Galileo Galilei (1564-1642) was born on February 15, 1564 in Pisa, northwest Italy. His father, Fincenzio Galilei, was proficient in music theory and acoustics and wrote the book "Musical Dialogues" . In 1574, the family moved to Florence, a large city in eastern Italy. Galileo was influenced by his father since childhood and was extremely interested in music, poetry, painting and machinery. Like his father, Galileo was not superstitious about authority. At the age of 17, he followed his father's orders and entered the University of Pisa to study medicine. However, he felt that medicine was boring. However, he was very interested in listening to family friend and famous scholar O. Ricci's lectures on Euclidean geometry and Galilean statics outside class. Later he became a great physicist, astronomer, and pioneer of the scientific revolution. He was one of the great scientists who changed the world. He died of illness on January 8, 1642, at the age of 78.
His academic career can be divided into the following three periods
1. Early period of activity
In 1583, Galileo noticed the swing of a hanging lamp in the Pisa church, and then conducted simulation experiments with copper balls suspended from wires, confirming the isochronism of the small swing and the relationship between the length of the pendulum and the period. The impact of this led to the creation of the pulsometer to measure short time intervals. In 1585, he dropped out of school due to family poverty and worked as a tutor, but he still worked hard to educate himself. In 1586, he invented the buoyant balance and wrote the paper "Little Balance".
In 1587, he took his paper on the calculation method of the center of gravity of solids to the University of Rome to meet the famous mathematician and calendarist Professor C. Clavius, and was greatly praised and encouraged. Clavius ??gave him in return the logic and natural philosophy lecture notes of Professor P. Vara of the University of Rome, which were of great help to his future work.
In 1588, he gave an academic lecture at the Florence Academy on the graphic conception of purgatory in Dante's "Divine Comedy", and his literary and mathematical talents were highly praised. The following year he published a paper on several methods for calculating the center of gravity of solids, including several new theorems of statics. Because of these achievements, the University of Pisa hired him to teach geometry and astronomy. The following year he discovered the cycloid.
The textbooks at the University of Pisa at that time were all written by scholars of the Aristotelian school, and the books were full of theological and metaphysical dogmas. Galileo often expressed bitter objections and was discriminated against and ostracized by the school of thought. In 1591, his father died of illness and the family burden increased, so he decided to leave Pisa.
2． During the Padua period, in 1592 Galileo moved to the University of Padua to teach. Padua belongs to the Principality of Venice, far away from Rome, not directly controlled by the Holy See, and has relatively free academic thought. In this good atmosphere, he often participated in various academic and cultural activities inside and outside the school, and debated with colleagues with various ideological viewpoints. At this time, while absorbing the mathematical and mechanical research results of his predecessors such as N.F. Tartaglia, G.B. Benedetti, F. Comendino and others, he often inspected factories, workshops, mines and various military and civilian projects. , make extensive friends with technical employees from various industries, help them solve technical problems, learn production technology knowledge and various new experiences, and get inspiration.
During this period, he conducted in-depth and systematic research on the motion of falling bodies, projectile motion, statics, hydraulics, and some civil and military buildings; he discovered the principle of inertia and developed thermometers and telescopes.
In 1597, he received J. Kepler read the book "The Mysterious Universe" as a gift. He began to believe in the heliocentric theory and recognized that the earth has two motions: revolution and rotation. But at this time, he was so impressed by Plato's idea of ??the most natural and perfect circular motion that he was not interested in Kepler's theory of planetary elliptical orbits.
In 1604, a supernova appeared in the sky, and the light lasted for 18 months. He took the opportunity to give several popular science lectures in Venice to promote the Copernican theory. Because of his eloquent speech, the audience gradually increased, eventually reaching more than a thousand people.
