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Show Unlverslt'( Jou1lllll • MDnclilY, AIIIIUSt 5, 1996 • (continued from page 6) machines, fortifications, canals, etc.-accompanied by careful notation. Leonardo was left handed, and he wrote in a right-to-left script that can be read with a mirror. He kept a small pad of paper on his belt, or in his pocket, on w hich he scribbled tentat ive ideas which were later transferred to larger sheets of paper. Thousands of these sheets survi ve. Many were combined into " notebooks," of which 3 1 have been identified. Taken together, they constitute one of the most remarkable collections ever penned by a single individual; and they reveal Leonardo's intellectual interest in every field of inqui ry open to him. eonardo's interest was not just in subjects suitable for painting, but in every object to which the laws of nature pertained, the most important of which was man. He viewed man as the embodiment of the physical universe. Man, for Leonardo, was somet hing of a miracle; the human body, something divine. . The body, as Leonardo envisioned it, required a lifegiving source and a life preserving force. Leonardo was content to draw upon Aristotelian sciences for that, believing, as most people in his day still believed, that this cosmic fo rce of the uni verse is located in the soul and is in tum capable of being transmitted to other organs of the body. Everywhere Leonardo looked he saw force at work. Primal mechanical fo rces were to be seen not only in gravita tion, energy, and momentum, but in the flight of birds, in the movement of water and of air, in the growth of plants and ani mals, in the flame of a candle, in smoke and in clouds. It is in the analysis of this force tha t Leonardo displays his incomparable ingenuity. And he displays, too, his ability to assemble the dispara te elements of his knowledge under a guidi ng principle: nature is subject to law-a Jaw of necessity and order without which all would be chaos. "Force, I define," says Leonardo "as a spiritual power, incorporeal or invisible which with brief life is produced in those bodies which as the result of accidental violence are brought out of their natural state and condition." But, then, considering that Leonardo saw this force as clearly in the waves of a woman's hair as in the waves of the water or the currents of the air, it became evident that it would be extremely difficult to separate Leonardo the scientist from Leonardo the painter-because, in sketching these various phenomena, his hand moved in the same way. To see how readily Leonardo mixes art and science one need only review his ideas about their relationship, because for him art and science were not two separate things. He saw himself first and foremost as a painter in search of knowledge, of understanding. But that can be had only with the eye which "knows how to see," of the hand which "knows how to follow the intellect." Art, then, is ultimately an experience of the intellect; and it is the work of the hand which defines the compass of man's thought. It is inst ructive to trace in Leonardo's own words the primacy of the sense of sight: "Now do you not see that the eye embraces the beauty of the whole? It is the lord of astronomy and the maker of cosmograpby; it counsels and corrects all the arts of mankind; it leads men to different parts of the world; it is the prince of mathematics, and the sciences fo unded on it are absolutely certain. It has measured the distances and sizes of the stars; it has found the elements and their locations; it divines the fut ure from the course of the stars; it has given birth to architecture, and to perspective, and to the divine art of painting." T he idea that the senses could yield the truth about nature would have come as news to most of Leonardo's contemporaries, who still clung to the authority of the scholastic tradition. But for Leonardo, experience was more important than authority. Anyone who argues by referring to authori ty," he writes, "is not using his mind but rather his memory." That is why he broke from the philosophy of the schools that believed not only that reality can be mirrored but tha t it can be captured in a web of words. "Necessity," wrote Leonardo, "constrains the mind of the painter to transmute itself into nature's own mind, and to make itself an interpreter between nature and art." The artist thus becomes a transmitter of the data of experience, and he alone is pre-eminently qualified to probe and unfold the secrets of nature. On this view, art is the road man takes to knowledge, and, eventually, to action. In a Platonic sense, this process becomes an act of love-"the union with the thing that is known." The act is essentially creative, because the knowledge of nature gleaned from observation makes it possible for man to overcome his limitations and learn a new power over nature. As it was acknowledged by Renaissance thinkers that God revealed himself in nature, it was natural to seek Him there. It was, in fact, a religious expression to do so. It is not, however, in his words but in his hundreds of drawings of machines, many of them his own inventions, that Leonardo revealed himself so stunningly as a scientist. Leonardo's scientific insights, no less than Galileo's, were a result of theories advanced by the Greeks, the Arabs, the medieval scholars Albert of Saxoriy, John Buridan, and others who were uncomfortable with Aristotle's principles. Aristotle believed that if force is not continually exerted on a body it will slow down and cease to move. 11 I 7 But what applies to bodies subjected to obstruction of the medium they exist in is not true of celestial bodies, a fact that Aristotle did not recognize. Now, in what sense can Leonardo be sa id to anticipate Galileo and others who were to work out a whole new theory of mechanics ? In regard "to the principles of motion, Leonardo made monu mental contributions. " Every motion," says Leonardo, " tends to maintain itself, that is, every body that is moved always moves as long as the impression of the moti ve forces remains in it." In another place, he wri tes, "Every body will follow its path in a straight line as long as the violence done by its motive force persists in · it." The principle of inertia- the tendency to persist in a straight line or at rest- is apparent in these passages, although complicated somewhat by the "impetus theory" of the 14th century scholars in Paris and London. Also reminiscent of Galileo are some of the properties of an enclosed plane di scovered by Leonardo. Apart from his anti cipation of Galileo, there is an anticipation of Newton in Leonardo's princi ple of reaction: 11 An object offers as much resistance to the air as the air offers to the object." " Every body goes in a direction opposite to the place from which it is driven by the object that strikes it .... 11 In other words, an action is equal to and contrary to the reaction. Leona rdo, it may be concluded, clearly had an understanding of the first and third laws of motion. T o appreciate even more fully Leonardo's contribution to science, one can look at his work on the impact of elastic and inelastic bodies, his work on the propelling action of the screw, his understanding of the principle of the syphon, of communicating vessels, of the parachute, of the inverted images obtained by a convergent lens and rectified by another lens. The list seems endless. Even in the science of anatomy, Leonardo's competency was so certain that, had he continued his studies, he almost certainly would have arrived at the conclusions reached by Vesalius and Harvey. uch of Leonardo's fondness for experimental science was put to work as a military engineer, which involved his competency as a hydraulic engineer. His studies in military art and architecture and the mechanics and technology to support it were pursued while he was still in Florence. In 1503 he was serving as a military engineer for the city of Florence. Along with Machiavelli, he worked on his plan to divert the Amo River, so that Pisa would be cut off from traffic with the sea and be forced to surrender. Before departing from Milan in 1482, to enter the service of Ludovico, the Duke of Milan, Leonardo -composed a letter outlining his qualifications. He mentions portable bridges, scaling ladders, means of cutting off water from trenches during a siege, methods of destroying fortresses; he mentions mortars, gunpowder, cannon-resistant ships, means of moving forces by traveling underneath enemy trenches or underneath a river; he mentions chariots armed with artillery [tanks!; and he mentions his knowledge of cannons, and, light ordnance. Yet, while Leonardo made significant contributions to military hardware and tactics, (continued on page 8) |