Leonardo da Vinci sketched a ball bearing using balls between two rings to reduce friction.
Around 1498, Leonardo explored the idea of separating moving surfaces with rolling balls. Instead of allowing one surface to slide directly over another, the balls would roll between them, reducing resistance and helping rotary motion run more smoothly.
His design is an early documented example of the principle behind rolling-element bearings. It was not a modern sealed bearing, and Leonardo’s sketch did not lead directly to mass-produced industrial bearings. Nevertheless, the drawing shows that he understood an important mechanical advantage of rolling contact.
Ball bearings later became essential in machinery, bicycles, vehicles, turbines, and many other systems. They are sometimes confused with plain bearings, which reduce friction by letting surfaces slide over a lubricant or low-friction material rather than roll over balls.