www.ncbi.nlm.nih.gov/books/NBK572295/">25% of people today are missing at least</a> one wisdom tooth completely, meaning it never formed at all. While people occasionally don’t grow other teeth, it’s <a href="https://pubmed.ncbi.nlm.nih.gov/34292692/">much more common for wisdom teeth</a>. </p>
<p>Scientists are not sure why this is the case, but it <a href="https://doi.org/10.1007/s11914-022-00761-8">may have to do with the genes</a> <a href="https://doi.org/10.3390/genes9050255">you inherit from your parents</a>. Some scientists have argued that the <a href="https://doi.org/10.1093/ejo/cjad057">lack of wisdom teeth is an advantage</a> for modern, smaller-jawed humans. It’s certainly easier to fit fewer teeth into a smaller jaw.</p>
<p>Sometimes, due to lack of space, wisdom teeth can get stuck inside the jawbone and never fully come up – or they only partially emerge. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A radiograph showing a back molar growing sideways into its neighbor." src="https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560516/original/file-20231120-18-71m6oo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&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 impacted wisdom tooth will never come up properly.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Impacted_Wisdom_Tooth_aka_Lower_Right_Third_Molar_48_RVG_IOPA_Xray.jpg">Nizil Shah/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
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<p>A so-called impacted wisdom tooth happens <a href="https://pubmed.ncbi.nlm.nih.gov/2205795/">more often in the lower jaw</a> than in the upper jaw. In cases where wisdom teeth are only partially up, people can sometimes experience pain, tooth decay or gum inflammation, which is why they have them pulled by a dentist.</p>
<p>But wisdom teeth don’t usually need to be removed if they are fully erupted in the mouth, positioned correctly and healthy.</p>
<p>Dentists can examine your mouth to see if your wisdom teeth are present, or look at X-ray pictures of your jaw if these last molars haven’t yet emerged and you suspect they may be impacted.</p>
<p>Dentists can also advise you if any treatment – or removal – is recommended for your wisdom teeth. In the meantime, <a href="https://www.mouthhealthy.org/all-topics-a-z/brushing-your-teeth">brushing</a> at least twice a day and <a href="https://www.mouthhealthy.org/all-topics-a-z/flossing">flossing</a> daily will help keep all your teeth healthy. </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/216148/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ariadne Letra receives funding from the National Institute for Dental and Craniofacial Research.</span></em></p><p class="fine-print"><em><span>Seth M. Weinberg receives funding from the National Institutes of Health. </span></em></p>
Two dental experts explain that these furthest-back molars may be a not-so-necessary leftover from early human evolution.
Ariadne Letra, Professor of Dental Medicine, University of Pittsburgh
Seth M. Weinberg, Professor of Oral and Craniofacial Sciences and Human Genetics, University of Pittsburgh
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/215064
2023-12-06T00:00:07Z
2023-12-06T00:00:07Z
Curious Kids: why do some farts smell and some don’t? And why do some farts feel hot?
<figure><img src="https://images.theconversation.com/files/563527/original/file-20231205-25-zu7j1t.jpg?ixlib=rb-1.1.0&rect=27%2C315%2C5979%2C3692&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://theconversation.com/drafts/219203/edit#">Shutterstock</a></span></figcaption></figure><blockquote>
<p><strong>Why do some farts smell and some don’t, and some feel hot? – Kian, age 6, from Maleny in Queensland</strong></p>
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<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Kian, thanks for your interesting questions!</p>
<p>Let’s start with the smell. Whether or not farts smell depends on what you’ve been eating and whether or not you have an upset tummy. </p>
<p>Having a tummy bug can also <a href="https://pubmed.ncbi.nlm.nih.gov/30191735/">change the smell of your poo</a>, especially if you have diarrhoea (runny poo). This is because of the smell of undigested food and the bugs, too.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-whales-fart-and-sneeze-159636">Curious kids: do whales fart and sneeze?</a>
</strong>
</em>
</p>
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<h2>Really smelly farts</h2>
<p>When you digest food your intestines produce gas as part of the normal process of breaking food down. </p>
<p>Most <a href="https://pubmed.ncbi.nlm.nih.gov/19830557/">gasses produced</a> – like carbon dioxide, nitrogen, hydrogen and methane – don’t smell at all. That is why you can fart sometimes and nobody really notices. </p>
<p>But there is one gas found in some farts that is <em>really</em> <em>really</em> smelly. It’s called <a href="https://www.health.wa.gov.au/articles/f_i/hydrogen-sulfide-and-public-health">hydrogen sulphide</a> and has the nickname “rotten egg gas” because that is exactly what it smells like. </p>
<p>This is why sometimes you can do a small fart but everyone has to hold their nose. These smelly farts contain <em>more</em> hydrogen sulphide.</p>
<h2>Food and farts</h2>
<p>If you eat foods that have a lot of sulphur, your gut will produce more hydrogen sulphide. </p>
