Experiments show Da Vinci understood gravity – 04/16/2023 – Science

There wasn’t a moment of inspiration with an apple. Nor the creation of a universal law. Only the noblest pleasure—which was, in Leonardo Da Vinci’s own opinion, the joy of understanding.

He watched the rain fall, how the clouds move quickly in the sky, and also how to give greater range to the projectiles launched from his rudimentary machine gun, one of the many devices he invented.

“It was this motivation that made him investigate why these objects were falling without any force behind them.”

So says Mory Gharib, professor of Aeronautics and Medical Engineering at the California Institute of Technology (Caltech), in the USA.

He and Chris Roh — at the time a postdoctoral researcher at Caltech and now an assistant professor at Cornell University (USA) — discovered another genius of the Italian polymath: some experiments that show his quest to understand gravity.

And to understand the meaning of the discovery, it is necessary to clarify the chronology of events.

Da Vinci died in 1519, and it wasn’t until 1604 that Galileo Galilei established that all bodies fall in a vacuum with the same acceleration.

Nearly two centuries later, in 1687, Isaac Newton proposed the universal law of gravity—the one in the famous apple anecdote.

But then what did Da Vinci observe before Galileo and Newton, and what does his discovery mean?

a chance encounter

Mory Gharib was reviewing a British Library publication of the Codex Arundel, a compendium of da Vinci’s articles ranging from science and art to personal notes.

He was looking for some flow visualization techniques, something to discuss in his graduate course.

“I was flipping through it. And suddenly a very white triangle caught my eye.” Gharib jokes that, having seen “The Da Vinci Code” (a film based on Dan Brown’s best seller), she thought “it could be something”.

“It was just a triangle. Nothing in it. And three inscriptions on each side written like he did, in a mirror image, upside down,” he adds.

On the hypotenuse, the longest side of the triangle, was written “Equatione di Moti“(equation of motion).

“I was interested in understanding what Leonardo meant by that phrase.”

There were more triangles and an experiment. In it, Da Vinci describes a pitcher probably full of sand from which he pours its contents, while moving it in a straight line and parallel to the ground, at the same speed with which the grains fall.

His notes make it clear that he knew that sand does not fall with constant velocity but accelerates, and that it does not fall horizontally but forms the hypotenuse of a triangle.

Specifically, Roh believes da Vinci was “very curious to see the progression of how the object falls and where it is at each moment. If it starts at one point, where does it end and with what effect”.

“The experiment he carried out allowed him to predict the results, albeit with inaccuracies, very close to what actually happens. And so he tried to understand what the quantitative constant of gravity is.”

Scientists say da Vinci even created an algorithm “useful enough” to be able to say precisely where that object should land.

They also reveal that in Da Vinci’s papers there is a paragraph where he says that “when an object falls, it basically goes towards the center of the Earth. This is very close to saying that the two objects are attracted to each other, and perhaps this may be the only evidence we have that he came very close to understanding gravity.”

And that, for the thinking of that time, was a great advance.

Aristotelian theory

In Da Vinci’s time, there were several theories about why and how objects fall to the ground. But the most common was the Aristotelian theory, explains Carlos Molina, astronomer and director of the Planetarium in Bogotá, Colombia.

For Aristotle, he explains, objects fall because of the feeling they had.

“It was the need for bodies to reach their natural place, and this was measured by the impetus, that is, how much was the desire to reach their natural place”, says Molina.

Thus, the greater the “impetus”, the greater the will to reach that natural place on the part of the so-called “serious bodies”.

“The heavier it was, the more momentum it had. And that acted as a description of how it happened and why it happened.”

Molina, after seeing the documents and the discovery of Gharib and Roh, explains that Leonardo “systematized an experiment to deduce that gravity is a kind of acceleration, as Galileo did (years later), and that this acceleration tells us that space is greater the greater the time, in geometric proportion”.

‘If you can’t measure something, make it measurable’

In Da Vinci’s time there were no clocks that accurately measured time.

But this was not an obstacle for him.

“He was a very hands-on engineer. He said to himself, ‘If I can’t measure the real number, I’ll create a situation where I can get close,'” explains Mori Gharib.

So what he did was he traded time for space. And it measured how objects fall from different heights.

“If you can’t measure something, make it measurable,” says Gharib.

“It’s again amazing how he understood time and made very correct fundamental assumptions that all objects arrive at the same time as long as they are at the same height,” adds Roh.

“The limitation was not being able to measure time, and he solved that.”

experiments

“What this tells us is that, through systematic experiments, Da Vinci reached a conclusion similar to that of Galileo”, says Molina.

Solo explains that Da Vinci “wasn’t a great promoter of his deepest work and he didn’t even write (the experiment) in the traditional way, but in front of the mirror, codified. Maybe he wasn’t so fully convinced of it to spread it”.

For Gharib and Roh, what this shows is that “he was an experimenter trying to test things and see how they worked, and then trying to explain them. First he did the experiments, and then he tried to understand their nature.”

All the experts consulted agree that it was da Vinci’s systematic experimentation that led him to reach a conclusion similar to that of Galileo almost a hundred years earlier.

Would anything have changed if Galileo or Newton had known about these experiments?

Molina says that without a doubt this would have been a source of inspiration for both of them.

“Newton said that he stood on the shoulders of giants to elaborate his theories. He knew the works of scholars before him. If da Vinci’s work was known at the time, it would be something that Newton would have noticed”, he points out.

Da Vinci observed moving clouds, falling hail, and then tried to replicate this in his laboratory.

“His way of seeing nature, of visualizing things, allowed him to see what we do today with super-technological cameras to analyze the same triangle that Da Vinci did”, says Gharib.

If this discovery shows anything, say Gharib and Roh, it’s the importance of stopping and observing your surroundings.