Solving the Great Shower Curtain Mystery 244
parvati writes: "The New York Times is reporting that a UMass professor, Dr. David Schmidt, used computer modeling to figure out why shower curtains suck inward during showers. He designed an image of his mother-in-law's shower, filled it with 50,000 3D velocity/pressure sensors, and turned on the virtual water. 1.5 trillion calculations later, he found that drag on the falling water drops creates a mini-hurricance, producing a low-pressure 'eye' that attracts the shower curtain."
Re:Moral of the story (Score:1)
By continuously monitoring the position of the shower curtain, they could detect the inward bowing of the curtain and then compensate by evacuating an appropriate amount of air from the bathroom.
This would keep things cheap for customer by allowing them to keep their current curtains.
Re:Bernouli's (sp) Theory (Score:1)
And what's the deal with calling yourself Dirac?
You know that the quantum unit of work (i.e the smallest amount of work it's possible to do without doing nothing) is the Dirac? It's defined as the amount of useful research Dirac published per year.
Re:Great! (Score:1)
Re:My own data (Score:4)
Really, I don't mean to flame, but just because something is old, dirty, used, etc. dosen't mean that it is not worth putting a little elbow grease into. The environment is turning into shit. It may be nice and shiny where you are, but there are places (like where that shower curtian would go) that absolutely suck. It all has to go somewhere.
I'm not saying keep everything! Of course, there are practicality reasons -- it may not be practical to clean the curtain if the chemicals to do so cost more than replacing it, or will potentially cause more environmental damage than just tossing the curtian.
Then there is the lack of education. You may not know how to clean the shower curtian. I can't tell you how many times I have found electronics (tv's, computers, a few SGI's from LockheedMartin, you know the standard faire...) that were in some simple state of disrepair. I changed the plug and coord on a 32" tele that I found by my dumpster in the alley; otherwise it was in supreme condition. It works excelent! I assume they left it there because they either didn't have the time to fix it, or they didn't know how. This was an $800 dollar tv in it's day. Unless someone is so rich to spend an hour (as if) trying to fix it, it just seems unlikely.
$800/hour! It makes me realize that fix-it guys can make it good if they market right.
That said, I am an american. But as a whole, I really hate america for their lazy-throw_away-buy_a_new_one-McCulture attitude, and unthoughtfulness. They then go and prosecute anyone who does not agree with their opinion. I may be misjudging you, but as a whole, america agrees with a hearty "Smack my fro!"
Hampton Inns (Score:1)
Re:My own data (Score:1)
Your bathroom only costs $1.99 to replace?
Interesting contribution (Score:2)
Re:Finally! A believable answer (Score:2)
Or, more to the point, try blowing into an open plastic bag. The sides will still tend to come together.
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Re:Moral of the story (simple solution) (Score:1)
I guess I'm odd - at age 17 I never had an urge to just trash something. Though there have been times lately (many moons later) where I have really felt like walking around with a 30 pound sledge!
Moral of the story (Score:5)
Better yet, the plexiglass doors...that'd be one shower to make them bow in!
Re:Million dollar funding superchallenge! (Score:1)
Because state DMV's never cared to properly adjust the contrast on their printing equipment.
Polaroid makes ID making systems which correct themselves for those kinda factors automagically...they seem to create ok pictures (see this [counterfeitlibrary.com], in particular check out CO, DC and WV.)
Consider moving to NJ or VT--they still issue non-photo licenses.
Re:Causes (Score:1)
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Thanks for this information (Score:2)
I can finally get to sleep tonight.
Wait. Does the refrigerator light stay on after I shut the door? Oh man, I hope somebody submits a link answering that question next.
Re:Great! (Score:1)
Humorous anecdote: I had a similar situation in my 2nd year calculus course at the University of Wisconsin - Madison. It was a lecture about 5 hours prior to an exam and a student asked if a certain type of problem would be on the exam. The professor said no, but it was still important to know, and spent 10 minutes explaining how to do that type of problem. The student replied "thanks, but I just wanted to know if it was on the exam or not." This pissed the professor off so much that he altered the test to include that type of problem.
Re:Finally! A believable answer - NOT (Score:2)
While certain military and stunt aircraft can fly upside down, they are probably neither as stable nor as effecient. They rely as much on powerful engines as they do on lift from the wings.
