The Silent Flight of Owls, Explained (2017) | Hacker News Reader

The Silent Flight of Owls, Explained (2017)

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An interesting fact is that this has influenced the design of computer fans: https://news.softpedia.com/news/Lenovo-Details-Its-Unique-Ow...

Thanks for sharing! I have heard this called biomimicry. When you take inspiration from nature to create designs.

I enjoyed this video on the concept: https://www.youtube.com/watch?v=sf4oW8OtaPY

"The best ideas might not be ours , they might be already invented." I find biomimicry fascinating in how it promotes egoless engineering. Solving problems rather than being _right_.

Once you start looking for biomimicry you see it everywhere. Nature is full of good ideas!

I still remember what a friend told me in college who was a biology major. Apparently the human foot is the most complex piece of engineering we know. We only get one pair for life, they take lots of abuse, but still work great.

Here's the sound of owl flying: https://www.youtube.com/watch?v=d_FEaFgJyfA

That may be true from afar. But not when they fly by very near your head. They (some Owls, unlikely Barn Owls because of darker colors) startled me several times walking in the evenings or night, coming from somewhere above and behind me, diving into some garden or park, producing a strong whooosh about half meter away, then a short squeak/shriek, and lifting off with something mouse/mole/rat-like in its claws.

Like fighter jets, you only hear them when it's too late for their prey.

Witnessing an owl in the evening is truly awe-inspiring!

I was at the beach next to an airport recently. There was a small private jet doing practice approaches along the runway but not landing. It really was the case that I would't hear it until it was on top of me. Also had some raptors silently swoop in and steal my lunch out of my had at that beach. Jerks.

My dad (jet pilot) told me how he'd do ground attack in Korea against a fixed gun position:

1. Come in with the sun at your back. The gun crew cannot see or hear you.

2. Attack straight down. Gun crew is extremely reluctant to fire straight up for obvious reasons. This is extremely dangerous for the pilot, too, as you have to be exceedingly careful not to overspeed the jet and you have to pull out in time. But he figured it was less dangerous than a flak shell fired at him.

3. Come in flat at treetop level off to the side at high speed. The gun crew cannot crank the gun around fast enough to get the jet in its sights. Then turn in hard and blast away before they can get the gun aimed.

> Come in with the sun at your back.

Did he also mention this tactic for air attack?

Changing technologies (and different dominance asymmetries) seem to swing a pendulum between antagonistic scenarios of advertising (We're here, and we're badass, so don't mess with us) and concealment ("We'd given the bulk of Chrome's Zurich account to a dozen world charities. There was too much there to move, and we knew we had to break her, burn her straight down, or she might come after us."). In the air scenario, I've read that visual-era twentieth century air forces would use either silver or camouflage livery depending upon their perception of their own local air superiority.

Bonus clip: https://www.youtube.com/watch?v=2CFckjfP-1E (sorry, my memory said "owl" but it's really goshawk)

For air-to-air combat, the original and best set of tactics are the:

  https://en.wikipedia.org/wiki/Dicta_Boelcke

The sun at your back is #1.

As for camouflage, Richthofen's Flying Circus was famous for eschewing camo and using bright colors to draw attention.

Excerpts from the "Book of Five Rings" (by Miyamoto Musashi, ca. 1645)

> Stand in the sun; that is, take up an attitude with the sun behind you. If the situation does not allow this, you must try to keep the sun on your right side.

> You must look down on the enemy, and take up your attitude on slightly higher places.

Similar discussion, which also contains one of the funniest comments I've seen on HN: https://news.ycombinator.com/item?id=23248779

That was a delightful thread.

An interesting observation from this line of work (based on other articles in the area): the silence of owl flight depends on the frequency of the sound. Mice have a range of frequencies that they can hear. If you line up the two curves, you can see evolution in action. Owl flight becomes quieter just at the low end of the sound frequency that mice can hear.

BBC nature video about silent owl flight. Flight and audio comparisons of owls and some other birds.

https://youtu.be/d_FEaFgJyfA

Reply on news.ycombinator.com