How wings really work

January 25, 2012

(PhysOrg.com) -- A 1-minute video released by the University of Cambridge sets the record straight on a much misunderstood concept – how wings lift.

It’s one of the most tenacious myths in physics and it frustrates aerodynamicists the world over. Now, University of Cambridge’s Professor Holger Babinsky has created a 1-minute video that he hopes will finally lay to rest a commonly used yet misleading explanation of how lift.

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“A wing lifts when the air pressure above it is lowered. It’s often said that this happens because the airflow moving over the top, curved surface has a longer distance to travel and needs to go faster to have the same transit time as the air travelling along the lower, flat surface. But this is wrong,” he explained. “I don’t know when the explanation first surfaced but it’s been around for decades. You find it taught in textbooks, explained on television and even described in aircraft manuals for pilots. In the worst case, it can lead to a fundamental misunderstanding of some of the most important principles of aerodynamics.”

To show that this common explanation is wrong, Babinsky filmed pulses of smoke flowing around an aerofoil (the shape of a wing in cross-section). When the video is paused, it’s clear that the transit times above and below the wing are not equal: the air moves faster over the top surface and has already gone past the end of the wing by the time the flow below the aerofoil reaches the end of the lower surface.

“What actually causes lift is introducing a shape into the airflow, which curves the streamlines and introduces pressure changes – lower pressure on the upper surface and higher pressure on the lower surface,” clarified Babinsky, from the Department of Engineering. “This is why a flat surface like a sail is able to cause lift – here the distance on each side is the same but it is slightly curved when it is rigged and so it acts as an aerofoil. In other words, it’s the curvature that creates lift, not the distance.”

Babinsky is quick to stress that he is far from the only aerodynamicist who is frustrated by the perpetuation of the myth: colleagues have in the past expressed their concerns in print and online. Where he hopes his video will help debunk the myth once and for all is by providing a quick and visual demonstration to show that the most commonly used explanation cannot possibly be correct. The original video, created by Babinsky a few years ago using a wind tunnel, has now been re-edited in high quality with a voice-over in which he explains the phenomenon as it happens.

Babinsky’s research focuses on the fundamental aspects of aerodynamics as they relate to aircraft wings, Formula I racing cars, articulated lorries and wind turbines. One of his visions is to design a wing that will enable aircraft to fly faster and more efficiently. Using a massive wind tunnel within the Department of Engineering, Babinsky and his team have been modelling the shockwaves that are created on aircraft wings and that restrict the plane’s top speed.

The newly released video will support lectures Babinsky will be giving as part of a series of University of Cambridge Subject Masterclasses aimed at Year 12 school children: “It’s important to put out this video because when I give this lecture to school kids I start by giving the wrong explanation and asking who has heard it and every time 95% of the audience puts their hand up. Only a handful will know that it is wrong.”

Provided by University of Cambridge (news : web)

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Veneficus
Jan 25, 2012

Rank: 1.3 / 5 (12)
Nice try, but unfortunately the video still does not explain why the difference in speed is not creating the pressure difference. Actually, the video even shows that the air at the top is moving even faster than assumed in the wrong explanation. If the air is moving even faster, this would create an even bigger pressure difference, in fact strengthening the wrong side of the argument...
wealthychef
Jan 25, 2012

Rank: 5 / 5 (16)
Nice try, but unfortunately the video still does not explain why the difference in speed is not creating the pressure difference. Actually, the video even shows that the air at the top is moving even faster than assumed in the wrong explanation. If the air is moving even faster, this would create an even bigger pressure difference, in fact strengthening the wrong side of the argument...


