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Physicists Finally Solve the Falling-Paper Problem
neutron_p writes "The so-called "falling paper" problem has long intrigued scientists. James C. Maxwell pondered the tumbling motions of playing cards in 1853. Why don't flat things fall straight down? Pieces of paper fall down, then rise into the air, then glide along, then again rise... It occurs in a seemingly chaotic manner. Now researchers at Cornell University have solved the falling paper problem by calculating the motions of a scientific journal page in flight and there were a few surprises." There's also a story in the Cornell Sun.
Now they just need to solve the 8+ folds problem...
better save it here for posterity :-)
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Image: The seemingly chaotic motions of this page from a scientific journal became part of a computer modeling exercise to show why flat things don't fall straight down., J. Wang and U. Pensavento/Cornell University. Copyright Physical Review Letters 2004
The same falling-paper principles apply, the physicists believe, to naturally flat things like leaves. If they are right, Wang and Pensavento may have finally solved the mystery of why autumn leaves depart from a neighbor's tree on a windless day . .
. . . rise into the air . . . . . . rise again . .
. . . glide along . .
. . . and have to be raked from yards that don't contain a single tree.
As Wang explains, "Leaves and paper fall and rise in a seeming chaotic manner. As they fall, air swirls up around their edges, which makes them flutter and tumble. Because the flow changes dramatically around the sharp edges of leaves and paper, known as flow singularity, it makes the prediction of the falling trajectory a challenge."
Among the first scientists to be intrigued by the behavior of falling paper was Scottish physicist James C. Maxwell, who pondered the tumbling motions of playing cards in 1853. But while Maxwell was a brilliant mathematician, he lacked the today's computer-modeling techniques, not to mention access to fast, powerful computers. Wang and Pensavento put those advanced tools to good use to show why the falling trajectory of thin flat things -- and the behavior of airflow and other forces -- is not predicted by the classical aerodynamic theory.
"There were a few surprises," Wang notes. "We found the flat paper rises on its own as it falls, which would not happen if the force due to air is similar to that on an airfoil. Instead, the force depends strongly on the coupling between the rotating and translational motions of the object."
Wang and Pesavento also showed that the falling-paper effect is almost twice as effective for slowing an object's descent, compared with the parachute effect (that is, if an object falls straight down). And that evidently benefits trees and other plants that need to disperse seeds some distance from the point of origin. Plants with flattened seedpods also take advantage of the falling-paper effect.
The research was funded by National Science Foundation, the U.S. Air Force Office of Scientific Research and the Packard Foundation.
Says the professor who does not use the falling-paper effect to grade student essays and forecast their future: "What is predictable is that as the autumn leaves tumble down, they drift in particular directions, depending on the way they turn. This may explain, Wang adds, "why you are getting the leaves from your neighbor."
Source: Cornell University
With great numbers come great responsibility!
Prof. Wang from TaM was my math teacher. Smart lady. She went crazy explaning the use of hyperbolic trig functions. At the time I had no idea what she was talking about, but now I see it actually has a use. Her other research is in the fields of insect flight. Looks like Calculus isn't useless after all.
Paper is affected by air as it falls! Astounding. ;-)
air currents? Dumbass scientists with nothing better to live for than proving evolution and why pieces of paper fall slowly. Why not cure cancer you retards?
You know, when they finally do find the cure for cancer through a process that involves falling paper, I bet someone is going to feel awfully silly.
It has little to do with air currents, I suppose, since this behavior is exhibited even in a room with no (detectable) wind.
This is just a rehash of an old study showing why open-faced peanut butter sandwiches always land face down.
Sheesh, evil *and* a jerk. -- Jade
Has anyone combined this with other falling-object problems?
For example, if one butters one side of the paper, will it still land face down, even if it's floating about?
Since cats fall on their feet, what happens if you wrap playing cards on each of their legs? Will their happy flight downwards be interrupted by randomly flying limbs?
What if you wrap the cat in a piece of paper that has been formed to make a Moebius strip, butter the other side of the animal, then tie it together to another cat? I suspect this may be the way to create time travel or a perpetual motion machine.
I hereby ask everyone to funnel funds towards this dynamic Cat, Toast, and Paper Research. I approximate we have about 4 years to prepare to salute our new Paper Machie Strawberry Jelly Cat Overlords.
Small potatoes make the steak look bigger.
