tag:theconversation.com,2011:/global/topics/flight-mechanics-8541/articles
Flight mechanics – The Conversation
2020-07-22T03:35:02Z
tag:theconversation.com,2011:article/142654
2020-07-22T03:35:02Z
2020-07-22T03:35:02Z
Curious Kids: why can’t humans grow wings?
<figure><img src="https://images.theconversation.com/files/348561/original/file-20200721-29-unkkvw.jpg?ixlib=rb-1.1.0&rect=38%2C96%2C4254%2C2761&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><blockquote>
<p><strong>Why can’t humans grow wings? Christina, age 9, Beijing, China.</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>Hi Christina! Great question.</p>
<p>Humans are animals that have backbones. This means we’re in a group called “<a href="https://www.britannica.com/animal/vertebrate">vertebrates</a>” – along with fish, amphibians (such as frogs), reptiles, birds and mammals. </p>
<p>A long time ago, humans weren’t around. We actually came from 500-million-year-old <a href="https://nhpbs.org/wild/agnatha.asp">fish</a> that had no arms, legs or jaws. But slowly, from one fish parent to the next, they changed. Some started to grow arms and legs, eventually leading to humans as they are today. </p>
<p>These very slow changes happen to all animals over millions of years, in a process we call evolution. Every part of the human body, and every other animal, evolved in this way.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-scientists-know-evolution-is-real-122039">Curious Kids: how do scientists know evolution is real?</a>
</strong>
</em>
</p>
<hr>
<h2>Two arms, two legs: a basic vertebrate body plan</h2>
<p>Fish were the first vertebrates to have pairs of limbs. For humans, these are our arms and legs. Fish have pairs of fins at their front and back. </p>
<p>A long time ago, some fish <a href="https://theconversation.com/when-fish-gave-us-the-finger-this-ancient-four-limbed-fish-reveals-the-origins-of-the-human-hand-129072">evolved bones</a> in their fins that would later become human fingers. This pattern of having pairs of two limbs (four in total) resulted in the bodies vertebrates have today. </p>
<p>All vertebrates today have the same body plan: two arms, two legs, a head with two eyes, two nostrils, a mouth with teeth, and so on. </p>
<p>However over the course of evolution, some animals didn’t quite follow this plan exactly. Their bodies needed to be different to suit their lifestyle – whether this was swimming or flying. This is how wings came about.</p>
<h2>How animals started to fly</h2>
<p>Wings of flying vertebrates, such as birds, are simply modified arms that help them fly. </p>
<p>You may have heard of pterosaurs – the (<a href="https://www.nationalgeographic.com/magazine/2017/11/pterosaurs-weirdest-wonders-on-wings/">sometimes huge</a>) flying creatures that lived at the time as dinosaurs. Pterosaurs also slowly formed their wings over many, many years. They did this by growing one long finger connecting a thin layer of skin called a membrane to the rest of their body. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348565/original/file-20200721-21-m6pqb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pterosaurs weren’t dinosaurs – rather, they were flying reptiles.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>One group of <a href="https://www.nhm.ac.uk/discover/how-dinosaurs-evolved-into-birds.html">dinosaurs evolved into birds</a> about 160 million years ago. </p>
<p>This happened well after dinosaurs first gained feathers to help keep their bodies cool or warm as needed. Then, from one parent to the next, they slowly gained longer front arms to eventually make wings. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348569/original/file-20200721-25-y9pn94.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One extinct dinosaur called archaeopteryx looked a bit like a dinosaur, and a bit like bird too. It is often pointed to as an evolutionary link between today’s birds and extinct feathered dinosaurs.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Why didn’t humans evolve to have wings?</h2>
<p>Now let’s look at why humans can’t grow wings. </p>
<p>All living things, including vertebrates, have genes. These are like little instruction booklets inside our bodies that decide how we grow and what our bodies can do. We can’t change what our genes do. For example, your genes are the reason your eyes may be black, or brown, or blue – but you can’t control this.</p>
<p>We also have genes called “<a href="http://encyclopedia.kids.net.au/page/ho/Hox_gene">hox genes</a>”. These make sure our bodies grow a certain way as we get older. For instance, while you might grow taller thank your siblings, hox genes make sure you only grow two arms and two legs – and not eight legs like a spider. In fact, a spider’s own hox genes are what give it eight legs.</p>
<p>So one main reason humans can’t grow wings is because our genes only let us grow arms and legs.</p>
<h2>What if we did have wings though?</h2>
<p>Even if humans did have wings, we wouldn’t immediately be able to fly.</p>
<p>To fly, we would also need the right body size and metabolism. Metabolism is our body’s ability to use fuel (such as from the food we eat) to make energy, which helps us move.</p>
