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Note: The author is not entirely serious. It's part of a series called Mystifications: A short series of semi-satirical pop science articles, called "Here's why

Note: The author is not entirely serious. It's part of a series called Mystifications: A short series of semi-satirical pop science articles, called "Here's why we don't understand". The science presented is mostly accurate. The first article was "we don’t understand electricity" and now it's "we don’t understand flight". You'll find the articles more enjoyable if you think of it as a thought experiment about the depth of knowledge - the author is a physics professor and he clearly knows what he's talking about.

Sniffnoy 5y ago
Hm, I was hoping this article would explain in what sense we don't understand flight, or in what sense people think we don't understand flight, but it didn't seem to answer that question...
- garmaine 5y ago
  We understand flight perfectly well. Although the common explanations are often BS.
  - k__ 5y ago
    Reminds me of learning what electricity is. I learned it multiple times. In middle school, in high school, in university, on youtube explained by a quantum physicist. Everytime I understood less of it.
    - handrous 5y ago
      I once read a book called "There Are No Electrons". I'm not sure I'd recommend it, but its approach was interesting: the author reasons that unless you're in grad school studying physics (and perhaps even then), everything you've been taught about electricity is a lie anyway, so the author attempts to present a framework of easier to understand lies intended to make the reader able to better reason about and predict the behavior of electrical systems, than if the reader had only the lies that are usually taught.
      - HPsquared 5y ago
        For everyone other than the aforementioned physics grad student, it's a lie. For the physics grad student, it's a mystery.
        beckingz 5y ago
        Turns out, the world is really really complicated. So it's better to say that our models are simplified, not lies.
        zamfi 5y ago
        All models are wrong, but some are useful. (George Box)
        a1369209993 5y ago
        > So it's better to say that our models are simplified, not lies. To be fair, for most purposes (atoms, molecules, metals) there usually (very-) technically aren't any electrons, just configurations of the relevant quantum fields (eg in the form of electron orbitals) whose asociated conserved quantities would allow them to convert into a certain number of free-flying electron particles if you dumped in enough energy to make up the difference. You see this a bit more obviously with ('virtual'[0]) photons, where some non-particulate field configurations simply can't be thought of as particles at all (eg attactive electromagnetic forces). 0: https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/ https://profmattstrassler.com/articles-and-posts/particle-ph...
        PaulDavisThe1st 5y ago
        More generally: we have stories that say that "things behave as if they are made of ..." but too many people misread or mishear them and think that the form is "things are made of ..." There are no quantum fields either, just as there are no atoms. Things (of the right size) behave as if there they were composed of quantum fields (or electrons or atoms), and the less we have to say "... except that ...", the more comfortable we are with the story.
    - laurent92 5y ago