The difference in speed IS creating the pressure difference. The video appears to be debunking the idea that the transit time over the top and bottom of the wings need to be the same. What the video does not explain at all is why the air goes faster over the top than the bottom. It simply says "because it's a curved surface," which begs the question and leaves the layman still mystified.
Sanescience
Jan 25, 2012

Rank: 5 / 5 (1)
I have always preferred the explanation that something flies when an equal amount of airmass*momentum is directed to counteract gravity on that something.
jwilcos
Jan 25, 2012

Rank: 5 / 5 (14)
The video titled "how wings really work" does not explain how wings really work. It just complains that what someone else said is wrong.
Moose Dr_
Jan 25, 2012

Rank: 4.5 / 5 (2)
jwilcos, you hit the nail on the head.
loneislander
Jan 25, 2012

Rank: 3.4 / 5 (5)
Thinking of which stream is faster is the problem. The lower stream is slower so where did its energy go? Clearly the ~increased~ pressure under the wing, caused by the average angle of the airfoil being tilted to force extra air below the wing, plus the slowing of that air, causes lift. What's the mystery? Take a flat board about 1/8" inch thick and tilt it upward and it will fly upward -- there's no "airfoil" in the sense of these wing designs (which are designed that way to get the air to remain laminar until it passes the wing surface -- no other reason.)

Two things have always amazed me about this: 1) that most pilots actually believe the standard version, and 2) that there was any controversy in the first place.
jrsm
Jan 25, 2012

Rank: 4 / 5 (3)
then how does a plane fly upside down? Not wing curvature because the wing is essentiall upside down and the lift should be downward. However the angle of attack of the wing has to change in order to generate the required lift. Wing probably isn't particularly efficent though.
Lurker2358
Jan 25, 2012

Rank: 1.1 / 5 (7)
The lift is not caused by pressure at all.

The text book explaination is full of it.

It's caused by conservation laws and the FORCE of the air hitting the bottom side of the wing, which in this case is deflecting the bottom stream DOWNWARD. But for every action there is an equal and opposite reaction, which is LIFT on the plane.

You can test this very easily using a FAN or for God's sake a WIND TURBINE, which turns NOT because of any bernoulli effect, but by simply re-directing a force vector, which due to conservation laws, requires an equal oposite force vector to offset.

If I'm wrong, wind turbines and fans simply would not work. If you have a big enough fan, it blows itself over, and again, it has nothing to do with bernoulli. You can do this with, non-curved wings and it will still work.
julianpenrod
Jan 25, 2012

Rank: 3.7 / 5 (3)
Among other thigs, the "explanation" depends on the cross section of wing shown. The one in the movie has it delibrerately tipped upward in the front, which is not the case in flight. This produces an obstruction that slows air down underneath. In textbooks, the wing cross section is horizontal, with a flat underside and curved shape above, which is not seen in vehicles like the Wright brother plane whose wings were panels of cloth. In that "explanation", the air rushes over the curved surface faster to meet up with air moving along the lower surface. But this requires that the packet of air separated by the wing necessarily meets up at least closely when reaching the back of the wing. In both cases, Bernoulli's Priniple, stating lower velocity of a fluid supposedly produces higher pressure, creates a differential and that lifts the plane. But for every configuration, there always seems an alternative that works just as well.
Lurker2358
Jan 25, 2012

Rank: 1 / 5 (8)
At any rate, there's even another way to see that I'm right.

Take a BOAT, the faster it moves on the water, the higher it rises, because the water passing under the boat is deflected downward slightly, and this produces an equal and opposite force on the boat, pushing it up out of the water. Think of a hydrofoil or even a skiff going full speed.

The air on the video moves slower on the bottom side because it STRIKES the bottom face of the wing, transferring some of it's momentum into the wing as it is deflected downward. Total momentum is conserved, but the original "straight" vector has been split into equal vector sums: The momentum of the wing now moving upwards (which may be overcoming or breaking even with gravity,) and the momentum of the air now moving downwards.

The air moving over the top of the wing is nearly irrelevant, much like a boat in water.

Go back to school professors, or better yet get some real life experiences...instead of textbook BS...
julianpenrod
Jan 25, 2012

Rank: 1 / 5 (6)
Something as commonly seen and regularly experienced as powered flight and the explanation in textbooks for powered flight is challenged and, except for some constrrnation in many comments, there is little uproar. An explanation decades old, that supposedly was used to design aircraft, is shown as flawed, but there is no real sign of consternation over aerodynamics and a field called "science" that would allow, this lie to promulgate oin the first place. And how many thought to bring up the fact that this diqualifies all the "answers" so many were willing to say "science" provides? An "explanation" relied on for decades is shown wrong, but how many will take this as reason to question other things "science" says, and how many will say, "well, they were wrong there, but everything else they say is true, because they're 'scientists'"?
sigfpe
Jan 25, 2012

Rank: 5 / 5 (7)
> The lift is not caused by pressure at all.
> It's caused by conservation laws and the FORCE of the air hitting the bottom side of the wing,

Pressure is the force per unit area so you're contradicting yourself.
Lurker2358
Jan 25, 2012

Rank: 1.4 / 5 (5)
julianpenrod:

Perfect example of why "knowing exactly how or why something works" is not necessarily even important.

