## Wednesday, 22 April 2009

### Strain

I wonder then, what is taking place in the aether around the north and south poles of a bar magnet? What impression does our watermelon make upon the aether? In the previous post, we've discussed the aether flowing through either end of a bar magnet - just like a two way tunnel of moving traffic. The bar magnet appears to strain under the influence of the aether streaming through. The tensions surrounding the bar magnet convey something rather familiar; tensions perhaps, that are recognisable in other places, and different situations. Maybe there are clues to be found elsewhere, like in the pond at the bottom of the garden.

Some insects spend their entire lives on the surface of a pond. These insects, such as a water strider, are able to manipulate surface tensions in water. If you look at the impression made on the surface of the water by the leg of a water strider, you can see that the tension appears as circlular around the leg. The apparent sphere of influence starts and ends with the length of the foot. I'm not sure about you, but to me, those tensions around the leg of the water strider could look, with the right amount of imagination, a bit like a coffee bean. (?)

There is no great mystery about what holds the water strider up. The legs are bent in such a way that a long piece, called the "tarsal segment" rests on the surface of the water. It is the curvature force resulting from surface tension, which makes the surface behave like a trampoline. But getting around on the surface of the water is another problem. How can you walk on a surface that is practically frictionless? Nature has come up with a few remarkable solutions, which, strange as it may seem, may also be relative to magnetism. I found the following site excellent for a bug's eye view of the surface of a pond:
http://www-math.mit.edu/~dhu/Climberweb/climberweb.html

The meniscus presents something of an obstacle to most insects which inhabit the surface of a pond. The word meniscus is taken from Greek, meaning "crescent". The meniscus is a curve in the surface of the water, and is produced in response to an object or land. The effect is barely noticeable to us, but for an insect, it's a little bit daunting. I guess it's like trying to climb the ramp of a skatepark half-pipe - covered head-to-toe in butter. The larva of pyrrhalta - the waterlily leaf beetle - demonstrates the solution to the meniscus-climbing problem by arching its back, and pulling up on the free surface with its head and tail (pictured above). In this way it is able to climb the meniscus, and board land. So, is a bar magnet, in some way, arching its back in the fluid of the aether?

The pyrrhalta larva is compressing itself to deform the water surface. The insect is converting muscular strain to the surface energy that powers its ascent. The larva does not need to envoke propulsion - she glides in - she comes into port like the QE2 - but fast! The larva no longer plays the part of the boat, the water itself becomes the mode of transport; the boat IS the water! The water strider uses the same solution, except that it plucks the water surface upward with its forelegs, and hind legs, while pushing down with the middle legs. The following site is just brilliant, and explains all this far better than I. It also uncovers a surprising relationship between the flight of birds, and the motion of water striders....
http://www.ams.org/happening-series/hap6-fluiddynamics.pdf

This site is great, and has lots of colourful snaps of the water strider's ethereal motion...
http://www-math.mit.edu/~dhu/Striderweb/striderweb.html

The water strider is also seen to manipulate the meniscii it generates, in order to propel itself across the surface of the water. The study of water striders by Bush et al, MIT, revealed their legs to be like the oars of a rowboat, creating swirling vortices that carry momentum beneath the surface of the water, which propel the insect forward. The strider thus generates thrust by rowing, using its legs as oars, and the meniscii beneath its driving legs as blades. The vortices are not spirals though, but instead are made up of an unusual U-shape; a horseshoe shape; half a bundt cake (in the picture below); (and for those who have a taste for something a little more mathematical) half a toroidal vortex ring in which the ring has been sliced parallel to its axis of symmetry (I prefer cake). Of interest perhaps, in the realms of polarity, these vortices created by the water strider are dipolar; one vortice turns in a clockwise direction, and the other turns counter-clockwise.

The water strider is doing something to the surface of the water, where it's legs, in some manner or other, are simulating the core of a torus. In my world, a bar magnet is the core of the torus. The bar magnet transfers its' "muscle strain" to the fluid of the aether, and inviting this fluid to flow through at a rate both persistent, and consistent. When we apply iron filings to a bar magnet, it feels like we are seeing the outside of the magnetic field, or the skin of the watermelon. Is it possible that the horseshoe created by the water strider gives us an opportunity to glimpse the inner workings of a torus which represents the magnetic field? Basically, are we seeing the watermelon chopped in half?

I wonder if it is possible that the legs of the water strider are imitating the behaviour of a bar magnet. The legs might be designed in such a way as to generate a change in pressure on the water's surface; a change in pressure which helps create tensions, perhaps. Could the construction of the water striders' foot reveal a way of inducing the aether to flow? Is it the case that the water strider is not just simply pushing water backwards - perhaps there is something else, another force at work, which pulls the insect forward?

Many thanks:

http://davieswx.blogspot.com/2008/11/twin-horseshoe-vortices-6-17-08-in.html
http://www.weatherscapes.com/album.php?cat=clouds&subcat=horseshoe_vortices
http://www.iem.efei.br/professores/luizantonio/vortex-formation.htm
http://www.nature.com/nature/journal/v424/n6949/fig_tab/424621a_F1.html
http://jeb.biologists.org/cgi/content/full/207/10/1601
http://www.ams.org/happening-series/hap6-fluiddynamics.pdf
http://www.interactives.co.uk/me_toroidalvortex.htm
http://www.egr.msu.edu/tmual/CHuck/ring.html
http://www.woodrow.org/teachers/esi/1999/princeton/projects/fluid_dynamics/vortex.html
http://www.bioedonline.org/news/news.cfm?art=2531
http://www.uni.edu/~iowawet/H2OProperties.html
http://www.exo.net/~pauld/activities/astronomy/icybodies2.htm
http://web.mit.edu/newsoffice/2001/ketterle-0411.html