  THE AGE OF GALILEO Galileo and the Battle for Truth For eighteen centuries after the time of Archimedes no inventions of importance were made. Men sought for truth where truth could not be found. They looked within their mouldy manuscripts and asked, "What do the great philosophers say ought to happen?" instead of looking at nature and asking, "What does happen?" And when a man arose who dared to doubt the authority of the old masters and turn to nature to find out the truth, all the weapons at the command of the old school were hurled against him. Let us, at this distance, blame neither the one side nor the other. The conflict was inevitable. It was an accident of history that the brunt of the attack fell upon a man born in Italy in 1564, and that the battle was fought chiefly in the "Eternal City," from which centuries before had marched the legions that conquered the world. The boy, Galileo, who was to become the central figure of the great conflict, was talented in many ways. In lute-playing his skill excelled that of his father, who was one of the noted musicians of his day. His skill in drawing was His preference was for mechanics, but, as this subject offered little prospect of profitable work, he took up the study of medicine in accordance with his father's wishes. In his eighteenth year he entered the University of Pisa. Here he found men who refused to think for themselves, but decided every question by referring to what the ancient philosophers said. Galileo could not endure such slavish submission to authority. So strongly did he assert himself that he was nicknamed "The Wrangler," and, by his wrangling, he lost a scholarship in the university. He neglected his medical studies and secretly studied mathematics. His father, learning of this, consented to his becoming a mathematician. Thus he followed his bent, though it seemed to lead directly to poverty. The Pendulum Clock It was while a student at the University of Pisa that he discovered a law of pendulums which makes possible our pendulum clocks. While at his devotions in the cathedral, he observed the swinging of the bronze lamp which had been drawn back for lighting. Timing its swinging by means of his pulse, the only timepiece in his possession, he found that the time of one swing remained the same, though the length of the swing grew smaller and smaller. This It had only one hand, which is not shown in the picture. Lack of funds compelled him to leave the university without completing his course. He returned to the parental roof and continued his scientific studies. The writings of Archimedes were his favorite study. With Archimedes' famous experiment on King Hiero's crown as a starting-point, he discovered the laws of floating bodies, which explain why a ship or other object floats on water, and invented a balance for weighing objects in water. But such employment won nothing more substantial than honor and fame. Food and clothing were needed. For two years he strove without success to secure employment. At the end of that time he was appointed professor of mathematics in the University of Pisa at the magnificent salary of sixty scudi (about sixty-three dollars) per year. "But any port in a storm; and in Galileo's needy circumstances even this wretched salary was not to be rejected." Moreover, he could add somewhat to his income by private tutoring. Galileo's Experiment with Falling Shot While teaching at the University of Pisa, he performed his famous experiment of dropping from the top of the leaning tower two shot, one weighing ten pounds, the other one pound. Now, according to Aristotle, the ten-pound shot should fall in one-tenth the time required by the one-pound shot. But the assembled company of professors and students saw the two shot start together, fall together, and About this time Galileo incurred the wrath of the Grand Duke of Tuscany, from whom he had received his appointment. He was commissioned to examine a machine invented by a nephew of the Grand Duke for the purpose of cleaning harbors. Galileo plainly said that the machine was worthless. It was tried, and his opinion proved true. But like the kings of olden time who killed the bearer of evil tidings even though the tidings were true, his enemies made his position so unpleasant that he resigned. He had neither employment nor money. His father's death occurring about this time, threw upon him the care of a mother, a worthless brother, and two sisters. In his distress he sought help from a friend, and secured an appointment as professor of mathematics in the University of Padua. His salary was one hundred and eighty florins (about ninety-five dollars), while other professors received more than ten times as much. While at Padua, Galileo was busy inventing. He invented the sector, which is to be found in most cases of mathematical instruments and is used in certain kinds of drawing. He also invented an air thermometer (Fig. 3), the first instrument for measuring temperature. When the air in the bulb grows cooler it contracts, and the air outside forces the Water up the tube. When the air in the bulb grows warmer it expands and forces the water down in the tube. In 1604 there appeared a new star of great brilliancy. It continued to shine with varying brightness for eighteen months, and then vanished. This was a strange event, and Galileo made use of it. He proved that the new star must lie among the most distant of the heavenly bodies, and this fact did not agree with Aristotle's view that the heavens are perfect, and therefore never change. A heated controversy followed, and Galileo came out boldly in favor of the theory that the earth revolves about