In July 1609, there was a rumor that a Dutch optician invented a telescope for people to enjoy. He didn't see the actual object, but after thinking about it, he made a telescope with an organ pipe and a convex-concave lens each, with a magnification of 3, and later increased it to 9. He invited the Venetian senators to the top of the tower to use telescopes to view the distant views, and the viewers were all pleasantly surprised. The Senate subsequently appointed him a tenured professor at the University of Padua. At the beginning of 1610, he increased the magnification of the telescope to 33 to observe the sun, moon and stars. He made many new discoveries, such as the uneven surface of the moon, the light emitted by the moon and other planets is reflected light from the sun, and there are 4 Mercury Satellites, the Milky Way was originally a collection of countless luminous bodies, Saturn's variable elliptical shape, etc., opened up a new world of astronomy. In March of that year, his book "The Starry Sky Messenger" was published, which shocked the whole of Europe. Later, the profit and loss and size changes of Venus were discovered, which was a strong support for the heliocentric theory.
When Galileo later looked back on his 18 years in Padua, he believed that this was the period in his life when his work was most developed and his spirit was the most comfortable. In fact, this was also the period of his greatest academic achievement.
3． Tuscany Period Galileo's fruitful achievements in physics and astronomy research over the past 20 years inspired him to pursue greater academic aspirations. In order to have enough time to devote himself to scientific research, in the spring of 1610, he resigned from the university teaching position and accepted the invitation of the Grand Duke of Tuscany to serve as the chief mathematician and philosopher of the court and the honorary position of chief professor of mathematics at the University of Pisa.
In order to protect science from church interference, Galileo went to Rome many times. In 1611 he went to Rome for the second time, with the aim of winning religious, political and academic recognition for his astronomical discoveries. He was warmly received in Rome by dignitaries, including Pope Paul V and several prelates, and was admitted as a fellow of the Lindsay Institute. The Jesuit fathers at the time acknowledged the facts of his observations, but disagreed with his interpretation. In May of this year, at a conference at the University of Rome, several high-ranking priests publicly announced Galileo's astronomical achievements.
In the same year, he observed sunspots and their motion, compared the motion rules of sunspots with the projection principle of circular motion, and demonstrated that sunspots are on the surface of the sun; he also discovered that the sun rotates. In 1613 he published three correspondence discussing the sunspot problem. In addition, in 1612 he published the book "Dialogues on Floating Bodies in the Water".
In 1615, a cunning clergy group and many people in the church who were hostile to Galileo jointly attacked Galileo's arguments for defending Copernican theory and accused him of violating Christian doctrine. After hearing the news, he went to Rome for the third time that winter, trying to restore his reputation and asking the Holy See not to punish him for maintaining Copernican views, nor to publicly suppress him from promoting Copernican theory. The Holy See acquiesced in the previous move. requested, but declined the latter. Pope Paul V issued the famous "Injunction of 1616" in 1616, prohibiting him from maintaining, teaching or defending heliocentrism in oral or written form.
In 1624, he went to Rome for the fourth time, hoping that his old friend the new Pope Urban VIII would sympathize with and understand his wishes in order to maintain the vitality of the emerging science. He visited 6 times, trying to explain that heliocentric theory could be reconciled with Christian doctrine, saying that "the Bible teaches people how to enter the kingdom of heaven, not how the celestial bodies operate"; he also tried to persuade some archbishops with this, but to no avail. . Urban VIII insisted that the "1616 ban" remain unchanged; he was only allowed to write a book that introduced both the heliocentric theory and the geocentric theory, but his attitude towards the two theories must not be biased, and it must be written as a mathematical hypothesis. During this year of hard work, he developed a microscope that "can magnify a fly into a hen."
In the next six years, he wrote the book "Dialogue on the Two World Systems of Ptolemy and Copernicus". In 1630, he went to Rome for the fifth time and obtained the "publishing license" for this book ". The book was finally published in 1632. Although the book remains neutral on the surface, it actually defends the Copernican system and contains many implicit mockeries of the pope and bishops, going far beyond the scope of a discussion based solely on mathematical assumptions. The whole book has a humorous tone and is listed as a literary masterpiece in the history of Italian literature.
