ITEM: Ball bearings
INVENTED: 1794 USE: Rolling objects
The Romans, Greeks, Celts, and Chinese all independently devised uses for these friction-reducing mechanisms as far back as 900 B.C. As did Leonardo da Vinci during the Renaissance (see: helicopter drawings). The first modern incarnation of ball bearings—a 1794 patent that showed how small orbs could spin in grooves between an axle and wheel—was meant to make it easier for horses to pull a carriage. Seventy-five years later, a Parisian bike mechanic placed them in the hub of a vélocipede, helping a rider win one of the world’s first bicycle road races. Nearly every contemporary rotating machine relies on bearings to reduce rubbing and keep things rolling: They allow hard drives to spin disks, help the Mars rovers steer, and, yes, let your fidget spinner whirl.