People use fire for cooking and other work for thousands of years before any remotely correct theory of chemistry or atomic matter existed.

Metallurgy also existed for thousands of years before anyone had any idea what oxygen or carbon were, or why or how or why they influenced metal's strength. In fact, there was no real explaination for this at all until about 200 years ago, and no good explaination till a few decades ago. Still finding better steel alloys today, sometimes even by accident, as usual!

All perfect examples of why the "Perfect knowledge" requirement of the peer review process is such a joke, particularly in fringe fields of science such as alternative energy.

Example:

It does not matter "why" cold fusion works, IF it works. IF it works and IF it produces a net, usable amount of energy, that is all that matters for practical use.
Deathclock
Jan 25, 2012

Rank: 5 / 5 (7)
An explanation decades old, that supposedly was used to design aircraft, is shown as flawed, but there is no real sign of consternation over aerodynamics and a field called "science" that would allow, this lie to promulgate oin the first place. And how many thought to bring up the fact that this diqualifies all the "answers" so many were willing to say "science" provides? An "explanation" relied on for decades is shown wrong, but how many will take this as reason to question other things "science" says, and how many will say, "well, they were wrong there, but everything else they say is true, because they're 'scientists'"?


What the hell are you babbling about now?

The article states at the very beginning:

"Its one of the most tenacious myths in physics and it frustrates aerodynamicists the world over."

Scientists knew this all along, the problem is with the laypersons that consistently fail to understand the science, such as yourself.
Telekinetic
Jan 25, 2012

Rank: 5 / 5 (5)
The aborigines utilized this technology thousands of years ago when they invented an extremely effective hunting instrument- the boomerang.
julianpenrod
Jan 25, 2012

Rank: 1.2 / 5 (5)
Deathclock seems to have set themselves to be a personal persecutor for me. The persecution, among other things, consisting of lambasting me for things I say that aren't wrong, merely pretending they are wrong and using venom and vulgarity to emphasize it.
Deathclock asserts that "scientists" knew the common explanation for how wings work was wrong "all along", and claims "the problem is with the laypersons that consistently fail to understand the science".
The "scientists" wrote the textbooks the incorrect "explanation" was included in, that the article mentions. "Scientists" contributed to the "aircraft manuals for pilots" the article mentions. "Scientists" have no record of aggressively, or even significantly trying to disabuse this "explanation", or else this article would not have been written.
When a sociopath wants to attack you but has nothing wrong they can target, they will say what you do that is right is illegitimate.
Deathclock
Jan 25, 2012

Rank: 5 / 5 (5)
The "scientists" wrote the textbooks


Not necessarily... it could very well be that most text books written by scientists gave the correct explanation, and the textbooks with the incorrect explanation were not written by scientists, or scientists from other fields of expertise.

"Scientists" contributed to the "aircraft manuals for pilots" the article mentions.


This is even less likely.

"Scientists" have no record of aggressively, or even significantly trying to disabuse this "explanation", or else this article would not have been written.


This very article is the attempt to correct the myth... This article that you are replying to proves that you are incorrect about this point...

How much more can you possibly fail?
julianpenrod
Jan 25, 2012

Rank: 1 / 5 (5)
Deathclock's "proof" that "scientists" had nothing to do with the "myth" about how wings work, that it is all the fault of laypersons, is that "it could very well be that most" books written by "scientists" were correct and that incorrect textbooks were not written by "scientists". Would Deatchclock allow the use of conditionals as part of a conclusive, definitive assertion without condemnation? Too, Deathclock asserts, it is not likely that "scientists" contributed to pilot manuals. But, if the explanations offered were all wrong, why wasn't there a concerted effort by "scientists" to correct them, to make the truth eminently widely known, long before this? Apparently, whatever is making Deathclock determined to harass me is steadily robbing them of the ability to assess their actions.
jsa09
Jan 25, 2012

Rank: not rated yet
I am very surprised that Holger Babinsky was so silly as to make a video to demonstrate lift through curvature where he clearly has his wing tilted at an angle into the air stream.

