Airflow across a wing
Why Hacker News recommends it
Linked in lift-theory arguments as a clear demonstration that air over the top of a wing does not need to catch up with air underneath.
What it is
A one-minute clip from Cambridge's Prof. Holger Babinsky that debunks the equal transit time explanation of lift. It shows how air actually flows over a wing.
Recommended by 0 HN commenters across 0 different months, 2021 to 2025.
What Hacker News said
Cites slavak · 2021-06 · on “Why we don’t understand heavier-than-air flight”
You're right- there isn't, and it doesn't. In fact a parcel of air moving over the top of the wing will beat its counterpart moving below it to the trailing edge. This[1] video has a very good demonstration of this. (Relevant part begins around 0:25.) So saying that air on top of the wing moves faster, creating a pressure differential and thus lift, is absolutely correct. The problem begins when some people try to come up with an intuitive explanation for _why_ the air would need to speed up. "Because this is the lowest energy state that conserves energy, momentum, and mass" isn't a very satisfying answer; neither is "because this system of PDEs say so"; so they came up with the "equal trans
Cites dmkirwan · 2021-10 · on “Incorrect Lift Theory”
Funnily enough, there's another web page on the NASA domain that outlines the "longer path" or "equal transit" theories as the correct cause of lift on an aircraft wing: [LINK] When I was studying for my PPL, they taught us using the equal transit theory, though the instructor couldn't help himself from telling us that it was a simplification. This video from Cambridge University illustrates what happens to the airflow over an aerofoil: [this video]
Cites timr · 2025-08 · on “GPT-5”
> right, the other is that if you remove every incorrect statement from the AI "explanation", the answer it would have given is "airplane wings generate lift because they are shaped to generate lift". ...only if you omit the parts where it talks about pressure differentials, caused by airspeed differences, create lift? Both of these points are true. You have to be motivated to ignore them. [this video]