The New York Times
When Leonardo da Vinci wasn’t painting a masterpiece or dreaming of flying machines, he was pondering the mysteries of gravity. The Renaissance thinker considered himself as much a man of science as an artist, and spent countless hours exploring how the “attraction of one object to another” affected things like the flight of birds and the fall of water.
Now scientists have discovered that Leonardo performed detailed experiments that sought to clarify the nature of gravity a century before Galileo and nearly two centuries before Sir Isaac Newton made his investigation an exact science. The scientists’ study of their gravitational ideas and experiments was published this month in the journal Leonardo.
“Nothing could stop him,” Morteza Gharib, author of the article and professor of aeronautics at the California Institute of Technology, said in an interview. “He was way ahead in his thinking. He couldn’t wait for the future.”
Z. Jane Wang, a professor of physics at Cornell University who has studied some of Leonardo’s pioneering analyzes but was not involved in the work cited, said the new study revealed a man determined to find an iron law of nature that would explain the general dynamics of falling objects.
“It’s not enough” to call the polymath an artist, Wang said. More precisely, she added, he was a man “par excellence” of the Renaissance, when not only art and literature, but also science and explorations of nature flourished.
Leonardo is famous for his technical ingenuity and versatility, and for his sketches of flying machines and fighting vehicles. He also made advances in geology, optics, anatomy, engineering, and hydrodynamics, the branch of science that explores the behavior of fluids.
Walter Isaacson, in his biography of Leonardo, reports that, as a keen observer of nature, he paid close attention to how birds change their center of gravity as they twist, turn, and maneuver in the wind. He also said that Leonardo realized that gravitational pull prevented the seas from breaking away from the Earth.
Gharib said he learned about Leonardo’s gravity experiments while looking at an online version of the Codex Arundel, named after the Earl of Arundel, the British collector who acquired it in the early 17th century. Leonardo composed the collection of hundreds of works between 1478 and 1518 —that is, between the ages of 26 and 66—, a year before his death. The documents are in the British Library. The collection features his famous mirror writing, as well as diagrams, drawings and text covering a variety of topics in art and science.
What attracted Gharib’s attention was what he calls the “mysterious triangle” near the top of page 143. Its strangeness lay in the fact that Leonardo’s drawing showed an adjoining pitcher and, emerging from its spout, a series of circles. which form the hypotenuse of the triangle. Gharib used a computer program to flip the triangle and adjacent areas of writing upside down.
Suddenly, the still image seemed to come to life. “I could see movement,” Gharib recalled. “I could see him dumping things.” It was a special moment that revealed Leonardo’s early experiment.
The effects of gravity are usually thought of as causing something to fall—be it a thrown ball or Newton’s apocryphal apple. Looking at Leonardo’s drawing, Gharib realized that he had managed to divide the effects of gravity into two parts that revealed an aspect of nature normally kept hidden.
The first effect was the natural downward pull. The second was added when the pitcher’s bearer moved it along a straight path parallel to the ground, spilling sand or something else along the way. In the drawing, Leonardo noted where the pitcher’s movement had begun, marking it with the capital letter A. Then, to show the falling material, he added a series of vertical lines descending from the top line of the triangle, and the series lengthened. as the pitcher moved away from the starting point. Their increasing lengths defined the hypotenuse.
The scheme turned the hidden nature of gravity into visible increments. The pitcher experiment, Gharib said, revealed that gravity was a constant force that resulted in a constant acceleration — a constant gain in velocity. Leonardo illustrated the gain as the contents of the jug falling lower and lower over time. He managed to deconstruct gravity.
Researchers say Leonardo wrote in the codex that he witnessed fast-moving clouds from which hail pellets fell, which they believe inspired the experiment.
Gharib said that “the fascinating part” of Leonardo’s achievement was allowing him to estimate a constant of nature, the gravitational constant, represented today in physics by the letter G. The constant quantifies the exact force of gravity’s attraction and therefore how speed she can accelerate an object.
Despite the roughness of his experimental setup 500 years ago, Gharib said, Leonardo was able to calculate the gravitational constant within 10% of the modern value.
“It’s incomprehensible,” Gharib said. “That’s the beauty of what Leonardo does.”
The researchers say that Galileo and Newton were better able to tackle the gravitational question because they had better math tools and better ways to accurately measure time when objects fall.
Gharib agreed with Wang in seeing Leonardo as much more than an artist, and suggested that his fame as a pioneering scientist could soar if experts with technical knowledge investigated the Codex Arundel and other sources. In his biography, Isaacson reports that over 7,200 pages of Leonardo’s notes and sketches survive to this day.
Gharib said he hesitated to look deeper into the Codex Arundel lest he be tempted to focus exclusively on Leonardo’s mind. “I’m like a kid in a toy store,” he said. “I’m afraid to even look.”
He said that many art historians have examined the Codex Arundel, but not scientists. “It’s an open book that they haven’t looked at, haven’t spent time exploring,” he said. “There are so many other things to discover.”
Translated by Luiz Roberto M. Gonçalves
