Your link literally says pressure differential is the reason, and that curvature matters:
> “What actually causes lift is introducing a shape into the airflow, which curves the streamlines and introduces pressure changes – lower pressure on the upper surface and higher pressure on the lower surface,” clarified Babinsky, from the Department of Engineering. “This is why a flat surface like a sail is able to cause lift – here the distance on each side is the same but it is slightly curved when it is rigged and so it acts as an aerofoil. In other words, it’s the curvature that creates lift, not the distance.”
So I'd characterize this answer as "correct, but incomplete" or "correct, but simplified". It's a case where a PhD in fluid dynamics might state the explanation one way to an expert audience, but another way to a room full of children.
Pressure differential is absolutely one of the main components of lift (although I believe conservation of momentum is another - the coanda effect changes the direction of the airflows and there's 2nd law stuff happening on the bottom edge too), but the idea that the pressure differential is caused by the fact that "air over the top has to travel farther in the same amount of time" because the airfoil is curved is completely incorrect, as the video in my link shows.
It's "completely incorrect" only if you're being pedantic. It's "partially correct" if you're talking casually to a group of regular people. It's "good enough" if you're talking to a classroom of children. Audience matters.
The hilarious thing about this subthread is that it's already getting filled with hyper-technical but wrong alternative explanations by people eager to show that they know more than the robot.
"air over the top has to travel farther in the same amount of time" is just wrong, it doesn't have to, and in fact it doesn't.
It's called the "equal transit-time fallacy" if you want to look it up, or follow the link I provided in my comment, or perhaps the NASA link someone else offered.
I'm not saying that particular point is wrong. I'm saying that for most people, it doesn't matter, and the reason the "fallacy" persists is because it's a good enough explanation for the layman that is easy to conceptualize.
Pretty much any scientific question is fractal like this: there's a superficial explanation, then one below that, and so on. None are "completely incorrect", but the more detailed ones are better.
The real question is: if you prompt the bot for the better, deeper explanation, what does it do?
So I worry that you think that the equal transit time thing is true, but is just one effect among others. This is not the case. There are a number of different effects, including bernoulli and coanda and newtons third law that all contribute to lift, but none of the things that actually happen have anything to do with equal transit time.
The equal transit time is not a partially correct explanation, it's something that doesn't happen. It's not a superficial explanation, it's a wrong explanation. It's not even a good lie-to-children, as it doesn't help predict or understand any part of the system at any level. It instead teaches magical thinking.
As to whether it matters? If I am told that I can ask my question to a system and it will respond like a team of PhDs, that it is useful to help someone with their homework and physical understanding, but it gives me instead information that is incorrect and misleading, I would say the system is not working as it is intended to.
Even if I accept that "audience matters" as you say, the suggested audience is helping someone with their physics homework. This would not be a suitable explanation for someone doing physics homework.
> So I worry that you think that the equal transit time thing is true,
Wow. Thanks for your worry, but it's not a problem. I do understand the difference, and yet it doesn't have anything to do with the argument I'm making, which is about presentation.
> It's not even a good lie-to-children, as it doesn't help predict or understand any part of the system at any level.
...which is irrelevant in the context. I get the meta-point that you're (sort of) making that you can't shut your brain off and just hope the bot spits out 100% pedantic explanations of scientific phenomenon. That's true, but also...fine?
These things are spitting out probable text. If (as many have observed) this is a common enough explanation to be in textbooks, then I'm not particularly surprised if an LLM emits it as well. The real question is: what happens when you prompt it to go deeper?
You're missing that this isn't an issue of granularity or specificity; "equal time" is just wrong.
If this is "right enough" for you, I'm curious if you tell your bots to "go deeper" on every question you ask. And at what level you expect it to start telling you actual truths and not some oft-repeated lie.
This is an LLM advertised as functioning at a "doctorate" level in everything. I think it's reasonable to expect more than the high school classroom "good enough" explanation.
No, it's never good enough, because it's flat-out wrong. This statement:
> Air over the top has to travel farther in the same amount of time
is not true. The air on top does not travel farther in the same amount of time. The air slows down and travels a shorter distance in the same amount of time.
It's only "good enough for a classroom of children" in the same way that storks delivering babies is—i.e., if you're content to simply lie rather than bothering to tell the truth.
> “What actually causes lift is introducing a shape into the airflow, which curves the streamlines and introduces pressure changes – lower pressure on the upper surface and higher pressure on the lower surface,” clarified Babinsky, from the Department of Engineering. “This is why a flat surface like a sail is able to cause lift – here the distance on each side is the same but it is slightly curved when it is rigged and so it acts as an aerofoil. In other words, it’s the curvature that creates lift, not the distance.”
So I'd characterize this answer as "correct, but incomplete" or "correct, but simplified". It's a case where a PhD in fluid dynamics might state the explanation one way to an expert audience, but another way to a room full of children.