4． Persecution by the Holy See and Later Life Six months after the publication of "Dialogue", the Holy See ordered it to stop selling it, believing that the author had blatantly violated the "1616 prohibition" and that the problem was serious and needed urgent review. It turned out that someone provoked in front of Pope Urban VIII that Galileo made some ridiculous and wrong remarks in the "Dialogue" through the mouth of the simple-minded and conservative Simplicius and the pope's usual expressions, which made him very angry. Furious. The group that had supported him as pope fiercely advocated severe punishment of Galileo, while the Holy Roman Empire and the Kingdom of Spain believed that condoning Galileo would have a significant impact on heretical ideas in each country and issued a joint warning. Under these internal and external pressures and instigations, the Pope ignored old friendships and issued an order in the autumn of that year for Galileo to stand trial at the Roman Inquisition.
Galileo, who was nearly seventy years old and frail, was forced to go to Rome in the cold winter when he fell ill. He was interrogated three times under the threat of torture and was not allowed to stand trial at all. After several tortures, he was finally sentenced jointly by 10 cardinals on June 22, 1633 in the hall of the Santa Maria Nunnery. The main crime was violating the "1616 Prohibition" and biblical teachings. Galileo was forced to kneel on the cold stone floor and sign the "letter of repentance" that had been written by the Holy See. The presiding judge announced that Galileo was sentenced to life imprisonment; the "Dialogue" must be burned, and the publication or reprinting of his other works was prohibited. This judgment was immediately notified to the entire Catholic world, and all cities with universities must gather to read it as a warning to others.
Galileo was both a diligent scientist and a devout Catholic. He firmly believed that the task of scientists is to explore the laws of nature, while the function of the church is to manage people's souls and should not infringe on each other. Therefore, he did not want to escape before being tried, nor did he openly resist during the trial, but always obeyed the treatment of the Holy See. He believed that it was unwise for the Holy See to exercise power outside the scope of theology, but he could only express his dissatisfaction privately. Obviously, G. Bruno was burned at the stake and T. Campanella was put on death row for a long time. The experiences of these two outstanding Italian philosophers cast a terrible shadow on his spirit.
The sentence of the Inquisition was later changed to house arrest, and his student and old friend Archbishop A. Piccolomini was assigned to guard him in a private residence in Siena. It was stipulated that he was prohibited from receiving guests and wrote every day. All materials must be turned in. Under Piccoromini's careful care and encouragement, Galileo cheered up again and accepted Piccoromini's advice to continue studying uncontroversial physics issues. So he still used the three dialogue characters in "Dialogue", using dialogue style and simpler writing style to write his most mature scientific thoughts and research results into "Dialogue Collection of Dialogues and Mathematical Proofs about Two New Sciences" .
The two new sciences are the mechanics of materials (see elastic mechanics) and dynamics. The manuscript was completed in 1636. Since the church prohibited the publication of any of his works, he had to ask a Venetian friend to secretly take it out of the country and publish it in Leiden, the Netherlands, in 1638.
Just five months after Galileo stayed at Piccoromini’s house, someone wrote an anonymous letter to the Holy See accusing Piccolomini of treating Galileo favorably. The Holy See ordered Galileo to move to his own former residence in Arcetri near Florence in December of that year, under the care of his eldest daughter Virginia, but the prohibition remained the same. She took good care of her father, but died of illness four months later.
Galileo repeatedly requested to go out for medical treatment, but was not allowed. He became blind in 1637. The following year he was allowed to live in his son's home. During this period, in addition to the Grand Duke of Tuscany, he was visited by the famous British poet and political commentator J. Milton and the French scientist and philosopher P. Gassendi. His student and old friend B. Castelli also discussed with him the problem of using Jupiter satellites to calculate the longitude of the ground. At this time, the restrictions and surveillance imposed by the Holy See on him had been significantly relaxed.
In the summer of 1639, Galileo was allowed to accept the intelligent and studious 18-year-old V. Viviani as his last student, and he could take care of him by his side. This young man made him very satisfied. In October 1641, Castelli introduced his student and former secretary E. Torricelli to accompany him. Together with the blind old scientist, they discussed how to design a mechanical clock using the isochrony of a pendulum. They also discussed issues such as collision theory, the moon's balance motion, and the height of the mine water column under atmospheric pressure. Therefore, until his death, He is still doing scientific research.
