Wednesday, November 30, 2005

A Computer Named Scotty

I never was employed as a computer, but the summer that I let my father talk me, against my better judgment, into working as a gravity observer on a seismic exploration crew up in the Northwest Territories of Canada near the confluence of the Liard and the Nahanni rivers---a land that was primarily muskeg, which is just a fancy word for swamp---I worked for a computer who, because of his Glaswegian accent, was inevitably known as ``Scotty.''

It was my job to go slogging through the swamp with a gravity meter on my back and, every so often, when I came across a stake with certain markings placed on it by the surveyors, I would unsling the gravity meter, place it on a tripod, and look through an eye piece with a vernier dial, twisting the dial until a little bubble, very much like the bubble in a carpenter's level, appeared in the very center of the eyepiece. At that point I could, by reading the numbers on the dial, supposedly determine the force of gravity acting at that particular location to the nearest thousandth of a gal or so. [A gal is the centimeter-gram-second unit of acceleration, equal to one centimeter per second per second.] As I recall, being rather a klutz, I never could reach quite that degree of accuracy.

I was looking for buried riverbeds that could, if unaccounted for, mess up the seismic data. The gravity meter did a pretty good job of sensing the presence of a buried river bed, but it it also sensed other things like the variation in tidal forces that occurred as the moon made its journey around the earth. In order to filter out such unwanted noise I had to get back to the point where I made my first reading within two hours and make another reading and then Scotty, the computer, had to adjust my readings taking into account the drift that had taken place over the two hour period.

I was supposed to collect the raw data; Scotty was supposed to manipulate it. That is, after all, what computers are supposed to do: manipulate data. So I supplied the data that I had collected to him, and someone---a seismologist---gave Scotty instructions as to how he was to process that data. But there were actually a couple of evenings that Scotty handed me a slide rule and gave me some hasty instruction on how to use it in order to filter out the noise attributable to tidal forces and things like that that messed up the data I had collected.

Scotty just wanted me to recheck some computations that had already been done by someone else, but arguably that allows me to claim with at least some legitimacy that I myself was a computer for a couple of evenings. I'm not quite sure that I ever understood exactly what it was that I was doing on those evenings, other than sliding scales back and forth inside a slide rule, but that sliding did produce numbers which satisfied Scotty. After all, we computers are not required---or even encouraged---to understand what it is that we are doing.

I just followed the instructions that Scotty gave to me and those instructions were, by definition, instructions to a computer. It is, I think, worth noting that a set of instructions to a computer is exactly what our legal system defines as a ``computer program.'' It may even be worth remembering that the earliest computer programs were sets of instructions to human beings like Scotty and myself.

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