The Physics of War (11 page)

GALILEO

Tartaglia made important advances in the understanding of the trajectories of projectiles, but many problems remained. A better understanding of the nature of motion was needed, along with some sort of understanding of gravity. The first real breakthrough came from Galileo Galilei in Italy. He is frequently referred to as the father of modern physics, and there's no doubt that his achievements were phenomenal. Indeed, he was the first scientist to make a significant break with the teachings of Aristotle, which had been accepted for centuries. All the problems could not be solved, but the stage was set for another of the early giants of science: Isaac Newton.

Born in Pisa, Italy, Galileo was the oldest of seven children. His father was a musician and composer who dabbled in mathematics and experimentation. He even made an important breakthrough in physics, showing that in a stretched string, the pitch or frequency varies as the square root of the tension. Galileo no doubt got his skepticism of established authority from his father.
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Galileo's father was well aware of the fact that musicians and mathematicians were among the lowest paid professions. He encouraged his son to go into medicine, which was highly paid. And indeed, at age seventeen Galileo entered the University of Pisa to study medicine. But he soon got bored. A class in mathematics led to an interest in math and science, and Galileo decided he wanted to switch his focus. His father was extremely disappointed, for he knew that mathematicians made no more money than musicians, but he finally agreed.
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Galileo lectured at the University of Pisa in 1589 and was appointed to a chair in mathematics in 1592. He then moved on to the University of Padua, where he remained until 1610.

The Ballistics Problem

Within a few years Galileo made major contributions to the study of the trajectory of projectiles, which was of critical concern to gunners. It all started with his interest in gravity. Aristotle had said that all objects fall toward the earth with a speed that depends on their weight, and for years this appeared to be reasonable. It could easily be seen, for example, that very light feathers fell much slower than heavy stones. Galileo was skeptical, and according to legend he carried several balls of different weights to the top of the tower of Pisa and released them. The balls all struck the ground at the same time. Aristotle was wrong. Actually, there is no evidence that Galileo performed this experiment, but it is an interesting story nevertheless.
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Galileo wanted to go further, however. It was now obvious to him that the balls accelerated as they fell, so they had different velocities at different positions above the earth. Indeed, the farther they fell, the greater their velocity, and Galileo wanted to measure their acceleration. But because objects fell so fast, it was difficult to set up a straightforward experiment. So he decided to slow things down. The best way to do this was to let the object roll down an incline. The object would speed up in the same way because gravity was still acting on it. Again, he noticed that the acceleration of the balls down the incline was independent of their mass. In other words, they all got to the bottom with the same speed, regardless of how much they weighed. A detailed study of this motion led to several important conclusions.

Earlier Galileo had discovered something similar with pendulums. While at church he had noticed objects at the end of long ropes swinging as a result of air currents in the church. Clocks were not available at this time so he used his pulse to time them, and he noticed that regardless of the distance they swung (called the amplitude) they took the same time to complete a swing. Again, it
was gravity that was pulling the weight downward (along with the current), causing the objects to swing. Galileo was never able to measure the acceleration of gravity, but we now know that it is 32 ft/sec
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, and we know that it acts on all objects on earth. He did, however, show that the square of the period of the pendulum varied directly with the length of the pendulum.

Building on his discoveries in relation to gravity, Galileo decided to look at projectile motion carefully in an effort to thoroughly understand it. He imagined first of all that there was no air resistance, as he knew that the air around a projectile acted on it to change its motion. As a first step, it was best to ignore it. Second, he considered the forces that were acting on the projectile. Obviously the first force was the expanding gas from the gunpowder that thrust the projectile from the cannon barrel. Once it was out of the barrel, this force was gone, and the projectile would have a constant velocity if no other forces were acting on it. In stating this, Galileo was imagining a new concept that we now call inertia. All bodies in motion have a certain amount of inertia, and as a result of it they will continue in motion with the same velocity unless this inertia is overcome by an outside force. In the above case there was an outside force acting on the projectile after it left the barrel, namely gravity, and gravity would cause it to fall in the same way any object falls when released. The only difference in this case was that the projectile also had a horizontal velocity.

These results helped to give Galileo a better understanding of projectile motion. As a result of his observations he came to the following conclusions:

• Bodies fall with uniform acceleration (as long as the resistance of the medium is neglected).
  
• Objects in motion retain their motion unless some sort of force acts on them.
  
• The law of acceleration: the total distance from rest under acceleration is proportional to time squared.
  

His big break with previous ideas was the statement that a force was present only during the acceleration of the projectile. Once the force was taken away, the object no longer accelerated, but it continued at a constant velocity unless acted upon by another force. This was in conflict with Aristotle's idea that a projectile in motion was under a constant force; in other words, it had a “reservoir” of force that was gradually used up. Galileo said this was incorrect.