The smart thing would be to have his wing horizontal and have a clear demonstration of the principles he claims are working in this case.

As has been stated once you introduce an angle of attack then you will have two more forces at work whether the wing is curved or not.

Force 1 is energy transference from air stream striking the wing.

Force 2 is the reduced air pressure above the wing caused by the natural tendency for things to travel in a straight line.

Both these forces will be acting on any plain that is tilted into the airflow.

A wing with a curved top and a flat bottom still provides lift and it can be demonstrated that the air along the bottom of the wing is not impeded but the air over the top of the wing is. So in the case of a normal curved wing the lift is generated from above.
jsa09
Jan 25, 2012

Rank: 5 / 5 (3)
By the way it is the rare scientist that writes text books. Most texts are written by teachers who may or may not have a clear understanding of all the principles involved in the things they write about. They will of course, think that they understand but it is more like Chinese whispers than anything else.
Deathclock
Jan 25, 2012

Rank: not rated yet
By the way it is the rare scientist that writes text books. Most texts are written by teachers who may or may not have a clear understanding of all the principles involved in the things they write about. They will of course, think that they understand but it is more like Chinese whispers than anything else.


Yes, thank you.
julianpenrod
Jan 25, 2012

Rank: 1 / 5 (6)
Deathclock may have jsa09 to do the dirty work of verbally "validating" them for them, but that doesn't make it true. Textbooks are regularly subjected to scrutiny. There is a regular process of review of contents. If jsa09 is so certain textbooks are so unreliable, why weren't they making a big deal about this everywhere? Why were they so content to let misinformation, that they indicate they knew was there, go without declaiming it widely? And it still doesn't explain why "scientists" didn't raise a wide and obvious ruckus.
Deathclock
Jan 25, 2012

Rank: 4 / 5 (4)
They were too busy raising a ruckus about the nutty creationists wanting their unscientific drivel to be taught in science classes...
kochevnik
Jan 26, 2012

Rank: 3.7 / 5 (3)
And it still doesn't explain why "scientists" didn't raise a wide and obvious ruckus.
When I want to know a subject well I just read a Russian expert. Not perfect but generally they have a more grounded, understandable description of the dynamics.
jsa09
Jan 26, 2012

Rank: 4.5 / 5 (2)
@ julianpenrod In many cases scientists do not read educational texts. They are not particularly interested in what information other people are learning. They are more interested in what there peers are up to, so that they do not fall behind. And also they are pretty focused on their current research.
MarkyMark
Jan 26, 2012

Rank: 5 / 5 (5)

Example:

It does not matter "why" cold fusion works, IF it works. IF it works and IF it produces a net, usable amount of energy, that is all that matters for practical use.

Cold Fusion doesant work...........it does not produce a net, useable amount of energy.

@ julianpenrod i am curious what fringe theory\religion your belief in fueled your distrust of Science in generall? Was it Creationism, flat Earth theory, the theory that Fox news is a source of truth?
marraco
Jan 26, 2012

Rank: 5 / 5 (1)
The wing on the video has an angle of attack too large, so the lift force over the wing is in fact a mix of the difference of pressures and the impact force of the air. That confuses a lot of people here.

But in normal conditions the wing is not so inclined, and the only significant force is the difference of pressure caused by the difference of speeds.

Is simple to make a home experiment of the lift force: just put the curved side of a spoon against a tap water jet. Despite the water crashing on the spoon, the water is not pushed out by the water, but pulled into the water.
Wings work the same way.
jsa09
Jan 26, 2012

Rank: not rated yet
On the other hand when a scientist does decide that people are learning something the wrong way - it may be a case of oversimplifying in the opposite direction and cause more confusion than they solve.