Galileo died of illness on January 8, 1642. The funeral was sloppy and crude. It was not until the next century that the remains were moved to the cathedral in his hometown.
The continuous development of science forced the Holy See to announce the lifting of the ban on Copernicus' "On the Revolution of the Celestial Bodies" in 1757; in 1882, the Holy See reluctantly recognized the heliocentric theory. On November 10, 1979, Vatican Pope J. Paul II publicly vindicated Galileo on behalf of the Holy See, believing that the Holy See made a serious mistake in persecuting him more than 300 years ago. This showed that the imperial court finally recognized Galileo's proposition that religion should not interfere with science.
2. Scientific achievements
1. New scientific ideas and scientific research methods
Before Galileo’s research results were recognized, physics and even the entire natural sciences were just a branch of philosophy and did not achieve their own independent status. At that time, philosophers were bound by the framework of theology and Aristotle's dogma. They thought hard and debated, but could not come up with objective laws that were consistent with reality. Galileo dared to challenge the traditional authoritative thinking. He did not first speculate on the causes of things, but first observed natural phenomena and discovered natural laws. He abandoned the theological view of the universe and believed that the world was an orderly whole obeying simple laws. To understand nature, one must conduct systematic experimental quantitative observations to find out its precise quantitative relationships.
Based on such new scientific ideas, Galileo advocated a research method that combined mathematics and experiments; this research method was the source of his great achievements in science and was also his most important contribution to modern science. contribute. The use of mathematical methods to study physical problems was not originally initiated by Galileo. It can be traced back to Galileo in the 3rd century BC, the Oxford School and the Paris School in the 14th century, and the Italian academic circles in the 15th and 16th centuries. All have made certain achievements in this regard, but they Experimental methods were not given top priority, and thus no breakthroughs were made in thinking. Galileo's emphasis on experiments can be seen in a letter he wrote to Duchess Cristina in 1615: "I would like to ask these clever and careful priests to seriously consider the speculative principles and the principles confirmed by experiment." You must know that the opinions of professors who do experimental work are not determined solely by subjective wishes."
Galileo's research method that combines mathematics and experiment is generally speaking. There are three steps: ① First extract the main part of the intuitive understanding obtained from the phenomenon and express it in the simplest mathematical form to establish the concept of quantity; ② Then use mathematical methods to derive another easy-to-experimentally-verified value from this formula Quantitative relationship; ③ Then confirm this quantitative relationship through experiments. His research on the law of uniform acceleration of falling objects is the best illustration.
2． Innovation in physics concepts and principles
The principle of inertia and the new concepts of force and acceleration require a large force to push a heavy object, while a small force is required to push a light object. This is people's intuitive experience. Aristotle drew a universal conclusion based on this: all objects have the nature to remain stationary or to find their "natural destination". He believed that "anything that moves must have a mover" and used the law of proportion to control the driving force. Connect with speed. Galileo came up with a new concept. He observed that an object sliding upward along a smooth inclined surface was decelerated to varying degrees due to different inclination angles. The smaller the inclination angle, the smaller the deceleration. If it is sliding on a horizontal surface without resistance, it should keep sliding at the original speed forever.
This leads to the conclusion: "A moving object, if it has a certain speed, will always maintain this speed as long as there is no external reason to increase or decrease the speed - this condition is only true on a horizontal plane. It is possible, because in the case of inclined planes, the downward inclined plane provides the cause of acceleration, and the upward inclined plane provides the cause of deceleration; it follows that only motion on the horizontal plane is invariant" ("Two Gates" Dialogue on the New Science, Day 3, Question 9, Hypothesis 23 Note). In this way, Galileo proposed the concept of inertia for the first time, and for the first time connected external forces with "external causes causing acceleration or deceleration", that is, changes in motion. Combined with the aforementioned uniformly accelerated motion experiments, Galileo proposed the new concepts of inertia and acceleration, as well as the new motion laws of uniformly accelerated motion of objects under the action of gravity, which laid the foundation for the establishment of the Newtonian mechanics theoretical system. Specifically, there are the following aspects.