<p>Some <a href="https://en.wikipedia.org/wiki/Brassica">vegetables</a> have a lot of <a href="https://www.healthline.com/nutrition/foods-with-sulfur#food-beverage-sources">sulphur</a>, such as broccoli, Brussels sprouts, cauliflower, cabbage, kale, turnips and Asian greens. </p>
<p><a href="https://pubmed.ncbi.nlm.nih.gov/10198924/">Meat</a> does too. If you eat a really huge piece of meat, your body can have trouble digesting it all at once. </p>
<figure class="align-center ">
<img alt="Digestive system" src="https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563550/original/file-20231205-23-8elmtu.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">
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<span class="caption">Food moves from our stomach, through our intestines, and out through the anus.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/medical-education-chart-biology-digestive-system-638539159">Shutterstock</a></span>
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<p>As you digest food, it moves from your stomach into the <a href="https://www.healthdirect.gov.au/digestive-system#what-is">large intestine or colon</a>. Once the foods with sulphur get there, bugs in your gut break them down and produce the hydrogen sulphide gas. </p>
<p>If a lot of it builds up and gets released in a fart, it will be very, very smelly. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-much-food-should-my-child-be-eating-and-how-can-i-get-them-to-eat-more-healthily-130470">How much food should my child be eating? And how can I get them to eat more healthily?</a>
</strong>
</em>
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<h2>So why do farts sometimes feel hot?</h2>
<p>Farts sometimes feel hot because of the temperature difference between inside your body, which is a very warm 37 degrees, and the air temperature outside, which is usually cooler. </p>
<p>This means that fart gas feels hot as it moves from your large intestine, leaves through the opening in your bottom called the <a href="https://www.healthdirect.gov.au/digestive-system#what-is">anus</a>, and touches the cooler skin. </p>
<p>You’re not as likely to notice the temperature if farts comes out really fast because speedy ones don’t have as much contact with your bottom.</p>
<p>There is another reason why farts can feel hot. Sometimes people get a hot or burning feeling in their bottom after they eat really spicy food. This is due to a spicy food chemical called <a href="https://en.wikipedia.org/wiki/Capsaicin">capsaicin</a>. </p>
<figure class="align-center ">
<img alt="Older child eating spicy soup." src="https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563551/original/file-20231205-15-82bjts.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">Sometimes farts feel hot after eating spicy foods.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/happy-boy-eating-noodles-long-hands-2370482909">Shutterstock</a></span>
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<p>If you eat food that has chilli or hot spices in it, the capsaicin makes your mouth feel hot. When you eat lots and lots of spicy food, some of the capsaicin <a href="https://pubmed.ncbi.nlm.nih.gov/35644413/">travels all the way to your large intestine</a> and gets passed out in your poo. </p>
<p>The capsaicin then gives you a <a href="https://pubmed.ncbi.nlm.nih.gov/36601592/">hot feeling in your bottom</a> when you go to the toilet. The reaction is the same as that burning feeling in your mouth after eating spicy food, except it happens at the other end.</p>
<h2>Did you know there are fart-proof undies?</h2>
<p>Researchers did some experiments to test whether they could catch fart smells by getting people to wear <a href="https://pubmed.ncbi.nlm.nih.gov/15667499/">special undies</a> that can absorb hydrogen sulphide gas. </p>
<p>And the experiments worked! </p>
<p>Now a <a href="https://shreddies.com.au/about/">company in Australia sells</a> these undies to help people who have gut problems. Their company says it wants to help people “fart with confidence”.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-what-happens-when-you-hold-in-a-fart-98310">Health Check: what happens when you hold in a fart?</a>
</strong>
</em>
</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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/215064/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Clare Collins AO is a Laureate Professor in Nutrition and Dietetics at the University of Newcastle, NSW and a Hunter Medical Research Institute (HMRI) affiliated researcher. She is a National Health and Medical Research Council (NHMRC) Leadership Fellow and has received research grants from NHMRC, ARC, MRFF, HMRI, Diabetes Australia, Heart Foundation, Bill and Melinda Gates Foundation, nib foundation, Rijk Zwaan Australia, WA Dept. Health, Meat and Livestock Australia, and Greater Charitable Foundation. She has consulted to SHINE Australia, Novo Nordisk, Quality Bakers, the Sax Institute, Dietitians Australia and the ABC. She was a team member conducting systematic reviews to inform the 2013 Australian Dietary Guidelines update and the Heart Foundation evidence reviews on meat and dietary patterns.</span></em></p>
Kian, age 6, has some interesting questions about farts that we’re probably all wondering about.
