What Anderson said, however, is that there is actually no agreement on what generates the aerodynamic force known as lift. 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? Adding to the confusion is the fact that accounts of lift exist on two separate levels of abstraction: the technical and the nontechnical.
They are complementary rather than contradictory, but they differ in their aims. One exists as a strictly mathematical theory, a realm in which the analysis medium consists of equations, symbols, computer simulations and numbers.
There is little, if any, serious disagreement as to what the appropriate equations or their solutions are. The objective of technical mathematical theory is to make accurate predictions and to project results that are useful to aeronautical engineers engaged in the complex business of designing aircraft.
But by themselves, equations are not explanations, and neither are their solutions. There is a second, nontechnical level of analysis that is intended to provide us with a physical, commonsense explanation of lift. The objective of the nontechnical approach is to give us an intuitive understanding of the actual forces and factors that are at work in holding an airplane aloft. This approach exists not on the level of numbers and equations but rather on the level of concepts and principles that are familiar and intelligible to nonspecialists.
It is on this second, nontechnical level where the controversies lie. Two different theories are commonly proposed to explain lift, and advocates on both sides argue their viewpoints in articles, in books and online. The problem is that each of these two nontechnical theories is correct in itself. But neither produces a complete explanation of lift, one that provides a full accounting of all the basic forces, factors and physical conditions governing aerodynamic lift, with no issues left dangling, unexplained or unknown.
Does such a theory even exist? Bernoulli came from a family of mathematicians. In other words, the theorem does not say how the higher velocity above the wing came about to begin with. There are plenty of bad explanations for the higher velocity. Because the top parcel travels farther than the lower parcel in a given amount of time, it must go faster. The fallacy here is that there is no physical reason that the two parcels must reach the trailing edge simultaneously.
And indeed, they do not: the empirical fact is that the air atop moves much faster than the equal transit time theory could account for. It involves holding a sheet of paper horizontally at your mouth and blowing across the curved top of it. The page rises, supposedly illustrating the Bernoulli effect.
The opposite result ought to occur when you blow across the bottom of the sheet: the velocity of the moving air below it should pull the page downward. Instead, paradoxically, the page rises. On a highway, when two or more lanes of traffic merge into one, the cars involved do not go faster; there is instead a mass slowdown and possibly even a traffic jam. That lower pressure, added to the force of gravity, should have the overall effect of pulling the plane downward rather than holding it up.
Moreover, aircraft with symmetrical airfoils, with equal curvature on the top and bottom—or even with flat top and bottom surfaces—are also capable of flying inverted, so long as the airfoil meets the oncoming wind at an appropriate angle of attack.
The theory states that a wing keeps an airplane up by pushing the air down. The Newtonian account applies to wings of any shape, curved or flat, symmetrical or not. It holds for aircraft flying inverted or right-side up. The forces at work are also familiar from ordinary experience—for example, when you stick your hand out of a moving car and tilt it upward, the air is deflected downward, and your hand rises. But taken by itself, the principle of action and reaction also fails to explain the lower pressure atop the wing, which exists in that region irrespective of whether the airfoil is cambered.
It is only when an airplane lands and comes to a halt that the region of lower pressure atop the wing disappears, returns to ambient pressure, and becomes the same at both top and bottom. But as long as a plane is flying, that region of lower pressure is an inescapable element of aerodynamic lift, and it must be explained. Because this activity requires some clouds. Head outside with some friends or family members and lay out a blanket so you can comfortably gaze at the clouds as they cross the sky.
What shapes do you see? Pick out a certain area of the sky and see what you can see. Do your friends or family members see the same things you do? Compare your observations. How are they similar? How are they different? Have fun cloudgazing and using your imagination to give the random clouds some meaning! If you're up for a challenge, try this fun experiment at home with just a few simple supplies.
Grab a clear plastic 2-liter bottle, matches you'll need an adult to help with this experiment and some warm water. Just follow the directions to create your very own Cloud in a Bottle! Did you get it? Test your knowledge. Wonder Words airplane track sky trail trace streak artificial fume dense exhaust vapor contrail condensation evaporate canvas navigation smoke fade Take the Wonder Word Challenge.