the sun, the prevailing notion then being that the earth does not move, but that the sun and other heavenly bodies revolve around it. The Telescope In 1609 Galileo learned of a discovery that was to be of great value to the world, but a source of untold trouble to himself. An apprentice of a Dutch optician, while playing with spectacle lenses, chanced to observe that if two of the lenses were placed in a certain position objects seen through them appeared much nearer. Galileo, learning of this, set to work to construct a spy-glass, applying his knowledge of light. In one day he had constructed such an instrument, in which he used two lenses like the lenses of the modern opera-glass. Thus, while the Dutchman's discovery was by accident, Galileo's was by reasoning, and was the more fruitful, as we shall see. Galileo continued improving his telescope until he had made one which would magnify thirty times. He was the first to apply the telescope to the study of the heavenly bodies. The most startling of his discoveries was that of This aroused the fury of his enemies, who ridiculed the idea of there being new planets; "for," they said, "to see these planets they must first be put inside the telescope." The excitement was intense. Poets chanted the praise of Galileo. A public fÊte was held in his honor. One of his pupils was imprisoned in the tower of San Marco, where he had gone to make observations with his telescope, and could not escape until the crowd had satisfied their curiosity. Some of the philosophers refused to look lest they should see and be convinced. Galileo's Struggle His enemies sought to steal from him the honor of his discoveries. Some claimed to have made the discoveries before Galileo did. Others claimed that his discoveries were false, that their only use was to gratify Galileo's vanity and thirst for gold. In these trying times the friendship of the great astronomer Kepler warded off some of the most exasperating attacks. Galileo's fame spread throughout Europe. Students came in great numbers, so that he had little leisure left for his own studies. He therefore decided to leave Padua, and secured an appointment as mathematician and philosopher to the Grand Duke of Tuscany. This appointment took him to Florence. It was here that an incident occurred that marked the beginning of a persecution which continued to the end of his life. As we read the story of this conflict let us remember that At a dinner at the table of the Grand Duke in Pisa the conversation turned on the moons of Jupiter. Some praised Galileo. Others condemned him, saying that the Holy Scriptures were opposed to his theory of the motion of the earth. A friend reported the incident to Galileo, and he replied to the arguments of his opponents in a letter which was made public. No doubt the sting of his sarcasm made his enemies more bitter. He admitted that the Scriptures cannot lie or err, but this, he said, does not hold good of those who attempt to explain the Scriptures. In another letter, he quoted with approval a saying of Cardinal Baronius, "The Holy Spirit intended to teach us in the Bible how to go to Heaven, not how the heavens go." The first shot had been fired. The battle was on, and the Church, because it possessed the most powerful weapons of attack, was used by the combined forces to break the power of Galileo's reasoning. He went to Rome to make his defence, but was commanded by the Holy Office not to hold or teach that the sun is immovable, and that the earth moves about the sun. During another visit to Rome there was shown to Galileo In violation of the decree of the Church, to which he had submitted, he published his most famous work in which he defended the theory that the earth moves about the sun. The book was the outcome of his life-work, but the Church believed it dangerous. He was summoned to Rome. Confined to a sick-bed, he pleaded for delay, which was granted. Before he recovered, however, the summons was made imperative. He must go to Rome, or be carried in irons. He went in a litter, carried by servants of the Grand Duke. In Rome he was to appear before the Inquisition. There he was treated with a consideration never before accorded to a prisoner of the Inquisition. Nor was he subjected to torture, as has been stated by some. He was found guilty of teaching the doctrine that the sun does not move, and that the earth moves about the sun. He was compelled to recant, and sentenced to the prison of the Holy Office and, by way of penance, to repeat once a week for three years the seven penitential Psalms. He yielded without reserve to the decree of the Inquisition, renounced his "errors and heresies," and, with his hand on the Bible, took oath never again to teach the forbidden doctrine. And now, though a shattered old man of seventy-four, In his study of machines Galileo found that no machine will do work of itself. Whenever a machine is at work, a man or a horse, or some other power, is at work upon the machine. In no case will a machine do work without receiving an equal amount of work. Torricelli and the Barometer Galileo had a pump which he found would not work when the water was thirty-five feet below the valve. He thought the pump was injured, and sent for the maker. The maker assured him that no pump would do better. This led Torricelli, one of Galileo's pupils, to the discovery of the barometer. Men had said that water rises in a pump because nature abhors a vacuum. Torricelli believed that air-pressure and not nature's "horror of a vacuum" is the cause of water rising in a pump. He invented the barometer to measure air-pressure. The first barometer was a glass tube filled