Leonardo da Vinci sketched a ball bearing as a low-friction replacement for sliding contact.
In notes associated with his mechanical studies, Leonardo explored balls arranged between rings so that one surface could rotate against another with less rubbing. This is the basic principle of a ball bearing: rolling elements separate moving surfaces and reduce friction.
The idea was valuable for machines because friction wastes energy and creates heat and wear. Leonardo’s design is often cited as an early recorded bearing concept, although ancient and medieval engineers had already used rollers and other forms of rolling support. Leonardo did not invent every form of bearing.
Modern ball bearings use carefully manufactured steel, ceramic, or other balls held by races and often a cage. Leonardo’s sketch lacked the industrial precision and standardization needed for modern production, but it showed a clear understanding of how rolling could improve mechanical motion.