      > I learned multiple times. Everytime I understood less of it. Isn’t that how to spot seniority? The junior says “I know ReactJS and SpringBoot!” The senior says: “I don’t know much…” Unrelated, but that reminds me how my Masters Degree teachers touted the importance of their subject in their introduction course, all explaining the Ariane V explosion from a completely different angle: - The measurements professor: “Ariane V crashed because engineers tripped themselves into different imperial/metric units, this is why Measurements & Precision is the most important topic!” - The programming teacher: “They fit a long inside an integer and it looped to negative, which inverted the trajectory of Ariane V and triggered its destruction, this is why learning C properly is the core of your teaching this year.” - The quality assurance teacher: “They didn’t check the contract of the component! This is why QA is the most important when creating big systems!” - The management teacher: “It’s the story of two teams who designed two components with different assumptions, one team worked in imperial units and they didn’t communicate clearly about assumptions, that’s why management is the one topic you should really work on.” They were all right. Or rather, they were all wrong: Everyone knows Ariane V exploded because the officer pushed a red button ;)
      - salawat 5y ago
        >They were all right. Or rather, they were all wrong: Everyone knows Ariane V exploded because the officer pushed a red button ;) ...and this is why learning the value of drawing the boundaries and selecting stop points in the analysis of complex topics, and the employment of humor is a powerful rhetorical tool. This is why you composition is the most important topic this semester! Sorry... Couldn't resist. <Queue the follow up psychology is the most important topic you'll learn this semester, followed by Biology, Social Psychology, Anthropology, all getting stucktrying to get in the door. Also, what school teaches QA These days?
        laurent92 5y ago
        > Also, what school teaches QA These days? Interesting question! INSA Lyon in France, but that was in 2005, you could mock that the Old Continent does a lot of V-Cycle waterfall projects and had missed the Agile turn of 2001. BUT learning how processes help is, instead, a very important step to judge what exactly we give up with Agile. The irony is I went on creating software for requirements, and I can testify that all of the hardware industry does QA more diligently than ever!
  - PaulHoule 5y ago
    We understand flight well enough to make highly optimized airplanes. There are some old controversies that are largely settled. The Microsoft Flight Simulator manual in 1980 "teached the controversy" but it was really settled decades before that. People still remember the controversy from back then and keep repeating it and probably will still do it when people are living in space colonies. The Bernoulli effect explanation is bogus. An alternate (correct) explanation is that if you just took a piece of cardboard, held it sideways, and moved it laterally it would push the air down and thus the cardboard would be pushed up. If you like vector fields you can show that there is a topological defect (vortex ring) that is threaded through the wings and comes around to the other side. If you do an integral around the ring you can show the vortex holds the plane up.
    - hattar 5y ago
      > The Bernoulli effect explanation is bogus. I hear this but never seem to get any further info. Why are wings shaped with a curved top and flat bottom? Is there a good summary I can go read to understand this all?
      - jadyoyster 5y ago
        This page explain things well: https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicsofflight.html https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicso... AFAIK the wing shape thing is about reducing drag (turbulence?)–not essential but hard to fly well without a nicely shaped wing.
        axiolite 5y ago
        That's a terribly oversimplified explanation. May I recommend this one instead: https://www.nasa.gov/sites/default/files/atoms/files/foam_wing_k-12.pdf https://www.nasa.gov/sites/default/files/atoms/files/foam_wi... When learning about flight, keep asking yourself "Then how do planes fly upside down?" Any explanation which does not mesh with sustained, inverted flight is oversimplified to the point of uselessness and inaccuracy.
skywal_l 5y ago