Chris Cothrun
Curator of Chaos
Re:It's not thermal? (Score:2)
Re:Sci Am - Amateur Scientist (Score:1)
Re:Finally! A believable answer (Score:1)
Re:Why would he want to do that? (Score:2)
Re:Registration-free link (Score:5)
Cut to the chase already, Slashdot. Beg, borrow or buy a damned registered partner account with the NYTimes and be done with it!
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World's biggest shower stall (Score:3)
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Re:Finally! A believable answer (Score:2)
This is getting waaaay off topic...
There's no 'reverse lift' when you're flying upside down.
A plane's wing is optimized to provide lift and reduce drag when it's right-side up. Just because wings are optimized, it doesn't mean that other things won't work.
You can, for example, make a regular plane with flat boards as wings. You have to tilt them up at a high angle of attack, which greatly increases drag. With sufficient power, you'll get off the ground.
When flying inverted, it's the same sort of thing. You have to increase the angle of attack (as you mention) and you'll get lift, even if you're using the wing "wrong". Takes more power, causes more drag, but it will work.
Re:Million dollar funding superchallenge! (Score:2)
Re:If there's one thing nerdier... (Score:2)
Yes, guilty as charged. I'm just saying. When you say, "News for Nerds", I certainly can't argue. But how this constitutes "Stuff that matters.", I certainly can't imagine. Nevertheless...
I'm pretty sure that the comma in there implies boolean OR. "News for nerds" is true, thus the whole statement is true. ;) I've got glass-like doors on my shower, so this doesn't really "matter" to me either...
Re:Million dollar funding superchallenge! (Score:2)
Re:Could prove useful (Score:4)
Re:Great! (Score:2)
Re:My own data (Score:2)
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I was just wondering that (Score:2)
A mini-hurricane.. so does this mean that given an arbitrarily large shower and curtain, you could control the weather? My plan to take over the world is coming together at last..
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Re:Finally! A believable answer (Score:2)
Sorry guys, it's to do with rotation over the wing sections. How do we think a spinning cricket/golf ball generates lift? The 'blowing air downwards' theory is all well and good, but in practice the air gets blown downwards as a by-product of what's really going on.
If you're really up for it, "Aero-Hydrodynamics of sailing" by C.A.Marchaj is the book to get.
Dave
Re:Finally! A believable answer (Score:2)
As far as planes flying upside-down, the angle of attack is critical in determining the magnitude and direction of the lift vector. That's why you raise the nose of an airplane to make it go up...increasing the angle of attack moves the stagnation point of the free stream down on the airfoil, increasing the distance the air must travel over the top of the air foil.
Curvature is not necessary to generate lift. Flat plates (like your hand out the car window, or the balsa wood wing on your dime-store glider) generate lift due only to their angle of attack.
Re:Bernoulli's principle (Score:2)
A symmetrical airfoil with zero angle of attack produces no lift. Think about the rudder on an airplane or a ship. However, when the AOA changes, the airfoil is no longer symmetrical with respect to the airflow.
My own data (Score:5)
Idiot (Score:2)
Re:Finally! A believable answer (Score:2)
Re:It's not thermal? (Score:2)
to see for yourself, take a hot shower with
both sides of the curtain sealed to the wall
with water in a cool room. for obvious
reasons this works better in winter...
now watch how the curtain sucks inward.
then separate the curtain from both walls--
12 inches on the side farther from the shower
head and 6 inches on the side closer.
it no longer sucks in because the convection
currents have more area in that plane through
which to travel.
just my two cents...
Re:Million dollar funding superchallenge! (Score:3)
question 2. you're ugly
question 3. you're a dork
see, I answered your questions and I don't even know you. Good luck finding anyone willing to shell out grant money for those.
Could prove useful (Score:2)
Okay, so it sounds silly. But who's to say that something profound won't come of this! I say more power to people doing esoteric research.
Re:Finally! A believable answer (Score:2)
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Re:Finally! A believable answer (Score:2)
If there's one thing nerdier... (Score:2)
Yes, guilty as charged. I'm just saying. When you say, "News for Nerds", I certainly can't argue. But how this constitutes "Stuff that matters.", I certainly can't imagine. Nevertheless...
