Leonardo da Vinci studied a ball bearing using balls between rotating surfaces to reduce friction.
Leonardo’s notebooks contain sketches of bearings and related mechanisms, generally dated to the late 15th century. One design placed balls between rings so that the parts could rotate with less sliding friction. The balls also helped prevent the rotating rings from pressing directly against one another.
The concept addressed a basic engineering problem: moving surfaces lose energy and wear when they rub together. Rolling contact usually produces less friction than sliding contact, making bearings valuable in machines, vehicles, and industrial equipment.
Leonardo was not the inventor of every bearing form, and his sketches did not create the modern standardized bearing industry. Modern ball bearings depend on precise manufacturing, hardened materials, cages, lubrication, and controlled tolerances. His designs are historically important because they show an early systematic attempt to keep bearing balls separated and make rotary motion more efficient.