7 ms·

Indeed. As to the whole "we don't actually understand how it works" - we still can't make up our minds as to how wings work, so this isn't overly novel. Sure,

Indeed. As to the whole "we don't actually understand how it works" - we still can't make up our minds as to how wings work, so this isn't overly novel. Sure, we can explain the outcome, but whether it's Navier-Stokes or Bernoulli or something else, we can't make up our minds. I suspect this will be similar for a long while - although puts physics hat on I think this is likely a relativistic temporal quantisation effect.

ColinWright 12y ago
> ... we still can't make up our > minds as to how wings work, ... Interestingly, I recently spoke to an aerodynamicist and mentioned this, and I was severely lectured. In the follow-up he mellowed a little, but I suspect the "we" in your statement refers to laypersons who don't have advanced training in aeronautics, and yet claim to understand about flow pressure, Bernoulli, etc. I've been convinced that the people who genuinely work with these things and study them properly, actually do know how wings work. You may not, I may not, the mythical "man on the street" may not, but there are people who really, really do.
- madaxe_again 12y ago
  No, I've a masters degree in Physics, and did several research projects on turbulent/laminar flow. We have a detailed understanding of a variety of theories which correctly represent the lift effect experienced on a body moving through a flow, yet none of them do it perfectly or completely. We can implement the technology well, but not without the aid of wind-tunnels and brute-force computer simulations in order to validate our designs - had we a perfect mathematical understanding of lift - we would not need to. Another example from Physics - quantum mechanics. We can describe the properties of a QM system, its outcomes based on inputs, the probabilities of states - yet we have not got the blindingest clue as to how it works. We have theories, but again, none are perfect - for instance see the Pilot Wave formulation of QM, which implies a deterministic universe, and isn't wrong, but isn't generally accepted - even though it describes QM systems well, for what little of it has been formulated in the last century.
  - tobinfricke 12y ago
    Fluid flow is complicated, true - but the basic physical phenomenon of lift is very simple and completely understood: wings redirect air downwards, and the reaction force is what we call lift.
    - madaxe_again 12y ago
      Agreed, but it's the fluid flow bit that complicates it. We absolutely understand lift in the Newtonian sense of a reaction, but wings, we're still learning about. If we weren't, we wouldn't have developed winglets and other such adaptations, as we slowly but surely assemble the theoretical particles into a coherent whole.
      - timdierks 12y ago
        Inventing new engineering solutions to existing problems (e.g. winglets) is totally different from not understanding the situation at all.
      - tobinfricke 12y ago
        If we weren't, we wouldn't have developed winglets and other such adaptations... Is the development of new programming languages evidence that we don't "understand" computers? In some very abstract sense, yes, but in a more practical sense - no.
        moron4hire 12y ago
        No, but I'd say it means we don't understand software.
      - crusso 12y ago
        Yes, but your original comment in this thread is just a semantic ruse. Saying we can't decide how wings work is not at all in the same category as saying these guys don't know how Q works. One "not knowing" is about not knowing exactly precisely how to model something perfectly because it has so much complexity. The other not "not knowing" is about not having even a basic working theory that doesn't use mumbo jumbo and stands up to scrutiny.
- happyscrappy 12y ago
  Does Feynman's "if you can't explain it to a laymen in a few paragraphs then you don't truly understand it" no longer hold?
  - Luc 12y ago
    I'd really like the source for that quote, because it's dumb for obvious reasons, and I don't know Feynman to be dumb. In fact he said pretty much the opposite to the interviewer asking about magnets in this well known video: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