<p>Birds have very higher metabolisms than us. A hummingbird’s heart can beat up to 1,200 times per minute, while a human athlete’s heart might only go as fast as 220 beats per minute. This means hummingbirds can burn energy better than humans.</p>
<p>Flying birds also have much lighter bones that help them <a href="https://www.discovery.com/nature/Why-Do-Birds-Have-Hollow-Bones">breathe better</a>, feathers that help lift them while flying, and powerful <a href="https://www.birdwatchingdaily.com/news/science/eldon-greij-describes-amazing-way-birds-breathe/">lungs</a> that keep oxygen pumping through their bodies.</p>
<p>Unless humans had all of this, we wouldn’t be able to fly even if we did have wings. Dinosaurs also only evolved to become birds by making their bodies much smaller and lighter over time.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-are-humans-going-to-evolve-again-116990">Curious Kids: are humans going to evolve again?</a>
</strong>
</em>
</p>
<hr>
<h2>What about dragons?</h2>
<p>While we know dragons aren’t real, some imaginary dragons have bodies close to real-life vertebrates.</p>
<p>Dragons such as Smaug in the movie The Hobbit have wings and legs only. So if Smaug was real he might actually have been able to fly, as long as he was light, had a high metabolism and a membrane to form his wings. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=400&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=400&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348572/original/file-20200721-23-bau9h6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=400&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">If Smaug the dragon was real, he may have been able to fly! (Lucky he’s not).</span>
<span class="attribution"><span class="source">Warner Bros</span></span>
</figcaption>
</figure>
<p>On the other hand, the dragon Night Fury from How to Train Your Dragon has arms, legs <em>and</em> wings. In real life, this would be like having two legs and two pairs of arms. </p>
<p>Night Fury breaks the basic rules of evolution as no vertebrate has ever evolved to have this combination of arms and legs. Insects can, but they don’t have backbones so they’re not vertebrates. </p>
<p>So if Night Fury was real, scientists may have to call him an insect.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=317&fit=crop&dpr=1 600w, https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=317&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=317&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=399&fit=crop&dpr=1 754w, https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=399&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/347543/original/file-20200715-33-185c8vi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=399&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Night Fury from How to Train Your Dragon is a very likeable, but not a very realistic character.</span>
<span class="attribution"><span class="source">DreamWorks Animation/IMDB</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/142654/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Long receives funding from The Australian Research Council.</span></em></p>
Human genes are one of the main reasons we can’t grow wings. And even if humans did have wings, they wouldn’t necessarily allow us to fly.
John Long, Strategic Professor in Palaeontology, Flinders University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/54207
2016-02-09T13:31:35Z
2016-02-09T13:31:35Z
Why Leonardo da Vinci was a genius
<figure><img src="https://images.theconversation.com/files/110608/original/image-20160208-2586-1hfc7vv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">© Science Museum</span></span></figcaption></figure><p>Leonardo da Vinci, as we know, was the epitome of the Renaissance man. We know that he was a genius, a polymath, a pioneer in fields as diverse as anatomy and hydrodynamics. We know that Leonardo invented the tank, the helicopter, the flying machine, the parachute, and the self-powered vehicle. We know that he was a “man ahead of his time” and that his visionary inventions weren’t to be realised for centuries.</p>
<p>Well, not exactly. Leonardo the inventor is subject to legends in much the same way as the Mona Lisa. But the reality beneath the stories is no less exciting, as the Science Museum’s new exhibition <a href="http://www.sciencemuseum.org.uk/visitmuseum/Plan_your_visit/exhibitions/leonardo">Leonardo da Vinci: The Mechanics of Genius</a> makes abundantly clear.</p>
<p>He was trained in Florence in the 1470s, when the workshops of some major artists not only took on art in every kind of medium but also tasks that we would now classify as engineering – both civil and military. His master, <a href="http://www.britannica.com/biography/Andrea-del-Verrocchio">Andrea del Verrocchio</a>, was famed chiefly as a sculptor, but was also responsible for the soldering and erection of the great copper ball on top of the dome of Florence’s cathedral. This brought the young engineer into direct contact with the lifting and construction devices of the great <a href="http://www.britannica.com/biography/Filippo-Brunelleschi">Filippo Brunelleschi</a>, architect of the dome. </p>
