Slashdot Mirror
Make A Hole - And Sustain It Indefinitely
Mick Ohrberg writes "Florian Merkt, Robert Deegan, and Erin Rericha, all at the University of Texas, have shown that a hole created in a water and cornstarch mixture with a puff of air can be persistent if the mixture is shaken at about 120Hz with acceleration being in the 12g-25g range. The physics behind the phenomenon has not yet been explained."
The physics behind the phenomenon has not yet been explained.
:(
Some kind of resonance... or the opposite of it?
Sorry, I'm not a physics nerd
I'm no physicist, so I have no idea what the implications of this are. The article and PDF gave no indication either. Anyone care to share?
...Rob
The American Dream isn't an SUV and a house in the suburbs; it's Don't Tread On Me.
It seems that the world of physics as it relates to lots of macro sized particles interacting isn't very well explored.
I remember reading an article years ago, about research into mixed nuts. Basically they wanted to find out why the brazil nuts always tended to come to the top. It turns out it's a semi-complex interaction, when the can is shaken vertically, the nuts closer to the walls are pulled down due to the friction and they fall into the gap created at the bottom of the can, creating a sort of convection current. The larger brazils had less contact area with the wall and were not as likely to be pulled back down IIRC.
It's just kinda funny that we understand all kinds of interactions down on the atomic level, but are still researching basic things like the way mixed nuts or raisin bran sort and settle.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
It's quite simple, really. The glass container in which the corn starch is stored resonates perfectly at 120Hz. Had the researchers used a difference thickness, weight or purity of glass, the required frequency would be different, though far less stable. What they have done, in effect, is open a very small gateway into a sub-level dimension. It is fortunate that they did not accelerate the container to a rate generating more force, which would have caused the hole to open larger; they might have inadvertently unleashed one of these.
scale the whole project up, and easy access to sunken boats?
treasure is always a good incentive...
I downloaded the removed video when the site was on Fark this week. You can get it off my server here (3.8 meg wmv).
Your reality is lies and balderdash and I'm delighted to say that I have no grasp of it whatsoever. - Baron Munchausen
So as the force from the air in the hole impacting with the edges of the hole increases as the frequency increases at some point it'll reach the point where it goes hard.
Just like if you hit silly putty with a hammer.
Similar to the 'liquid body armor' reported on Slashdot a while back, cornstarch + water is a "sheer-thickening" fluid, or a fluid that increases its viscosity when it experiences sheer (or tangential force).
Perhaps the interaction between the cornstarch/water and the vibrations cause the cornstarch/water to increase its viscosity and "hold" up the walls of the hole.
Favorite
- Zav - Imagine a Beowulf cluster of insensitive clods...
Dude, that already exists here
How much cornstarch do you need for the Red Sea anyway?
Given that cornstarch and water is a shear-thickening fluid, and the vibration (at 15-25g no less) is certainly a shear force, this phenomenon is almost certainly due to the vibration causing the cornstarch and water to gain viscosity. This wouldn't necessarily give you a stable hole, though, so it's probably also helped by the cohesive forces in the fluid and some other effects, too.
I would guess that it's not that the scientists don't know why this is happening, just that their models aren't accurate/precise enough to predict it. Or maybe they left out some effect or force that is normally negligible in the models, but suddenly becomes important in this situation.
We just need a lot of corn starch.
Doesn't ACME have a patent on portable holes? I think these guys may want to check with their lawyers...
Equipment needed:
1 bowl, medium size
1 pack of cornflour (presumably cornstarch is the US word for cornflour)
1 source of water
Put approximately 'some' cornflour in the bowl.
Add water and stir until you have a liquid.
Mess about with the amounts of water and cornflour until you have a reasonably thin liquid, but one which if you punch (!) will not splatter all over the place. If you stir it with a spoon, very slowly, it will feel like water. If you try and stir it fast, you will feel great resistance.
You may want to try the spoon test before the punch test.
The scientific name for this substance is 'gloop'.
Rik
The waters "congealed" and this certainly looks like "congealed" to me. The waters also fell back again quickly enough to engulf a million soldiers cannon weapons out on the Saudi shore, which doesn't sound like enormous amounts of cornstarch. Four million people could only carry a limited amount of it along with their other supplies.
The most likely explanation is that "a strong east wind" was just that, and cold, too. People forget that the desert gets damn cold at night, cold enough for the natives to make ice and ice-cream without compressors or Peltier devices. If a very cold tornado-force wind, maybe like the downbursts that kill passenger jets, hit the Saudi edge of the crossing it would scoop out a trench towards the Egyptian edge and freeze the sides. When it all melted, the Egyptian edge would melt first, collapsing in a rush towards the Saudi edge and producing the effects described.
Even the bit about their wheels being taken off "so that they drove heavily" might find explanation in their axles shrinking faster in the cold than their wheels and/or their gorm [Webster] freezing up and changing its behaviour.
There are many sources besides the bible recording the event, including a couple of Phoenecian pillars which stood at each edge of the crossing. The Egyptian one had fallen down and was pretty badly eroded, and the Saudi one has been whisked off to a museum and replaced with a marker, but the surviving inscription commemorated Moses' crossing as a part of the glorious history of Solomon.
Since something corresponding fairly closely to the bible's description happened there, the pragmatic approach is to find a reasonable explanation for it.
-calyxa
Decay! Decay! Decay! -Helium
This is grade school science fair type stuff. Corn starch forms very long polymer-like molecules. Thats why corn starch thickens when you stir it -- its molecules get tangled on each other. Obviously the sound they are pumping into the corn strach is agitating the molecules and causing them to be act like a sheer liquid.
Religion is a gateway psychosis. -- Dave Foley
My physics is a bit rusty, but isn't this just a special case of a standing wave?
How'd they come across this?
Hey Joe... Let's take some water... and add some cornstarch.. and then. hmm... apply a really high frequency, and then puff some air down into it.
Ya know Bob, that's a really great idea.
-Jesse
Nothing says "unprofessional job" like wrinkles in your duct tape.