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Comment by smallbugfound | Hacker News Reader

No idea why you would provide the equal transit time theorem to students, it makes such a low amount of sense that you're inevitably going to get your students extremely confused if they are paying any attention at all.

"Why does the air have to transit in the same time period?"

"But _why_ is the air moving over the top faster? Weren't you going to tell me how a wing works?" Etc etc etc

It is the worst kind of lie-to-children (and adults) in my opinion, it's not a simplified true answer it's a whole cloth fabrication that vaguely gestures in the right direction, partially, if you are being generous.

The idea that people get tested on regurgitating it for a pilots license is crazy.

It's up there with those ridiculous tounge maps with taste regions on them.

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At the same time, it gives me some hope that humanity can still get smarter.

Progress in science and technology oscillates between breakthroughs and consolidation: new ideas are exciting but the repercussions and formalism need some time to sink in. If you don't give it enough time you are left with overly elaborate and confusing frameworks. Usually the academics sort this kind of thing out before it goes into mass market education but it's never too late to simplify.

> it makes such a low amount of sense that you're inevitably going to get your students extremely confused if they are paying any attention at all.

Normally because you encounter this with the Bernoulli experiment about blowing over paper causing lower pressure, or the experiment where a spoon or ping pong ball gets pulled into running water. Both of which also turn out to not be Bernoulli's principle (it's Coandă effect)!

The first question I asked as a kid was "So then why can planes fly upside down?" and flummoxed the entire room.

I think a lot of people pattern match on text throughout education because that's least action.

Mathematics has been my way to avoid that. And I'm quite inept at mathematics. But if I can develop an abstract intuition of a problem I feel like that takes a lot less space in my head than trying to hold words to that effect in memory.

Or as old man Cato said "Grasp the matter, words will follow"

I've always thought it should work the other way around too, people show diagrams where the lines get squished at the top then tell me the pressure had gone down which isn't intuitive.

> Why does the air have to transit in the same time period?

Because otherwise it would leave holes in it where one side moves too fast before joining back up.

It makes more sense if you imagine air to be incompressable.

air being incompressible makes even less sense, given how daily the experience of compressing air is

But the air does move faster above the wing without joining back up with the air moving below the wing, see the video jgord shared https://www.cam.ac.uk/research/news/how-wings-really-work

Not at all.

Imagine two roads, parallel mostly, but then one takes a detour, like this:

         ____
    ____/ __ \____
 -> _____/  \______
    _______________
 -> _______________

Now imagine them full of cars, bumper to bumper.

Now imagine the cars move, at the same speed, on both roads. Same number of cars will come in on the left as go out on the right.

The cars will be bumper to bumper, both on top and below (there'll just be more cars on top).

Why should cars that come in at the same time on the left exit at the same time on the right?

The air was already there, the wing is being pushed into it, it seems to me that when the wing has passed it needs to end up all touching the same pieces it was before otherwise the wing will leave gaps in the air.

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