<p>These artist-engineers were employed to produce a wide range of practical machines of the kind that rarely leave their mark in written and drawn records. Leonardo, for instance, produced ingenious designs for the sluices of lock gates. We know about this because of a memorandum in which he speaks of sluices for rivers that he arranged for the Venetians in 1500, when he was visiting the maritime republic.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110605/original/image-20160208-2625-mavkbn.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">Model of an armoured vehicle.</span>
<span class="attribution"><span class="source">© Archivio Museo Nazionale della Scienza e della Tecnologia Leonardo da Vinci – Alessandro Nassiri</span></span>
</figcaption>
</figure>
<p>Leading engineers also indulged in more visionary designs in their treatises. These involved a lot of “visual boasting” aimed at prospective or actual employers. Like all prospectuses, the treatises were designed to make an impression. Many of Leonardo’s most famous designs fall into this category. An example is the so-called “tank”, a kind of wood-and-steel woodlouse fringed by cacophonous arrays of guns, which was designed to scoot across the dusty battlefield. It is high on shock and awe and low on practicality – as the designer and his patron would have realised.</p>
<p>Other famous designs have been misread. The “helicopter” or airscrew, known only in a single thumbnail sketch, cannot have been for manned flight, since the whole machine would have revolved frantically. Rather, it is a device of technological entertainment. The same applies to the spring-driven “car”, which would have scuttled across a town square during a festival carrying a costumed figure, such as an angel. Its distance of travel would have been finite. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110606/original/image-20160208-2634-1m7e3sm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The aerial screw.</span>
<span class="attribution"><span class="source">© Claudio Divizia Hemera Thinkstock by Getty Images</span></span>
</figcaption>
</figure>
<p>Taking such designs down a peg – from helicopter to entertainment – does nothing to diminish Leonardo’s extraordinary inventiveness. Nobody was ever more adept in envisaging how to solve technical problems, often by transmitting motion in one plane into another using intricate arrays of gears, cams, axles and levers. </p>
<h2>Locating genius</h2>
<p>If we step back from the individual inventions, we can see that his genius an engineer rests on three foundations.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=855&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=855&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=855&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1075&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1075&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110609/original/image-20160208-2586-1xzssbr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1075&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Design of a spiral gear for a barrel spring.</span>
</figcaption>
</figure>
<p>The first is that he saw clearly how the design of machines must be informed by the mathematical laws of physics rather than just relying upon practice. For instance, he realised that if the power of an unwinding spring diminished according to a mathematical ratio, any device to compensate for this must be designed in accordance with the mathematics. As such, he invented a series of conical and spiral gears that could be mounted on the axle of a barrel-spring to counteract the unwinding.</p>
<p>He was also the first to design separate components that could be deployed in a variety of devices. His “elements of machines” ranged from complex units such as the gears for barrel springs and ring bearings for axles to relatively simple hinges.</p>
<p>And no-one ever drew machines with more attention to reality. The mental “sculpture” that he conducted in his mind was transmitted on to the paper with total conviction. He knew that such “portraits” of devices did not necessarily clarify all the details of construction, and needed to be amplified with drawings of the individual parts. The solid section above the barrel spring brilliantly shows how two cylindrical sleeves at either end of the axle of the conical lantern gear slide on the vertical shaft to accommodate its climb up the helter-skelter ramp.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110613/original/image-20160208-2625-1ou7qk3.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">Bird wings, mechanical and natural.</span>
<span class="attribution"><span class="source">© Science Museum</span></span>
</figcaption>
</figure>
<p>Leonardo’s famous efforts to devise various kinds of flying machines were directed by the emulation of nature – not literally to imitate a bird, but to apply the principles of bird flight to endow man with the capacity to fly in his own way. His genius lay in his aspiration to create “a second nature in the world”: his dual mastery of engineering design and natural law.</p><img src="https://counter.theconversation.com/content/54207/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Kemp 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>
He may not have invented the helicopter, but the real man is more than worthy of the myth.