(1) The principle of independence of motion and the laws of synthesis and decomposition of motion. In the study of ballistics, Galileo discovered that motion in the horizontal and vertical directions are independent and do not interfere with each other, but through the parallelogram law It can also synthesize actual movement tracks. He completely explained the parabolic nature of ballistics from uniformly accelerated motion perpendicular to the ground and uniform motion in the horizontal direction. This was a major gain in the synthetic study of motion and had practical significance.
(2) The concept of inertial reference system. When Galileo's physical principles defended Copernicus's theory of seismic motion, he applied the principle of independence of motion to explain in a popular way that when a stone falls from the top of the mast to the foot of the mast, The reason why it does not shift toward the stern. He further proposed the concept of an inertial reference system for the first time based on his famous statement that the laws of motion of objects in a cabin moving at a uniform speed remain unchanged. This principle was called the Galilean principle of relativity by A. Einstein and is the forerunner of the special theory of relativity.
(3) The discovery of the periodic properties of a simple pendulum. Galileo conducted experimental studies on the pendulum by observing the swing of a church hanging lamp. He found that the period of a simple pendulum is proportional to the square root of the length of the pendulum, and is proportional to the amplitude of the pendulum and the amplitude of the pendulum. Hammer weight is irrelevant. The discovery of this law laid the foundation for subsequent vibration theory and the design of mechanical timing devices.
(4) The speed of light is limited and its measurement. Previous people have never had a clear understanding of whether the speed of light is limited. Galileo observed the lightning phenomenon and believed that the speed of light was limited, and designed a lamp-shading scheme to measure the speed of light. However, limited to the experimental conditions at the time, what was actually measured using this measurement method was mainly the reaction of the experimenter and the movement time of the human hand, not the travel time of the light. However, if there is a light source with regular changes in light and dark or a high-speed mechanical control device instead of human hand movements, the true speed of light can be measured. Later, the Jupiter satellite method, the rotating gear method, the rotating mirror method, the Kerr box method, and the frequency conversion method Light speed measurement methods such as the flash method are all based on the light-masking scheme.
3． The development of several basic physical experimental instruments
Galileo not only designed and demonstrated many experiments himself, but also developed many experimental instruments himself. He has rich craft knowledge and exquisite production skills. Many of the experimental instruments he created were very influential at that time and for later generations. Here are a few:
(1) Buoyancy balance This is a rapid instrument that uses the principle of buoyancy. A direct-reading instrument for measuring the proportion of gold and silver content in gold and silver utensils and jewelry. This instrument was already used in the trade of gold and silver jewelry vessels.
(2) Thermometer The thermometer pioneered by Galileo is an open liquid thermometer. The glass tube contains colored water and alcohol, and the liquid surface is connected to the atmosphere. This was actually a hybrid of a thermometer and a barometer, as he did not have a clear understanding of changes in atmospheric pressure at the time. Despite this, its academic value is still great, and temperature has since become an objective physical quantity, no longer an uncertain subjective feeling.
(3) Telescope The telescope made by Galileo can observe the true image of objects. After improvement, its magnification was gradually increased from 3 to 33; it not only points to the starry sky, but can also be used in ship fortresses, achieving unprecedented fruitful discoveries. This telescope has a simple structure, but its magnification and resolution capabilities are greatly limited by spherical aberration and chromatic aberration.
4． Completely overthrowing Aristotle's view of matter
The view of nature that was absolutely dominant in the European Middle Ages was Aristotle's view of nature that had been modified by theology. It became a system for feudal theocratic rulers to control the people. Tools of thought. Aristotle believed that the earth and everything on it are composed of the four elements of air, fire, water, and earth. They are all ugly, unclean, imperfect, and subject to change and birth and death. Fire and air make up the light objects that flow upward, and water and earth make up the heavy objects that fall upward. The celestial bodies are pure, perfect, and eternal objects composed of "ether". And because "God hates a vacuum", a vacuum cannot exist. However, Galileo discovered from his telescope that the surface of the moon was uneven and not perfect, with peaks and depressions. Venus also waxed and waned; there were active sunspots on the surface of the sun; and the naked eye could directly see the explosion of a supernova and its gradual dimming and disappearance. These all break Aristotle's idea that heaven is superior to earth and that the properties of celestial bodies and terrestrial substances are vastly different. Through the study of floating bodies in hydrostatics, Galileo learned that all objects are heavy objects and there is no absolute light object. The celestial bodies, the earth and all things on earth are unified in material structure. Vacuum may also exist and be produced, and only in vacuum can the true properties of objects be studied.
