This is an exhibit idea I had while I was at Glasgow Science Centre. It consists of a gear train that gives 42 speed reductions each of about 2.5:1. The text on the side of the frame reads:
Use the switch on the red battery box to set the gears turning. Each gear is driven by the one before it, and turns about two-and-a-half times more slowly. The repetition of this small reduction in speed gives an astonishing result. For to get the rightmost gear to go around even once, you would have had to set the gears turning 12 billion years ago, at the birth of the Universe, the very beginning of time itself.
The machine is made out of the construction toy K'nex.
I discovered later (with no particular surprise) that this idea is not a new one. For example Arthur Ganson has done a similar thing, in which the first gear spins merrily away, oblivious of the fact that the last gear is embedded in concrete. But I still like my version. I like the fact that it is built out of a playful material. And for an exhibit concerned with something very long (the life of the Universe) it seems somehow right that the text fits neatly when strung out in a single line along the length of the machine.