Clare Collins, Laureate Professor in Nutrition and Dietetics, University of Newcastle
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/217885
2023-12-04T13:25:52Z
2023-12-04T13:25:52Z
Why isn’t there any sound in space? An astronomer explains why in space no one can hear you scream
<figure><img src="https://images.theconversation.com/files/560865/original/file-20231121-23-g49y80.png?ixlib=rb-1.1.0&rect=0%2C5%2C1957%2C1992&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Matter in deep space is very spread out, which makes it impossible for any sound waves to travel. </span> <span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2022/038/01G7JGTH21B5GN9VCYAHBXKSD1?news=true">NASA, ESA, CSA, STScI</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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<p><strong>How far can sound travel through space, since it’s so empty? Is there an echo in space? – Jasmine, age 14, Everson, Washington</strong></p>
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<p>In space, no one can hear you scream.</p>
<p>You may have heard this saying. It’s the tagline from the famous 1979 science fiction movie “<a href="https://screenrant.com/space-no-one-hear-scream-alien-movie-origin/">Alien</a>.” It’s a scary thought, but is it true? The simple answer is yes, no one can hear you scream in space because there is no sound or echo in space.</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">professor of astronomy</a>, which means I study space and how it works. Space is silent – for the most part.</p>
<h2>How sound works</h2>
<p>To understand why there’s no sound in space, first consider how sound works. <a href="https://www.scienceworld.ca/resource/sound/">Sound is a wave</a> of energy that moves through a solid, a liquid or a gas. </p>
<p>Sound is <a href="https://www.britannica.com/science/longitudinal-wave">a compression wave</a>. The energy created when your vocal cords vibrate slightly compresses the air in your throat, and the compressed energy travels outward. </p>
<p>A good analogy for sound is a <a href="https://www.scienceworld.ca/resource/modelling-sound-wave/">Slinky toy</a>. If you stretch out a Slinky and push hard on one end, a <a href="https://www.youtube.com/watch?v=GKzpVUUrwM8">compression wave travels</a> down the Slinky.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/fMJrtheQfZw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Slinky toys can demonstrate how sound waves, a type of compression wave, work.</span></figcaption>
</figure>
<p>When you talk, your vocal cords vibrate. They jostle air molecules in your throat above your vocal cords, which in turn jostle or bump into their neighbors, causing a sound to come out of your mouth. </p>
<p>Sound moves through air the same way it moves through your throat. Air molecules near your mouth bump into their neighbors, which in turn bump into their neighbors, and the sound moves through the air. The <a href="https://www.grc.nasa.gov/www/k-12/BGP/sound.html">sound wave travels quickly</a>, about 760 miles per hour (1,223 kilometers per hour), which is faster than a commercial jet.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/sQZtKAPv7lI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Sound waves are created when matter vibrates.</span></figcaption>
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<h2>Space is a vacuum</h2>
<p>So what about in space?</p>
<p>Space is a vacuum, which means it contains almost no matter. The word vacuum <a href="https://www.etymonline.com/word/vacuum">comes from the Latin word for empty</a>.</p>
<p>Sound is carried by atoms and molecules. In space, with no atoms or molecules to carry a sound wave, there’s no sound. There’s nothing to get in sound’s way out in space, but there’s nothing to carry it, so it doesn’t travel at all. No sound also means no echo. <a href="https://theconversation.com/curious-kids-what-makes-an-echo-109141">An echo</a> happens when a sound wave hits a hard, flat surface and bounces back in the direction it came from.</p>
<p>By the way, if you were caught in space outside your spacecraft with no spacesuit, the fact that no one could hear your cry for help is the least of your problems. Any air you still had in your lungs would expand because it was at higher pressure than the vacuum outside. Your lungs would rupture. In a mere <a href="https://www.space.com/how-long-could-you-survive-in-space-without-spacesuit">10 to 15 seconds</a>, you’d be unconscious due to a lack of oxygen. </p>
<h2>Sound in the solar system</h2>
<p>Scientists have wondered how human voices would sound on our nearest neighboring planets, Venus and Mars. This experiment is hypothetical because <a href="https://www.space.com/16907-what-is-the-temperature-of-mars.html">Mars is usually below freezing</a>, and its atmosphere is <a href="https://science.nasa.gov/mars/facts/">thin, unbreathable carbon dioxide</a>. <a href="https://science.nasa.gov/venus/facts/">Venus is even worse</a> – its air is hot enough to melt lead, with a thick carbon dioxide atmosphere.</p>
