Eternity machines: kinetic sculptures with a very long running time constructed by the US artist Arthur Ganson. The sculptures are powered by an electric motor that drives a multi-level reduction gearing whose final gearshaft is firmly embedded in a concrete or granite block.
Machine with Granite (by courtesy of ►Technorama Winterthur)
The machine depicted above is on display at the Technology Museum in Winterthur, Switzerland, and has a total of twelve gear reduction levels. Each level consists of a gear screw that acts on a pinion. The reduction ratio is 50:1 per level. The drive shaft rotates permanently at 200 rotations per minute.
What do you think is the running time of such a machine? Granite is relatively torsion-rigid. Since the gear has a tolerance of about 1 degree, the last pinion can still perform the three hundred and sixtieth part of a rotation before the electric motor will be blocked. Thus, the estimated running time will be 1/200 ∙ 5012 ∙ 1/360 = 3390842013888888 minutes, or 6.45 billion years. Of course, this presupposes that the Museum of Technology in Switzerland continues to pay its electricity bills throughout that time.