"LET'S GET READY TO RUMMMMMMMMMMMMBLE!"
Re:Finally! A believable answer (Score:2)
Since a shower curtain is considerably lighter than an airplane, I don't see why the water would need to move that fast in order to bring the shower curtain in. I still think the Bernoulli principle could be sufficient to explain the shower curtain problem.
Re:My own data (Score:2)
Wasn't the whole point of this article that it already sucks where shower curtains are?
Re:Finally! A believable answer (Score:2)
Re:Finally! A believable answer (Score:3)
I've never found this believable, and thought a recent scientific american article addressed the problem well. As I understand it the traditional explanation goes like 'the top of the wind has more curvature and so the air has to travel further when the flow isn't turbulent so it has to be moving faster and so by Bernoulli's principle implies that the pressure above the wing is lower than the pressure below the wing so there is a net force upwards'.
Where are Newton's laws of motion in this picture? And how does it explain airplanes successfully flying upside down? A more plausible answer(to me anyway) involves the angle of attack the wing makes. Air is forced downwards and by conservation of momentum something must be forced upwards - the plane. The curvature of the wing is necessary to maintain non-turbulent flow without which there wouldn't be a regular stream of air flowing downwards. Increasing the angle of attack too much causes this to break down.
I find this explanation intuitive and more in accord with the rest of my knowledge of physics, but I'd love to hear objections
The laser for instance? (Score:2)
Phillip.
What are we going to do tonight, Brain? (Score:5)
Re:Bernoulli's principle (Score:2)
Basically it refutes the way bernoulli's principle is taught(according to my recollection) by simply stating that there is no scientific reason why the air travelling on top would have to arrive at the end of the wing at the same time as air on bottom.
As a matter of fact they don't arrive simultanously although top still travels faster. The real reason planes stay up is due to the tendency of fluids(air counts) to stick to surfaces. Basically air travelling on top of the wing sticks to the wing and, as it is curved, is directed downwards. According to newtons laws this force has to be countered, and it is, by what we experience as lift. So as long as airflow around the wing has a downward component there is lift.
Bernoulli's law, however, does work good enough that it can be used as an approximation..
Finally! A believable answer (Score:5)
First a quick summary (apologies to those who read the article). Historically the billowing shower-curtain theorists have been divided into two camps:
- Those who appealed to the chimney effect - hot air rising within the shower causes cool air to come in from below. This hypothesis can be readily defeated by taking a cold shower and observing that the curtain billows nonetheless.
- Those who appealed to the Bernoulli principle - decreased pressure exerted by air in motion - the same physics that allows airplanes to fly and causes two sheets of paper to stick together when you blow between them (try it!). This hypothesis also seemed a bit shaky since (a) the air in a shower never seems to move that fast; and (b) there's a potential confusion of cause and effect going on here (for the shower curtain to billow, clearly something must be happening with the air pressure...).
Now comes David Schmidt to demonstrate that both of these camps are wrong (in this he and Cecil agree). His theory instead focuses on the deceleration of the water droplets by the air producing a cyclone effect within the shower. This theory is similar to, but distinct from, the ``entrainment'' theory that Cecil put forward so many years ago. And to me, significantly more believable.The same dynamics that causes hurricanes, right there in our very bathrooms! Score one for Schmidt and his finite element approach to a classic problem.
-Renard
Re:Registration-free link (Score:2)
Re:Bernouli's (sp) Theory (Score:3)
What you describe is NOT the cause of the movement, as determined by Dr. Schmidt. He clearly states that the motion results from the water droplets giving up energy to the air as drag occurs. Effectively even the cold water is heating the air due not to temperature but because of its slowing velocity. (lots of drops=lots of surface area to volume=lots of drag)
The article justs states that (something magic happens, and then) you have a miniature hurricane. Probably this is due to temperature differentials in the system, in the same way that weather is created in the "real world."
It really isn't overkill. It's a much more subtle problem than your comment indicates.
You should have shown that sooner... (Score:2)
Why would he want to do that? (Score:5)
Re:Great! (how it is useful - example) (Score:2)
Well, To address the poster to whom you were replying to:
Fuel economy - the efficiency of the combustion process (in an internal combustion engine) is directly proportional to the level of homogeneity [m-w.com] of the gas/air charge in the cylinders at the time of combustion (gas isn't actually fuel until you mix it homogenously with air).