Clearly in this case the scientist or engineer in question did not make a very clear case for his argument and has therefore added little of any worth for the layman.
JRi
Jan 26, 2012

Rank: not rated yet
Not an expert on this one, but I would think it this way: The airplane wing has two unsymmetries, it has curved upper surface byt ~flat bottom surface. The second unsymmetry comes from the highest point of the wing that is more in front than in just middle. The wing creates higher pressure to the front upper part, but lower pressure to the back upper part. Since FORCE = (under/over)pressure*Area, the net result is drag to up since the area of the rear upper part is larger. That's of course if one assumes that the over pressure in the front has same magnitude than the underpressure at the back upper part.
epsi00
Jan 26, 2012

Rank: not rated yet
Maybe we should put the matter to a vote. Reading the article and comments did not really help me understand why a plane fly. For every comment, there is a counter comment so the question of who is right is still out there for people, like me, who are not physicists.
All I know is that airplane wings look more like birds wings ( shape of feathers ) and we know that birds can fly. So here's my final answer. Airplane can fly because they have wings that resembles birds' wings and we know birds can fly and they don't even bother solving aerodynamics equations to tell them what to do.
Forestgnome
Jan 26, 2012

Rank: 5 / 5 (1)
Don't know if anyone noticed, but it looks like the velocity of air over the top of the wing increased as a result of the narrower passage between the wing and the wall of the tunnel. Not a very good demonstration. For those who espouse the pressure under the wing theory, take for example ground effects. Winged craft are considerably more efficient when flying a short distance from the ground because of the pressure buildup between the wing and the ground. I concur.
julianpenrod
Jan 26, 2012

Rank: 1 / 5 (6)
How interesting, jsa09's observation that "scientists" "are not particularly interested in what pother people are learing". So much for dedication to knowledge! But, if it's the case that they "don't read educational texts", why, as the article suggests, did the "myth" about how wings work "frustrate" aerodynamics experts? And if, as Deathclock agrees, "scientists" don't read or care what textbooks say, why does Deathclock say "scientists" " were too busy raising a ruckus about" creationism being taught in schools? And, were aerodynamicists complaining about creationism? Why weren't they complaining loudly about the "myth" about how wings work? For that matte, Babinsky is as much a "professor" as a "scientist", so why didn't other "professors" who apparently were just as devoted to "science" complaining widely before this?
Nigel_Milligan
Jan 26, 2012

Rank: not rated yet
From wikipedia
"The lift on an airfoil is primarily the result of its angle of attack and shape. When oriented at a suitable angle, the airfoil deflects the oncoming air, resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: Lift and drag. Most foil shapes require a positive angle of attack to generate lift, but cambered airfoils can generate lift at zero angle of attack. This "turning" of the air in the vicinity of the airfoil creates curved streamlines which results in lower pressure on one side and higher pressure on the other."

They are using a steep angle of attack and an almost symmetrical aerofoil.
theDuke
Jan 26, 2012

Rank: 2 / 5 (1)
there's no Lift, only Drag..

Angle of Attack is everything to make a wing fly.
johnboy
Jan 27, 2012

Rank: not rated yet
Nigel Milligan's wiki entry is the best explanation listed so far. A complete flat wing will generate lift so long as there is an angle of attack, as theDuke says. So why are wing surfaces curved? To reduce drag, to increase the range of angle of attack where lift it generated, and to control the pitch moment (twisting moment) on the wing. That's it, nothing else is involved. No curvature necessary, Prof. Babinsky.
loneislander
Jan 27, 2012

Rank: 5 / 5 (1)
"The one in the movie has it delibrerately tipped upward in the front, which is not the case in flight."

I've never seen a flying plane where the wing did not have a positive attack angle -- it would be impossible.

