Today, every motorist knows the name of the 16th century Italian mathematician, philosopher and physician Gerolamo Cardano. But not everyone who gets behind the steering wheel is aware that Cardano was also the first to introduce the numbers that Descartes would call imaginary 100 years later. It was the same Cardano that enriched mathematics by publishing the solution to a cubic equation, disclosed to him in confidence by Niccolò Tartaglia, and the solution to a quartic equation, produced by Lodovico Ferrari. A physician, philosopher and mathematician, Cardano, in the spirit of his time, was a part-time astrologist who earned the reputation of a heretic by making Jesus Christ’s horoscope.
Nevertheless, Cardano's name is forever associated with the Cardan shaft.
They say that as King Charles V of Spain was entering the conquered city of Milan in triumph in 1541, Cardano, as the Rector of College of Physicians, was invited to walk alongside the king’s carriage. In response, the grateful Cardano offered to supply a suspension made with two shafts connected to each other for the carriage so as to make the Emperor’s travel more comfortable. The Cardan suspension was born.