World’s smallest origami bird, why hummingbirds hum, physics meeting ‘ain’t got that swing’

Physics

Spring has arrived here in Bristol and the birds are going bonkers in our garden, especially the amorous wood pigeons. So this edition of the Red Folder is dedicated to our feathered friends.

Cornell University is famous for its ornithology lab, but now physicists at the US university have also gone to birds and created what they describe as the “world’s smallest origami bird”. Measuring about 60 microns across, the folding bird is actuated by an extremely thin layered material that bends when a voltage is applied to it. It was created by Qingkun Li, Itai Cohen, Paul McEuen and colleagues – who explain how and why they have created the tiny folding bird in the above video.

Hummingbirds are not quite as small as the Cornell origami bird, but their tiny size and habit of feeding on nectar from flowers means that they have a unique way of flying. Indeed, hummingbird refers to the humming sound that the birds’ wings make as they flap furiously to hover in front of flowers.

Now researchers at Eindhoven University of Technology and the spin-out company Sorama, both in the Netherlands, and Stanford University in the US have used a myriad array of sensing equipment to work out how the hum is generated. They found the hum is made by changes in the pressure differences between regions above and below the wings as the birds flap to create their upward hovering force. The team have developed a model to describe hum generation and say that it could be used to design quieter fans. You can read more in a paper in the journal eLife.

The saxophonist Charlie Parker was famously known as Bird and is much revered in music circles for his development of bebop in the 1940s. With a fast tempo and complex chord changes, this form of jazz continues to have an important influence on musicians today.

The riddle of swing

Bebop often incorporates highly syncopated rhythms, which I am sure delight the German physicist Theo Geisel who uses mathematics to study musical rhythms. At this week’s virtual March Meeting of the American Physical Society, Geisel gave a talk on “Psychophysics of musical rhythms and the riddle of swing”.

Geisel and colleagues at the Max Planck Institute for Dynamics and Self-Organization have shown that “certain systematic microtiming deviations between musicians do enhance and are relevant for the swing feel in jazz”.

Unfortunately, the recording of Geisel’s talk seems to have been expunged from the video of the meeting session, E14 Physics of Social Interactions III. However, you can read more about this fascinating topic in this open access paper: “Microtiming deviations and swing feel in jazz”.

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