[To Lurker:] The "force" is the pressure. How can these be thought of as different things? Surely you don't suggest the air pressure on the top of the wing is the same as the pressure on the bottom; I don't think that makes sense (but perhaps that's not what you were saying).
pilot62
Jan 28, 2012

Rank: not rated yet
Everyone wants to be a Scientist
PiperPacer
Jan 28, 2012

Rank: not rated yet
Sanescience has it. Something flies when an equal amount of airmass momentum is directed to counteract (the forces of)gravity on that something. The same explanation applies to propellors; it's just that the blast of air behind a turning propellor is much more easily observed than the downwash that occurs behind wings producing lift. As also observed, a flat board will produce lift (if given an angle of attack). Measuring airspeeds across this board will also reveal faster air moving across the top and slowed down air moving on the underside.
Cave_Man
Jan 29, 2012

Rank: 2 / 5 (1)
I got banned from the physics forums on this site for suggesting the gravity is the ultimate cause of lift. Nobody even bothered to say "well its not the direct cause of lift dur durdribble dribble" I was simply banned. For stating something that is in fact 100% correct.

Thanks mods, way to be educational.
Ethelred
Jan 29, 2012

Rank: 4 / 5 (4)
I have always preferred the explanation that something flies when an equal amount of airmass*momentum is directed to counteract gravity on that something.
Sometimes I go that way BUT the truth is the airmass's downward movement is the RESULT of the pressure of the pressure differential which is the actual cause of lift. More presurre up than down. Same as for the boyancy of a ship in water.

A lot of what I was taught over the years about physical effects are actually wrong. Boyancy is NOT due to the amount of water displaced. It is pressure differential. Rockets do NOT work by throwing stuff out the back. Again it is a pressure diferential with the stuff going out the back as a result which conserves momentem.

You can look at either way as the math works the same BUT the proximate cause is a pressure diferential.

Ethelred
Ethelred
Jan 29, 2012

Rank: 4 / 5 (4)
Odd that loneislander was downranked when he got it right. Curvature is involved of course but he has the essentials spot on.

So in the case of a normal curved wing the lift is generated from above.
No. Air can't pull. It CAN push up harder than it pushes down. The rest was right. It is the pressure differential between the top and bottom no matter how that differential is created.

@ julianpenrod In many cases scientists do not read educational texts.
Dr. Feynman wrote about, or rather told a story about, the time he worked on a school text commitee. He was the only scientist on the commitee and the only person that read all the books. The only one that was annoyed by some of the bad examples.

I have a sneaking suspicion that it hasn't changed much in the years since then.

Ethelred
Callippo
Jan 29, 2012

Rank: not rated yet
Its often said that this happens because the airflow moving over the top, curved surface has a longer distance to travel and needs to go faster to have the same transit time as the air traveling along the lower, flat surface.
Isn't it how Bernoulli's paradox is supposed to work? The faster flow of air makes a suction at the upper side of wing, which results into uplift force. IMO this description is not wrong, it's just another perspective of the same problem.
Ethelred
Jan 29, 2012

Rank: 3.7 / 5 (3)
I got banned from the physics forums on this site for suggesting the gravity is the ultimate cause of lift.
Well its wrong but I wouldn't ban you for it myself unless you were posting it as much as Zephir does his silly nonsense.

For stating something that is in fact 100% correct.
Except it isn't. Pressure is the cause. Yes gravity is the reason there is a planet, with air, a Sun and a place to fly the plane but that is rather a long way to go to avoid the proximate cause of lift.

Ethelred
Callippo
Jan 29, 2012

Rank: 1 / 5 (1)
for suggesting the gravity is the ultimate cause of lift
At the hypothetical planet without gravity the planes with wings couldn't fly at all. Such a comment is a sign of creative, consequential thinking. No wonder, the superficially thinking people (those, who are relying on the intersubjectively accepted memorized truths) feel so upset with it.
Callippo
Jan 29, 2012

Rank: 1 / 5 (1)
Because the gravity is the primary reason of why planes CANNOT fly, it brings the question of how the explanation can remain general for still being considered as an explanation at all. Apparently, we have to do with Hamiltonian geometry of intrinsic and extrinsic perspectives here: the relevant explanation is such an explanation, which enables to derive the theorem in more straightforward way (i.e. with lower Hamiltonian), than the negation of it. Gravitational explanation apparently belongs into extrinsic perspective, as it enables to explain a much more, than just uplift force. But what the people are usually expect here is the intrinsic explanation, which is relevant just to the closest category of subjects explained. The strictly deterministic explanation is the formal description of phenomena, only relevant to subject explained. Such an description is not considered as an explanation too, because it cannot be generalized to other subject at all.
Tausch
Jan 29, 2012

Rank: not rated yet
:)
Rarely will you find a child who has not made the famous one sheet of paper 'plane'.