Atomization of the gasoline is very important but simply atomizing it isn't good enough in many cases. New research has led to "direct injection" which places the fuel injector in the combustion chamber like a spark plug instead of on the other side of the intake valves. I believe Seat [seat.co.uk] (an Audi/VW subsidiary) has introduced one of the worlds first direct injection engines which uses gasoline injection at a pressure of 1450psi (normal cars use under 50psi)! At these pressures, things like mini hurricanes become very important to understanding exactly what is going on in the combustion chamber.
Thinkaboutit
Now I know... (Score:2)
Re:Bernouli's (sp) Theory (Score:2)
I agree that seems like overkill... One's physical common sense easily answer's this problem, to a first approximation of course. Think of the stream of water pushing the surrounding air downwards. This creates a region of lower pressure compared to the air outside of the shower curtain. Alas, the curtain would move towards the area of lower pressure.
Of course, this just explains the large, global effect. More interesting (and complicated) stuff occurs, such as these vortices the author describes, but the overall effect is pretty simple to undertsand.
Paul
Re:That's cool! (Score:3)
The pursuit of knowledge.
There is yet 3 stages of science.
Observation.
Discovery.
Technology.
Ask any geek, the more "sexy" stage of science is the last one, the stage where that we can lay our hands on it and turn into something usefully and productive. Yet the first 2 stages of science are seen as a "waste of time" or sometimes even "worthless". Hardly NOT so! You can have this sexy technology without the other two!
The guy in the above article did both 1 and 2 for us, it is our turn to make 3 happen. What could we use this for? Oh I don't know, say find a way to better predict when a hurricane is coming? Now that would be "sexy" technology that you would see on the 6:00 news.
That is not his job, he did 1 and 2 and did it very well if I might add, very detailed and very though.
The next guy that says "this guy has way to much time on his hand" really needs to think about it and really ask himself if he is in it for the "geek" or the "glory"
If the "glory" is what you are into that is fine, but please do give up respect to the guy in the above article that did all the "geek" for you.
Re:Could prove useful (Score:2)
Re:Finally! A believable answer (Score:3)
You're trying too hard here, why can't you both be right? Planes that fly upside down do not do so indefinately, and require a greater amount of thrust and angle of attack to overcome gravity and 'reverse lift' than an aircraft in normal flight. They also are incapable of maintaining a constant altitude during inverted flight, with few exceptions (trust me, I used to fly stunt planes, it's not as simple as it appears).
Basically, when inverted, the angle of attack is changed such that the 'reverse lift' (downward force generated by pressure differential) is minimized as much as possible, at the same time allowing some thrust to be converted to lift (by pointing the prop/jet output slightly down). This is basically the the 'kite' type of flight that you refer to.
Now, about those exceptions - aircraft capable of producing enough thrust to overcome gravity without the help of lift are often known as rockets, or in some cases military aircraft. Take a Mig27, with ~40,000lbs of thrust and wighing only ~30,000lbs, the wings are almost superflous, however they still remain, primarily as control surfaces, and efficiency aids (fuel goes fast when producing enough thrust to throw a 20 ton mass directly skyward).
I know it seems a tad illogical at first, but get a good hands-on book on flying, and try some of the experiments, you'll be amazed at what is proveable....
How to avoid being attacked in the shower. (Score:3)
Quality of Slashdot Readers (Score:5)
-Elentar
Re:Bernouli's (sp) Theory (Score:2)
Re:It's not thermal? (Score:2)
You, my friend, need to take a cold shower.
No, really. As the article says, the curtain still sucks inwards during cold showers.
Timely article! (Score:3)
This is just in time, since I'm currently staying with my mother-in-law while my house is being remodeled, and she has a particularly irritating shower curtain!
Hey, I've been critical of Slashdot's editorial policies in the past, but here is NEWS I CAN USE!!!
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Re:Could prove useful (Score:2)
Perhaps it could be used as a giant air conditioning unit. Of course, it'd probably draw a lot more power than a straight A/C box...
Re:Million dollar funding superchallenge! (Score:3)
What if this isn't true? I always assumed the shower curtain thing was heat conduction, and I was wrong.
