The Physics of War (10 page)

As a takeoff from his parachute he also designed a glider that also likely would have worked. Again, the first gliders didn't emerge for another hundred years.

Helicopter

Closely associated with the inventions above was a simple helicopter. Leonardo got the idea from a Chinese toy that came into his possession. The device he envisioned was a giant whirling pinwheel in the shape of a screw. He knew enough about aerodynamics to know that as it spun it could produce an upward force, and as this force built up under the blade, it would lift the craft into the
air as a result of the pressure produced. In his model several men on cranks were needed to turn the blade. Unfortunately, he didn't know about Newton's third law (for every action there is an equal and opposite reaction), so his idea wouldn't have worked. Nevertheless, it was an ingenious thought for the time.

Diving Suit

One of the greatest dangers to seaports or cities on large rivers was invasion from the water. You could fight ships by bombarding them using cannons on the shore, but this usually wasn't too effective. Leonardo hit upon another idea for destroying them. He made drawings of diving suits that could be used by men under water. According to his idea, they would cut holes in the bottom of ships and sink them. Divers would carry breathing hoses connected to a bell containing air they could breathe. He even designed a facemask with glass goggles that would allow the diver to see underwater. The idea was, of course, one that is commonly used today.

Giant Crossbow

Although crossbows had been used for many years, and muskets and cannons were now beginning to replace them, the crossbow was still a frightening weapon that created considerable fear. Leonardo's giant crossbow appeared to be designed mostly to scare, intimidate, and terrorize the enemy. It measured twenty-seven yards across and was carried on six wheels. It was designed to fire large stones or perhaps flaming bombs rather than arrows. A crank was used to pull back the bow to load the device.

Leonardo's giant crossbow.

Water and Hydrodynamic Inventions

Water and hydrodynamics played a large role in Leonardo's inventions. As mentioned earlier, he spent years studying the motion of water as it struck various types of surfaces. This led him to design several machines that used the force of water. Paddle wheels, for example, were used in several of his devices. In addition, he designed light, movable bridges that could be assembled quickly so that troops could cross rivers.

Ball Bearings

Another invention that might not seem as important as some of the others is the ball bearing. Ball bearings are spheres that roll smoothly between moving surfaces and help reduce friction. Leonardo used them quite effectively in many of his machines in a way in which they had never been used before. And there is no doubt that they are used extensively today. Driveshafts, for example, would not be possible without them.

First Automobile and Computer

He also designed a programmable driverless vehicle that he no doubt thought of as a toy. In essence it was little more than a small cart, but it was powered by a spring similar to those used in early clocks, and it was able to move on its own when the spring was wound up. Of particular importance, a group of gears was used that forced it to travel a certain route.

Convex Lens–Grinding Machine

There is no indication that Leonardo invented any sort of telescope or microscope, but he did make convex lenses, and he didn't grind them by hand. He had a lens-grinding machine that did the work for him, and he left detailed plans for constructing it.

In his lens-grinding machine he used a handle that rotated a wheel, which, in turn, operated a gear that rotated a shaft that turned a geared dish. The glass to be ground sat in the dish.

Mortar Shells and Cannons

One of the major problems with mortar shells was their stability in flight. Leonardo showed that adding fins to a mortar increased its stability, and he made other advances in mortar technology. In a letter written to Ludovico Sforza he stated, “I also have types of mortars that are very convenient and easy to transport…. When a place cannot be reduced by the methods of bombards either because of its height or location, I have methods for destroying any fortress or stronghold, even if it be founded upon rock.”
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Leonardo's notebooks also show cannons that hurled large numbers of small stones and created considerable smoke upon striking their targets. And he made drawings of triple-barreled cannons and also a steam cannon.

Other Helpful Inventions

Scaling ladders that could be used to get over castle walls were quite crude at the time. Leonardo designed ladders that could be adjusted in height and that were particularly light.

Also among his drawings were plans for double hulls on ships, which would give them considerable protection from sinking. And finally, one of his most surprising and innovative constructions was a robotic man. Amazingly, the robotic man could stand, sit, move its head, raise and lower its arms, and open and close its mouth. It was built using pulleys, weights, and gears. It was built primarily for the entertainment of Ludovico Sforza.

LEONARDO'S ATTITUDE TOWARD WAR

Since he spent so much time designing engines and machines that would be used to kill humans, it might be thought that Leonardo was fascinated by war, and perhaps that he enjoyed it. But quite the opposite is true. He actually detested war and killing of any kind—not only the killing of people, but also the killing of animals. In fact, he could not bring himself to eat animal flesh. He was a vegetarian throughout his life, and he would often buy birds that were destined for slaughter in the marketplace so that he could set them free. Although he frequently stated that he hated and felt guilty about what he was doing, designing war machines was one of the best ways for him to make a decent living.

He was no doubt thankful that most of his killing machines were never actually built in his lifetime. Indeed, he didn't even publish them, and they weren't published until 165 years after his death.

