Mind over Computer 43

Mind over Computer 43 British readers — and you roll it once around the wheel of your car. The small sweet will turn many times. Now put a pencil through the hole in the sweet, jack up your car so the wheel is off the ground, hold the sweet next to the wheel of your car and press the accelerator. The sweet will spin round very fast and probably disintegrate in a shower of minty sugar. This is the principle of gearing. A small circle has to do a lot of work to keep up with a big circle. It’s very predictable. The sweet will turn a set number of times for each rotation of the car wheel, equal to the ratio of the circumferences of the two circles. Gears usually have teeth to lock the wheels together, but this is really just to make sure they can’t slip against one another when they transfer huge forces, such as in racing cars. Some passenger cars have been built with smooth gears; a friend of mine had one at university. If he put his foot down too hard, the gears would slip, heat up and you would get a terrific smell of burning rubber. If you were lucky you could leave the car for a few hours and all would be well. But, if not, you had to replace the rubber belt, which was very expensive. Toothed gears generally win out. Toothed gears also have the enormous benefit of being digital. This is quite important if you want to keep things accurate. Gears can’t move a fraction of a tooth so if a toothed gear has ‘slipped’ forward a small amount, it will be kicked back into position when it meshes with another gear. In a modern mechanical clock, a balance wheel swings back and forth on a spring and moves the main gear one notch forward each time it passes its central position. Gears divide this down to move the hour and minute hands. If I put the hands of a clock at midday and let the clock tick 86,400 times, the clock hands will come back to the same place. Once you understand how a clock works you can play a trick. If you tell me the number of ticks the clock has tocked, I can tell you the exact position the hands will be in. To a small child this might be dressed up as a magicians trick — but, of course, it is simply a matter of dividing the number of ticks by 60 and then 60 again to calculate the amount of time elapsed. This type of precisely predictable behavior is called deterministic behavior. Something is deterministic if you can set it up in a particular way and know the exact state later or, conversely, examine something and trace it back into the past. Modern computers scale up clockwork and make it much more efficient; gears are translated into electronic logic gates and a quartz crystal vibrates at 1000 million ticks per second to give us the clock tick. On each tick, the computer can do a mathematical operation, store and retrieve information, or branch down an avenue in its program. Using HOUSE_OVERSIGHT_015733