Thanks for pointing that out. Not long ago, on Fox news, the star pundit Bill O'reilly used to tell babyboomers that we don't understand tides and that was the proof that god existed. Never underestimate people cluelessness.
- exporectomy 5y ago
  Though I don't know what idea he was referring to, tides can be pretty hard to predict accurately. Obviously nothing to do with God, but it's probably fair to say there are aspects of them we don't understand or at least can't simulate arbitrarily far into the future. "In an analysis of the tides in Venice Lagoon, at the head of the Adriatic Sea, where the tides seem to pick up because of near-resonancy of the basin, Vittori (1992) observed that consecutive tidal maxima are highly irregular. She argued this to be indicative of low-dimensional chaos. Whether the low-order dynamics to which this is due is either inherited from the dynamics of the local wind fields or of a genuinely oceanographic nature is not clear." [1] [1] https://journals.ametsoc.org/view/journals/phoc/32/3/1520-0485_2002_032_0870_ct_2.0.co_2.xml https://journals.ametsoc.org/view/journals/phoc/32/3/1520-04...
  - tsimionescu 5y ago
    This was the video in question: https://m.youtube.com/watch?v=HABNe7_D22k?t=1m52s https://m.youtube.com/watch?v=HABNe7_D22k?t=1m52s. It's not about predicting the exact movement of tides, he's arguing science fundamentally can't explain the regularity of tides...
    - exporectomy 5y ago
      Oh, well that's different. Funny though, the guy he's interviewing said Islam is a scam and Muslims are suckers who have fallen for it. Funny what you can get away with if you couch it right.
      - tsimionescu 5y ago
        To be fair, he claims that ALL religions are a scam, not specifically Islam. I can tell you for sure that Bill O'Reilly wasn't grilling him for his bad treatment of Muslims!
tempestn 5y ago
In this case I took it to be poking some fun at the two conflicting 'intuitive' explanations for a wing producing lift: one being that air strikes the bottom of the wing as it moves forward, pushing upward on it, and the other being that air moves faster under the flat underside of the wing than over the curved upper side, causing a pressure differential. Of course reality is more complex than either simple answer, and the real answer is something more like, "The wing behaves approximately as described by this equation."
- jobigoud 5y ago
  Air moves faster on the upper side, creating a pressure differential.
  - NickNameNick 5y ago
    Why does the air move faster on the upper side of the wing? It's not because there's a magic force that requires air particles parted be the leading edge to rejoin thier partner at the trailing edge. The air particles on the upper surface reach the trailing edge much sooner than the ones under the wing.
    - rcxdude 5y ago
      Because the pressure on the top is lower :) (this is half-serious: the whole problem with these explanations is that cause and effect for all of these variables is not straightforward: you can see from the navier-stokes equations they are all dependent on each other).
      - tomsto 5y ago
        Kind of. Actually the real ‘cause’ in my understanding is 1) the curved geometry of the suction (upper) side of the aerofoil and 2) the fact that the flow remains attached to it. Everything else - you can actually approximate the curved surface to a circle and apply equations of circular motion to a parcel of air to satisfy yourself with why the flow is accelerating. And Newton’s 3rd law explains how lift is generated on the wing. In my view there’s no need to use Navier-Stokes to explain how an aerofoil works, if you simplify the geometry to make a special case. Most of the lift comes from the suction side. Actually, if you really want to test an explanation, try to apply the same reasoning to explain how a sailing boat can sail upwind (or at least up to about 45 degrees off).
varispeed 5y ago
Well, I secretly knew this video is true: https://youtu.be/JYAq-7sOzXQ?t=98 https://youtu.be/JYAq-7sOzXQ?t=98