    - happyscrappy 12y ago
      Hmm. The closest I can find is this: "Once I asked him to explain to me, so that I can understand it, why spin-1/2 particles obey Fermi-Dirac statistics. Gauging his audience perfectly, he said, "I'll prepare a freshman lecture on it." But a few days later he came to me and said: "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it." David L. Goodstein, "Richard P. Feynman, Teacher," Physics Today, volume 42, number 2, February 1989, p. 70-75, at p. 75
      - snowwrestler 12y ago
        I think Feynman is drawing a distinction between being able to calculate an accurate prediction, and "understanding" things intuitively enough to describe with plain English.
  - tobinfricke 12y ago
    I also generally subscribe to the idea that, if you can't adequately explain something to someone unfamiliar with the idea, then you don't properly understand it yourself. But my inability to explain something to someone says nothing about whether the phenomenon "is understood" in the more general sense.
  - genericuser 12y ago
    I have never heard the quote with the middle section you included "to a laymen in a few paragraphs" I have frequently heard the quote without that section, that section seems flawed in that a layman would need to have all the underlying concepts explained to them also, indicating that application of the quote would not scale, as more underlying concepts were necessary to include.
tobinfricke 12y ago
We understand perfectly well how wings work. What is it with Hacker News and anti-intellectualism?
- DanBC 12y ago
  For various values of "we". http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html > There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. There are lots of bits of science where we have "useful lies" used to explain things to people, but when you get more in depth things get trickier. Clifford Stoll uses the question "Why is the sky blue?" as an example. You keep asking "Why?" as a response and see how far someone goes. Most people will say "light scatters"; some might say "Rayleigh scattering". Of course, there is a difference between "Science knows but the general population hasn't learnt it" and "science doesn't know" but for a surprising amount of stuff science doesn't know, yet.
  - tobinfricke 12y ago
    By "we", I mean humanity as a whole. Nobody would contest that there are a lot of widespread misconceptions about how an airplane - or, for that matter, anything - works. A nice blog post on the topic is Sean Carroll's article, "The Laws Underlying The Physics of Everyday Life Are Completely Understood" (http://blogs.discovermagazine.com/cosmicvariance/2010/09/23/the-laws-underlying-the-physics-of-everyday-life-are-completely-understood/#.U-N3cps-uHc http://blogs.discovermagazine.com/cosmicvariance/2010/09/23/...).
    - DanBC 12y ago
      https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8 Feynman: "Magnets repel each other." Interviewer: "What I want to know is what's going on ..." Feynman: "Magnets repel each other." Interviewer: "...between those two bits of metal." Feynman: "Magnets repel each other." Interviewer: "Well then, but what does that mean? Or why are they doing that? Or how are they doing it?" Feynman: "Ah, [pause] uh you're asking ..." Interviewer: "I must say that's a perfectly reasonable question to ask" Feynman: "Of course! It's a perfectly reasonable question." See also his quote about quantum mechanics - "There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe there ever was such a time. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot of people understood the theory of relativity in some way or other, certainly more than twelve. On the other hand, I think I can safely say that nobody understands quantum mechanics." https://en.wikiquote.org/wiki/Talk:Richard_Feynman#.22If_you_think_you_understand_quantum_mechanics.2C_you_don.27t_understand_quantum_mechanics..22 https://en.wikiquote.org/wiki/Talk:Richard_Feynman#.22If_you...
tfgg 12y ago
None of the things mentioned so far that we "don't know how they work" are on a par with this. Flying with wings doesn't violate fundamental, and experimentally very well supported, symmetries like conservation of momentum, nor do high temperature superconductors. Your final sentence is actually nonsense.
