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.<p>"Why does the air have to transit in the same time period?"<p>"But _why_ is the air moving over the top faster? Weren't you going to tell me how a wing works?" Etc etc etc<p>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.<p>The idea that people get tested on regurgitating it for a pilots license is crazy.<p>It's up there with those ridiculous tounge maps with taste regions on them.
Handy video showing relative speed above and below the curved wing surface, and non-equal times :<p><a href="https://www.cam.ac.uk/research/news/how-wings-really-work" rel="nofollow">https://www.cam.ac.uk/research/news/how-wings-really-work</a>
Glad to see this posted more!<p>I was asking about this 9 months ago and it started quite a thread [1]. I remember learning about this in grade school, finding it pretty confusing, and wondering why a simple "newton's third law" wouldn't suffice. That's incomplete but at least not wrong.<p>[1]: <a href="https://news.ycombinator.com/item?id=40835223">https://news.ycombinator.com/item?id=40835223</a>
“Just like the "explanation" of seasons by the Earth's changing distance to the Sun, or textbook pseudo-explanations of history, like the "crisis" over the discovery of irrationals, or Maxwell's "mathematical" reason for adding an extra term to Ampere's equation.”<p>Love it! Anyone have any others?
I remember being taught this in A level physics case study of lift alongside a better third law explanation, with absolutely no acknowledgement or justification for one over the other. It caused a bit of a scandal among the class. Gave me a very sceptical view of physics education in general which I took to my physics undergrad and PhD
If you google “how does a plane generate lift”, the first result you get is a link from nasa.gov which claims that lift is generated this way. Kind of funny considering the SE question includes a screenshot of another NASA resource claiming this is false.
William Fraser over on YouTube has a video[1] on aerodynamic lift which I found interesting.<p>In it he briefly touches on the equal transit time explanation, and how the steady-state snapsot presented doesn't really have enough information to tell how the flow field developed.<p>He's been writing a particle-based simulator which he wants to use to show how lift develops from that perspective[2], still a work in progress.<p>Just sharing as I found them interesting and cleared up some confusions I had.<p>[1]: <a href="https://youtu.be/ZUBwc67c5_Y" rel="nofollow">https://youtu.be/ZUBwc67c5_Y</a><p>[2]: <a href="https://youtu.be/IVLpbOQUdqU" rel="nofollow">https://youtu.be/IVLpbOQUdqU</a>
I recently encountered this in a sailing class when the teacher was explaining how "pull-mode" works in sailing, where the wind is coming from ahead of the vessel and pulls the sails rather than pushing them. I knew this theory to be debunked and yet couldn't work out the answer from non-debunked physics (and certainly didn't want to disrupt the class by arguing physics with someone who's been sailing for 50+ years - if it worked for him, it'll probably work for me, even if debunked).<p>Modern sailing vessels <i>always</i> sail into the wind, because they're always going faster than the wind blows. I do find the physics of this fascinating.
Fluid mechanics has always seemed so complex that scientists joke
about it. Supposedly [0] Werner Heisenberg and/or Horace Lamb quipped
that when they died they'd ask God about relativity, quantum
electrodynamics and turbulence... and they didn't expect he would have
an answer for the last.<p>[0] <a href="https://boards.straightdope.com/t/did-heisenberg-really-say-this-about-what-he-would-ask-god/631918" rel="nofollow">https://boards.straightdope.com/t/did-heisenberg-really-say-...</a>
It’s still the explanation on NASA.gov<p><a href="https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicsofflight.html" rel="nofollow">https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicso...</a>
Ok so let's see if HN can put something together:<p>- The wing deflects the air down, so that's one way of creating lift, but most wings are not just flat<p>- An airplane can fly upside down<p>- It's a bad idea to take off behind another plane<p>- Modern wingtips have special shapes that makes them more efficient<p>- Answer has something to do with vorticity, but what exactly?<p>Hopefully we can get something better than whatever AI uses to explain these. I haven't asked it yet, but I get the feeling it would produce something plausible sounding that I won't be able to easily refute, ie it would trick me into thinking I understood it.