Leonardo da Vinci studied a ball bearing as a way to reduce friction between moving parts.
His sketches from around 1498 show balls placed between moving surfaces so that sliding friction could be replaced by rolling contact. The arrangement resembles a modern bearing, although Leonardo’s design did not include all the features needed for a practical sealed bearing.
The idea was part of his broader study of machines, motion, and friction. Bearings allow shafts or other components to turn more easily by supporting loads while reducing resistance. Leonardo recognized that rolling elements could improve the efficiency of mechanical systems.
The drawing is often described as an early ball-bearing concept, not the invention of the complete modern bearing industry. Later engineers developed cages, races, lubrication systems, and manufacturing methods that made bearings durable and precise. A ball bearing is also different from a gear: gears transmit torque through teeth, while bearings support motion and reduce friction.