TARTAGLIA

Cannons were continually being improved, and their range was increasing, but there was still a serious problem: accuracy. Most shells went over the heads of the enemy soldiers or fell in front of them. It was understood that a cannon's range depended somehow on the angle at which it was pointed, but little else was known. The man who would solve the problem—at least partially—was Niccolò Tartaglia.
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Tartaglia was born in 1500 in the northern Italian town of Brescia in 1500. His father was a mail carrier who was murdered when Niccolò was only six. As a result, his family, which included his mother and a sister, was thrown into poverty. To makes things worse, Brescia was invaded by French troops a few years later, when Niccolò was twelve. To the dismay and annoyance of the powerful French army, the Brescian military held them off for seven days. And when the Brescian forces were finally overcome, the French leader was so annoyed by their fierce resistance that he decided to kill everyone in the town as revenge. Tartaglia, his mother, and his sister hid in the local cathedral, but it didn't help. A French soldier found them and slashed Niccolò across the face and jaw with his saber. Thinking he had killed him, he left. When the French left the town, Niccolò's mother took him to their home and nursed him back to health, but the wound left him with a severe scar across his face and a bad stutter. As a result, Niccolò took on the new name Tartaglia, which means stutterer.
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Niccolò received some education early on, but he was mostly self-taught. He soon found that he was proficient in mathematics, and concentrated on it for several years. Eventually he learned enough mathematics to become a teacher, and he got a job teaching in Verona, but he was poorly paid for this work. In 1534 he moved to Venice, where he continued teaching mathematics. He later became a professor of mathematics and eventually became famous for his mathematical talent and knowledge.

It was about this time that he was approached by one of the gunners in the Venetian army. The gunner told Tartaglia about his cannon's inaccuracy, asking him for advice. Tartaglia soon became intrigued by the problem. The first thing he determined was that the maximum range could be achieved when the barrel of the cannon was pointed at an angle of forty-five degrees from the horizontal (neglecting air friction). He then began looking into other problems. What path did the projectile trace out? What kept it moving after it left the barrel of the cannon? Gunners could not answer these questions at the time. Tartaglia had just translated the early works of Aristotle and Euclid into Italian, and he was familiar with Aristotle's ideas in relation to projectile motion. According to Aristotle, all
motion of this type was straight-line motion; in other words, the projectile would move out of the cannon in a straight line and continue along this line until it ran out of what he called “impetus,” then it would fall directly to earth.

Tartaglia made arrangements with the gunner to watch a test firing of cannonballs at several different angles. The gunners thought the problem might have been related to the cannon itself, or perhaps the gunpowder. But Tartaglia immediately saw that they were not to blame; the problem was more fundamental, and it arose because of misunderstandings of how and why the cannonball acted as it did after it left the barrel.

Following Aristotle, Tartaglia defined two types of motion: natural motion and violent motion. Natural motion was the motion of a free-falling body, such as a stone. He stated that all objects that were “evenly heavy”—in other words, objects that were made of dense material, such as earth, and had a generally smooth circular form, so they didn't have significant resistance to air—had natural motion. He stated that such bodies fell directly toward earth in a straight line at an accelerated rate, but he was not sure of the magnitude of the acceleration, and he had no idea what caused it.

Projectiles, on the other hand, underwent violent motion. The view at that time was that the projectile accelerated as it left the barrel. No one knew for sure whether this was the case, however, because the projectile's high speed made it invisible at this point. But it seemed reasonable. Tartaglia came to the conclusion that this wasn't true. He was sure the projectile started to lose speed the moment it left the barrel because it was no longer under the influence of the propelling force created by the expanding gases in the barrel.

His initial idea was that the projectile went through three phases. The initial phase was a straight line extending out from the direction of the gun's barrel. At some point, however, the ball would begin to lose “force,” and its trajectory would become a curve. Finally, when it had lost all its “force,” it would fall vertically to the earth. He published his ideas in his book
New Science
in 1537. But as he thought about it more, he realized that his ideas could not be correct, and he finally decided that the first stage of the projectile's flight was actually a slightly curved trajectory. Furthermore, he now became convinced that a certain amount of force was impressed into the body when it was projected into the air, and when this force was exhausted the violent motion of the projectile became natural motion. He added these refinements in his second book on the subject in 1546. He argued that the trajectory was a result of a struggle between the speed of the ball and the force that was pulling it toward the earth. He also argued that a body could possess both natural and violent motion at the same time in certain cases.

Based on this work, Tartaglia developed a “gunner's quadrant” to assist artillerymen in aiming their cannons. One leg of the device was inserted in the barrel of the gun, and a heavy weight showed the angle of elevation of the barrel. The gunner could then consult tables developed by Tartaglia that showed the range of the gun for various angles. These tables were used for many years. They were not highly accurate, but they were the best that was available at the time. Nevertheless, a new science had been developed, namely ballistics, and it would become increasingly important in warfare over the years.

It's interesting that Tartaglia eventually became very tortured and remorseful about his contributions to the killing of his fellow humans. He had experienced war firsthand as a youth, and he hated it. He worried about what God would think of his work. It bothered him so much that in a fit of remorse he decided to destroy all his papers and notes related to ballistics.

Soon, however, the French formed an alliance with the Ottoman Turks, and together they invaded Italy. With the possibility of war coming home to him again, he relented and reconstructed all his previous work, giving it to Italy's defensive forces.

Tartaglia's contribution was significant, but many questions remained unanswered. He didn't know what kind of a “force” pulled the projectile back to earth, or how strong it was, and he knew nothing about what we now call inertia. The task of developing an understanding of these concepts was left to Galileo.