The Physics of War (13 page)

THE THIRTY YEARS' WAR

As cannons and handguns improved, they became more deadly, and, as a result, things soon began to change. For the most part, battles became less intimate, with one group firing at another from a distance. Gunners never saw the people they killed. At the same time, however, warfare became more devastating and gruesome. Armies would march through villages pillaging, burning, looting, and raping, and sometimes they would even obliterate entire villages.
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Muskets were by this time fairly accurate at several hundred yards, and cannon bombardment had become devastating. There was little protection from either of these. Because of this, warfare became common, with few breaks between battles. One of the most devastating wars was the Thirty Years' War, which lasted from 1618 to 1648. It actually wiped out a large fraction of the male population of several countries, and it was one of the longest continuous wars in the history of the world. It began as a religious war, mostly between the Protestants of France, Sweden, and Holland and the Catholics of the Holy Roman Empire. At the time the Holy Roman Empire was made up of a collection of largely independent states, including Spain, Austria, and Bavaria. As time passed, however, religion began to play less and less a role, and the war developed into a more general conflict based on politics.
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Many of the main battles of the Thirty Years' War took place in what is now Germany. Needless to say, developments in physics and all sciences were at a standstill during these years. By the war's end, most of the countries involved were not only bankrupt, but also in ruins. Physics did play a role, however, in its contribution to the weapons and tactics used.

The war began in 1617 when an Austrian prince, Ferdinand II, was chosen to become the king of Bohemia. Within a year of ascending to the throne Ferdinand, a Catholic, began closing Protestant churches. The Protestants, as expected, rebelled, and when Ferdinand sent two Catholic counselors to the
Hradčany Castle in Prague as administrators of his new government, Protestants seize them and threw them through a plateglass window that was seventy feet above the ground. Miraculously they survived, but the war was now on.

The Catholic king of Spain and the monarch of Bavaria sided with Ferdinand. Several German princes sided with the Protestants. Between 1618 and 1625 the Protestants suffered defeat after defeat. The key players on the Catholic side where the Habsburgs, a royal family that ruled the Holy Roman Empire, along with Austria, Bohemia, and Spain. Many of the other countries in the region feared the Habsburgs, and the French, English, and Dutch formed a league to oppose them. They backed Christian IV of Denmark and encouraged him to invade Germany in support of the Protestants. Against Christian's army was a Habsburg army under Albert of Wallenstein, and Christian's army was crushingly defeated. Over several years the Protestants lost considerable land and suffered defeat in most battles. Then came Swedish intervention.

SWEDISH INTERVENTION

The Holy Roman Empire and its Catholic allies were soon in for a surprise. The young king of Sweden, Gustav Adolphus, began to worry that the war was getting too close to Sweden; he feared a move against Sweden and decided to act before it happened. Adolphus had become king of Sweden in 1611 at the age of seventeen. He was young, but he had been prepared well by his father, and he was a natural leader. Over the years he had taught himself the latest techniques in artillery, military strategy, logistics, and organization. Furthermore, he already had considerable experience leading troops to war; at the age of thirty-one he had led Sweden to war against Poland, and won.

His troops were some of the best in the world. Gustav drilled them continuously, and he was a strong disciplinarian. He wanted perfection, or close to it; in particular, he wanted maximum gunfire from his troops at all times. In his effort to achieve this goal he reduced the weight of muskets so that they were easier to handle, and he introduced paper cartridges and containers of premeasured powder. Loading had to be done as quickly as possible. His military could fire with high accuracy at speeds three times faster than most of his rivals. In addition, he made important tactical changes. His troops charged the enemy from the front and sides, firing as they went. Then they would quickly retreat and reload for another assault. He emphasized attack over defense, and mobility was also emphasized. And finally, unlike most armies, his army was cross-trained. Infantry and cannon gunners could easily exchange places, and everyone was taught to ride horses, so
a cavalry man could easily be replaced. He made so many advances, in fact, that he is frequently referred to as the father of modern warfare.
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So when he attacked northern Germany in 1630 he was well-prepared, and he easily overcame the opposing Catholic army. Unlike most armies that plundered and looted the countries they occupied, Gustav did not allow his troops to plunder and loot. Forging forward, Adolphus met the army of the Count of Tilly in 1631, and he quickly overcame it. Then he continued across Germany to the Rhine, where he stopped in preparation for an invasion of the Holy Roman Empire. The following year he invaded Bavaria again, quickly overcoming his Catholic opponents.

In 1632 he had a coalition army of about twenty thousand men. General Wallenstein, whom he had fought earlier, led a Catholic army that had almost the same number of men. They approached one another at Lützen, Germany. Adolphus and his troops bedded down and prepared to attack at dawn, but when they woke, the entire area was immersed in a thick log. The delay helped Wallenstein get his cavalry into position, and it caused several problems for Adolphus. The fog didn't lift, and Adolphus finally decided to attack under the cover of fog. But when he attacked, confusion reigned; it was difficult to distinguish the enemy, and Gustav and a small contingent of mounted soldiers soon lost contact with the main branch of their cavalry. The confusion that followed led to a tremendous slaughter on both sides, and during it, Adolphus was hit by a bullet. His horse panicked and began running wildly through the fog until Adolphus finally fell off. As he lay on the ground several enemy soldiers who were probably ignorant of who he was shot him again. In the end the Swedes won, but their leader was now dead, and this was a tremendous blow to them.

Interestingly, Wallenstein survived the war but was assassinated shortly after it. And the overall war was still not finished. It continued for another sixteen years, coming to an end in 1648. Adolphus was hailed as a hero in Sweden, and he has been revered ever since. He is now referred to as Adolphus the Great.