Try this:
<ALTERNATE HYPOTHESIS>
The answering machine voice dorkification effect is caused by a neural association/feedback change. When you speak, your brain is not only hearing the sounds you make, but is also sending commands to your vocal apparatus instructing it to make those sounds. The correlation between hearing and speech center activity results in a difference in perception from just hearing alone.
</ALTERNATE HYPOTHESIS>
Weird you say? There's even a precedent for my idea. When you move your eyes, images sweep across them at hundreds of degrees per second - but the world doesn't look like it's moving to you. But if you look at a screen, hold your eyes still, and sweep images at those rates everything looks like it's moving. Why? Because when you move your eye, your brain takes a copy of the eye-motion commands and subtracts that motion from what the eye really sees, resulting in a perception that the world didn't move.
I admit, it's pretty far-fetched and I'm still inclined to believe the eustachian tube hypothesis, but the truth is we don't know unless someone's actually done the science to tell.
Research like this is great because it replaces supposition with real knowledge. Three cheers to this shower dude.
The next step... (Score:4)
Re:That's cool! (Score:3)
1) Everyone ignores it
2) Everyone attacks it
3) Everyone claims it is obvious
* Blatantly plagiarized from some quantum physicist whose name I can't recall, probably Wheeler.
Another Registration-free link (Score:2)
-Mynn the Museless
Re:Quality of Slashdot Readers (Score:2)
Or (d) Many slashdot readers are trying to get their two cents in before they get buried way down at comment #932 or something.
Such is the path to karma whoring.... Even Taco suggests posting early to increase karma.
Perhaps there should be some kind of time delay between introducing the article and allowing comments?
Re:My own data (Score:3)
My own research suggests that the likelyhood of the shower curtain being attracted to your skin is directly proportional to the amout of scum on it.
Here's a neat trick: try CLEANING your shower curtain.
After that, try the same cleaning trick on the rest of your bathroom.
Re:Great! (Score:5)
Now I can die happy knowing that shower curtains get sucked inward due to a small hurricane. I love science! We could be spending research time finding a way to get 500 miles to a gallon instead of worrying about showers.
Think of it as an indirect approach. For example, I was reading somewhere (cannot recall the source, but it was some magazine) about a scientist who decided to figure out why it was that coffee spills always dried with a dark ring around the outside. A whole lot of research later, science now knows a lot more about how molecules interact in fluids, which has led to practical applications such as (among many others that I cannot remember) fast-drying paint.
Many people make the same argument you're making about fields like pure mathematics -- the research doesn't always have any immediate practical value. But the knowledge often makes itself valuable in everyday life in unanticipated ways. How do you really know if a particular scientific "discovery" is useful unless you know what that discovery is in advance?
It's a disturbing trend nowadays that believes research time should only be spent on immediately practical applications. The pursuit of pure knowledge, or even simple curiousity, is increasingly pushed to the side. Yes, research is time-consuming and often expensive, but to solely measure the value of attaining knowledge based on its immediately foreseeable applications is (IMO) somewhat short-sighted.
Now I admit, I have no idea how knowing that a shower creates a small huricane will become personally useful to me. But that does not mean that some aspect of this will not become useful in the future.
Bernouli's (sp) Theory (Score:2)
-Hyperbolix
The title was correct. (Score:2)
Registration-free link (Score:4)
Re:My own data (Score:2)
Hell, why would you spend $1.99 on a shower curtain when you can eat for two weeks on that?
IBM had PL/1, with syntax worse than JOSS,
Re:OT: NYTimes (Score:2)
Trolls throughout history:
Anybody else notice this? (Score:3)
Second, I think it's pretty obvious - this guy is definitely geek material. I mean, come on - crunching a 1.5 trillion calculation program over the span of two weeks on your free time? How many of us would love to have an excuse to do something like that?
Honestly, I wouldn't be surprised if he reads Slashdot :)
-Karl /dos]# file msdos.sys
-------------
[root@kgutwin
Grants (Score:2)
Re:You should have shown that sooner... (Score:2)
___
Re:Million dollar funding superchallenge! (Score:2)
Re:My own data (Score:2)
BTW, I'm not American, I'm Canadian. So there
Re:My own data (Score:4)
Frank Lloyd Wright beat you to it (Score:3)
Fallingwater [wpconline.org]
Built in the '50s. Widely regarded as one of the most reconized private homes in America. (Now a museum, of course, but originally a residence.)