Galileo decided that the most logical curve the projectile would undergo as a result of this was a parabola. What is a parabola? The best way to understand it is to think of a cone (see figure). If you slice through it parallel to the base, you'll
get a circle, but if you slice through it at an angle, you'll get a parabola (as long as you don't pass through the base).

A parabola, the second curve from the top.

Military Compass

As a result of his work on projectile motion, Galileo developed a “geometric military compass.” It was a takeoff on Tartaglia's device for gunners, but it had many improvements. It gave gunners a new and safer way for aiming their cannons more accurately. Furthermore, it had scales and numbers on it that told them how much gunpowder was needed for cannonballs of various weights and sizes.

Like Tartaglia, Galileo abhorred war and felt guilty about developing war weapons, but he felt they were necessary. Also, his wages were relatively low, and it was something that paid well. So not only did he develop the gunner's compass; he had over a hundred built and sold, and he made an excellent profit on them. Furthermore, he taught a class to gunners on how to use the new device, and he also wrote a book on it, which he sold.

Interestingly, with minimal modifications, the same device was eventually used in surveying.

The Telescope

Although it isn't exclusively an instrument of war, the telescope is invaluable in relation to it. The first telescope was built by Hans Lippershey of the Netherlands in 1604. Galileo heard of it within a short time, and he set out to build one. He was already familiar with the grinding of lenses, so he was able to construct one quite quickly. He completed his first telescope in 1609, and it was a significant improvement on Lippershey's model; it had a power of about three (in other words, it magnified three times). Soon after he built an improved one of about eight power, and he presented it to the lawmakers of Venice in 1609. They were thoroughly awed and impressed, and they quickly realized that it would be helpful in the event of an attack, particularly from sea. The sail of an enemy ship, for example, could be seen at least two hours before it could be seen with the naked eye, and this would give a tremendous advantage. He was awarded a stipend for building additional telescopes.

But the military use was of little interest to Galileo; he was more interested in what telescopes would show him above the earth in the night sky. And over the next few years Galileo revolutionized astronomy. He discovered that Jupiter had four tiny moons, and that Venus presented phases like our moon when seen close up. He also noticed that Saturn had a strange ring around it, and he went on to study our moon, noting that it was covered with craters. And even the sun was different than thought: it was not the pure, clear disk that everyone had assumed. It was covered with dark spots—what are now called sunspots. And finally he looked in detail at the Milky Way and found that it was composed of thousands (perhaps millions) of individual stars. Indeed, over a relatively short period of time he made more discoveries in astronomy than had ever been made in the centuries before him, and even after him.

And Galileo didn't stop with the telescope; he also constructed a microscope. Again it wasn't the first, but it was likely the best available at that time. He used it for examining insects and various other small objects.

Other Inventions

The telescope and microscope were not the only devices Galileo constructed. In 1593 he built one of the first thermometers. It was based on the expansion and contraction of air in a ball that moved water in an attached tube. He even tried to market it, but he was unsuccessful.

Galileo was one of the first to understand the role of frequency (or pitch) in relation to sound, and he made an attempt to determine the speed of light, but was unsuccessful. And he invented a device for determining how much heavier metal was than water.

Galileo is perhaps best known for his objection to the idea of the earth-centered universe that was accepted in his day. He was sure that the sun was at the center of the solar system, and he was eventually condemned by the church for his ideas.

For several decades after the death of Galileo there was almost continuous warfare. This period included the Thirty Years' War of 1618 to 1648, which was one of the most costly wars in terms of human life in the history of the world. The deadliness of this conflict was largely a result of the new weapons that were devised. So let's start with these weapons, and the guns, in particular.

THE GUNS OF WAR

In the previous chapters we saw how the cannon was developed and how it evolved, but within a short time after its first use men were beginning to think about something smaller that could be handheld, and soon the first hand cannons appeared. They came about mainly as a result of the problems of steel armor; that is, it could still withstand most of the arrows from the longbows (unless they happened to strike the right place) and it was quite effective against the bolts of the crossbow. Something was needed that could easily penetrate this armor. Cannon shells were certainly adequate, but they were large and unwieldy. Something smaller was needed, and it finally came in the form of the hand cannon. Hand cannons were first used in China in the thirteenth century, but they were generally inaccurate and difficult to use; nevertheless, the bullets from them could penetrate most types of armor at close range.
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The barrels of the earliest guns were about four feet long, and they were made from wrought iron or bronze. Attached to the barrel was a wooden stock. One of the main difficulties in using these early guns was that two men were needed because it took two hands to aim and hold them steady and another pair of hands to light and hold a match to the touchhole. It was possible for the gunner to prop his gun in a support and light his own gun, but it was difficult. The earliest hand cannons were also relatively heavy, at about twenty to twenty-five pounds, but they could fire projectiles up to one hundred yards.