<p>On Mars, your voice would sound tinny and hollow, like the <a href="https://www.youtube.com/watch?v=cE26bD_-hN4">sound of a piccolo</a>. <a href="https://www.nbcnews.com/science/cosmic-log/how-would-you-sound-mars-flna659387">On Venus</a>, the pitch of your voice would be much deeper, like the sound of a booming bass guitar. The reason is the thickness of the atmosphere. On Mars the thin air creates a high-pitched sound, and on Venus the thick air creates a low-pitched sound. The team that worked this out <a href="https://www.southampton.ac.uk/news/2012/04/the-sounds-of-mars-and-venus.page">simulated other solar system sounds</a>, like a waterfall on Saturn’s moon Titan.</p>
<h2>Deep space sounds</h2>
<p>While space is a good enough vacuum that normal sound can’t travel through it, it’s actually not a perfect vacuum, and it does have some particles floating through it.</p>
<p><a href="https://www.universetoday.com/34074/interplanetary-space/">Beyond the Earth</a> and its atmosphere, there are five particles in a typical cubic centimeter – the volume of a sugar cube – that are mostly hydrogen atoms. By contrast, the air you are breathing is 10 billion billion (10<sup>19)</sup> times more dense. The density goes down with distance from the Sun, and in <a href="https://www.space.com/interstellar-space-definition-explanation">the space between stars</a> there are 0.1 particles per cubic centimeter. In vast <a href="https://www.livescience.com/why-is-space-a-vacuum.html">voids between galaxies</a>, it is a million times lower still – fantastically empty.</p>
<p>The voids of space are kept very hot by radiation from stars. The very spread-out matter found there is in a physical state <a href="https://www.psfc.mit.edu/vision/what_is_plasma">called a plasma</a>. </p>
<p>A plasma is a gas in which electrons are separated from protons. In a plasma, the <a href="https://www.iflscience.com/is-there-really-no-sound-in-space-69612">physics of sound waves get complicated</a>. Waves travel much faster in this low-density medium, and their wavelength is much longer.</p>
<p>In 2022, NASA released a <a href="https://www.vice.com/en/article/y3p3dv/nasa-has-captured-actual-sound-in-space-and-its-honestly-terrifying">spectacular example of sound in space</a>. It used X-ray data to make an audible recording that represents the way a massive black hole stirs up plasma in the Perseus galaxy cluster, 250 million light years from Earth. The black hole itself emits no sound, but the diffuse plasma around it carries very long wavelength sound waves.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1561442514078314496"}"></div></p>
<p>The natural sound is far too low a frequency for the human ear to hear, 57 octaves below middle C, which is the middle note on a piano and in the middle of the range of sound people can hear. But after raising the frequency to the audible range, the result is chilling – it’s the sound of a black hole growling in deep space.</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/217885/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation. </span></em></p>
Sound needs matter to propagate, so the vast vacuum of space is not just empty − it’s silent.
Chris Impey, University Distinguished Professor of Astronomy, University of Arizona
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/213211
2023-11-27T13:40:22Z
2023-11-27T13:40:22Z
Why are bullies so mean? A youth psychology expert explains what’s behind their harmful behavior
<figure><img src="https://images.theconversation.com/files/555404/original/file-20231023-19-fns0q3.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C6781%2C3574&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spreading rumors about others is one form of bullying.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/young-sad-teenage-girl-feeling-lonely-and-excluded-royalty-free-image/1413738081?phrase=bullying+school&adppopup=true">LumiNola/E+ via Getty Images</a></span></figcaption></figure><figure class="align-left ">
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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>Why are bullies so mean? – Daisy, age 9, Lake Oswego, Oregon</strong></p>
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<hr>
<p>Being bullied can make your life miserable, and decades of research prove it: Bullied children and teens <a href="https://doi.org/10.1080/00405841.2016.1148988">are at risk</a> for anxiety, depression, dropping out of school, peer rejection, social isolation and self-harm.</p>
<p>Adults can be bullied too, often at a job, and they <a href="https://doi.org/10.1016/j.avb.2020.101508">may suffer just as much</a> as kids do. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/iFlrCuSyhvU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You can help stop bullying in your school or workplace.</span></figcaption>
</figure>
<p><a href="https://www.cehd.udel.edu/faculty-bio/sara-goldstein/">I’m a professor</a> who studies child and adolescent development. That includes learning how people become bullies – and how they can be stopped. </p>
<p>First, let’s <a href="https://psycnet.apa.org/fulltext/2015-20405-003.pdf">define what bullying is</a>: It’s mean-spirited, harmful behavior by someone with more power or status – like a popular kid at school or a supervisor at work – who repeatedly picks on, harasses, irritates or injures a person with less power or status. </p>
