Flatow - Present at the future: from evolution to nanotechnology, candid and controversial conversations on science and nature

FROM EVOLUTION TO NANOTECHNOLOGY, CANDID AND CONTROVERSIAL CONVERSATIONS ON SCIENCE AND NATURE

One of the joys of being a science journalist is the aha! moment. That brilliant flash of light, that moment of epiphany, when all the cylinders in your head click and you come to understand something you had never understood before. Sometimes your mouth may actually fall open as your eyes wander around the room, not really seeing anything but not under conscious control of your brain, which has just latched on to an idea that had eluded it for quite some time.

As I say, one of the joys of being a science journalist, especially the host of a popular radio program such as Science Friday , is the ability to share that moment with millions of others. And one of those moments, among many others, stands out in my mind. It involves solving a problem I was having with one the most widely accepted truths about the world around us: why airplanes fly.

Like every science journalist who ponders how things work, I was more than casually acquainted with the commonly accepted ideas about the physics of flight. After all, the explanation for why airplanes fly is one of those unquestioned beliefs in science education, a dogma that has been repeated for generations and taught in eighth-grade science class along with why the sky is blue. (Oh, you were out that day?) In fact I have mouthed the simple explanation countless times on radio and television talk shows. I had sung its praises in my own (previous) books. High-school teachers who coach award-winning teams in science competitions would all say the same thing: The basis for why airplanes fly is a concept in physics called Bernoullis principle. We all know that. No-brainer. Period. End of discussion.

Just what is Bernoullis principle? Its quite simple to state: Daniel Bernoulli, a Swiss mathematician, discovered in 1733 that the faster a fluid flows, the lower its pressure.

And that explanation has been used ever since the 1930s to explain why an airplane flies. In short, the explanation states that because of the design of a wing, air will fly faster over the top than the bottom. According to Bernoulli, faster-flowing air on top means less pressure on top. More pressure on the bottom than on the top lifts the wing. So the wing is literally sucked up into the sky, the same way you suck up soda in a straw. Complex science-fair projects and even simple strips of paper over which you blowthe paper flies uphave been used for decades to demonstrate Bernoullis principle. And as I say, I too, when asked to explain in simple terms what makes an airplane lift off the ground, would say the same thing: Bernoullis principle.

That all came to an end one day in 1989. After that day, I would no longer freely mention Bernoulli and flight in the same breath, unless it was to denounce the principle. Because on that day I met a man who would change my life forever. And I vowed to set the record straight.

I had just finished making a speech to a group of folks at a science conference at the University of Vermont. After polite applause and a brief question-and-answer period, people began to file out. Just as I was about to collect my papers and head for the door, the real answer to why airplanes fly appeared before me in the form of Norman Smith. Norman Smith had spent more than two decades as a research aerodynamicist for NASA and before that for its pre-space predecessor, the National Advisory Committee for Aeronautics. He was the author of more than a dozen science books as well. And now in his later years, after a very successful career in aviation, he was on a one-man crusade: to get rid of Bernoullis principle as the explanation for why airplanes fly.

I listened to your speech and was very impressed with what you had to say, said Smith. Except for one thing. That explanation about why airplanes fly.

Oh. Did I say something wrong?

Yes, you did. That explanation you gave, the one using Bernoullis principle, is no longer acceptable. Its old and not really accurate.

Smith was trying to be polite. What he would have really liked to have said, I think, was You dummy, get with the program. Heres another guy Im going to have to reeducate.

Education was what Smith did best. As far back as 1972, in a book and in an article published in that most sacred of all science-teacher magazines, The Physics Teacher, Smith met the enemy wherever he found it. Wherever teachers banked on Bernoulli to teach the theory of flightin newspapers, in magazines, in a lecture hallSmith was there to remove Bernoulli from its central role in flight. He called it the Bernoulli myth and said it was the most persistent, pernicious error in school science books.

Not only is Bernoulli used to explain aircraft lift, Smith lamented, but I have found articles on ornithology that borrow the error to explain bird-wing lift!

Smith handed me a copy of one of his magazine articles from The Physics Teacher and asked me to read and see for myself.

The math is pretty easy for a smart guy like you.

By now I was more than intrigued. Embarrassed might be a good word. Here I had just lectured to hundreds of peopleI was a role model, an author, an expertand now, if Smith was right, I was an idiot. Smith could see my sheepish look, and his smile told me Not to worry; youve merely made a mistake common to physics teachers around the world. Join the crowd .

Just what is the right explanation, then? I needed to hear his take.

Very simple: Newton. And his laws of motion. You can easilyand correctlyexplain why airplanes fly from first principles. No need to resort to Bernoulli. He was createdreally pulled out of a hataround World War II when the airplane was becoming popular and people wanted a simple explanation. But in reality it takes more time to explain the complicated workings of Bernoullis principle than it does the simple laws of Newton. In this case its very simple: Airplanes fly because the wing makes the air go down, so the airplane goes up. Actionreaction. Newtons third law. How hard is that to understand?

I took Smiths papers home and read them. They made a lot of sense. I researched Smith and uncovered other articles about him and his quixotic quest to set the record straight. Jerry Bishop, a highly respected colleague of mine and science writing icon of the Wall Street Journal , had come across Smith in 1972 and had written a major Wall Street Journal article about the quest. Being the great journalist that he is, Jerry presented the case but never reached a conclusion. He let the reader decide.

But I was convinced. Of course it was Newton! The beauty of flight was in this detail.

Thus began my own crusade to replace Bernoulli with Newton, just as Smith had tried to do. I soon found and talked with other like-minded science teachers who had begun to make their own contributions. They began to question the very basics of accepted textbook ideas about how air flows over a wing, and they discovered that they were wrong.

I chatted with airplane pilots who had never once relied on Bernoulli to fly. They talked about angle of attack and stalling the wing and airspeed and such. A helicopter pilot showed me his movable wing planehis copterand told me to take a close look at its shape. He pointed to the end of the wing and said, Does this look at like your textbook Bernoulli airfoil? Of course not: its symmetrical. Contrary to Bernoulli dogma, wings dont have to be rounded on top and flat on the bottom. See? Mine are symmetrical, rounded on top as well as bottom. And Im getting off the ground!