I'm not sure that researchers from Theoritical and Applied Mechanics can do much for cancer research.
Remember, Civil Engineers make the targets, Mechanical Engineers (or TAM nerds) make the bombs.
I'd thought that if the page weren't straight up and down, you'd get lift on the leading edge, causing that edge to rise up, slowing the fall until it gets high enough to stall. When I RTFA, it said that the page's rotation was enough to change the direction from clean drop to a sideways motion. Go know.
Good, inexpensive web hosting
The article says that the slowing-down effect for paper-like objects is much larger than normal "parachuting" effect. I wonder if this could be used in some way for parachutes.
by calculating the motions of a scientific journal page in flight
... they still need to repeat the experiment with different types of journals; psychology, home decorating, sports and paranormal to be absolutely sure.
..and it was well behaved and obeyed the laws of physics. I want to see what happens when they repeat it with a bible page.
Paperweight - stop it going floating in the first place.
Due to lack of disk space this user has been discontinued
Physicists Finally Solve the Failing-Paper Problem
Oh, if only :~(
<mutter>back to studying I guess.</mutter>
A government is a body of people notably ungoverned - AC
I would guess the maths works for any flexible membrane moving in a fluid so it may well have extensive applications in medical engineering.
This seemingly simple problem like many other (more important problems like understanding air turbalance) is an exercise in solving the navier-stokes equation for a fixed set of boundary or initial conditions. The Navier-Stokes equation is the equation that describes the flow of fluids on the large scale. It is a non-linear partial differential equation and is in some cases extremely difficuilt to solve (There is a $1,000,000 prize for the answer to the question: Do smooth initial conditions always lead to smooth solutions?). This may not seem very significant but it is probably very difficuilt to solve.
Actually, this problem is important for aerodynamic theory. Items like airfoils, and spheres are well understood, but other shapes are confusing because of chaos. Understanding how paper falls is one step in understanding how different aerodynamical surfaces operate. The article states that falling paper is twice as effective at slowing down a falling object. Surely thats not minor concern. Additionally understanding the aerodynamical properties of low profile objects can help us understand aircraft (or spacecraft) failures.
This might be useful for future Rover missions (or, um Beagle missions). You'll lose accuracy, but at least you wouldn't hit the ground like a falling rock.
Logic, macros, and more
The researchers also found in the study that tumbling is slower than just parachuting down.
Could this information be used to redesign parachutes? Could a skydiver use some kind of tumbling mechanism instead of a traditional 'chute?
Granted, it might be hard to pack the thing in a backpack, though.
Notice the "Related Stories" section. It is blank. This doesn't relate to anything. Does that tell you something?
Finally, a possible answer to why Toast ALWAYS falls butter side down in uncontrolled experiments !
Of course, this still doesn't mean we can get a perpetual motion engine by strapping said toast to a cats back, but we can hope !
I see a new form of energy just round the corner, CatToastOnics !
A slashdotting - you get the stick first and then the carrot !
Sounds like they need to figure out the motions of falling big old heavy solid objects before they worry about this one.
Just two words for you: Dumbass Retard.
Thank you.
Logic, macros, and more
>>"This could help us understand basic mechanisms of how an insect flies, how leaves fall, or how fish swim," Pesavento said.
Hmmm... I always though that insects fly and fish swim by flapping the wings... and Newton came out with the Law of gravitation that explained how leaves fell long ago... but hey, who am I? not certainly a PHD to theorise such an abstract thought.
And physicists are supposed to do what about cancer? Please, let physicists do physics, and physicians do medicine!
Logic, macros, and more
A link to the paper can be found at the authors'homepage. Complex phyics models are already a part of Physics engines in most graphics rendering systems. Insect and Bird flight is a well studied problem in character animation.
And Aero engineers (like me) make the delivery systems.
Planetes
"One World, One Web, One Program" - Microsoft Promo Ad
"Ein Volk, Ein Reich, Ein Fuhrer" - Adolf Hitl
And it's another physorg dead-end. Rather than mirror it or anything, a little googling will find the original material. Here's The original spam-free press release and Professor Wang's home page with a full citation for the paper.
Plants with flattened seedpods also take advantage of the falling-paper effect.
A specific example of this is the sycamore seed. As a matter of fact, landing a helicopter without motor assistance is called "the sycamore landing". It utilizes the exact same theory these phycisists has explained. So - It's not the theory that's new - it's the level of detail.