<p><a href="https://doi.org/10.1007/978-3-031-13134-9_3">Bullying can take many forms</a> – physical, like pushing, shoving and hitting; relational, such as spreading rumors, keeping somebody out of a friend group or just rude remarks; or sexual harassment and stalking behavior. </p>
<p>Sometimes, bullies target someone because of their race, religion, sexual orientation or appearance. People from the LGBTQ+ community, or who are overweight, or with a physical or developmental disability are <a href="https://doi.org/10.1016/j.dr.2018.02.001">more likely to be bullied</a>. As a result, they <a href="https://doi.org/10.1007/978-3-031-13134-9_3">may develop mental health problems</a>, including depression, anxiety and self-harming behavior.</p>
<h2>So why do bullies do it?</h2>
<p>People learn how to bully others early on through what psychologists call modeling and social learning. This means bullies see other people bullying and they essentially model, or copy, this aggressive behavior. </p>
<p>Media is <a href="https://doi.org/10.1002/9781119011071.iemp0166">a big culprit here</a>. When mean or violent conduct is glamorized and gamified in music, video games, TV and movies, bullies will imitate what they see and hear, especially if it seems cool or if it’s rewarded. </p>
<p>Family <a href="https://doi.org/10.1097/CHI.0b013e31819cb017">is also an influence</a>. If children grow up in a home without kindness and closeness, but with plenty of physical punishment and heavy conflict – including parents fighting with each other – then children view this behavior as acceptable. They can go on to treat their peers this way. </p>
<p>A similar thing happens when a kid falls into a group of friends who are bullies; they become <a href="https://doi.org/10.1017/S095457941900083X">more likely to bully others themselves</a>. To say it another way, they bully because they think it makes them look cool in front of their friends.</p>
<p>And bullies bully for <a href="https://www.healthdirect.gov.au/bullying#:%7E">lots of other reasons</a>. Some do it because it makes them feel better about themselves when they put other people down. Other bullies discovered that force and intimidation worked for them in the past, so it’s a go-to strategy to get what they want. Still others simply have difficulty controlling themselves and can’t calm down when they’re angry. </p>
<p>And with some bullies, it’s just a way to get ahead. For instance, an adult bully in the workplace <a href="https://www.routledge.com/Bullying-and-Harassment-in-the-Workplace-Theory-Research-and-Practice/Einarsen-Hoel-Zapf-Cooper/p/book/9781138615991">may spread an embarrassing rumor</a> about a co-worker to keep a rival from being promoted. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/tJsGGsPNakw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Dealing with cyberbullies.</span></figcaption>
</figure>
<h2>How to handle bullies</h2>
<p>Fortunately, there are lots of ways to stop a bully.</p>
<p>If you’re a child or teenager, talk about what has happened with a trusted adult – a parent, teacher, principal or counselor. They will help you figure out your next move. Schools are familiar with this sort of problem; they have <a href="https://doi.org/10.1007/978-3-031-13134-9_3">policies in place</a> to protect victims of bullying. </p>
<p>If you’re an adult who has been bullied in the workplace, talk to your human resources department or a neutral supervisor who can advise you on next steps. You are also legally protected – employment laws <a href="https://www.eeoc.gov/harassment">prohibit harassment and discriminatory behavior</a>. </p>
<p>Whatever your age, it’s a good idea to talk to friends or family members who may not be involved in the incident but who will offer support. Engaging in coping activities – like exercising, or relaxing with a walk – <a href="https://doi.org/10.5817/CP2019-4-2">may also help</a>. </p>
<p>You can also use the <a href="https://www.crisistextline.org/topics/bullying/#bullying-and-suicide-8">Crisis Text Line</a>, available 24/7, by texting 741741. Or call the <a href="https://www.cybersmile.org/advice-help/category/who-to-call">Stop Bullying Now Hotline</a> at 1-800-273-8255; the link also provides international numbers. Or call 988 to reach the national <a href="https://988lifeline.org/">Suicide & Crisis Lifeline</a>.</p>
<p>And a final word: Bullying is not acceptable. It’s not just “kids being kids,” or that you’re “too sensitive.” If a bully is bothering you, don’t try to handle it alone – getting help is the way to get through.</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/213211/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Goldstein 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>
No matter your age, if you’re being bullied − there’s help out there.
Sara Goldstein, Professor of Human Development, University of Delaware
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/213202
2023-11-20T13:15:30Z
2023-11-20T13:15:30Z
How do crystals form?