Sniffnoy 5y ago

Hm, I was hoping this article would explain in what sense we don't understand flight, or in what sense people think we don't understand flight, but it didn't seem to answer that question...

garmaine 5y ago
We understand flight perfectly well. Although the common explanations are often BS.
- k__ 5y ago
  Reminds me of learning what electricity is. I learned it multiple times. In middle school, in high school, in university, on youtube explained by a quantum physicist. Everytime I understood less of it.
  - handrous 5y ago
    I once read a book called "There Are No Electrons". I'm not sure I'd recommend it, but its approach was interesting: the author reasons that unless you're in grad school studying physics (and perhaps even then), everything you've been taught about electricity is a lie anyway, so the author attempts to present a framework of easier to understand lies intended to make the reader able to better reason about and predict the behavior of electrical systems, than if the reader had only the lies that are usually taught.
    - HPsquared 5y ago
      For everyone other than the aforementioned physics grad student, it's a lie. For the physics grad student, it's a mystery.
      - beckingz 5y ago
        Turns out, the world is really really complicated. So it's better to say that our models are simplified, not lies.
        zamfi 5y ago
        All models are wrong, but some are useful. (George Box)
        a1369209993 5y ago
        > So it's better to say that our models are simplified, not lies. To be fair, for most purposes (atoms, molecules, metals) there usually (very-) technically aren't any electrons, just configurations of the relevant quantum fields (eg in the form of electron orbitals) whose asociated conserved quantities would allow them to convert into a certain number of free-flying electron particles if you dumped in enough energy to make up the difference. You see this a bit more obviously with ('virtual'[0]) photons, where some non-particulate field configurations simply can't be thought of as particles at all (eg attactive electromagnetic forces). 0: https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/ https://profmattstrassler.com/articles-and-posts/particle-ph...
        PaulDavisThe1st 5y ago
        More generally: we have stories that say that "things behave as if they are made of ..." but too many people misread or mishear them and think that the form is "things are made of ..." There are no quantum fields either, just as there are no atoms. Things (of the right size) behave as if there they were composed of quantum fields (or electrons or atoms), and the less we have to say "... except that ...", the more comfortable we are with the story.
  - laurent92 5y ago
    > I learned multiple times. Everytime I understood less of it. Isn’t that how to spot seniority? The junior says “I know ReactJS and SpringBoot!” The senior says: “I don’t know much…” Unrelated, but that reminds me how my Masters Degree teachers touted the importance of their subject in their introduction course, all explaining the Ariane V explosion from a completely different angle: - The measurements professor: “Ariane V crashed because engineers tripped themselves into different imperial/metric units, this is why Measurements & Precision is the most important topic!” - The programming teacher: “They fit a long inside an integer and it looped to negative, which inverted the trajectory of Ariane V and triggered its destruction, this is why learning C properly is the core of your teaching this year.” - The quality assurance teacher: “They didn’t check the contract of the component! This is why QA is the most important when creating big systems!” - The management teacher: “It’s the story of two teams who designed two components with different assumptions, one team worked in imperial units and they didn’t communicate clearly about assumptions, that’s why management is the one topic you should really work on.” They were all right. Or rather, they were all wrong: Everyone knows Ariane V exploded because the officer pushed a red button ;)
    - salawat 5y ago
      >They were all right. Or rather, they were all wrong: Everyone knows Ariane V exploded because the officer pushed a red button ;) ...and this is why learning the value of drawing the boundaries and selecting stop points in the analysis of complex topics, and the employment of humor is a powerful rhetorical tool. This is why you composition is the most important topic this semester! Sorry... Couldn't resist. <Queue the follow up psychology is the most important topic you'll learn this semester, followed by Biology, Social Psychology, Anthropology, all getting stucktrying to get in the door. Also, what school teaches QA These days?
      - laurent92 5y ago
        > Also, what school teaches QA These days? Interesting question! INSA Lyon in France, but that was in 2005, you could mock that the Old Continent does a lot of V-Cycle waterfall projects and had missed the Agile turn of 2001. BUT learning how processes help is, instead, a very important step to judge what exactly we give up with Agile. The irony is I went on creating software for requirements, and I can testify that all of the hardware industry does QA more diligently than ever!
- PaulHoule 5y ago
  We understand flight well enough to make highly optimized airplanes. There are some old controversies that are largely settled. The Microsoft Flight Simulator manual in 1980 "teached the controversy" but it was really settled decades before that. People still remember the controversy from back then and keep repeating it and probably will still do it when people are living in space colonies. The Bernoulli effect explanation is bogus. An alternate (correct) explanation is that if you just took a piece of cardboard, held it sideways, and moved it laterally it would push the air down and thus the cardboard would be pushed up. If you like vector fields you can show that there is a topological defect (vortex ring) that is threaded through the wings and comes around to the other side. If you do an integral around the ring you can show the vortex holds the plane up.
  - hattar 5y ago
    > The Bernoulli effect explanation is bogus. I hear this but never seem to get any further info. Why are wings shaped with a curved top and flat bottom? Is there a good summary I can go read to understand this all?
    - jadyoyster 5y ago
      This page explain things well: https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicsofflight.html https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/dynamicso... AFAIK the wing shape thing is about reducing drag (turbulence?)–not essential but hard to fly well without a nicely shaped wing.
      - axiolite 5y ago
        That's a terribly oversimplified explanation. May I recommend this one instead: https://www.nasa.gov/sites/default/files/atoms/files/foam_wing_k-12.pdf https://www.nasa.gov/sites/default/files/atoms/files/foam_wi... When learning about flight, keep asking yourself "Then how do planes fly upside down?" Any explanation which does not mesh with sustained, inverted flight is oversimplified to the point of uselessness and inaccuracy.