Underholdning.info
Really now, besides being an old and tired joke, doesn't this apply to all thin and flat objects similar to paper? Isn't it precisely these jumps in abstract and basic understanding of our world that lead the way for good things, whether it's advancement of basic knowledge (some of which may be applied later) or a novel application of that knowledge? Curious investigation of our world is a necessary precursor to science, and it's absurd to suggest that these sorts of inquiries aren't valuable when the existence of science depends on them.
-Oobob
Sure a cure for cancer would be nice, but atleast I can use this to calculate how many of those leaves from my neighbor's damned tree are going to end up on my lawn.
Maybe now I can bill him for raking...
Brandon Petersen
Get Firefox!
what they say about first borns being the overacheievers is so true...
System.out.println(syynnapse.getSig());
It's a Farkism. Educate yourself. (mod parent down -1, Stupid)
ResidntGeek
They've problery already found the cure. Now they just try to calculate were it landed... Everything got an purpose...
For all you know...cancer may be nature's way of positive evolution by getting rid of weaker members.
So shut up, because mechanics students can't do shit about cancer either way.
I saw a presentation by Jane Wang about this work last year. She's also done a lot of work on the dynamics of insect flight which she considers to be a closely related problem to this one.
My only political goal is to see to it that no political party achieves its goals.
ROTFL!
This is the winner of the award "most interesting insightful funny joke on slashdot" ever.
The Internet is full. Go Away!!!
Lunar eclipses are boring.
This is my
Now they can make even better-looking animation movies!
-- Cheers!
Trolling? Dumbass a.c.'s with nothing better to live for than whining about peopl with actual jobs and careers. Why not cure cancer you retards?
I was thinking of converting to paganism, but where the hell can you find sacrificial virgins these days?
It's amazing how many basic problems were left behind in the multibillion race to find the latest useless particle.
It's not that understanding particle physics is not useful. What bugs me it that it was done at the cost of neglecting other equally important areas of physics.
Congratulations. Within the span of two words you have personally offended (along with the parent poster):
- people who can't speak
- donkeys
- mentally retarded people
In the future, I would kindly request that you try to be more politically correct and just say 'fuck you'.HTH. HAND.
?-|||-----x<*))))><
You are a useless piece of shit.
Always was, and always will be.
'fuck you' is offensive to people who have no or non-functional genitalia, you insensitive clod! That includes most of the slashdot editors, a large portion of the trolls, victims of ritual female genital mutilation, mules, and Barbie.
Sheesh, scientists having to turn to Hollywood for their inspiration ...
/me waving hands frantically in the air..
I know why it falls peanut butter side down!
OK, why?
The gods got a sense of humor, and are always dickin with us!
Phys Rev Lett. 1994 Sep 5;73(10):1372-1375. Related Articles, Links
_ 1
Behavior of a falling paper.
Tanabe Y, Kaneko K.
http://prola.aps.org/abstract/PRL/v73/i10/p1372
Researcher 1: We're going to lose funding if we don't put out some new studies... any ideas?
Researcher 2: But we don't have enough funding to finance any new studies!
Researcher 1: Well lets work with what we have. Get that box of stuff under my desk.
Researcher 2: It's just full of these stupid papers we've never looked at. *tosses said papers into air*
Both Researchers: Ahh hah!
If you're on the moon, where there is little or no atmosphere, they will fall straight down. Has anyone seen the video of the feather falling straight down without fluttering around at all?
Was it just me who got amused that Pesavento in Portuguese means Wind-weight?
:)
I wonder if Wang means somethign related.
-- SouNerd.com
The army has made deals with major defense contractors to provide soldiers with large pieces of paper to replace their now-obsolete parachutes.
This isn't fark. Go away.
And Electrical engineers (like me) make the flight systems.
Game Overdrive - Gaming News
...there still exist such things as hunger, disease, and others that would benefit from scientific research time. Why are we concerned with falling paper?
I know bad joke but I'm sorry I just couldn't resist :-)
Actually as silly as this paper seems it reminds me of Einstein's explanatation of Brownian Motion. Published the same year as his Special Relativity paper it was titled "On the Motion--Required by the Molecular Kinetic Theory of Heat--of Small Particles Suspended in a Stationary Liquid". I doubt this paper is as significant, but it may not be as trivial as it sounds when reported in laymans terms either.