- madaxe_again 12y ago
  My final sentence was getting at a mechanism by which momentum is conserved in this system. If you assume that time is quantisable (big assumption, I know), and that the planck time is lorenz invariant (not as much of an assumption), then an EM wave at a fixed frequency moving from one reference frame to another could experience quantisation due to the shifting time-base, resulting in an apparent net deceleration - resulting in a measurable acceleration of the system as a whole. And now I'll take off my fringe hat and get back to the day job.
  - marcosdumay 12y ago
    Well, the relativity principle states that things don't "move from one frame of reference to the other". You choose a frame, and observe things on that frame; changing the frame of reference is your choice, and must not alter the results in any way. Accepting a flaw in conservation of momentum is already hard enough without you (and the original paper) imposing a flaw on the relativity principle to explain it.
    - madaxe_again 12y ago
      Ah, the old "it's Einstein so it must be right" gambit. People used to say that about Newton - until experiment proved that he didn't have the full picture. It's highly improbable that relativity is any different. Yes, it gives demonstrably correct answers, but that doesn't mean that it holds in all cases. I mean, why would we be even talking about LQG if we thought relativity gave the full picture? You're right that I was wrong to say it moved from one reference frame to another, which is clearly bollocks - the EM undergoes an acceleration to relativistic mass, then a deceleration.
tobinfricke 12y ago
"We still can't make up our minds as to how wings work, so this isn't overly novel. Sure, we can explain the outcome, but whether it's Navier-Stokes or Bernoulli or something else, we can't make up our minds." Time to trot out my favorite quote about how airplanes fly, from Stick and Rudder by Wolfgang Langewiesche, page 9, published 1944: »The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down. It shoves the air down with its bottom surface, and it pulls the air down with its top surface; the latter action is the more important. But the really important thing to understand is that the wing, in whatever fashion, makes the air go down. In exerting a downward force upon the air, the wing receives an upward counterforce--by the same principle, known as Newton's law of action and reaction, which makes a gun recoil as it shoves the bullet out forward; and which makes the nozzle of a fire hose press backward heavily against the fireman as it shoots out a stream of water forward. Air is heavy; sea-level air weights about 2 pounds per cubic yard; thus, as your wings give a downward push to a cubic yard after cubic yard of that heavy stuff, they get upward reactions that are equally hefty. That's what keeps an airplane up. Newton's law says that, if the wing pushes the air down, the air must push the wing up. It also puts the same thing the other way 'round: if the wing is to hold the airplane up in the fluid, ever-yielding air, it can do so only by pushing the air down. All the fancy physics of Bernoulli's Theorem, all the highbrow math of the circulation theory, all the diagrams showing the airflow on a wing--all that is only an elaboration and more detailed description of just how Newton's law fulfills itself--for instance, the rather interesting but (for the pilot) really quite useless observation that the wing does most of its downwashing work by suction, with its top surface. ... Thus, if you will forget some of this excessive erudition, a wing becomes much easier to understand; it is in the last analysis nothing but an air deflector. It is an inclined plane, cleverly curved, to be sure, and elaborately streamlined, but still essentially an inclined plane. That's, after all, why that whole fascinating contraption of ours is called an air-plane.«
- SamReidHughes 12y ago
  Okay but there's a difference in the nature of the "pushing down" of a rocket, a plane, and a hovering helicopter, and in how much of an impulse is actually inflicted on an external mass.
idlewords 12y ago
There is no confusion among physicists about how wings work.

