So, get this. For years I explained a plane’s lift on the basis of the Bernoulli Theorem. It made sense, I thought. The rounded top of the wing means that air passing over it has a longer distance to travel than the air passing beneath the flat underside. Topside, the air flows faster to meet at the back of the wing the air passing by the flat underside. Faster flow, lower pressure, approaching a vacuum. And you know how Mother Nature abhors a vacuum. So, the wing rises (pushed from below?) to fill the relative void. The plane gets lift. Or so I thought. And then I picked up the February 2020 issue of Scientific American and read “The Enigma of Aerodynamic Lift” by Ed Regis.* Now, I’m not so sure.
Regis points out that if lift comes from a lower pressure over the curved airfoil that occurs because the air there must speed up to meet the air passing below the wing, then how is that a pilot can fly upside down? Good point. Brain explodes: Explanation based on Bernoulli Theorem now cast into doubt. What have I been saying all these years? How many students have I misled? And how did I get in all those multi-ton sky machines to fly blissfully so high above the ground?
Flying upside down (not sure why anyone would want to do that) is an airshow trick of long standing not recommended for commercial jumbo jets, of course. As many times as I have seen the inverted flight occur either in person or on film, it never occurred to me to question how the plane keeps its lift when the curved part of the wing is on the underside.
And that makes me wonder what else I never thought to question, not just the physics of flight or of any other Newtonian manifestation of forces in action, but also the actions of everyday people. What have I been missing? How have I allowed myself only partial explanations?
Possibly, living with partial or incomplete explanations is how we humans get through each day. After all, wouldn’t irrefutable explanations require extensive research and experimentation? And even if we did such inductive work, couldn’t we argue that Euclidean deduction is the only guarantee that we truly know what we say we know? We could run ten experiments with the same results, as you know, and not find out until we run the eleventh that we were wrong. I think of Jane Goodall, who stayed just a little longer in the field beyond her scheduled time to leave when she saw chimpanzees acting like a violent mob in an attack on a chimpanzee from a different family. Goodbye the notion of peaceful primates. Induction? I know we like to use it, filling ourselves with convincing anecdotes, but there’s always the chance that one more event will contradict the preceding events. No, science is right to frequently cast its lot with deduction.
Whether or not I’ll ever understand what keeps an airplane or a frisbee in flight is irrelevant. I can try all the alternatives, such as one that suggests the airfoil pushes down on the air below it. For me, right now, I’m at the “Who cares as long as it works” stage. I’ve been in planes; they’ve stayed in the air until the pilot made them not stay in the air. I was happy with my Bernoulli Theorem explanation when I glanced out the window at the curved surface of the wing.
What is more relevant here is that I learned how limited, how inductive, my knowledge has been. How many aspects of life have I believed I’ve understood right-side up without ever accounting for the possibility that I’ve been seeing things upside down?
*Vol. 322, Number 2. Pp. 44-51.
Regis points out that if lift comes from a lower pressure over the curved airfoil that occurs because the air there must speed up to meet the air passing below the wing, then how is that a pilot can fly upside down? Good point. Brain explodes: Explanation based on Bernoulli Theorem now cast into doubt. What have I been saying all these years? How many students have I misled? And how did I get in all those multi-ton sky machines to fly blissfully so high above the ground?
Flying upside down (not sure why anyone would want to do that) is an airshow trick of long standing not recommended for commercial jumbo jets, of course. As many times as I have seen the inverted flight occur either in person or on film, it never occurred to me to question how the plane keeps its lift when the curved part of the wing is on the underside.
And that makes me wonder what else I never thought to question, not just the physics of flight or of any other Newtonian manifestation of forces in action, but also the actions of everyday people. What have I been missing? How have I allowed myself only partial explanations?
Possibly, living with partial or incomplete explanations is how we humans get through each day. After all, wouldn’t irrefutable explanations require extensive research and experimentation? And even if we did such inductive work, couldn’t we argue that Euclidean deduction is the only guarantee that we truly know what we say we know? We could run ten experiments with the same results, as you know, and not find out until we run the eleventh that we were wrong. I think of Jane Goodall, who stayed just a little longer in the field beyond her scheduled time to leave when she saw chimpanzees acting like a violent mob in an attack on a chimpanzee from a different family. Goodbye the notion of peaceful primates. Induction? I know we like to use it, filling ourselves with convincing anecdotes, but there’s always the chance that one more event will contradict the preceding events. No, science is right to frequently cast its lot with deduction.
Whether or not I’ll ever understand what keeps an airplane or a frisbee in flight is irrelevant. I can try all the alternatives, such as one that suggests the airfoil pushes down on the air below it. For me, right now, I’m at the “Who cares as long as it works” stage. I’ve been in planes; they’ve stayed in the air until the pilot made them not stay in the air. I was happy with my Bernoulli Theorem explanation when I glanced out the window at the curved surface of the wing.
What is more relevant here is that I learned how limited, how inductive, my knowledge has been. How many aspects of life have I believed I’ve understood right-side up without ever accounting for the possibility that I’ve been seeing things upside down?
*Vol. 322, Number 2. Pp. 44-51.
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