<figure><img src="https://images.theconversation.com/files/557894/original/file-20231106-25-rk3zxx.jpg?ixlib=rb-1.1.0&rect=33%2C0%2C5595%2C3713&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Two crystalline materials together: kyanite (blue) embedded in quartz (white).</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/bladed-crystals-of-kyanite-in-quartz-from-brazil-news-photo/869774444">Photo 12/Universal Images Group 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">
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<span class="caption"></span>
</figcaption>
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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 crystals form? – Alyssa Marie, age 5, New Mexico</strong></p>
</blockquote>
<hr>
<p>Scientifically speaking, the term “crystal” refers to any solid that has an <a href="https://theconversation.com/why-does-nature-create-patterns-a-physicist-explains-the-molecular-level-processes-behind-crystals-stripes-and-basalt-columns-186433">ordered chemical structure</a>. This means that its parts are arranged in a precisely ordered pattern, like bricks in a wall. The “bricks” can be <a href="https://australian.museum/learn/minerals/what-are-minerals/crystal-shapes/">cubes or more complex shapes</a>.</p>
<p>I’m <a href="https://scholar.google.com/citations?user=EqUjQbwAAAAJ&hl=en">an Earth scientist and a teacher</a>, so I spend a lot of time thinking about minerals. These are solid substances that <a href="https://www.britannica.com/science/mineral-chemical-compound">are found naturally in the ground</a> and can’t be broken down further into different materials other than <a href="https://www.youtube.com/watch?v=wzTRPlG1L0o">their constituent atoms</a>. Rocks are mixtures of different minerals. <a href="https://www.geologyin.com/2016/03/what-is-difference-between-minerals-and.html">All minerals are crystals</a>, but not all crystals are minerals. </p>
<p>Most rock shops sell mineral crystals that occur in nature. One is <a href="https://theconversation.com/not-so-foolish-after-all-fools-gold-contains-a-newly-discovered-type-of-real-gold-161819">pyrite, which is known as fool’s gold</a> because it looks like real gold. Some shops also feature showy, human-made crystals such as <a href="https://www.zmescience.com/feature-post/natural-sciences/geology-and-paleontology/rocks-and-minerals/the-bismuth-crystal-why-it-looks-so-amazingly-trippy-and-why-its-actually-a-big-deal-for-science/">bismuth</a>, a natural element that forms crystals when it is melted and cooled. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A dark gray rock with a large concentration of shiny yellow material covering part of its surface." src="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557895/original/file-20231106-267473-4zr8g4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pyrite in black shale rock from a quarry in Indianapolis, Ind.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/uJq9jj">James St. John/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Why and how crystals form</h2>
<p>Crystals grow when molecules that are alike get close to each other and stick together, forming chemical bonds that act like Velcro between atoms. Mineral crystals cannot just start forming spontaneously – they need special conditions and a <a href="https://www.thoughtco.com/definition-of-nucleation-605425">nucleation site</a> to grow on. A nucleation site can be a rough edge of rock or a speck of dust that a molecule bumps into and sticks to, starting the crystallization chain reaction.</p>
<p>At or near the Earth’s surface, many molecules are dissolved in water that flows through or over the ground. If there are enough molecules in the water that are alike, they will separate from the water as solids – a process called precipitation. If they have a nucleation site, they will stick to it and start to form crystals. </p>
<p>Rock salt, which is actually <a href="https://www.britannica.com/science/halite">a mineral called halite</a>, grows this way. So does <a href="https://www.britannica.com/science/travertine">another mineral called travertine</a>, which sometimes forms flat ledges in caves and around hot springs, where water causes chemical reactions between the rock and the air. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="White rock terraces around a vent in the earth's surface releasing steam." src="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557876/original/file-20231106-23-phmp31.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Travertine ledges at Mammoth Hot Springs in Yellowstone National Park in Wyoming. Terraced pools form due to deposition of travertine from the hot spring fluids as they cool and release carbon dioxide.</span>
<span class="attribution"><a class="source" href="https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/P7190038.JPG">USGS</a></span>
</figcaption>
</figure>
<p>You can make “<a href="http://www.sciencekidsathome.com/science_experiments/growing_stalactites.html">salt stalactites</a>” at home by growing salt crystals on a string. In this experiment, the string is the nucleation site. When you dissolve Epsom salts in water and lower a string into it, then leave it for several days, the water will slowly evaporate and leave the Epsom salts behind. As that happens, salt crystals precipitate out of the water and grow crystals on the string.</p>