with quick-silver or mercury (Fig. 4). The tube was closed at the Otto Von Guericke and the Air-Pump About this time a German burgomaster, Otto von Guericke, of Magdeburg, was performing experiments on air-pressure. The Thirty Years' War had been raging for thirteen years. The Swedish King, Gustavus Adolphus, had landed in Germany, and was winning victory after victory over the imperial troops. Magdeburg had entered into an alliance with the Swedish King, by which he was granted free passage through the city, while, on the other hand, he promised protection to the city. The imperial army under Tilly and Pappenheim laid siege to the city. On the one side there was hope that Gustavus would arrive in time to effect a rescue; on the other, a determination to conquer before such aid could arrive. While Gustavus was on his way to the rescue, Magdeburg was taken by storm, and the most horrible scene of the Thirty Years' War was enacted. Tilly gave up the city to plunder, and his soldiers without mercy killed men, women, and children. In the midst of the scene of carnage the city was set on fire, and soon the horrors of fire were added to the Guericke's house and family were saved, but the sufferings of the city were not yet ended. In five years the enemy was again before the walls, and Magdeburg, then in the possession of the Swedes, was compelled to yield to the combined Saxon and imperial troops. Guericke entered the service of Saxony, and was again made mayor of the city. In the midst of these scenes of war, he found time to continue his studies. He made the first air-pump, and with it performed experiments which led to some very important results. The experiments which Guericke made with his air-pump aroused the attention of the princes, and especially Emperor Ferdinand. Guericke was called to perform his experiments before the Emperor. The most striking of these experiments he performed with two hollow copper hemispheres about a foot in diameter, fitted closely together. When the air was pumped out, sixteen horses were barely able to pull the hemispheres apart, though, when air was admitted, they fell apart of their own weight. Another experiment which astonished his audience was performed with the cylinder of a large pump (Fig. 5). A rope was tied to the piston. This rope was passed over a pulley, and a large number of men applied their strength to the rope to hold the piston in place. When the air was taken out of the cylinder, the piston was forced down by air-pressure, and the men were lifted violently from the ground. This experiment, as we shall see, was of great importance in the invention of the steam-engine. Men lifted from the ground by air-pressure. Guericke's study of air-pressure led him to make a water barometer (Fig. 6). This consisted of a glass tube about thirty feet long dipping into a dish of water. The tube was filled with water, and the top projected above the roof of the house. On the water in the tube he placed a wooden image of a man. In fair weather the image would be seen above the housetop. On the approach of a storm the image would drop out of sight. This led his superstitious neighbors to accuse him of being in league with Satan. In fair weather the image appeared above the housetop. When a storm was approaching the image dropped below the roof into the house. The first electrical machine was made by Guericke. This was simply a globe of sulphur turning on a wooden axle. He observed that when the dry hand was held against the revolving globe, the globe would attract bits of paper and other light objects. Robert Boyle and the Pressure of Air and Steam Robert Boyle, in England, improved the air-pump and performed many new and interesting experiments with it. One of his experiments was to make water boil by means of an air-pump without applying heat. It is now well known that water when boiling on a high mountain is not so hot as when boiling down in the valley. This is because the air-pressure is less on the mountain top than in the valley. By using an air-pump to remove the air-pressure, water may be made to boil when it is still quite cold to the hand. Boyle compared the action of air under pressure to a steel spring. The "spring" of the air is evident to us in the pneumatic tire of the bicycle or automobile. Boyle found that the more air is compressed the greater is its pressure or "spring," and that steam as it expands exerts Pascal and the Hydraulic Press It was Blaise Pascal, a Frenchman, who proved beyond the possibility of a doubt that air-pressure supports the mercury in a barometer, and lifts the water in a pump (Fig. 7). He had two mercury barometers exactly alike set up at the foot of a mountain. The mercury stood at the same height in each. Then one barometer was left at the foot of the mountain, and the other was carried to the summit, about three thousand feet high. The mercury in the second barometer then stood more than three inches lower than at first. As the barometer was carried down the mountain the mercury slowly rose until, at the foot, it stood at the same height as at first. The party stopped about half-way down the mountain, allowing the barometer to rest there for some time, and Air pressing down on the water in the well causes the water to rise in the pump. The air can do this only when the plunger is at work removing air or water and reducing the pressure inside the pump. It is now known that when a barometer is carried up to a height of nine hundred feet, the mercury stands an inch lower than at the earth's surface. For every nine hundred feet of elevation the mercury is lowered about one inch. In this way the height of a mountain