Men of genius make few mistakes, and for Leonardo da Vinci even scribbles and doodles are actually portals of discovery.
Professor Ian Hutchings from the University of Cambridge looked into one of da Vinci's notebooks from the Victoria & Albert Museum in London, and discovered that da Vinci had already formulated an important law of friction more than 200 years before it was first published, and almost 300 years before it was experimentally verified.
“The sketches and text show Leonardo understood the fundamentals of friction in 1493,” Hutchings said in a statement. “He knew that the force of friction acting between two sliding surfaces is proportional to the load pressing the surfaces together and that friction is independent of the apparent area of contact between the two surfaces.”
He added: “These are the ‘laws of friction’ that we nowadays usually credit to a French scientist, Guillaume Amontons, working two hundred years later.” Amontons’ laws of tribology (the science of friction) were published in 1699 and were verified by Charles-Augustin de Coulomb in 1781.
The folio, which is part of the Codex Forster, was already well known because it shows a sketch of an old woman with the words, in da Vinci's mirrored handwriting, “cosa bella mortal passa e non dura” (mortal beauty passes and does not last). The director of the museum described the friction sketches as “irrelevant notes and diagrams in red chalk.”
The irrelevant notes turn out to be the first written understanding that friction depends on the applied load (“la confregazione si fa di duplicata fatica in duplicato peso,” as written by da Vinci – “friction is of double the effort for double the weight”), as well as a sketch of an experiment to test the claim.
Hutchings didn’t stop at that single notebook; he also looked at the decades of written work by the Italian artist and discovered that da Vinci must have had an incredibly detailed understanding of friction, from its uses to the limitations it puts on machinery.
“Leonardo’s 20-year study of friction, which incorporated his empirical understanding into models for several mechanical systems, confirms his position as a remarkable and inspirational pioneer of tribology,” added Hutchings, who published his findings in the journal Wear.
Da Vinci's keen understanding of the natural world and physics continues to be incredible, but unfortunately his discovery of the laws of friction and many of his other ideas had little influence on science at the time, perhaps because few knew about his ideas.