No One Can Explain Why Planes Stay in the Air

No One Can Explain Why Planes Stay in the Air

• On a strictly mathematical level, engineers know how to design planes that will stay aloft. But equations don't explain why aerodynamic lift occurs.
  
  
• There are two competing theories that illuminate the forces and factors of lift. Both are incomplete explanations.
  
  
• Aerodynamicists have recently tried to close the gaps in understanding. Still, no consensus exists.
  

In December 2003, to commemorate the 100th anniversary of the first flight of the Wright brothers, the New York Times ran a story entitled “Staying Aloft; What Does Keep Them Up There?” The point of the piece was a simple question: What keeps planes in the air? To answer it, the Times turned to John D. Anderson, Jr., curator of aerodynamics at the National Air and Space Museum and author of several textbooks in the field.

What Anderson said, however, is that there is actually no agreement on what generates the aerodynamic force known as lift. “There is no simple one-liner answer to this,” he told the Times. People give different answers to the question, some with “religious fervor.” More than 15 years after that pronouncement, there are still different accounts of what generates lift, each with its own substantial rank of zealous defenders. At this point in the history of flight, this situation is slightly puzzling. After all, the natural processes of evolution, working mindlessly, at random and without any understanding of physics, solved the mechanical problem of aerodynamic lift for soaring birds eons ago. Why should it be so hard for scientists to explain what keeps birds, and airliners, up in the air?

I find this a very odd article. What the title means, apparently, is that on the one hand the mathematical equations governing the flow of air around the wing of an aircraft are well understood and can be solved accurately by computational means. But on the other, the solution of the equations can't be distilled into a simplified explanation that is understandable by a layperson with no knowledge of fluid mechanics, so "No one can explain it."

The odd thing to me is that anyone should expect that it should be possible to simplify a complicated physical process like this to the extent that anyone can understand it without understanding the underlying mechanisms. In fact, to my mind, it seems symptomatic of the modern misconception that anyone should be able to understand anything without spending years learning about it, because we all now have access to so much raw data through the Internet.

Reminds me of a radio comedy series "Cabin Pressure" where one character was explaining to another how an aeroplane wing generates lift. After hearing this reply, he then asked, so how can planes fly upside down?

The odd thing to me is that anyone should expect that it should be possible to simplify a complicated physical process like this to the extent that anyone can understand it without understanding the underlying mechanisms. In fact, to my mind, it seems symptomatic of the modern misconception that anyone should be able to understand anything without spending years learning about it, because we all now have access to so much raw data through the Internet.

Good point, applicable to many different fields.

I find this a very odd article. What the title means, apparently, is that on the one hand the mathematical equations governing the flow of air around the wing of an aircraft are well understood and can be solved accurately by computational means. But on the other, the solution of the equations can't be distilled into a simplified explanation that is understandable by a layperson with no knowledge of fluid mechanics, so "No one can explain it."

I don't [think] the problem is the lack of a simplified explanation, rather no explanation is fully satisfactory.

I am trying to understand where the level of mystery is - is it simply that we don't actually have clear explanations for force/energy/matter, is it the question of why the Laws of Nature exist in observed configuration, or is it that while we have explanations for a variety of complex phenomena within the terms of physics [we don't have that for lift]?

I think the article is trying to make a case it's the last, but I do think it could be more clearly presented.

I suppose in essence there is a very simple explanation for lift, which is that if the wing is up/down asymmetrical, then the flow of air and the resulting pressure field around it will also be up/down asymmetrical, and so in general there will be a net vertical component of force acting on the wing, either upwards or downwards. Put the wing the appropriate way up, and you'll have lift. But something tells me that's not the kind of simple explanation they're looking for.

I suppose in essence there is a very simple explanation for lift, which is that if the wing is up/down asymmetrical, then the flow of air and the resulting pressure field around it will also be up/down asymmetrical, and so in general there will be a net vertical component of force acting on the wing, either upwards or downwards. Put the wing the appropriate way up, and you'll have lift. But something tells me that's not the kind of simple explanation they're looking for.

