Leonardo da Vinci sketched an early ball-bearing design to reduce friction between moving surfaces.
His drawings show balls placed between rings or surfaces so that sliding motion could be replaced by rolling motion. Rolling generally creates less resistance than sliding, making the arrangement useful for rotating machinery. Leonardo included the concept in his mechanical studies during the Renaissance.
The design addressed a problem that appears throughout engineering: shafts, wheels, and other parts must move while carrying loads. Ball bearings distribute contact across rolling elements and can make machinery more efficient. Leonardo’s arrangement also included ideas intended to keep the balls separated, an important issue in practical bearing design.
Leonardo was not the first person to imagine rolling supports, and his drawing did not create the modern standardized bearing industry. Industrial ball bearings became practical much later as manufacturing precision, hardened materials, and lubrication improved.