In a tiny notebook owned by legendary inventor and scientist Leonardo da Vinci, notes previously dismissed as "irrelevant" have turned up a new discovery: da Vinci had a sophisticated understanding of the laws of friction almost 200 years before they were formalized. The research, from Professor Ian Hutchings of the University of Cambridge, goes on to demonstrate how da Vinci applied that knowledge to his machinery design work over the next 20 years.

The notes in question lie in a tiny notebook just 92 mm x 63 mm (3.6 x 2.5 in), dating from 1493 and currently kept in the Victoria and Albert Museum in London. In the 1920s, a previous director of the museum declared that the scribbles were nothing more than "irrelevant notes and diagrams in red chalk." Interest at the time was more focused on a sketch of an old woman at the top of the page, bearing a quote that translates to "mortal beauty passes and does not last" and speculated to depict an aged Helen of Troy.

As part of a detailed chronological study of da Vinci's work on friction, Hutchings determined that the diagrams beneath the portrait are particularly important to the field of tribology – the study of friction, wear and lubrication – as they represent the earliest written record of the laws of friction. The sketches show a weight hanging over a pulley, dragging a row of blocks in exactly the kind of experiment still used to demonstrate the concepts.

"The sketches and text show Leonardo understood the fundamentals of friction in 1493," says Hutchings. "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. These are the 'laws of friction' that we nowadays usually credit to a French scientist, Guillaume Amontons, working 200 years later."

That's not to say Amontons doesn't deserve some credit. While da Vinci may have discovered the laws of friction, his work had no direct influence on the subsequent development of the subject, meaning Amontons arrived at his conclusions independently.

Da Vinci is actually credited with the first systematic study of friction, but this is the first time researchers have been able to pinpoint when and how he first began to explore the ideas. The inventor went on to demonstrate that knowledge over a 20-year study, analyzing the interactions between wheels and axles, screw threads and pulleys in his machinery design sketches, as well as a clear understanding of how friction can be useful and times when it can reduce efficiency.

"Leonardo's sketches and notes were undoubtedly based on experiments, probably with lubricated contacts," says Hutchings. "He appreciated that friction depends on the nature of surfaces and the state of lubrication and his use and understanding of the ratios between frictional force and weight was much more nuanced than many have suggested."

Professor Hutchings's research appeared in the journal Wear.

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