Strangely, while they were relatively inaccurate, their flash and loud roar usually had a strong psychological effect on the enemy—particularly if the enemy had never seen them before. In many cases enemy soldiers fled in terror. Hand cannons were used extensively throughout Europe and Asia until about the 1520s. But as new developments in powder emerged, such as granulated powder, handguns began to improve. The first to appear after the hand cannon was the arquebus, which means “hook gun” in Dutch. What the hook referred to is still uncertain. Most believe it was the hook-shaped wooden stock. Later guns did, however, have a hook mechanism that held the match.

There is a problem with terminology, as some of the later guns were also called arquebuses. At any rate, it was first used in about 1458, and it was commonly used until about 1490. Again, it was a short-range weapon that was difficult to reload, but looked a lot more like our modern rifle than did the early hand cannon. Furthermore, advances in gunpowder had made it much more powerful. But it was heavy and usually had to be rested on a balance.

The arquebus was followed by the musket, but again there's a problem with terminology. Later on, almost all hand-held guns were called muskets, and the gunners that shot them were known as musketeers. They were muzzle-loaded and had a smooth-bore barrel. The earliest handheld guns were usually held against the chest, but within a short time they were designed for the shoulder, and gunsmiths eventually design curved stocks so that the gun could be held up against the shoulder to stop the recoil. This represented a considerable improvement over the arquebus in that a musketeer could usually get off two shots in about three minutes.

Over time the early musket evolved into the matchlock musket. Its main advantage was that it got rid of the problem of igniting the primer using a handheld match. The match was now attached to the gun and was applied when the trigger was pulled. Eventually the match became a slow-burning fuse, or, more exactly, a smoldering piece of cord. The matchlock also now had a primer pan. A spring-loaded lever was attached to the metal hook that held the smoldering cord. When the shooter pressed the lever with his fingers, the “match” was lowered into the priming pan, which was filled with powder. The priming pan was attached to the touchhole, which led to the charge in the barrel. The flash in the priming pan ignited the powder in the touchhole, which, in turn, ignited the powder in the barrel. Within a short time, however, the lever was replaced with a trigger.
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The matchlock was the main military weapon for many years, but it was cumbersome to load and fire. Before firing, the gunner had to go through many steps:

• Pour powder down the barrel, then place a wad and a bullet on top of it
  
• Fill the primer with different powder from another flask
  
• Cock the hook holding the smoldering cord, then blow on it and make sure it would ignite powder
  
• Pull the trigger
  

And even with all this, much of the time it wouldn't fire. If it was raining or the weather was bad the powder would be ineffective. Furthermore, the gunner was in danger because he carried so much open powder and the fuse was always lit. Accidents were common; sometimes, in fact, the gun would explode in his hands. Nevertheless, the matchlock was used for many years, and over the years it was improved. The length of the barrel went from about four feet down to about three. Rests or balances for the gun eventually became obsolete, and the powder gradually improved.

A significant improvement over the matchlock came in the early 1500s, but for the most part it was rarely used in military guns, and main reason was that it was expensive. The new gun became known as the wheel lock. The lighted fuse was the main problem: it was useless in rain, and it could be easily seen by the enemy. What was needed was a mechanism that created a spark that could light the primer pan. The design for such a mechanism was first discovered by Leonardo da Vinci in about 1490, but he kept most of his inventions secret, so it's not known if it helped the military at this time. The same design was found in a German book in 1507 in Austria, and it was eventually built by German gun makers early in the 1500s.
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The mechanism is similar to a modern cigarette lighter. In short, the spark was generated by a spinning grooved steel wheel that was pressed against a piece of pyrite. Another critical development was that the flash pan now had a cover to keep the powder in it dry. In preparing to fire, the gunner slid open the flash pan and poured powder into it and then slid the lid shut. The steel wheel was in the flash pan, and the lever holding the pyrite was above the pan, held in place by a spring. When the trigger was pulled, the wheel began spinning, the lid of the flash pan slid back, and the pyrite slammed down into the spinning wheel producing intense sparks. The sparks lit the primer, which in turn lit the powder in the touchhole, and it triggered the explosion in the barrel.
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German gun makers were quite enthusiastic about the wheel lock, but its mechanism was expensive and delicate. Basically, it was too expensive to be mass-produced for the military. However, it was used by aristocrats as a hunting weapon, and later the same mechanism was used in pistols. Pistols, in fact, were now favored by the cavalry, as they were easy to hold and fire.