<p>Many places in the Earth’s crust are hot enough for <a href="https://www.britannica.com/science/magma-rock">rocks to melt into magma</a>. As that magma cools down, mineral crystals grow from it, just like water freezing into ice cubes. These mineral crystals form at much higher temperatures than salt or travertine precipitating out of water. </p>
<h2>What crystals can tell scientists</h2>
<p>Earth scientists can learn a lot from different types of crystals. For example, the presence of certain mineral crystals in rocks can reveal the rocks’ age. This dating method is called <a href="https://www.britannica.com/science/geochronology">geochronology</a> – literally, measuring the age of materials from the Earth. </p>
<p>One of the most valued mineral crystals for geochronologists is <a href="https://geology.com/minerals/zircon.shtml">zircon</a>, which is so durable that it quite literally stands the test of time. The <a href="https://www.si.edu/newsdesk/releases/earths-oldest-minerals-date-onset-plate-tectonics-36-billion-years-ago">oldest zircons ever found</a> come from Australia and are about 4.3 billion years old – almost as <a href="https://www.amnh.org/exhibitions/darwin/the-world-before-darwin/how-old-is-earth">old as our planet itself</a>. Scientists use the chemical changes recorded within zircons as they grew as a reliable “clock” to <a href="https://knowablemagazine.org/article/physical-world/2021/keeping-time-zircons">figure out how old the rocks containing them are</a>.</p>
<p>Some crystals, including zircons, have growth rings, like the <a href="https://naturalsciences.org/calendar/news/science-at-home-tree-rings/">rings of a tree</a>, that form when layers of molecules accumulate as the mineral grows. These rings can tell scientists all kinds of things about <a href="https://theconversation.com/1-000-year-old-stalagmites-from-a-cave-in-india-show-the-monsoon-isnt-so-reliable-their-rings-reveal-a-history-of-long-deadly-droughts-189222">the environment in which they grew</a>. For example, changes in pressure, temperature and magma composition can all result in growth rings.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="White rectangular feldspar crystals with faintly visible growth rings are prominent against grey granodiorite rock." src="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=530&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=530&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=530&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=666&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=666&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559134/original/file-20231113-25-cx8jko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=666&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feldspar crystals with growth rings in granodiorite rock near Squamish, British Columbia.</span>
<span class="attribution"><span class="source">Natalie Bursztyn</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Sometimes mineral crystals grow as high pressure and temperatures within the Earth’s crust change rocks from one type to another in a process called <a href="https://www.amnh.org/exhibitions/permanent/planet-earth/how-do-we-read-the-rocks/three-types/metamorphic">metamorphism</a>. This process causes the elements and chemical bonds in the rock to rearrange themselves into new crystal structures. Lots of spectacular crystals grow in this way, including <a href="https://geology.com/minerals/garnet.shtml">garnet</a>, <a href="https://geology.com/minerals/kyanite.shtml">kyanite</a> and <a href="https://geology.com/minerals/staurolite.shtml">staurolite</a>.</p>
<h2>Amazing forms</h2>
<p>When a mineral precipitates from water or crystallizes from magma, the more space it has to grow, the bigger it can become. There is a <a href="https://cen.acs.org/physical-chemistry/geochemistry/Naicas-crystal-cave-captivates-chemists/97/i6">cave in Mexico full of giant gypsum crystals</a>, some of which are 40 feet (12 meters) long – the size of telephone poles.</p>
<p>Especially showy mineral crystals are also valuable as gemstones for jewelry once they are cut into new shapes and polished. The highest price ever paid for a gemstone was $71.2 million for the <a href="https://www.npr.org/sections/thetwo-way/2017/04/05/522739361/pink-star-diamond-sells-for-71-million-smashing-auction-record">CTF Pink Star diamond</a>, which went up for auction in 2017 and sold in less than five minutes.</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/213202/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Natalie Bursztyn 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>
There are a lot of myths about crystals − for example, that they are magical rocks with healing powers. An earth scientist explains some of their amazing true science.
Natalie Bursztyn, Lecturer in Geosciences, University of Montana
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/216163
2023-11-16T01:40:52Z
2023-11-16T01:40:52Z
Curious kids: what are tummy rumbles?
