Leonardo da Vinci sketched a ball bearing that used freely moving balls to reduce friction between rotating surfaces.
His notes and drawings show an arrangement in which balls could roll between components instead of allowing one solid surface to slide directly against another. Rolling contact generally produces less friction than sliding contact, making rotation easier and more efficient.
Leonardo’s design is often cited as an early ball-bearing concept, but it was not a modern sealed bearing. A practical bearing must keep the balls separated and properly aligned; otherwise they can bunch together and interfere with one another. Leonardo’s sketches explored this problem with cage-like arrangements.
Ball bearings later became essential in machinery, bicycles, vehicles, and industrial equipment. Leonardo should not be credited with inventing every later bearing technology, but his Renaissance drawings demonstrate an early understanding of the mechanical advantage of rolling elements.