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The Textbooks Were Wrong About How Your Tongue Works
(www.nytimes.com)
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this post was submitted on 04 Jun 2024
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There's lots of stuff textbooks get wrong simply because there's no easy way to explain how it ACTUALLY works at an appropriate grade level.
For example, wings and lift. We're told that the curved surface of a wing causes air to move faster on one side of the wing than the other and this generates lift.
No, that's not how it works, but you can be forgiven for thinking that since that's all most people are taught.
https://www.scientificamerican.com/video/no-one-can-explain-why-planes-stay-in-the-air/
I read the article you posted here (great read btw, thanks for posting) and I think just to quibble, that idea of lift (Bernoulli's Theorem) is not wrong, just insufficient. It sounds like that mechanism definitely contributes to the overall generated lift, but doesn't tell the whole story.
I really enjoyed the bit about Einstein designing an aerofoil and when it was tested, the pilot said the plane "waddled like a pregnant duck". Really interesting to see one of the smartest physicists to ever live just kinda give up on aeronautics and consider it a "youthful folly".
Not only doesn't tell the whole story, but there are parts of it that just aren't understood at all.
Two particles split by the wing reach the end of the wing at the same time, but the one on top of the wing is going faster? 🤔
What generates the low pressure zone on top of the wing? 🤔
Smarter people than me have been trying to figure it all out and while there are some good answers, they're competing answers. LOL.
Because it travels further, due to the curve, surely. So the air particles are more stretched across the top of the wing, and the pressure therefore lower than along the relatively straight underside of the wing. I thought that was the explanation. I'm interested to hear why that's not a complete enough answer though, because planes are clearly flying.
Some things to think about: symmetrical wings, with the same curve on bottom and top, can fly perfectly fine. Flat wings, with no curve at all, don't fly quite as well but with the proper angle of attack can also generate lift. Additionally, planes fly perfectly well upside down.
If this curve explanation were complete, how could those things work?
A symmetrical profile, when having a non zro angle of attack, is actually not symmetrical anymore.
Yes, those are all good points. I've decided the answer is related to the directionality of gravity somehow, but I'm not sure why. So you're already working with one acceleration vector when stationary. As in, the air underneath is being pushed on in a way the air above the wing isn't, almost like cavitation versus compression. Then you add the thrust vector and the little differentials add up to the point it generates lift. I'll keep thinking about it!
Science in the making, people /s
toss my salad with jelly or syrup
You've such a way with words
They don't actually reach the trailing edge at the same time afaik.
I’ve seen this exact article quoted several times with the “you’ve been wrong about this all along” and it’s like the people saying that don’t even bother to read. No it’s not saying that lift isn’t generated due to low pressure forces, like you’re claiming. It’s saying that it’s not a complete explanation. It’s missing some forces that make up the rest of the lift.
You can be forgiven for thinking that that’s not how it works 🙃
Like it says, it’s the most popular theory with scientists, they’re just still missing a complete explanation. Lift from low pressure is still the most popular partial explanation.
And, given the fact that having pressure-measurement manometer-arrays built into wings proves that the suction-side lift is greater than the pressure-side lift, and that this has been known since before The Great War..
some of us are inclined to consider the evidence to be valid.
Causes less air pressure at the upper side, so the lower side pushes up, no?
And the upside down flying is simply due to gliding mechanics, no?
Nope. Read the link, it's fascinating and complicated.
Not sure what you mean by this. But planes still generate lift when flying upside down. Wings with a symmetrical curve can also generate lift. Flat wings with no curve at all can also generate lift.
Pressure differences are definitely involved. That's the only way air pushes against things, after all, so the fact that there is a lift force implies a pressure difference. However the cause of the pressure difference is rather complicated.