ColinWright 12y ago

> ... we still can't make up our > minds as to how wings work, ... Interestingly, I recently spoke to an aerodynamicist and mentioned this, and I was severely lectured. In the follow-up he mellowed a little, but I suspect the "we" in your statement refers to laypersons who don't have advanced training in aeronautics, and yet claim to understand about flow pressure, Bernoulli, etc. I've been convinced that the people who genuinely work with these things and study them properly, actually do know how wings work. You may not, I may not, the mythical "man on the street" may not, but there are people who really, really do.

madaxe_again 12y ago
No, I've a masters degree in Physics, and did several research projects on turbulent/laminar flow. We have a detailed understanding of a variety of theories which correctly represent the lift effect experienced on a body moving through a flow, yet none of them do it perfectly or completely. We can implement the technology well, but not without the aid of wind-tunnels and brute-force computer simulations in order to validate our designs - had we a perfect mathematical understanding of lift - we would not need to. Another example from Physics - quantum mechanics. We can describe the properties of a QM system, its outcomes based on inputs, the probabilities of states - yet we have not got the blindingest clue as to how it works. We have theories, but again, none are perfect - for instance see the Pilot Wave formulation of QM, which implies a deterministic universe, and isn't wrong, but isn't generally accepted - even though it describes QM systems well, for what little of it has been formulated in the last century.
- tobinfricke 12y ago
  Fluid flow is complicated, true - but the basic physical phenomenon of lift is very simple and completely understood: wings redirect air downwards, and the reaction force is what we call lift.
  - madaxe_again 12y ago
    Agreed, but it's the fluid flow bit that complicates it. We absolutely understand lift in the Newtonian sense of a reaction, but wings, we're still learning about. If we weren't, we wouldn't have developed winglets and other such adaptations, as we slowly but surely assemble the theoretical particles into a coherent whole.
    - timdierks 12y ago
      Inventing new engineering solutions to existing problems (e.g. winglets) is totally different from not understanding the situation at all.
    - tobinfricke 12y ago
      If we weren't, we wouldn't have developed winglets and other such adaptations... Is the development of new programming languages evidence that we don't "understand" computers? In some very abstract sense, yes, but in a more practical sense - no.
      - moron4hire 12y ago
        No, but I'd say it means we don't understand software.
    - crusso 12y ago
      Yes, but your original comment in this thread is just a semantic ruse. Saying we can't decide how wings work is not at all in the same category as saying these guys don't know how Q works. One "not knowing" is about not knowing exactly precisely how to model something perfectly because it has so much complexity. The other not "not knowing" is about not having even a basic working theory that doesn't use mumbo jumbo and stands up to scrutiny.
happyscrappy 12y ago
Does Feynman's "if you can't explain it to a laymen in a few paragraphs then you don't truly understand it" no longer hold?
- Luc 12y ago
  I'd really like the source for that quote, because it's dumb for obvious reasons, and I don't know Feynman to be dumb. In fact he said pretty much the opposite to the interviewer asking about magnets in this well known video: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
  - happyscrappy 12y ago
    Hmm. The closest I can find is this: "Once I asked him to explain to me, so that I can understand it, why spin-1/2 particles obey Fermi-Dirac statistics. Gauging his audience perfectly, he said, "I'll prepare a freshman lecture on it." But a few days later he came to me and said: "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it." David L. Goodstein, "Richard P. Feynman, Teacher," Physics Today, volume 42, number 2, February 1989, p. 70-75, at p. 75
    - snowwrestler 12y ago
      I think Feynman is drawing a distinction between being able to calculate an accurate prediction, and "understanding" things intuitively enough to describe with plain English.
- tobinfricke 12y ago
  I also generally subscribe to the idea that, if you can't adequately explain something to someone unfamiliar with the idea, then you don't properly understand it yourself. But my inability to explain something to someone says nothing about whether the phenomenon "is understood" in the more general sense.
- genericuser 12y ago
  I have never heard the quote with the middle section you included "to a laymen in a few paragraphs" I have frequently heard the quote without that section, that section seems flawed in that a layman would need to have all the underlying concepts explained to them also, indicating that application of the quote would not scale, as more underlying concepts were necessary to include.

tobinfricke 12y ago

We understand perfectly well how wings work. What is it with Hacker News and anti-intellectualism?

DanBC 12y ago
For various values of "we". http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html > There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. There are lots of bits of science where we have "useful lies" used to explain things to people, but when you get more in depth things get trickier. Clifford Stoll uses the question "Why is the sky blue?" as an example. You keep asking "Why?" as a response and see how far someone goes. Most people will say "light scatters"; some might say "Rayleigh scattering". Of course, there is a difference between "Science knows but the general population hasn't learnt it" and "science doesn't know" but for a surprising amount of stuff science doesn't know, yet.
- tobinfricke 12y ago
  By "we", I mean humanity as a whole. Nobody would contest that there are a lot of widespread misconceptions about how an airplane - or, for that matter, anything - works. A nice blog post on the topic is Sean Carroll's article, "The Laws Underlying The Physics of Everyday Life Are Completely Understood" (http://blogs.discovermagazine.com/cosmicvariance/2010/09/23/the-laws-underlying-the-physics-of-everyday-life-are-completely-understood/#.U-N3cps-uHc http://blogs.discovermagazine.com/cosmicvariance/2010/09/23/...).
  - DanBC 12y ago
    https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8 Feynman: "Magnets repel each other." Interviewer: "What I want to know is what's going on ..." Feynman: "Magnets repel each other." Interviewer: "...between those two bits of metal." Feynman: "Magnets repel each other." Interviewer: "Well then, but what does that mean? Or why are they doing that? Or how are they doing it?" Feynman: "Ah, [pause] uh you're asking ..." Interviewer: "I must say that's a perfectly reasonable question to ask" Feynman: "Of course! It's a perfectly reasonable question." See also his quote about quantum mechanics - "There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe there ever was such a time. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot of people understood the theory of relativity in some way or other, certainly more than twelve. On the other hand, I think I can safely say that nobody understands quantum mechanics." https://en.wikiquote.org/wiki/Talk:Richard_Feynman#.22If_you_think_you_understand_quantum_mechanics.2C_you_don.27t_understand_quantum_mechanics..22 https://en.wikiquote.org/wiki/Talk:Richard_Feynman#.22If_you...