THE WAR AT SEA

Handheld guns spread quickly throughout Europe, and soon the long bow and the crossbow were gone. The musket was the main weapon, and its effectiveness tended to accelerate warfare in an already fragile arena. And while things were accelerating on land, developments were being made at sea. For the most part, though, progress was slower here, and there were more problems. One of the biggest problems was the mounting of large cannons on the deck of a ship. They were heavy, and if too many of them were mounted they would make the ship unstable.

But this wasn't the most serious problem. Navigation was a hit-or-miss process, particularly on the open sea. Because of this, most sea captains preferred to stay within sight of land. But they could only do this so long. It soon became known that the region beyond the open seas was rich with treasure. Not only was there gold, but there was sugar, tea, and spices that could be sold at a tremendous profit. The sea, however, now held another danger: pirates. Small, fast ships were waiting for large ships laden with treasure, and they quickly attacked any they found.

England, Spain, France, and Portugal were the main powers at the time, and they all wanted to build up their navies, both because of the lucrative trade with Asia and other lands and also because they needed a strong military force at sea. One of the first to realize a strong navy was critical to survival was Prince Henry of Portugal. He was born in 1394, the third son of King John I. At the age of twenty-one he headed up a military force that attacked and captured the military outpost of Ceota, in the Straits of Gibraltar.
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Because the feat so impressed his father, Henry was allowed to set up a naval institute in the southwest of Portugal at Sagres. Henry, the navigator, as he eventually became known, knew that a powerful navy was critical to the success of a country, and he set out to build the best navy in the world. It was also the key to incredible treasures beyond the seas.

As a first step, Henry began a search for the best mathematicians, astronomers, cartographers, and geographers in Europe. And in 1418 he assembled them all at his naval institute. He had several goals for the institute. One of the most important was developing better navigation, but he also wanted to design faster and better ships. Basically, his institute was a research and development facility that included one of the best libraries in the world.

Henry soon had two major goals: locate the best naval route to the main trade areas of Asia, and explore the west coast of Africa. The continent of Africa was a great unknown at the time, but there was a lot of speculation about the treasures that might be found there.

One of the first things that Henry did was develop and build a new type of ship, which was faster and more maneuverable than most ships on the seas. It was called the caravel. And he quickly sent out the first caravels to explore the west coast of Africa. In particular he wanted to explore as far south as possible. (Although he sent out many expeditions, he was not on any of them himself.) But there were problems. One of them was that navigators needed Polaris (the North Star) to navigate, and to their surprise and frustration, Polaris disappeared over the horizon when they moved too far south. Furthermore, there were many tales of monsters, wild waters, storms, and so on in the region, so sailors were very cautious about going too far.

Navigators had compasses to help guide them. The device, which consisted of a sliver or needle of magnetite, balanced so it could spin freely, had been developed many years earlier by the Chinese. They also had sailing charts, but they were inaccurate, as little was known about the region beyond the open seas.

Surprisingly, Henry could have made a major discovery in navigation on the open seas, but he let it slip through his fingers. An Italian cartographer and mathematician, Toscanelli, was working on new charts of the world, as it was known at the time. Born in Florence, Toscanelli had been educated in mathematics at the University of Padua in 1424. His main interest in his early years was astronomy, and he made numerous observations of comets, but he eventually became interested in cosmography—the study of the overall earth, as it was known. What did the overall earth look like? He was acquainted with the maps of early Greek geographers, and he had knowledge of Ptolemy's work and Marco Polo's trips to Asia. Using these sources, he set up a map showing Europe and Asia; he was convinced that their land mass covered approximately two-thirds of the surface area of the earth. He overlaid his map with a grid (squares of a particular size that covered the entire map). Not only did they cover the land areas, but they also covered the open sea. Excited about his new maps, he took them to Henry's naval institute, sure that his scholars would be excited about them also. To his disappointment, they showed little interest.
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Undeterred, Toscanelli then took his maps to Spain, where they were enthusiastically accepted. Indeed, it was just before Columbus was setting out on his well-known voyage of 1492 across the open sea, which resulted in his discovery of America. Columbus was delighted with the new maps and was said to have used them on his trip.

HENRY VIII OF ENGLAND

When most people hear the name Henry VIII they think of his problems with his many wives. Few know that he developed one of the strongest navies in the world at the time. He increased the English navy from eight ships to forty-six warships and thirteen other smaller vessels. And he was also responsible for important advances in the physics of naval warfare. He certainly wasn't interested in science, but he was determined to strengthen the English naval forces, mostly because he needed to protect English sea trade, which meant riches. Gold, silver, sugar, spices, and tea enticed him. But ships laden down with gold and other treasures were bait for pirates. Furthermore, Spain, Portugal, and France were also looking at what the lucrative trade market could do for them. Henry was also worried about an invasion from France.
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