A NEW ERA OF DISCOVERY: ISAAC NEWTON

Few advances in physics occurred in Europe during the Thirty Years' war, and England was still weak, so little happened there. But soon one of the greatest periods of scientific productivity would come, and one man, Isaac Newton, was mainly responsible for it. Newton had almost no interest in the military, and he did not work directly on any military project, but his discoveries had a tremendous effect on weapons and warfare, and because of Newton's insights,
humankind for the first time had a fundamental understanding of the physics behind them.

Newton was born in January 1643 at Woolsthorpe Manor in England—the same year that Galileo died. His father was a relatively well-to-do farmer, but he died before Newton was born. Newton's mother remarried shortly after his birth and left him with his grandparents. Later, he attended boarding school in Grantham, and from age twelve to seventeen he attended Kings School in Grantham. When he graduated, his mother decided to make a farmer out of him, but it didn't work out. He had no interest in farming, and the master at Kings School finally persuaded her to let him attend Cambridge University.
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Isaac Newton.

In June 1661 he entered Trinity College at Cambridge to study mathematics, physics, astronomy, and optics. Not much is known about his years at Cambridge, but his outstanding ability came to the attention of one of his teachers, Isaac Barrow. In 1665 the bubonic plague struck; Newton had to return home. The year that he spent there is now considered to be one of the most important years in the history of physics. It was during that year that (according to legend) he saw an apple fall from a tree in his yard and began to wonder why it fell. The event soon led to his famous “law of gravitation”—one of the most important breakthroughs in physics. During the same year he is said to have invented calculus, but strangely, he kept it secret for many years. And in the meantime a slightly different form of calculus was discovered by Leibniz in Germany, and, as a result, there was considerable controversy later about who actually invented calculus.

Soon after returning to Cambridge he was appointed professor of mathematics, a position that he held for the rest of his life. And during his early years he continued to make fundamental discoveries, particularly in the field of light and optics, but also in relation to motion and dynamics. He presented some of his discoveries to scholars at Cambridge and was surprised that he was criticized quite severely—and Newton was not a man who could take criticism. He continued his experiments, and he continued to make important discoveries, but he filed them away and kept them to himself for years. Indeed, if it hadn't been for the astronomer Edmond Halley, he might have taken them to his grave.

In 1687 Halley and a friend, physicist Robert Hooke, were having an argument about the mathematical form of the law of gravity; they had ideas about it, but they were uncertain. Halley knew Newton, and he was sure that Newton could resolve the argument, so he went to him. And sure enough, Newton had the answer. He told Halley that he had proved mathematically that it was an inverse-square law, and he offered to show it to them. He searched for the calculation he had made, but he couldn't find it, so he promised to send it to Halley later. Halley received it a few days later and was amazed. He went back to Newton to discuss the results with him and was amazed even more that not only had Newton discovered the law of gravity, but he had made numerous other discoveries that he had never published. This eventually led to one of the most important books ever published in physics, called
Philosophiae Naturalis Principia Mathematica
, or, as it's more commonly known, the
Principia.

Contained within the
Principia
were the three basic laws of motion, now referred to as Newton's laws. The first law stated that
a body will continue in a state of rest or motion in a straight line, unless acted upon by a force
. At the time this seemed to defy common sense. It didn't seem possible that objects in uniform motion continued their motion indefinitely. But unless a force acted on them to change their motion, they did. Newton's second law was concerned with this force. It stated that
an acceleration produced by a force acting on a body is directly proportional to the magnitude of the force, and inversely proportional to the mass of the object
. This was a language that was completely foreign to most people of the time, but it soon made a lot of sense, and it told us what would happen to an object in uniform motion if a force were applied to it. We can abbreviate the second law in the formula a = F/m, where a is the acceleration resulting from a force (F) on a mass (m).

Newton's third law introduced a new concept called momentum; it is defined as mass × velocity (m × v). And the third law states that
the total momentum of an isolated system of bodies remains constant
. In short, this means that the total momentum before an interaction (for example, a crash) will always be
equal to the total momentum after the interaction, assuming there are no outside influences.

It's easy to see that each of these three laws had a tremendous impact on war; they allowed for a better understanding of such things as the recoil of a gun, the impact of a bullet, and so on. But there was still the important question of how and why a bullet or cannon shell returned to Earth. Galileo had shed some light on it, but, for the most part, it was still a mystery. Newton solved this mystery with his law of gravity. It is as follows:
every particle in the universe attracts every other particle of matter with the force that is personal to the product of their masse
s
and inversely proportional to the square of the distance between them
. In mathematical terms this is F = m
₁
m
₂
/r
²
, where F is force, m
₁
and m
₂
are masses, and r is the distance between them.

Newton, of course, was not thinking of this equation in relation to weapons of war in any way, but he was interested in applying it to the moon to correctly predict its period around the earth. When he made the calculation it was close to what was observed, but not exact, and the reason was that the distance to the moon was not known accurately at the time, and neither was the acceleration of gravity.

These laws by themselves would have made Newton one of the greatest scientists of all time, but they aren't the only advances he made. He also made fundamental discoveries in relation to light and optics. In relation to light, for example, he showed that white light was composed of light of all colors, and a beam of white light could be dispersed into a beam of all colors using a prism. He also discovered the laws of reflection and refraction. And he invented the first reflecting telescope (most large telescopes now use reflectors). All his discoveries in light and optics were detailed in his book
Opticks
, which was published in 1730.