These posts express my own personal views, not those of my employer
"Physicists Finally Solve the Falling-Paper Problem"
Step 1: Get rock.
Step 2: Put rock on top of paper.
Optional Step: Remove rock when access to paper is required.
(Patent Pending)
"There were a few surprises," Wang notes. "We found the flat paper rises on its own as it falls, which would not happen if the force due to air is similar to that on an airfoil. Instead, the force depends strongly on the coupling between the rotating and translational motions of the object."
Anyone who has ever thrown playing cards, frisbee, venetian blind bomerang (you have to be old enough to have had wooden venetian blinds as a kid) would not be surprised at the quoted 'surprise'.
Where can I read the report or the equations?
..because this deck of Yu-gi-oh cards is falling straight down.
Maybe this effect only happens at lower latitudes? Its 45N here.
Because physicists study physics.. not disease and hunger. Not to mention the fact that having a world where veryone is equal, fat and happy is not ideal. Happiness is a relative thing. A major component of happiness is knowing that some other poor soul has things worse than ourselves. There will ALWAYS be winners and losers. Quit being such a bleeding-heart and accept life for what it is. It's been working for a billion years or so. Don't think you know better. Sheeshh..
What is your penile percentile?
...and your wife makes you see a "special friend".
Huh?
And I'll do your mom!
I know this is America, but since when is folding toilet paper considered mathematics?
What are you doing for a better world today?
How about selling your computer and feed some children in nigeria with the money?
Would have the nice side-effect that we wouldnt have to hear your wise-ass remarks.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
In other words, you can learn to drive in a parking lot or on the autobahn, but while their are merits to either approach, a lot of us prefer the parking lot.
Too bad physicists squander all our valuable resources on useless gadgets like MRI's, CAT scanners, pacemakers, lasers and microscopes. I guess you would have been happier in the days before science pushed aside leeches and unwashed hands in standard medical practice.
Only by expanding our understanding of everything around us can we hope to make things better. All of the people saying that people shouldn't study fluid dynamics because it has no applications to cancer have a pretty narrow minded view. If people were asked to explain the immediate benefit of their research, the world would be a very different place.
You could be on to something professor.
Perhaps a precursory experiment is in order.
In India, it's long been known that, if a tiger
is wearing all your clothes and chasing your naked self around a tree, that upon attaining sufficient angular velocity, you may climb the tree and watch said tiger chase himself until he turns to butter.
Here in the West, we know that tigers are nothing more than large cats and that a falling cat will always land foot side down.
What we don't know is what will happen if we take two tigers, attire them with little green jackets and all, strap them back to back, and hurl them from the top of a tall building. In the interest of completeness and safety, this experiment should incorporate a bucket (for the butter), a furrier, a Chinese cook (who can also make pancakes), and two birds in a bush.
"Instead, the force depends strongly on the coupling between the rotating and translational motions of the object."
Though this is a lightweight scientific breakthough, this sentence made me laugh a bit. So we have to take other forces into consideration than gravity if an object moves upward? Who would have thought. Coupling of rotating and translational motions? Come on guys, what other movements did you expect?
> Why not cure cancer you retards?
The "retards" already have a cure for cancer. It's just that the cure carries with it a number of unpleasant side-effects. [I have witnesed this first-hand.]
Why you should be asking for is a "better" cure for cancer. One that doesn't make the patient extremely sick after each dose and doesn't cause the patient's hair to fall out.
-Scott
Interestingly, when scientists were making progress in cancer treatments, I asked a similar question of "cancer? Dumbass scientists with nothing better to live for than proving evolution and curing cancer? Why not solve the falling paper dilemma you retards?
Neil is that you? Yeah yeah, it's me... Neil...
Flaimbait..?! BAH! He's right. Disease is a driving force in evolution. Weed out the weak and make for a stronger species! Stop curing cancer now!
What is your penile percentile?
I think we may have a winner....
" Because physicists study physics.. not disease and hunger."
Not only is hunger not a physics problem, it's not a scientific problem either. We know the scientific solution to hunger: eating. Further, we have plenty of food. If some individual is short of food, it is a political/economic problem. The classic example would be starvation in Ethiopia in the 80s: initial food donations never made it to the starving people because the government was *trying* to starve them. Donors had to bypass the Ethiopian government and deliver food directly to the starving to be effective.