tfgg 12y ago

None of the things mentioned so far that we "don't know how they work" are on a par with this. Flying with wings doesn't violate fundamental, and experimentally very well supported, symmetries like conservation of momentum, nor do high temperature superconductors. Your final sentence is actually nonsense.

madaxe_again 12y ago
My final sentence was getting at a mechanism by which momentum is conserved in this system. If you assume that time is quantisable (big assumption, I know), and that the planck time is lorenz invariant (not as much of an assumption), then an EM wave at a fixed frequency moving from one reference frame to another could experience quantisation due to the shifting time-base, resulting in an apparent net deceleration - resulting in a measurable acceleration of the system as a whole. And now I'll take off my fringe hat and get back to the day job.
- marcosdumay 12y ago
  Well, the relativity principle states that things don't "move from one frame of reference to the other". You choose a frame, and observe things on that frame; changing the frame of reference is your choice, and must not alter the results in any way. Accepting a flaw in conservation of momentum is already hard enough without you (and the original paper) imposing a flaw on the relativity principle to explain it.
  - madaxe_again 12y ago
    Ah, the old "it's Einstein so it must be right" gambit. People used to say that about Newton - until experiment proved that he didn't have the full picture. It's highly improbable that relativity is any different. Yes, it gives demonstrably correct answers, but that doesn't mean that it holds in all cases. I mean, why would we be even talking about LQG if we thought relativity gave the full picture? You're right that I was wrong to say it moved from one reference frame to another, which is clearly bollocks - the EM undergoes an acceleration to relativistic mass, then a deceleration.

tobinfricke 12y ago

"We still can't make up our minds as to how wings work, so this isn't overly novel. Sure, we can explain the outcome, but whether it's Navier-Stokes or Bernoulli or something else, we can't make up our minds." Time to trot out my favorite quote about how airplanes fly, from Stick and Rudder by Wolfgang Langewiesche, page 9, published 1944: »The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down. It shoves the air down with its bottom surface, and it pulls the air down with its top surface; the latter action is the more important. But the really important thing to understand is that the wing, in whatever fashion, makes the air go down. In exerting a downward force upon the air, the wing receives an upward counterforce--by the same principle, known as Newton's law of action and reaction, which makes a gun recoil as it shoves the bullet out forward; and which makes the nozzle of a fire hose press backward heavily against the fireman as it shoots out a stream of water forward. Air is heavy; sea-level air weights about 2 pounds per cubic yard; thus, as your wings give a downward push to a cubic yard after cubic yard of that heavy stuff, they get upward reactions that are equally hefty. That's what keeps an airplane up. Newton's law says that, if the wing pushes the air down, the air must push the wing up. It also puts the same thing the other way 'round: if the wing is to hold the airplane up in the fluid, ever-yielding air, it can do so only by pushing the air down. All the fancy physics of Bernoulli's Theorem, all the highbrow math of the circulation theory, all the diagrams showing the airflow on a wing--all that is only an elaboration and more detailed description of just how Newton's law fulfills itself--for instance, the rather interesting but (for the pilot) really quite useless observation that the wing does most of its downwashing work by suction, with its top surface. ... Thus, if you will forget some of this excessive erudition, a wing becomes much easier to understand; it is in the last analysis nothing but an air deflector. It is an inclined plane, cleverly curved, to be sure, and elaborately streamlined, but still essentially an inclined plane. That's, after all, why that whole fascinating contraption of ours is called an air-plane.«

SamReidHughes 12y ago
Okay but there's a difference in the nature of the "pushing down" of a rocket, a plane, and a hovering helicopter, and in how much of an impulse is actually inflicted on an external mass.

idlewords 12y ago

There is no confusion among physicists about how wings work.