The weight of observation: Leonardo da Vinci draws out the principles of gravity. From the article:

Now, scientists have discovered that Leonardo did detailed experiments that sought to illuminate the nature of gravity a century before Galileo and some two centuries ahead of Newton’s making its investigation an exact science….

“Nothing could stop him,” Morteza Gharib, an author of the paper and a professor of aeronautics at California Institute of Technology, said in an interview. “He was far ahead in his thinking. It could not wait for the future.”…

Leonardo has long been famous for his technical ingenuity and versatility, for his sketches of flying machines and fighting vehicles. He also made advances in geology, optics, anatomy, engineering and hydrodynamics, the arm of science that explores the behavior of fluids….

What caught Dr. Gharib’s eye is what he calls “a mysterious triangle” near the top of Page 143 [of The Codex Arundel]. Its strangeness lay in how Leonardo’s sketch showed an adjoining pitcher and, pouring from its spout, a series of circles that formed the triangle’s hypotenuse. Dr. Gharib used a computer program to flip the triangle and the adjacent areas of backward writing.

Suddenly, the static image seemed to come to life. “I could see motion,” Dr. Gharib recalled. “I could see him pouring stuff out.” It was a eureka moment that unveiled Leonardo’s precocious experiment.

The effects of gravity are typically seen as causing something to fall straight down — be it a dropped ball or Newton’s apocryphal apple. In gazing at Leonardo’s drawing, Dr. Gharib realized that he had managed to split the effects of gravity into two parts that revealed an aspect of nature normally kept hidden….

The setup turned gravity’s hidden nature into visible increments. The pitcher experiment, Dr. Gharib said, revealed that gravity was a constant force that resulted in a steady acceleration — a steady gain in speed. Leonardo illustrated the gain as the pitcher’s contents falling lower and lower over time. He succeeded in deconstructing gravity.

The researchers say Leonardo wrote in the codex that he witnessed fast-moving clouds from which pellets of hail had fallen, which they believe inspired the experiment.

Dr. Gharib said “the fascinating part” of Leonardo’s feat was that it let him estimate a constant of nature, the gravitational constant, represented today in physics by the letter G. The constant quantifies the exact strength of gravity’s pull and thus how quickly it can accelerate an object.

Despite the crudeness of his experimental setup 500 years ago, da Vinci, Dr. Gharib said, was able to calculate the gravitational constant to an accuracy within 10 percent of the modern value.

“It’s mind boggling,” Dr. Gharib said. “That’s the beauty of what Leonardo does.”

h/t Jonathan Reid