This becomes a top-level fundamental question about science, and how our culture receives it.  

The scientific process has two primary process steps - documentation of observation and analysis of that data - in relation to its contextual framework.  Flight is an observable as separation between two bodies with differences in gravity pull.  Lift is a semantic context.  Forces that "cause" lift are well formed by math modeling.  The forces are in a semantic context during and only in expression of the analysis outcome.  Lift is seen as a casual property of the physical event.  But in fact -  the physics of math models don't rely on people's context.

"Properties" of pre-20th century science are semantic to me.  21 century science is ice cold and succeeds in a context of an objective view.  Many properties are subjective human viewpoints and science has pushed that view to the side.  That water is wet is not open to measurement.  Wetting in science is measurable in terms of fluid based equations measuring diffusion boundaries conditions and fluid dynamics.

To get away from this conflated situation the modern way is to replace the semantic nature of properties with equations describing dispositions and propensities.  Starting with the pragmatic thinking of C. S. Peirce and developed further by many prominent thinkers since, it can recast the subjective vs objective issues in analysis.

Propensities: Probabilistic Dispositions

Not all dispositions are what Mackie [1973] calls `sure-fire' dispositions. Those are the dispositions, like the solubility of salt and the hardness of steel, which are always manifested if the disposition is still in fact present. Other dispositions may manifest themselves only probabilistically. The disposition of a radioactive nucleus to decay, for example, does not manifest itself as a definite event immediately after the nucleus was formed: that is just when the decay first becomes possible. Instead, the disposition to decay appears as a certain probability to decay in any time interval. And furthermore, this probability may vary with time even while (i.e. before) it is not being manifested.   After Popper [1959], we use the term propensity to refer to dispositions with any kind of probabilistic outcome. They will clearly come in handy when we want to describe quantum mechanics. - Ian Thompson

https://www.generativescience.org/books/pnb/everyday.html


The equations describe the interaction of the atmosphere, the earth's gravity and a flying machine well enough to accurately predict flight.  The cause of lift is NOT a property of planes - which is the kind of answer the general public expects.  

Please excuse this rant.  It is important to the question of understanding the observables related to psi.  The general public (and materialism) is conditioned to a simple property as a cause.

I don't [think] the explanation the article suggests would be complete is meant to be necessarily simple - rather it seems the explanation would simply satisfying at the level of accepted physics?

I don't [think] the explanation the article suggests would be complete is meant to be necessarily simple - rather it seems the explanation would simply satisfying at the level of accepted physics?

But isn't the word "satisfying" doing a lot of work there? It's not as though there's any suggestion that there's anything other than accepted physics at work, because when the equations for the detailed flow field and pressure distribution are solved, the results agree with experimental observations. But the flow field and pressure distribution are complicated. The problem is to make that theoretical description of something complicated satisfying to the layperson, as an explanation of the force it exerts.

The more I think about it, the more I reckon the layperson probably does intuitively understand that - looking at it a slightly different way - if there's a wind blowing, and if there's an object sitting there that isn't symmetrical with respect to the wind direction, then it will tend to be pushed to one side or the other, not just straight along.

But isn't the word "satisfying" doing a lot of work there? It's not as though there's any suggestion that there's anything other than accepted physics at work, because when the equations for the detailed flow field and pressure distribution are solved, the results agree with experimental observations. But the flow field and pressure distribution are complicated. The problem is to make that theoretical description of something complicated satisfying to the layperson, as an explanation of the force it exerts.

But the article (and common knowledge) doesn't say that the layman view of the physics (and I would be a member of that group) is unsatisfied with the concept of lift.  It is the experts who declare the competing views.  You and I strongly agree that the delineation of the forces and mass values can be modeled to create a math/logic simulation of a body in flight.

Do you see the correspondence between experts sharing their doubts with the public on flight, with their doubts on psi?  My take is that it goes to the philosophy of science regarding what are inter-connected causes and if they exist on multiple levels.