On this page
Most students know Leonardo da Vinci as the painter of the Mona Lisa. Fewer know that he spent years studying bird flight and anatomy, and that he recorded it all in notebooks he never published. This post looks at what those notebooks actually contain on flight and anatomy, where modern scholars think his drawings mislead, and a notebook habit you can borrow for physics and biology.
Who was Leonardo, and why do his notebooks matter?
The MacTutor biography of Leonardo gives his dates as 15 April 1452, in Vinci near Florence, to 2 May 1519, at Amboise in France. It describes his work in hydrodynamics, anatomy, mechanics, mathematics and optics, and notes that during his second period in Milan, from 1506, his scientific work took precedence over his painting.
His ideas survive mainly in notebooks. The Victoria and Albert Museum's record for the Codex Forster notebooks describes five of them, written between 1487 and 1505, covering perspective, light and shade, the human figure, anatomy, physiology and much more. They are written in Italian, in mirror script, running from right to left. After his death the manuscripts passed to his pupil Francesco Melzi and were later scattered among collectors. The notebooks were his working record, not books for readers.
What did Leonardo write about flight?
The Smithsonian's National Air and Space Museum, which displayed it in 2013, describes the Codex on the Flight of Birds as a notebook entirely on flight, produced in 1505 and 1506. Across his notebooks Leonardo wrote more than 35,000 words and made 500 sketches on flying machines, the nature of air and bird flight. The museum says the Codex outlines observations and early concepts that would find a place in the development of a successful aeroplane in the early twentieth century.
Two points keep this in proportion. First, he did not fly; the Wright brothers' powered flight came about four centuries later. Second, his strength was observation. His pages set observations of birds beside his ideas about the nature of air, trying to explain what he saw rather than only record it. That is the right starting point for physics even when the explanation is incomplete.
What did he discover about anatomy?
One of his cleverest experiments was on the brain. Scholars date to about 1508 to 1509 a wax cast of the brain ventricles that Leonardo made: he poured melted wax into the fluid-filled spaces inside an ox's brain so that, once it set, their shape could be seen and drawn. A 2022 study in Nuncius by Steinsiepe and Hauser calls this an ingenious approach and credits him with the first graphic representation of how the ventricles connect.
The same study adds a correction. Many writers since 1930 have said that Leonardo's drawing shows the paired lateral ventricles and the small openings between them. Using geometry and magnetic resonance imaging, the authors show that this is a misreading of the unusual section plane he drew. A midline cut like his cannot show both lateral ventricles at once.
That is a useful lesson in itself. A drawing can look completely realistic and still be read wrongly by later readers, even experts.
Where should we be careful with Leonardo?
He did not publish. Because the notebooks were private and scattered, they could not reach other scholars of his time the way a printed book could. Compare our post on Andreas Vesalius, whose printed anatomy reached readers across Europe.
Sketches are not working machines. A design on paper shows an idea, not proof that it works.
Popular claims grow. As the ventricle study shows, even specialists repeated an attractive interpretation for decades. Check what a drawing actually shows.
He also thought about astronomy. MacTutor notes that in the Codex Arundel, written about 1513, he suggested bringing the image of a planet onto a concave mirror to see its surface magnified.
What can a student take from Leonardo's way of working?
Draw to understand. Before you solve a mechanics problem, draw the forces. Before you learn a biology diagram, sketch it from memory and compare. The gaps you find are the gaps in your understanding.
Write the question next to the drawing. Leonardo's pages mix drawings and written notes. Keep a notebook where each diagram has one question beside it, such as "why does the tension change here?"
Use a model to see the hidden shape. His wax cast made an invisible space visible. In chemistry, build a molecule with a model kit; in physics, trace field lines on paper.
Revisit old pages. Go back to last month's diagrams and correct them. Leonardo's notebooks span decades.
If the hard part for you is picturing a three-dimensional structure or a moving system, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read.
This week, watch a crow or a pigeon land, sketch three positions of its wings and tail, and write one question about the forces beside each sketch.