can be measured, and a man in a balloon or an air-ship can tell at what height he is sailing. For this purpose, however, a barometer is used that is more easily carried than a mercury barometer. Pascal invented the hydraulic press, a machine with which he said he could multiply pressure to any extent, which reminds us of Archimedes' saying that, with his own hand, he could move the earth if only he had a place to stand. Pascal could so arrange his machine that a man pressing with a force of a hundred pounds on the handle could produce a pressure of many tons. In fact, a man can so arrange this machine that he can lift any weight whatever (Fig. 8). A one-pound weight holds up a hundred pounds. The hydraulic press has two cylinders. One cylinder One man with the machine can exert as much pressure as a hundred men could without the machine. The arrows show the direction in which the liquid is forced by the action of the plunger p. The large piston P is forced up, thus compressing the paper. Newton Sir Isaac Newton as a boy did not show any unusual talent. In school he was backward and inattentive for a number of years, until one day the boy above him in class gave him a kick in the stomach. This roused him and, to avenge the insult, he applied himself to study and quickly passed above his offending classmate. His strong spirit was aroused, and he soon took up his position at the head of his class. It was his delight to invent amusements for his classmates. He made paper kites, and carefully thought out the best shape for a kite and the number of points to which to attach the string. He would attach paper lanterns to At the age of fifteen, his mother, then a widow, removed him from school to take charge of the family estate. But the farm was not to his liking. The sheep went astray, Gravitation It was in the year following his graduation from Cambridge that he made his greatest discovery—that of the law of gravitation. A plague had broken out in Cambridge, to escape which Newton had retired to his estate at Woolsthorpe. Here he was sitting one day alone in the garden thinking of the wonderful power which causes all bodies to fall toward the earth. The same power, he thought, which causes an apple to fall to the ground causes bodies to fall on the tops of the highest mountains and in the deepest mines. May it not extend farther than the tops of the mountains? May it not extend even as far as the moon? And, if it does, is not this power alone able to hold the moon in its orbit, as it bends into a curve a stone thrown from the hand? There followed a long calculation requiring years to complete. Seeing that the results were likely to prove his theory of gravitation, he was so overcome that he could not finish the work. When this was done by one of his friends, it was found that Newton's thought was correct—that the force of gravitation which causes bodies to fall at the earth's surface is the same as the force which holds the moon in its orbit. As the earth and moon attract each Colors in Sunlight About the same time that he made his first discoveries regarding gravitation, he took up the study of light with a view to improving the construction of telescopes. His first experiment was to admit sunlight into a darkened room through a circular hole in the shutter, and allow this beam of light to pass through a glass prism to a white screen beyond. He expected to see a round spot of light, but to his surprise the light was drawn out into a band of brilliant colors. He found that the light which comes from the sun is not a simple thing, but is composed of colors, and these colors were separated by the glass prism. In the same way the colors of sunlight are separated by raindrops to form a rainbow. The colors may be again mingled together by passing them through a second prism. They will then form a white light. Suppose that the light of the sun were not composed of different colors, that all parts of white light were alike, then there would be no colors in nature. All the trees and flowers would have a dull, leaden hue, and the human countenance would have the appearance of a pencil-sketch or a photographic picture. The rainbow itself would dwindle into a narrow arch of white light; the sun would shine through a gray sky, and the beauty of the setting sun would be replaced by the gray of twilight (Fig. 11). Sunlight separated into the colors of the rainbow. The seven colors are: violet, indigo, blue, green, yellow, orange, red. One of Newton's inventions was a reflecting telescope—that is, a telescope in which a curved mirror was used in place of a lens. He made such a telescope only six inches long, which would magnify forty times. Newton was a member of the Convention Parliament, which declared James II. to be no longer King of England and tendered the crown to William and Mary. He was made a knight by Queen Anne in 1705. His knowledge of chemistry was used in the service of his country when he was Master of the Mint. It was his duty to superintend the recoining of the money of England, which had been debased by dishonest officials at the mint. He did his work without fear or favor. Once a bribe of £6000 ($30,000) was offered him. He Although Newton's discoveries in the world of thought were among the greatest ever made by man, he regarded them as insignificant compared with the truth yet undiscovered. He said of himself: "I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore and diverting myself in now and then finding a smoother pebble or a prettier shell than the ordinary, whilst the great ocean of truth lay all undiscovered before me." |
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