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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?
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?
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.
I think you may be misunderstanding where the name "Christian Science Monitor" is coming from. This is NOT a journal of science put out by Christians (creationist or otherwise) The CSM is a paper that was founded by a religous group founded in the 1800's known as the "Christian Scientists" or more formally "The Church of Christ, Scientist". The group is often considered a cult and is pretty much disavowed by both christians and scientists (and presumably christian scientists that are not "Christian Scientists"). From time to time they get in the papers because at the core of their beliefs is faith healing, or more accurately that there really is no such thing sickness anyway, so they will refuse medical treatment for themselves and their children.
The Christian Science Monitor itself is a highly respected paper and while I think it is still officially owned by the church I think they have a hands off approach to running it and if they are using it for "evangelistic" purposes they use it by putting out a very high quality paper that by it's quality lends credibility to their group rather than using it as a polemic tool in itself. It's seems it's sort of like the Moonies owning the Washington Times rather than like an official organ of the church.
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?"
The Christian Science Monitor is not run by scientists who are
Christians, but by Christian Scientists. Christian Science is
another shootoff religion; its relationship with Christianity is
about the same as that of the JWs or the Mormons; orthodox and
fundamental Christians usually consider them a cult.
(But note that Christians mean a different thing by "cult" than
the mainstream media do; TV and newspaper reporters say "cult" and
are talking about people who stockpile weapons, sacrifice chickens,
drink special Kool-Aid, believe aliens are coming on a comet,
et cetera; Christians say "cult" and mean a group that claims
to be Christian but has altered a major core doctrine, usually
the doctrine of the trinity. A cult is like a sect but more
extreme. This is an older use of the term. Other examples of
such cults include the Unitarians and the Seventh Day Adventists.)
There are of course scientists who are Christians, but they would
not be affiliated with the Christian Science Monitor.
Cut that out, or I will ship you to Norilsk in a box.
Water striders.
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.