When Leonardo da Vinci was not
painting a masterpiece or dreaming up 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 untold hours exploring how the “attraction of
one object to another” could affect such things as the flight of birds and the
fall of water.
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Now, scientists have discovered that
Leonardo did detailed experiments that sought to illuminate the nature of
gravity a century before Galileo and about two centuries before Sir Isaac
Newton’s making its investigation an exact science. The scientists’ study of
his gravitational ideas and experimentation was published this month in the
journal Leonardo.
“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.”
A ‘quintessential’ Renaissance figureZ. Jane Wang, a professor of physics at
Cornell University who has studied some of Leonardo’s pioneering analyses but
was not involved in the current paper, said the new study revealed a man
determined to find an iron law of nature that would shed light on the overall
dynamics of falling objects.
“Nothing could stop him… He was far ahead in his thinking. It could not wait for the future.”
“It’s not enough” to call the polymath an
artist, Wang said. More accurately, she added, he was “a quintessential” man of
the Renaissance, which gloried in the revival of not only art and literature
but science and explorations of nature.
Leonardo has long been 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 arm of science that explores the behavior
of fluids.
Walter Isaacson, in his biography of
Leonardo, reports that as a close observer of nature, he gave much attention to
how birds shift their center of gravity as they twist, turn, and maneuver in
the wind. He also said that Leonardo realized that gravitational attraction
kept the seas from falling off Earth.
Leonardo’s ‘mysterious triangle’Gharib said he learned of Leonardo’s
gravity experiments while examining an online version of the Codex Arundel,
named after a British collector, the Earl of Arundel, who acquired it in the
early 17th century. Leonardo composed the collection of hundreds of papers
between 1478 and 1518 — that is, between the ages of 26 and 66 — the year
before his death. The papers reside in the British Library. The collection
features his famous mirror-writing as well as diagrams, drawings, and texts
covering a range of topics in art and science.
What caught Gharib’s eye is what he calls
“a mysterious triangle” near the top of Page 143. 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. Gharib used a computer
program to flip the triangle and the adjacent areas of backward writing.
: “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
Suddenly, the static image seemed to come
to life. “I could see motion,” 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, 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 first effect was the natural downward
pull. The second was added when the holder of the pitcher moved it along a
straight path parallel to the ground, pouring out sand or something else along
the way. In the drawing, Leonardo noted where the movement of the pitcher had
begun, labeling it with the capital letter A. Then, to show the falling
material, he added a series of vertical lines going down from the triangle’s
top line, the series getting longer as the pitcher moved farther and farther
from its starting point. Their growing lengths defined the hypotenuse.
The setup turned gravity’s hidden nature
into visible increments. The pitcher experiment, 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.
Clouds and calculationsThe 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.
Many art historians had examined the Codex Arundel — but not scientists. “It’s an open book they haven’t looked at yet, haven’t spent time exploring.”
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, Leonardo, Gharib said, was able to calculate the
gravitational constant to an accuracy within 10 percent of the modern value.
“It’s mind boggling,” Gharib said. “That’s
the beauty of what Leonardo does.”
The researchers say that Galileo and Newton
could better address the gravitational question because they had better tools
of mathematics and better ways of measuring time precisely as objects fell.
Gharib agreed with Wang in seeing Leonardo
as far more than an artist and suggested that his fame as a pioneering
scientist could skyrocket if more technically knowledgeable experts probed the
Codex Arundel and other sources. In his biography, Isaacson reports that more
than 7,200 pages of Leonardo’s notes and scribbles survive to this day.
Gharib said he hesitated to peer more
deeply into the Codex Arundel lest he find himself tempted to focus exclusively
on the mind of Leonardo. “I’m like a kid in a toy store,” he said. “I’m afraid
of even looking at it.”
He said many art historians had examined
the Codex Arundel — but not scientists. “It’s an open book they haven’t looked
at yet, haven’t spent time exploring,” he said. “There are so many other things
to be discovered.”
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