From this folded sheet of paper you will be hard pressed to find what you label 'curvature' anywhere - or what type of 'antics' air must do to make this paper plane fly.

You will be hard pressed to find a child saying this type of plane doesn't fly.
Callippo
Jan 29, 2012

Rank: 1 / 5 (1)
But the flatness of paper sheet doesn't imply the flatness of air streamlines, does it? It's evident, the air cannot move along straight path even at the case of flat wings. Actually, the above simulation did a poor job in demonstration just of it - Babinsky should use a flat wing in his wind tunnel to demonstrate his stance.
Ethelred
Jan 29, 2012

Rank: 4 / 5 (4)
Just keep lying about others Zephir. Its a your good for.

Ethelred
Callippo
Jan 29, 2012

Rank: 1 / 5 (2)
In Czech we have a proverb "A shot goose is always the first one to squawk", which roughly means "If the cap fits, wear it".
Tausch
Jan 29, 2012

Rank: not rated yet
Heavier-than-air objects fall to the surface of the earth in air. I can even see why some see gravity as an underlying cause (already mentioned, commented on and dealt with).

May I suggested simply highlighting air molecules.
Once you highlight the medium air to show the various density field gradients taking place (as in many others fields of science using a color spectrum showing density gradients of various parameters), you will have a powerful, easily understood/intuitively grasp-bar, picture (demonstration) of where the 'pressure' in the form of 'lift' takes place and how.

Kids will see the molecules getting 'scrunch' on the earthward directed surfaces as opposed to the surfaces facing space-ward ('up').
Tausch
Jan 29, 2012

Rank: not rated yet
Typo - (second paragraph, third word):
Incorrect use of tense;
suggested=suggest
Sorry.
jmlvu
Jan 29, 2012

Rank: not rated yet
The text book explanation of lift always left me confused, and while I don't support creationist, this makes science look bad.

I'd like to see someone run a atomic scale simulation of a wing and show that atoms impart more momentum on the bottom of the wing than the top.
MorituriMax
Jan 29, 2012

Rank: 5 / 5 (1)
And despite not understanding this, airplanes by the hundreds of thousands have flown just fine for decades.
lomed
Jan 29, 2012

Rank: 5 / 5 (1)
At the hypothetical planet without gravity the planes with wings couldn't fly at all.
It depends on what one means by "fly". If one simply means controlled movement by manipulation of air flowing past a wing due to motion caused by a propeller, it would seem that flight is possible even without gravity (assuming the air remains at the same density). After all, the propeller would still pull the plane along, and the aerodynamic forces would still act to move the plane in the direction opposite to the underside of the plane (for ordinary wing shapes).

Of course, if by "fly" one means oppose the force of gravity via aerodynamic forces, absence of gravity would logically imply absence of flight.
Smashin_Z_1885
Jan 30, 2012

Rank: not rated yet
yeah nice try indeed. If this were the case, then why does a flat surface also race upwards when introduced into an airflow? This can be easily tested by holding a thin, flat object into an airflow and tilting it upward. It will be lifted very quickly. There is no curvature there. How does that work? The same effect works in water. Answer the question because I have no idea
Smashin_Z_1885
Jan 30, 2012

Rank: not rated yet
I think so-called 'lift' has more to do with effects at the molecular level, such as is the case when water is miraculously "pumped" up a huge tree. The effect there has been proven to be "molecular climbing", which is a purely mechanical effect. Since air is also composed of molecules, could this be the case also? We already know that air is composed of molecules, and so are 'wings'. No one, as far as I know, has studied the intimate effects of molecular movement in this way, as it applies to wing lift in a medium such as air. They simply use a wind tunnel and study the effects at the macroscopic scale, ignoring the microscopic mechanics of the systems. I don't know , any thoughts on that ?
Ethelred
Jan 31, 2012

Rank: 3.7 / 5 (3)
which roughly means "If the cap fits, wear it".
If the Crank lies it is still a lie and not a cap.

Ethelred
Rank 4.3 /5 (23 votes)
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