Slashdot Mirror
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.
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.
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
And physicists are supposed to do what about cancer? Please, let physicists do physics, and physicians do medicine!
Logic, macros, and more
This effect isn't completely new (at least I don't think so). The space shuttles would roll and yaw back and forth a few degrees on reentry to slow down faster. If you ignore the horizontal speed of the spacecraft, this is somewhat similar to a piece of paper falling (but obviously more controlled--sometimes). Seems to me that the two items might be conceptually related. That being the case, I wouldn't be suprised if we saw a new style of atmospheric slowdown in future space probes.
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
It's called a hand glider. Unfortunatly, it cannot be packed into a backpack and deployed after falling 1,000 feet out of a plane.
Kites do not work well as parachutes.
It lands on the butter side, since it has only one side.
Not quite... sycamore seeds fall with a twirling motion, much like a helicopter rotor. But autorotation (the proper name for that maneuver) doesn't rely on the physics they're talking about at all - heli blades are shaped such that the movement of air around the blades forces them to rotate, and the rotation generates lift. Not enough to keep the copter flying unpowered, but enough to prevent it from falling straight to the ground. The motion in the article is definitely not related to rigid airfoils with a fixed axis of rotation - the motion described in this article is that of a thin unconstrained flexible flat sheet.
Some people have made comments about using tumbling motion to build better parachutes - it probably wouldn't work for a parachute because a parachute requires some attachment of the load to the sheet, and that attachment will prevent the tumbling motion from happening, both by preventing the tumbling and also by loading specific points on the sheet instead of having the load effectively equally distributed.
---
Mod me down, you fucking twits. Go ahead. I dare you.
(I read with sigs off.)
I don't know why Slashdot doesn't do this more often)
Well, being the curious guy that I am, I tried both the original link and your coral link at the same time. (well, pretty close.)
Funny thing is, the original link opened, slowly, but much quicker than the coral link.
So, to get back to your question:
Q: Why don't we coral?
A: Because it's as effective as pigeonrank.
I think I need a new sig here.
It doesn't necessarily follow that this problem was solved now because of lack of funding. Rather, I'd say it's more likely that it means that the difficulty of the two problems is about equal.
...), and there's a lot of consideration being given to tricks to solve Navier-Stokes (and other more complicated models that include the fluid being conducting or charged, or in some GR framework). So it's reasonable to expect that with new algorithms popping up, and refinements on the old ones, suddenly some intractable problems become accessible.
We still can't solve the three-body problem analytically (except for some special cases), and thats been around for 400 years. And its not for lack of trying.
However, only within the last 50 years or so could we make approximations to the solution that work for long enough to be interesting and give insight into the problem. It's the availability of computers that makes it possible.
Fluid dynamics is a hot topic in astrophysics right now (simulating stars, gravitational collapse of nebulae, accretion discs and jets around blackholes,
So I don't think that this was a 'problem left behind', as much as a problem which is just now becoming solvable. (Part of) the reason we spend billions on particle physics and not on this sort of problem is that the minimal 'thing' to advance the science in particle physics costs billions, whereas nowadays one can run fairly large-scale simulations (of classical systems) on a $2000 laptop: the biggest cost for those problems is hiring students/postdocs/professors to work on them. So really there what funding enables is diversity in the problems being tackled (how many laptops can you afford? how many grad students?), rather than the speed at which any one particular problem is solved.
Of course, this isn't true of some problems (quantum systems) which you really do need 1000 cutting edge systems all networked together to solve even a simple problem. In that case, you're going to have to be willing to throw a fair amount of money at the problem before you can see any progress.
I dont' know... I'd say that it's the re-thickening process at step 3 that's the problem...
Falling paper doesn't have a huge gyroscopic effect, like a frisbee or boomerang does. So it's not obvious that the rotational motion will couple strongly to the translational motion.
describe and find solutions to motion problems
maximize or minimize functions (e.g. optimizing the cost of producing something)
talk about any relationship between two variables that's close to zero
straighten out complicated functions to handle them with computers (e.g. Taylor-series)
I could go on and on about that.. Come on!
This effect isn't completely new (at least I don't think so).
:)
Absolutely correct. The effect has been around since the dawn of time.
The theories presented are of course a more recent vintage...