Tuesday 3 January 2012

Dead Flies and Calculations

Remember slide rules? Eee when I were a lass we didn’t have fancy calculators... Now I’m going to relate a story about what slide rules are for and the kind of anarchic calculations you can perform with them.

I remember when I was in high school in the bustling metropolis of Mt Barker deep in the outback of Western Australia. I say “bustling” in the sense that the most movement on the main street on an average day then was when a stray sheep wandering across the deserted streets.

I would use a slide rule to the amazement of farm boys who were more interested in calculating the amount of sheep dip to use on their fathers flock. And could only use the fingers they had between them to do that. Working out the right amount of sheep dip for flocks of greater then ten caused a furrowed brow and the removal of shoes to use toes.

I remember one calculation which got me an award of sorts. The teacher was impressed by the effort and accuracy of the calculations, but somewhat disapproved of the subject. I’ll explain. 

First you catch a fly. Now W.A. in the late 60’s was awash with them as it was before the introduction of dung beetles. So catching one was relatively easy. Next you pop it in a match box for safe keeping and obtain a length of very thin cotton and a thumb tack. You tie a small knot of the cotton around the shaft of the thumb tack and push it into your school desk. Then you make a very small and loose knot in the other end. The length of the cotton should be around a foot or so. B says he used hair instead of cotton to achieve the same goal.

Now you retrieve your fly and gently place the loose knot between the head and thorax of the fly and tighten the noose ever so slightly. Not too much or you’ll end up with the premature loss of your fly.

Then you let the fly go. And hey presto! Your own private fair ground attraction. The fly buzzes around going up and down in weird loops reminiscent of those rides called crabs or spiders or whatever. Anyway, you use a stopwatch and a notebook and take readings until eventually in an heroic attempt to get away the fly decapitates itself. The head falls in a gentle arc in one direction and the body buzzes around for a second or so before dropping like a stone to the desk. A friend of mine at the time managed to get three flies in this macabre whirly gig. Cute.

Anyway, this is where you pull out your trusty slide rule and start calculating the trajectory of head and body. I did a 5 page dissertation with graphs, tables,  charts and drawings showing the mass to arc trajectories of various heads and bodies of normal flies, blue bottles and sand flies. The teacher wasn’t happy but had to concede that they were as accurate and complete as any scholarly document he had seen. He stuck it to the wall in the science room amongst the sad remnants of other pupils attempts to engage with science.

The other thing I “calculated” was the strength and length of rubber to use with “Gidgies” when hunting frogs. Huh? Oh, yes... A Gidgie is a arm mounted sling shot with about three foot of heavy rubber band. With a  strong arm (which I didn’t have) and a ball bearing you could punch a hole in a car door from 100 foot away. I haven’t done that myself, but I did know guys at school who did. Vandals. 

Anyway, I figured this out once when a friend of mine, Garry, and myself climbed up a water tank overlooking a dam in a farmers paddock. We were armed with Garry’s gidgie and a handful of ball bearings. We sat patiently until a frog would rise to the surface and Garry would take pot shots at them. They don’t die by the way. If you hit the water very close to them, they sort of go limp, roll over and sink a bit. After a while they start kicking limply and in a minute they are off swimming again. Sigh. We didn’t have video games or TV or psychedelically painted minis or any other distractions available to “townies.” It was the 60’s in an outback town after all. 

And that, my friends, is what slide rules are intended to calculate. Try doing the same with a calculator and all the fun is drained from the exercise.

I was 13 at the time. And bored out of my skull. I might just mention that my attempts to bring some sort of life to the classroom in this sort of manner earned me a large number bruises from chalk and duster projectiles from the unsympathetic teachers.

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