Butterfly Effect (Score:3)
Re:Interesting i i always thought that (Score:2)
Re:Great! (Score:2)
Re:Great! (Score:2)
If you gain advanced knowledge of someone coming to get you, you can prepare for their arrival.
Though it may not change the outcome, you can take some of them with you. That IS power.
Re:Great! (Score:2)
My intent was to point to a flawed attitude that some people have towards education. You are in that classroom to learn, for the sake of learning.
Re:Great! (Score:3)
You make a very valid point. One thing that has always burned me up, from my 1-12 grade years was when some mindless mundane would ask "Is this going to be on the test?" and if the answer was no they'd veg out and not learn what was to come.
For example, in and of itself it does no good for the ordinary person wo understand additive/subtractive properties of color when it comes to light/pigments however if you do know a little about them, it can help you to adjust the tint on your TV or adjust the color balance on your computer.
Trying to figure out which genetic traits were dominant/recessive in pea plants may have seemed like wasted research at the time, however that research was the foundation for later research that may (and probably will) lead to cures for diseases ranging from down's syndrom to cancer.
To quote the game company Midway, "There is no knowledge that is not power".
Re:What are we going to do tonight, Brain? (Score:4)
That's almost true, actually (Score:2)
It's a spinoff (Score:2)
Every little bit... (Score:2)
Perhaps... (Score:2)
Answers: (Score:4)
Driver's liscence photos always turn out bat because the DMV cares not a whit about how you look, so they don't bother with the higher-end cameras or even decent lighting that professional photographers use. Also, the photo is generally taken shortly after the driving exam, which tends to stress a person, effecting their appearence. Finally, few people bother to wear a nice shirt or whatever to make themselves look nicer in the photo.
People generally sound like dorks on answering machines because the sound quality on playback is usually poor, and strips most enotional nuances from speech. Thus, the recording sounds flat and "dorky". In addition, people are generally not used to giving monologues. When I talk, someone next to me usually gives a response, even if it's just "Shut up, Ethan". It's disconcerting to be prepared to speak with a person, and suddenly have to give all the information you intended to provide without any of the feedback you would have in a normal conversation. If you're calling to discuss, say, dinner plans, the other person you're calling can't ask for any clarifications (where are we eating? Which road should I take? Is it a formal dinner?) You need to provide all that information at once, and the added strain and performance anxiety leads to the normal verbal respones to stress. These include stammering, "null data" sounds such as "uh", "um", and mumbling. All of these sound "dorky". Of course, one could simply say "I'll call back later," but circumstances may not permit that, or you may simply feel pressured to provide the data to the machine then and there.
Of course, it is entirely possible that the reason you in particular sound dorky on answering machines, Nathdot, is that you are in fact a dork. I have not data to support that conclusion one way or the other, but it must be considered. After all, the simplest explanation is usually the correct one, as Occam's Razor asserts.
As for your plans to model and study these questions on supercomputers, well, more power to you! One problem, however: since you are studying absolutes (soda dribbles NEVER come out, liscense photos ALWAYS look bad, and you ALWAYS sound like a dork...on answering machines), how will you model each and every existing soda can, DMV camera, and answering machine? It's not enough even to model the different makes of these items, as each can, camera, or answering machine is at least slightly different from every other one, due to quirks in the manufacturing process. Even if you found a factor in one soda can using your supercomputer that contributed to "stuck soda", how would you prove all other soda cans have the same problem?
Great! (Score:2)
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That's cool! (Score:2)
Re:Great! (Score:3)
Yeah, in a perfect world of one-to-one dollar translation, there might be "better" things to spend it on, but, eh, it was cool, and he did it.
Good for him.
Million dollar funding superchallenge! (Score:5)
* Why the last dribbles of softdrink never make it out of the can
* Why drivers lisense photos always turn out bad
* Why I always sound like a dork on answering machines
I plan to model each one of these confounding human mysteries on a supercomputer using not 1, not 2, but 3 trillion!!! calculations...
Now!... Gimme that sweet sweet grant money!
:)