<figure><img src="https://images.theconversation.com/files/559029/original/file-20231113-23-u0w67y.jpg?ixlib=rb-1.1.0&rect=32%2C16%2C5431%2C3620&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-school-kids-eating-lunch-talking-1177724494">Shutterstock</a></span></figcaption></figure><blockquote>
<p><strong>What are tummy rumbles? – Anouk, aged 10, Coburg</strong></p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>This is a great question, and one lots of people ask!</p>
<p>There are a few different reasons for “tummy rumbles” or the (sometimes weird) noises your stomach makes. </p>
<p>For the most part, these are part of the normal workings of not only your stomach, but also your intestines. These are parts of your <a href="https://www.youtube.com/watch?v=ZBZWgrfZFbU">digestive system</a>, which <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/23-introduction">kicks into gear</a> when you eat. It breaks down (digests) food and then the nutrients are absorbed by the body. Whatever is left comes out as poo (also called faeces). </p>
<p>Your entire digestive system (starting at your mouth and ending at the anus, or back opening of your bottom) is one hollow tube. It’s a bit similar to the water pipes in a house, that can be empty, or have water flowing though them. Sometimes your digestive system is empty and the organs are hollow and sometimes there is food moving through it.</p>
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<h2>When eating really starts</h2>
<p>The process of digestion actually starts before you eat anything! When you <a href="https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/22%3A_Digestive_System/22.14%3A_Phases_of_Digestion/22.14A%3A_Cephalic_Phase">see or smell or think about food</a> (particularly food you like), your brain activates nerves that stimulate your digestive system, so it can prepare itself for food arriving. </p>
<p>The first step involves increasing saliva in your mouth (that “mouth watering” feeling). This is mixed with food and make it easier to chew and swallow. </p>
<p>Next, the cells in your stomach and intestines produce and release chemicals called enzymes to break down the food when it gets there. Your stomach starts moving in “waves” to mix all of those chemicals together. </p>
<p>This is where you might hear some noises. Air in your stomach can get trapped against the wall. When a wave comes through it can sound like a bubble popping, or make a gurgling or rumbling sound that you can hear and sometimes feel. The medical name for these is <a href="https://www.osmosis.org/answers/borborygmi">borborygmi</a> (pronounced BOR-BUH-RIG-MAI).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&rect=47%2C18%2C6279%2C3974&q=45&auto=format&w=1000&fit=clip"><img alt="child holds paper model of stomach and digestion" src="https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&rect=47%2C18%2C6279%2C3974&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559025/original/file-20231113-17-afxben.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Picture your digestive system like a long tube from your mouth to your bottom.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/child-holding-decorative-model-intestine-healthy-2029232828">Shutterstock</a></span>
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</figure>
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<h2>An empty stomach can be a noisier stomach</h2>
<p>When your stomach is pretty empty and then liquid arrives from swallowed saliva, acid and enzymes, you can imagine it’s going to slosh around and create some noise that can echo in there. </p>
<p>When you are hungry (and thinking about food) your stomach might “growl”. While your stomach is waiting for food it’s moving liquid around to get ready for it and creating pockets of air that get squashed, creating noises. </p>
<p>Further down your digestive tract, in the intestine, muscular waves push everything down the tube, making sure there is space for new food to arrive. This can also create noises.</p>
<h2>Then you eat something (hopefully) delicious</h2>
<p>The food you eat moves through your stomach and slowly into the intestine, where similar mixing movements happen break it down in the body. Air (also called gas) in the intestine makes noise when it moves, like it did in the stomach. </p>
<p>Even though this noise can sometimes be annoying or embarrassing, and you would like it to go away, the mixing that happens in the intestine is important. It’s how you get all of the nutrients (things like <a href="https://www.niddk.nih.gov/-/media/Files/Digestive-Diseases/Digestive_System_508.pdf">carbohydrates, fats, proteins, vitamins, minerals</a> and more) from food. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="girl looks hungrily at hamburger" src="https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559032/original/file-20231113-21-wg8y9j.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">Just thinking about eating can trigger waves of anticipation in our stomach.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/adorable-little-girl-her-tongue-out-2142082743">Shutterstock</a></span>
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<p>The mixing (and the noises) mean food is mixing with the chemicals and breaking everything you’ve eaten down into small units, called molecules. Once these are small enough, the cells that line your intestine can take them in, a process called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4956471/">absorption</a>. </p>
<p>Once the nutrients get into your blood stream, <a href="https://med.libretexts.org/Bookshelves/Nutrition/An_Introduction_to_Nutrition_(Zimmerman)/03%3A_Nutrition_and_the_Human_Body/3.04%3A_Nutrients_Are_Essential_for_Organ_Function">organs</a> like your heart, lungs, brains and kidneys can use them to do their jobs in the body from pumping blood to breathing in air to telling the body what to do next.</p>
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Read more:
<a href="https://theconversation.com/what-happens-if-you-need-to-pee-while-youre-asleep-204789">What happens if you need to pee while you're asleep?</a>
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<h2>Should you worry about tummy noises?</h2>
<p>These are the most common causes of tummy rumbles, but they can happen after you swallow air when you talk, drink or eat and it travels into your stomach or intestines.</p>
<p>The noises made by your digestive system are important – they mean it is working properly. However, if the noises come with any pain or diarrhoea it could be a sign of a food intolerance or other digestive issue and you should get it checked out.</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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/216163/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrea Stringer receives funding from a National Health and Medical Research Council (NHMRC) Ideas Grant. </span></em></p>
The process of digestion actually starts before you eat anything! Tummy rumbles can too.
Andrea Stringer, Associate professor, University of South Australia
Licensed as Creative Commons – attribution, no derivatives.