Two things:
1) like wambaugh said, physicists contribute towards the improvement of medical care as it is
2) simply throwing more money and people at a problem doesn't necessarily get it solved any quicker; 9 women can't have a baby in one month
It's official. Most of you are morons.
OTOH, curing cancer is a pseudoscientific attempt to interfere with the clear intention of the divine. In fact, by curing cancer, and going beyond the understanding of the divine to the prideful attempt to compete with the divine, we are surely condemning ourselves to eternal suffering. All to prevent a few years of suffering in this life. How gauche.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
You're right- physicists have made contributions to medicine- i was in no way implying that physicists cannot- but the original poster was implying that the research wasn't worth conducting because it didn't have medical applications.
Logic, macros, and more
Still no cure for cancer.
Well, get back to your research then. I'm sure you'll crack that one yet.
Yes, you're quite right, except that 'fuck you' is mysogynist- at least in the image it evokes...
Logic, macros, and more
Leeches are being used today to help prevent clotting after a patient has had an extremity such as a finger or toe re-attached.
Pesavento, in portuguese, means "weighs wind".
Boooring ... learn to joke, dude.
"If we took the money that the physicists receive"
/. in *your* free time and get to work on that cure for cancer.
There is no evidence that the physicist and the mathematician received any extra money here. They probably are both lecturers (someone already posted about having the mathematician for a class). They may well be doing the research part in their free time. If you have a problem with that, maybe you should stop reading
For that matter, why aren't you criticizing smokers? Not only do they make themselves more likely to get cancer, they also take frequent breaks to smoke. I wouldn't be at all surprised to find out that smoke breaks take more time than the sum total of cancer research. Eliminating smoking would free up physicians who are currently working on cancer to do research and provide more time for non-physicians to do maid work, etc. to free up physicians to concentrate on their cancer research.
The results of physics research also free up people by cutting costs in other areas. If we still had a hunter/gatherer economy, we wouldn't be able to waste people on non-essentials like medicine, much less medical *research*. Not to mention the point that the advances in understanding chaotic systems may be applicable in areas other than physics (e.g. medicine). While statistical analysis (from mathematics!) suggests possible causes of cancer, we still don't understand what actually happens.
How much physics could a physician physic if a physician were physically a physicist?
its been driving me crazy and distracting me from my much less important work for a cancer cure.
You wont get any solace here for your feeble mind. If you're going to be stuck in a cube for the rest of your life as a code monkey becuase you couldn't handle the simple task of getting a good SAT score or taking a few AP classes, then tough shit.
I served in an Army psychological warfare unit in Viet Nam that had produced and delivered, by 1970, enough leaflets to cover the entire country of South Viet Nam to a depth of more than 6 inches. Delivery was divided between Army helicopters and Air Force planes.
It's not surprising to see the Air Force funding further study on this subject.
Darn, I really wanted to see a zero g cat :P
There are a zillion things to sort out before worrying about this one...
It's just one of those junk research papers you get sometimes. Universities will fund anything if you dress it up in enough language, like the guy who got a half million dollar grant for researching "the effect of alchohol on the human body" then spent the next year getting very very drunk.
Why are you posting on slashdot instead of searching for the cure to cancer?
Did they put butter on one side?
And Oil executives choose the targets.
With any luck it will fly around a bit, swoopishly. The circulation caused by the back-spin generates lift, same as airfoil-shape induced circulation (faster airflow on top, slower on the bottom) as per that well known Kutta-Joukowski formula s * b * mu * gamma.
Which is apropos of nothing. Also, the Navier-Stokes equations can't be solved around a singularity like the edge without a simplification which usually takes the form of an assumed boundary layer of some sort (probably laminar at these Reynolds numbers which makes it a lot easier). Also, N-S is initial-condition sensitive because the solutions have bad scale missmatch, so you'll want to use your duodecaduple precision math library.
I didn't really understand from the blurb if they were talking about bendy things like paper pages. That would make it a fluid-structural coupled problem. Very tricky. The hardest part of that is getting the fluids guys to return the structures guys' phone calls.