Join the Discussion. Lilly Feb 19, So, why the same airplane can stop doing it from one moment to another in same weather conditions? Feb 20, Hey, Lilly! It's now or never. Jan 15, Sep 25, We're glad you enjoyed the video, tom! Thanks for being our Wonder Friend! John Jun 21, I am just curious. I remember back when I was a kid I am now 36 that when the high flying planes left their contrails they would fade shortly after. Why has this changed over the last 10 years or so?
There is now a white haze that lingers and spreads out behind many of these planes. What is your theory about this? Do you have any information that can enlighten us? Maybe some references to follow up on?
Appreciate any info you can provide. Jun 28, Jake smith Feb 23, Seriously , look up former Ex government employee Kristen Meghan. She is a Geo engineering whistle-blower. There are plenty of smarter people than you and I that understand what's going on. Make sure you know the facts before you have google put mis information about this subject on the web for children.
Shame on you guys. And just so you know, all commercial air liners planes don't make fake smoke. Feb 23, Thanks for being so respectful, Jake! Kiki Jan 8, Jan 9, Tess Feb 21, You are liars of the worst kind. These are not contrails, this is weather modification, geo engineering program. How dare you make light of it as kids are breathing it and dying.
You are murdering people for the govt. You stink. Feb 22, Yogesh Oct 29, I didn't know about this white tracks like why these plains are leaving this type of track N then I searched on Google N Wonderopolis you rally helped me in this topic Oct 31, You're very welcome, Yogesh!
Dakota Jun 19, Jun 20, And if you were to say like some that was 2 lines would it go away before you finish. Nancy Jun 19, This is really cool the way they write massages in the air with a plane. Hi, Nancy! We appreciate your comment! B Jun 19, I have never seen it be done before but it looks pretty. The work they do is awesome. Teiona M. Jun 19, I liked that you guys told us about why air planes leave trails.
Also how they leave letters with the air planes. Monet Gray Jun 19, I liked how you can write words in the sky with the planes. I also like when you make shapes that's really pretty. Once i went to a air show and it had people sky writing and it was really cool. I would love if someone did that to me. That sounds like a lot of fun, Monet Gray! We bet you learned a lot! Anya A. Thats cool how people can purpose by skywriting. I didnt know that skywritting was way back to I saw a air show before its really cool.
Cole H Jun 19, I didnt know that the "special smoke" was made from the exhaust overheating and oil being sprayed on it. Pretty odd. Jun 21, S May 6, Funny because when I was younger and saw sky writing or airplane trails I always used to think that they were a special thing only for me and no one else.
I don't know why that is just how my brain used to work, now reading this I am very interested!!! Wonderopolis May 6, Ilma May 6, I never knew that airplane engine produces exhaust, just like the car do. I also didn't know that pilots have to learn different patterns and work on the smoking machines, and be able to write unique messages in the sky. It is also way different, how the skywriters use to do things in olden days than comparing to today.
Hung May 6, I never knew most of those facts until today. That was what i had to do for my homework. So I liked it. Great, Hung! I do believe the lines in the skies create magical sunsets and direct us to spiritual awakenings. Wonderopolis Apr 20, Earnest Hemingway Apr 1, Wonderopolis Apr 1, Ryan Jan 23, Let me begin by informing you that I work in the Aerospace Industry as an engineer. Your article has some useful information. You are buying into the narrative. I'm not arguing that planes exhaust water vapor as a result of combustion, nor am I arguing that the water condensation will dissipate and fade away.
There is science behind what you are saying, but I want you to do something. Look at our sky. Next time you are walking around the yard or into wal-mart or whatever and you see the plane actually leaving the so called "condensation trails", look around.
It is almost guaranteed that you will not only see one. These planes are spraying whatever they are spraying in a strategical pattern. Return to that same spot each hour over the course of hours. So there you have it — flight — in a nutshell.
Open in Our App. Download it here. By Rick Adams El Segundo. Jumbo jets Have you ever wondered how those things stay in the sky? Why Is the Sky Blue?
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