This completely overturned Aristotle's material view based on subjective conjecture, and thus fundamentally shaken the ideological rule of feudal theocracy.
5. The pioneer of the Scientific Revolution and the father of modern science
Galileo Galilei was a great Italian physicist and astronomer and the pioneer of the Scientific Revolution. He has made epoch-making contributions in the process of emancipation of human thought and development of civilization. Under the social conditions at that time, he fought unremittingly for academic freedom that was not suppressed by power and old traditions, and for the development of modern science, and made a deafening voice to the world. Therefore, he is a pioneer of the scientific revolution. Historically, he was the first to integrate mathematics, physics and astronomy based on scientific experiments, expanding, deepening and changing mankind's understanding of material movement and the universe. In order to confirm and spread N, Copernicus' heliocentric theory, Galileo devoted his life. As a result, he was persecuted by the church in his later years and imprisoned for life. With his systematic experiments and observations, he overturned the purely speculative traditional view of nature represented by Aristotle, and created modern science with a strict logical system based on experimental facts. Therefore, he is called the "Father of Modern Science". His work laid the foundation for the establishment of I. Newton's theoretical system. Although he was finally deprived of personal freedom in his later years, his will to create new science did not waver. His spirit and achievements in pursuing scientific truth will always be admired by future generations.
3. Interesting anecdotes
1. He doesn’t love medicine but loves mathematics
In 1581, when Galileo was 17 years old, he was admitted to the University of Pisa, where Galileo was born. His father insisted that he study medicine because medicine in 16th-century Italy was considered the most effective first step on a college student's path to success and eventual wealth.
Galileo reluctantly complied with his father's wishes, but within a few months greater disagreements began to arise. Galileo was a young man with many talents. He was a gifted musician, an excellent painter, and a talented writer. But in his first year in Pisa, Galileo had no interest in medicine and discovered his true passion, which changed his life path.
During his first semester at the University of Pisa, Galileo spent his spare time listening to mathematics lectures. He became fascinated by the rigorous beauty of this subject. In particular, the subject of Euclidean geometry - a branch of mathematics named after the Greek Euclid, the father of geometry - taught by the court mathematician Ostillo Leach - deeply interested him. attracted him.
Galileo attended Leach's lectures week after week. Soon after, the court mathematician began to notice a fit, handsome young man who always sat at the back of the lecture hall and listened intently to his every word. At the end of each lecture, Galileo always asked Leach many probing questions. The mathematician realized that he had a very talented student in his subject, so he persuaded Galileo to give up studying medicine at the university and study mathematics instead.
Although his father was angry, Galileo continued to pursue his hobby and changed subjects. He insisted that he was no longer a child and that this time he would not do what his father asked him to do. Before the end of his first semester, Galileo was already an undergraduate in mathematics.
2． The nickname "Debater"
When he was still studying at the University of Pisa, Galileo couldn't stand the attitude of philosophers towards science. express your own opinion. At many points he would become very agitated, raising his voice and arguing loudly with his peers and speakers.
Galileo was indeed a bit naughty by nature, but fundamentally he was a polite and disciplined student. He was well-liked by some of his classmates and gained a good reputation for his wit and enthusiasm. However, on matters of mathematics and physics, he was not afraid to make his views clear. The fact is that Galileo debated so much in college that he earned the nickname "The Debater."
