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New Theory on Water Strider Propulsion
capt.Hij writes "There is an interesting
article at the Christian Science Monitor about how water skimmers are able to move the way they do. This new theory debunks the previously accepted theory and answers why smaller, younger water skimmers are also able to move the same way as their elders: 'As he looked into the question, he adds, he learned that the reigning explanation leaves an unsolved puzzle: If these tiny insects propel themselves in the way many researchers think they do, then baby water striders should go nowhere fast.'" There's also a BBC story with pictures.
They move by using their mid leg pair as oars and the back pair as steering wheels. Previously, researchers thought they generated small waves, but baby water striders are too small to generate waves big enough to move on. The new research show that the waves are a biproduct of using the middle pair as oars, not the reason they move. Pictures here, same news in norwegian here.
Very good article on this in scientific american, if anyone is interested!
The Independent has a related article here.
I want to drag this out as long as possible. Bring me my protractor.
My mother was raised literally on the river (towboat pilot Dad), and knows how to "scull" (propel a small boat from the stern using a single oar or paddle.) The oar stays in the water and does describe a circular or elliptical path. It's about the weirdest means of locomotion I've ever seen, and doesn't look like it should work. But I can vouch that it does.
I could never do it, although I was just a kid the last time I tried. Anyone here who can?
Everybody whose anybody knows waterstriders use anti-matter as propulsion.
All I know about water skimmers/skippers is they're a bugger to hit with rocks, unless you get a really big, flat rock and even then you mostly just get yourself wet and still miss the skimmer.
"Those who would sacrifice liberty for security deserve neither!"
a) It's in Christian Science Monitor
b) It's about skimming over the water.
Chances are, Jesus features in the answer.
A longer article mentioned a bigger strider they studied.
I found it amazing that the robot was half the size of the Asian giant water strider.
An 8 inch Water Strider might make a cool pet!
What would it eat? How big of a pond would you need? Does anyone have experience with these critters?
Row Row Row your bug, rowing down the stream...
But really though, if all it does is rowing, don't we already have tons of models that uses rowing? I mean, it's not electronic, but rowing's been around for centuries!
I'm not the devil.. just his advocate.
I think it's an interesting reflection on humanity when evolution can throw up designs that we can't properly understand even with all of our apparent science and technology (bees, water striders, the thought process). It just goes to show that for every fact or theory we think we know there are far more that we don't, which gives me great confidence in the progress of human science and technology over the next few thousand years.
They move because they put their faith in jesus and he spirits them along over the water on the wings of christ.
Damn dude, it said the CHRISTIAN science monitor.
You remember.. the people who don't believe in evolution? Or stem cell research? Or cloning?
Are water striders one of those bugs they have everywhere like flies/mosquitos/etc. We have them in oz, here in the UK, in asia and the US. Anywhere else.
-- Karma Karma Karma Karma, Karma Chameleon - Boy George
... is a bug!
Walking on water isn't hard. Everyone can do it - just make sure that the temperature of the fluid-to-be-walked-on is subzero.
I've been doing sweep oar rowing and sculling for years... It's something that anyone can do, but few can master. The blade (the oar) moves in a roughly ellpitical track in the water, over a very small range, as the boat is propelled forwards. The range of motion is dependant upon the skill of the oarsman, and how he/she appiles pressure to the stroke. Too much too soon, and you 'rip', causing turbulence, and allowing the blade to move excessively through the water... Too little, and the blade won't lock onto the water, and will just float through the water... Of course, this is neglecting balance etc., which is no mean feat in a boat some 5 inches wide at the waterline!
A few of my colleagues have been looking into the effects of surface tension in various liquids and you'll be amazed to learn what you can do if you have the right circumstances.
H20 doesn't have that much surface tension becuase of its low valency, but other liquids such as bromine are held together by strong Van der Waals attractions meaning that they have much stronger surface tensions. In one famous experiment at MIT researches showed just how strong the surface tension could be by placing a cat onto a large pool of bromine and observing that not only did it not sink but that it could also move abount (albeit with difficulty). Some people have suggested (tongue in cheek) that if Jesus could have introduced bromine into the red sea then that would explain how he could have walked on water.
All that glitters has a high refractive index.
the microorganisms that live symbiotically inside of me think of me as "God".
I would say that unlike parent post, the CSM is actually quite objective.
Go take a gander at the original BBC article with the photos. The one with the blue dye in the water showing the eddies created by the movement is practically a natural reproduction of Van Gogh's brushwork!
It's like having insects do impressionist painting. Truly beautiful. If I can find a high-res photo, I think I've got my new wallpaper.
Design for Use, not Construction!
It seems that we have a Christian source of information related to walking on water?
:-)
At least it is their own IP
It's not the Red Sea, it's the Lake of Gennesaret.
;)
The Rea Sea was the one where the surface tension didn't hold up to the weight of the Egyptian Army
Just my E0.02.
Now this is a troll if I ever saw one. Bromine is the only liquid nonmetallic element. It is a heavy, mobile, reddish-brown liquid, volatilizing readily at room temperature. It is toxic comparable to chlorine. The surface tension of bromine is LESS then that of the water.
Cat (or any other live being) in a large pool of bromine has a life expectancy of a few minutes. And yes it would sink.
No, faith is believe in the absence of complete proof; it can still have supporting evidence. Blind faith has no proof. Science itself requires a modicum of faith.
Not so! For you see, the cat can stay aloft as long as it still has lives to use. It would only sink and die following the expiriation of its last life. ;)
"Doctor" and "Bush". After the last few years, I have a lot of trouble visualizing that...
I am a viral sig. Please copy me and help me spread. Thank you.
Sometimes it takes a lot of scientific training to work out things country people have known for a long time - digitalis, willow bark, cowpox, and all those interesting rain-forest rmedies the drugs companies are "patenting".
Panurge has posted for the last time. Thanks for the positive moderations.
Actually if you look at the guy's home page at MIT you'll see that he isn't spenging his life studying just this but fluid dynamics generally. He seems to have a particular interest in the fine points of stuff you see everyday like the fluid dynamics of wine in a glass and soap film
I suppose you might still consider this boring but I sort of like the idea of the brainy mathematician walking around looking at everyday things nobody (not even other scientists) really notices and saying "I wonder why it does that?"
> Now all we need is to figure out how to make water have enough tension to hold a person. Hrmm...
Simple. This happens naturally where I live. I simply have to wait until, say, mid-November. The surface tension remains high until some time in spring. It only works for water kept outside or in an unheated building.
-srw
water boatmen are not water striders
Suchetha
learn from yesterday, plan for tomorrow, party tonight
or one out of three ain't bad
From my point of view. My background is in fluid mechanics, and even though I've only obtained my master's, I couldn't have told that scientist where the momentum was transfered.
:(
The same thing for aircraft: tip vortices and a bound vortex on the wing alter the direction of the incoming air, which changes the air's momentum and provides lift. And all that happens because of friction between the molecules of air on the surface of the wing, and their neighbors directly above them. Then THEIR neighbors directly above them, and so on until you get to the overall flowfield.
And when you get to the tip of the wing, the downwash pulls the air past the tips into a vortex.
Those scientists that study these kinds of things would do well to actually study vortex dynamics (Kelvin's theorem would have told them the answer!). They would rather try and reinvent the wheel though.