Equine Mammals Are Considerably Smaller
What if you wrap the cat in a piece of paper that has been formed to make a Moebius strip, butter the other side of the animal, then tie it together to another cat? I suspect this may be the way to create time travel or a perpetual motion machine.
you can use My neighbors cat and I'll give you t the peanut butter if you want to try it
ps don't return the cat
Diplomacy is the art of saying "Nice doggie" until you can find a rock. Will Rogers
And some other attention-starved geek who didn't get enough hugs from mommy as a child (me) will also pipe up in this thread about his job.
The parents is making a joke, that is the actual reason toast lands buttered side up.
The buttered side is heavier, so it starts to flip. But due to the height of the avg table, it doesn't have time to complete a full rotation, so it lands on the buttered side.
If you were to drop it from say the top a fridge, it would most likely land buttered side up.
(or, um Beagle missions)
:)
You're just asking for "flamebait" points.
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
ps. mod me as troll
_ In Egypt Networks: Network Solutions with a Twist
Thus, by stopping cancer, you're actually -helping- evolution by ensuring that only the useful and non-fatal mutations continue into the next generation.
I know, I know. IHBT. IHL. HAND.
120 character sigs suck. Make it 250.
Lunar Eclipses hapen all the time... well sort of, But falling paper!...well that happens all the time too but........ ...She folded it 12 times and shes cute looking and she got an A without having to...do any...thing. test test, is this thing on?, can you hear me up the back? Try the veal. I'm here all week, thank you, your beautiful.
"Persistance is Fertile" - Me. I can quote myself if I want to.
How about determining where a ball is going to fall. is that crazy? then think about Roulette.
"Persistance is Fertile" - Me. I can quote myself if I want to.
But since when is an 'in soviet russia' joke a troll?
I guess a couple of my freaks got some mod points.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
Because some genius came up with a simple circular one-way association involving three items, to be propagated universally as a fair way of deciding the winner between opponents.
Actually, evolution weed out the unfit, and make fit species to survive. The problem is the "fitness".
The "fitness" of cancer disease is death for all. I don't know about you, but I wouldn't want that "fitness" function in the first place.
Do you remember the nature program where there are drought in a land and animals fight and eat each other to survive, only to die off one by one, where none is left?
That is the true evolution with disease. Disease is not here to let us be stronger, it is here to kill us all. Why would virus evolve, making the specific "fitness" change? Because the "general fitness" is to destroy.
Actually, curing cancer is a divine purpose for us to better understand some part of the divine design of life.
Many of the discoveries in medicine made us wonder more about the miracles of life.
Hunger is not a problem, it is a proper body function notifying the body that it's time to eat. Starvation is not a modern scientific problem, it is a political problem restricted to tyrannies.
Contribute to civilization: ari.aynrand.org/donate
You have a material for at least 4 patents in your post. Quick!
Do you have any idea how complicated your circulatory system is?
Those are easy....
The psychology journal page will behave erratically as it falls.
The home-decorating page will form into a lovely table centerpiece as it falls.
The sports page will arc through the air and land in a round waste-basket making a swoosh sound as it does so.
The paranormal journal page will either vanish in midflight or will hover with no visible means of support for a short time before it suddenly accellerates horizontaly making several sharp course changes before disappearing from sight.
McFly777
- - -
"What do people mean when they say the computer went down on them?" -Marilyn Pittman
Funnily enough, this exact same behaviour was exhibited by a model of the Titanic when dropped into a water tank to simulate her journey to the bottom of the ocean. Maybe the equations that are described in this paper also apply to ships of several thousand tons too?
My web domain.
Hi, I looked through posts and didn't see any discussion of this:
When I was a grad student in physics back in the late '90s, I remember seeing some papers posted on a bulletin board about a study of coins falling in water. This system, and the system of pages falling in air clearly have some similarities that, of course, the popular press isn't going to bother pointing out.
But, fyi, the falling paper problem is still more complicated, since the air affects not only the motion of the paper, but its shape as well.
One thing that wasn't clear from the article, however, were what sort of computational techniques they are using. Solving Navier-Stokes is extremely difficult, and subject to all kinds of artifacts of the computational setup (e.g. discretization scale, location of boundary conditions,, etc..) Not that I'm doubting the editors of PRL, just that it would have been nice to see a bit more detail.
Why not prevent cancer instead of worrying about curing it?
if while reading this article you picked up a piece of paper and dropped it beside your desk to test out this effect, even though you've seen it a million times.