skywal_l 5y ago

Thanks for pointing that out. Not long ago, on Fox news, the star pundit Bill O'reilly used to tell babyboomers that we don't understand tides and that was the proof that god existed. Never underestimate people cluelessness.

exporectomy 5y ago
Though I don't know what idea he was referring to, tides can be pretty hard to predict accurately. Obviously nothing to do with God, but it's probably fair to say there are aspects of them we don't understand or at least can't simulate arbitrarily far into the future. "In an analysis of the tides in Venice Lagoon, at the head of the Adriatic Sea, where the tides seem to pick up because of near-resonancy of the basin, Vittori (1992) observed that consecutive tidal maxima are highly irregular. She argued this to be indicative of low-dimensional chaos. Whether the low-order dynamics to which this is due is either inherited from the dynamics of the local wind fields or of a genuinely oceanographic nature is not clear." [1] [1] https://journals.ametsoc.org/view/journals/phoc/32/3/1520-0485_2002_032_0870_ct_2.0.co_2.xml https://journals.ametsoc.org/view/journals/phoc/32/3/1520-04...
- tsimionescu 5y ago
  This was the video in question: https://m.youtube.com/watch?v=HABNe7_D22k?t=1m52s https://m.youtube.com/watch?v=HABNe7_D22k?t=1m52s. It's not about predicting the exact movement of tides, he's arguing science fundamentally can't explain the regularity of tides...
  - exporectomy 5y ago
    Oh, well that's different. Funny though, the guy he's interviewing said Islam is a scam and Muslims are suckers who have fallen for it. Funny what you can get away with if you couch it right.
    - tsimionescu 5y ago
      To be fair, he claims that ALL religions are a scam, not specifically Islam. I can tell you for sure that Bill O'Reilly wasn't grilling him for his bad treatment of Muslims!

tempestn 5y ago

In this case I took it to be poking some fun at the two conflicting 'intuitive' explanations for a wing producing lift: one being that air strikes the bottom of the wing as it moves forward, pushing upward on it, and the other being that air moves faster under the flat underside of the wing than over the curved upper side, causing a pressure differential. Of course reality is more complex than either simple answer, and the real answer is something more like, "The wing behaves approximately as described by this equation."

jobigoud 5y ago
Air moves faster on the upper side, creating a pressure differential.
- NickNameNick 5y ago
  Why does the air move faster on the upper side of the wing? It's not because there's a magic force that requires air particles parted be the leading edge to rejoin thier partner at the trailing edge. The air particles on the upper surface reach the trailing edge much sooner than the ones under the wing.
  - rcxdude 5y ago
    Because the pressure on the top is lower :) (this is half-serious: the whole problem with these explanations is that cause and effect for all of these variables is not straightforward: you can see from the navier-stokes equations they are all dependent on each other).
    - tomsto 5y ago
      Kind of. Actually the real ‘cause’ in my understanding is 1) the curved geometry of the suction (upper) side of the aerofoil and 2) the fact that the flow remains attached to it. Everything else - you can actually approximate the curved surface to a circle and apply equations of circular motion to a parcel of air to satisfy yourself with why the flow is accelerating. And Newton’s 3rd law explains how lift is generated on the wing. In my view there’s no need to use Navier-Stokes to explain how an aerofoil works, if you simplify the geometry to make a special case. Most of the lift comes from the suction side. Actually, if you really want to test an explanation, try to apply the same reasoning to explain how a sailing boat can sail upwind (or at least up to about 45 degrees off).

varispeed 5y ago

Well, I secretly knew this video is true: https://youtu.be/JYAq-7sOzXQ?t=98 https://youtu.be/JYAq-7sOzXQ?t=98