Leonardo da Vinci studied the ball bearing as a way to reduce friction between moving surfaces.
His notebooks contain sketches of balls placed between rings or tracks so that motion could occur through rolling rather than sliding. Rolling contact generally produces less friction than sliding contact, making the principle useful in machines with rotating parts.
Leonardo’s studies are frequently described as an early ball-bearing concept, although historians distinguish between a drawn mechanism, a working prototype, and the standardized bearings manufactured much later. His arrangement also addressed a practical problem: loose balls could bunch together and increase friction unless spacing was controlled.
Modern ball bearings use carefully manufactured races, rolling elements, cages, lubrication, and precise tolerances. Leonardo did not create the complete industrial bearing system used today, but his drawings show a clear understanding of the mechanical advantage of rolling contact.