The main focus of his argument is that just sitting there and thinking hard like the Greeks cannot promote the progress of science. Aristotle did not conduct a single experiment in his life. He simply relies on the use of logic to reach conclusions. Galileo argued that that alone was not enough. Aristotle's entire philosophical system is interconnected. One principle leads to another principle, and one point of view supports another point of view. If any part of his philosophical system is wrong, it is tantamount to declaring that all of his philosophical content is problematic.
Galileo’s approach to the problem was exactly the opposite of Aristotle’s. At the University of Pisa, he insisted that science could only be based on experiment. An idea can be based on inspiration at first, but it can only be proven and accepted through experimentation - a view that is taken for granted today.
Most of Galileo's colleagues at the university did not agree with his views. Galileo understood the attitude of the Church, and he was clever enough to argue that his view was merely one of many suggestions, without drawing further attention to his anti-Aristotelian ideas.
This was at least the approach Galileo took in public...
3. The Story of the Leaning Tower of Pisa
In Galileo’s long life, many famous events occurred that were commemorated and recorded by later generations. Perhaps the most popular story is an experiment he is said to have performed atop the Leaning Tower of Pisa in 1591.
This leaning tower is located in the city of Pisa. This unusual structure, built in 1174, has tilted some 17 feet since its inception. By the 16th century, the Leaning Tower of Pisa had become a building of historical significance, attracting the attention of tourists from all over Italy.
Infuriated by the views of his colleagues who adamantly refused to consider his anti-Aristotelian views, Galileo decided to use a special kind of evidence to prove the Greek philosopher wrong.
One of Aristotle's main points in physics is that if two objects with different weights are allowed to fall under the influence of gravity, the heavier one will fall to the ground. . But, like all his arguments, Aristotle did not test this argument; it was simply accepted as an indisputable fact.
To prove his point. Galileo climbed to the top of the Leaning Tower with two assistants and two lead balls of different weights.
Climbing the tower was very thrilling. He had to climb hundreds of worn and slippery steps. The stairs were inside the stone wall and spiraled steeply upward. By the time he climbed to the top of the tower, Galileo was covered in sweat and extremely tired. But he has a great job to do. Motivated by anger and frustration, he climbed to the bell tower on the top platform. Zhong Lou tilted to one side, the angle was very scary. He tried his best to overcome the dizziness and pressed his body against the highest point. He had never been on such a tall building before.
He stood on the edge of the bell tower with two shot put, 179 feet above the ground. He looked out over Pisa. He saw his university colleagues who had been persuaded to come under the tower, and he stretched out a hand to test whether there was wind. There happened to be no wind that day.
Two assistants stood against the edge of the bell tower, each holding a shot put in their hands. At an opportune moment, Galileo sent a signal to his assistants. The two assistants let go of the shot put in their hands at the same moment, letting them fall to the grass below under the influence of gravity.
Sure enough, people clearly saw that the two shot balls hit the ground almost at the same time, which indeed proved that Aristotle's argument about falling bodies was completely wrong.
Although there is sufficient evidence to prove that Galileo did not conduct a falling body experiment here, and in fact this experiment is not very convincing, people still prefer to believe it. Because it is full of drama, it has brought pizza a worldwide reputation.
4． Life when teaching at the University of Padua
Life at the University of Padua satisfied Galileo, but although he could earn a large salary, it was difficult to support his family. He had to recruit students privately, as he had done at the University of Pisa.
Through long-term teaching work, Galileo gradually became busy. He not only taught local astronomy and mathematics enthusiasts, but also taught machine-making craftsmanship to the army mechanics stationed in the city. .
A few years later, Galileo's financial situation gradually improved, and he was able to buy a small house in the city. He began dating a Venetian woman named Marina Gamba. The two did not marry, but they lived together for more than 10 years. In 1610, when Galileo moved again, Marina stayed in Padua and they separated. During the years they lived together, they had two daughters and a son.
As he grew older, Galileo showed no interest in marrying Marina and seemed to become more and more obsessed with his academic research. He never forgot all those who depended on him for support, but he was definitely not a loving father or a devoted husband. Throughout his life he really had only one true passion - natural science.
The 18 years in Padua were the happiest period of Galileo’s life. It was during these years that he made some of his most important discoveries
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