In a ploy to immortalize themselves in the Guinness Book of World Records, a team of engineers in Michigan created a 6-foot by 12-foot clock replete with 11 working gears, made entirely of ice. Unseasonably warm weather the day they were supposed to run the clock curtailed the demonstration, but they did keep it going for a few seconds prior to meltdown.The creators of the ice gears were the first to admit that commercial possibilities for their cool invention were totally nonexistent; conventional gears are, understandably, made of more resilient materials, such as aluminum, bronze, steel and even plastic. Gears are usually circular, and they operate in groups of two or more, called gear trains. One gear receives energy from an external source, such as a motor or a cyclist\u2019s legs. As it turns, its teeth connect with those of a second gear, thereby transferring energy and torque along the gear train to a final drive shaft at the other end. The shaft transfers the energy to its final destination, most often a wheel. Gears have powered textile mills and ten-speeds, water wheels and wristwatches. And without the differential gears that let their wheels rotate at unequal speeds, cars would have a tough time hugging the curves of a road. It is thought that some form of gear may have existed as far back as 300 B.C., a rack-and-pinion affair that was an integral part of a water clock invented by the barber Ctesibios of Alexandria. But the earliest surviving gears are found in the Antikythera Mechanism, an incredibly sophisticated astronomical calculator built in Rhodes around 80 B.C. It was discovered centuries later among other treasures in a sunken shipwreck, its 32 bronze gears still intact.