Martin Kemp, Emeritus Professor of the History of Art, University of Oxford
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/34177
2014-11-25T10:11:07Z
2014-11-25T10:11:07Z
Longing for the ‘golden age’ of air travel? Be careful what you wish for
<figure><img src="https://images.theconversation.com/files/65369/original/image-20141124-19618-1prlyn8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Prior to the introduction of jets, most commercial airplanes were propeller driven, like the DC-3 pictured here. These planes had a limited cruising altitude -- and experienced much more turbulence. </span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:DC3_on_ice.jpg">NOAA Photo Library</a></span></figcaption></figure><p>Long lines at security checkpoints, tiny plastic cups of soda, small bags of pretzels, planes filled to capacity, fees attached to every amenity – all reflect the realities of 21st century commercial air travel. It’s no wonder that many travelers have become nostalgic for the so-called “golden age” of air travel in the United States. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=767&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=767&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=767&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=964&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=964&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65138/original/image-20141120-4490-wfmox9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=964&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Airlines often advertised their flights as relaxing and luxurious.</span>
<span class="attribution"><a class="source" href="http://library.duke.edu/digitalcollections/adaccess_T1755/">Duke University Libraries</a></span>
</figcaption>
</figure>
<p>During the 1950s, airlines promoted commercial air travel as glamorous: stewardesses served full meals on real china, airline seats were large (and frequently empty) with ample leg-room, and passengers always dressed well.</p>
<p>After jets were introduced in the late 1950s, passengers could travel to even the most distant locations at speeds unimaginable a mere decade before. An airline trip from New York to London that could take up to 15 hours in the early 1950s could be made in less than seven hours by the early 1960s.</p>
<p>But airline nostalgia can be tricky, and “golden ages” are seldom as idyllic as they seem.</p>
<p>Until the introduction of jets in 1958, most of the nation’s commercial planes were propeller-driven aircraft, like the DC-4. Most of these planes were unpressurized, and with a maximum cruising altitude of 10,000 to 12,000 feet, they were unable to fly over bad weather. Delays were frequent, turbulence common, and air sickness bags often needed. </p>
<p>Some planes were spacious and pressurized: the <a href="http://everythingnice.org/wp-content/uploads/2009/07/PanAm-cutawayS.jpg">Boeing Stratocruiser</a>, for example, could seat 50 first class passengers or 81 coach passengers compared to the DC-3’s 21 passengers. It could cruise at 32,000 feet, which allowed Stratocruiser to fly above most bad weather it encountered. But only 56 of these planes were ever in service. </p>
<p>While the later DC-6 and DC-7 were pressurized, they still flew much lower than the soon-to-appear jets – 20,000 feet compared to 30,000 feet – and often encountered turbulence. The piston engines were bulky, complex and difficult to maintain, which contributed to frequent delays. </p>
<p>For much of this period, the old saying “Time to spare, go by air” still rang true.</p>
<p>Through the 1930s and into the 1940s, almost everyone flew first class. Airlines did encourage more people to fly in the 1950s and 1960s by introducing coach or tourist fares, but the savings were relative: less expensive than first class, but still pricey. In 1955, for example, so-called “bargain fares” from New York to Paris were the equivalent of just over $2,600 in 2014 dollars. Although the advent of jets did result in lower fares, the cost was still out of reach of most Americans. The most likely frequent flier was a white, male businessman traveling on his company’s expense account, and in the 1960s, airlines – with young attractive stewardesses in short skirts – clearly catered to their most frequent flyers. </p>
<p>The demographics of travelers did begin to shift during this period. More women, more young people, and retirees began to fly; still, airline travel remained financially out-of-reach for most.</p>
<p>If it was a golden age, it only was for the very few.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bKqQgNZylLw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Jet planes were introduced in the late 1950s, resulting in shorter flight times. But their ticket prices out of reach for the average traveler.</span></figcaption>
</figure>
<p>People also forget that well into the 1960s, air travel was far more dangerous than it is today. In the 1950s and 1960s US airlines experienced at least a half dozen crashes per year – most leading to fatalities of all on board. People today may bemoan the crowded airplanes and lack of on-board amenities, but the number of fatalities per million miles flown has dropped dramatically since since the late 1970s, especially compared to the 1960s. Through at least the 1970s, airports even prominently featured kiosks selling flight insurance.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=433&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=433&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=433&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=544&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=544&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65137/original/image-20141120-4490-umbmsc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=544&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In an era when airline travel was far more dangerous than it is today, kiosks in airports used to sell insurance.</span>
<span class="attribution"><a class="source" href="http://mentalfloss.com/article/57239/10-things-we-no-longer-see-airports">Mental Floss</a></span>
</figcaption>
</figure>
<p>And we can’t forget hijackings. By the mid-1960s so many airplanes had been hijacked that <a href="http://www.latinamericanstudies.org/hijackers/flying-high.htm">“Take me to Cuba”</a> became a punch line for stand-up comics. In 1971 <a href="http://nymag.com/news/features/39593/index2.html">D.B. Cooper</a> – a hijacker who parachuted from a Boeing 727 after extorting $200,000 – might have been able to achieve folk hero status. But one reason US airline passengers today (generally) tolerate security checkpoints is that they want some kind of assurance that their aircraft will remain safe.</p>
<p>And if the previous examples don’t dull the sheen of air travel’s “golden age,” remember: in-flight smoking was both permitted and encouraged.</p><img src="https://counter.theconversation.com/content/34177/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Janet Bednarek 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>
Sure, you got meals served on china. But planes were frequently delayed, hijacked, and prone to fatal crashes.
Janet Bednarek, Professor of History, University of Dayton
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/21940
2014-01-15T18:05:28Z
2014-01-15T18:05:28Z
Doing maths on the fly, birds form V for efficiency
<figure><img src="https://images.theconversation.com/files/38853/original/qcgkv56w-1389371636.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Following the leader has its benefits.</span> <span class="attribution"><span class="source">Markus Unsöld</span></span></figcaption></figure><p>Across the globe, hundreds of species of birds can be seen flying in V-formations. We have long suspected that these formation might help birds fly with less effort. Yet the precise mechanics have remained unknown – until now.</p>
<p>Expending less effort in long flights can be the difference between life and death for migratory birds. Higher efficiency saves precious fuel needed for journeys that can often be thousands of kilometres long. Cyclists in Tour de France know this well. </p>
<p>These cyclists ride in a group called the <em>peloton</em> where the leader plows through the onrushing air, while teammates riding behind him burn fewer calories. After some time, the leader swaps places to spread out the effort among the group.</p>
<p>Just like cyclists, it might seem intuitive that birds do the same when flying in a V-formation. But flying is complicated by the fact that birds flap their wings, which changes how the air flows around them.</p>
<p>Aerodynamic theory predicts birds should save energy if they carefully adjust their position and flapping speed in a formation. This made <a href="http://arc.aiaa.org/doi/abs/10.2514/6.2007-4182">some scientists question</a> whether birds have the required sensory precision to achieve this feat in mid-air.</p>
<p>In a study just published in <a href="http://dx.doi.org/10.1038/nature12939">Nature</a>, an international team led by Steven Portugal of the Royal Veterinary College in London shows that birds defy these expectations: they really can fine-tune their flight formations to be more efficient.</p>
<h2>As the crow flies</h2>
<p>When a bird flies, it creates spinning loops of air behind it called vortices. Part of the vortex system pushes air upwards– known as upwash – while the opposite side of the vortex pushes air downwards – known as downwash. To fly with less effort, a bird should time its flapping to press its wings through the upwash created by the bird in front of it. It also wants to avoid the downwash.</p>
<p>By precisely recording the spacing of ibises in formation, along with the timing of their wingbeats, Portugal and colleagues were able to show that ibises time their wingbeats for maximum efficiency. That is, they take advantage of the upwash and avoid the downwash. The ibises also altered their wingbeat patterns based on the style of formation: birds flying in a “V” formation timed their movements differently to those flying in a single file line, just as they need to for maximum efficiency.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38858/original/37ffg7m7-1389372473.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Markus Unsold</span></span>
</figcaption>
</figure>
<p>The research was done using rare northern bald ibises. These large birds are the subject of a special conservation program to reintroduce them to the wild. Those used in the study hatched at Zoo Vienna, Austria, in March 2011, and were “imprinted” with human foster parents, which allowed the humans to train them in basic survival skills, just as their real parents would have. This they could achieve, because some birds get “imprinted” by the first suitable moving object they encounter during a critical period shortly after hatching. They then follow and learn from this surrogate like they would from a biological parent.</p>
<p>At four months, the birds began doing training flights behind an ultralight aircraft. They were then led along a migration route from Austria to Italy, the route they would then follow in the future when released into the wild.</p>
<p>The ibises were fitted with tiny location loggers and their flight filmed. They flew in formation with one another, following the path set by the paraplane. When the flapping speed and positioning of the birds was analysed after the journey, Portugal found the timing matched what theory predicts the birds should use to maximise their efficiency.</p>
<p>The team used ibises because they had special access to captive-raised birds, but other birds probably use the same trick when they fly in formation. How these birds are able to sense and predict such subtle changes in air flow is still a mystery.</p>
<p>It may be that birds have sensory abilities we weren’t previously aware of. It might also be that ibises, and possibly other birds, have an innate ability to do the required mathematics, quite literally, on the fly: judging the distance to the next bird and counting wingbeat cycles as they go. Either way, it is clear that birds still have a lot to teach us about their abilities and success as flying animals.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fKkzqk3RMLc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/21940/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Habib 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>
Across the globe, hundreds of species of birds can be seen flying in V-formations. We have long suspected that these formation might help birds fly with less effort. Yet the precise mechanics have remained…
Michael Habib, Assistant Professor of Cell and Neurobiology, University of Southern California
Licensed as Creative Commons – attribution, no derivatives.