1587, he took a paper on the calculation of solid center of gravity to the University of Rome to meet Professor C. Clavius, a famous mathematician and calendarist, and was greatly praised and encouraged. Clavius brought back his lectures on logic and natural philosophy from P Vara, a professor at the University of Rome, which was of great help to his future work.
From 65438 to 0588, he gave an academic lecture on the graphic conception of purgatory in A. Dante's Divine Comedy, and his literary and mathematical talents were greatly praised. The following year, he published several papers on the calculation of solid center of gravity, including some new statics theorems. Because of these achievements, the University of Pisa hired him to teach geometry and astronomy. The next year he discovered the cycloid. At that time, the textbooks of Pisa University were all written by Aristotelian scholars, and the books were full of theological and metaphysical dogmas. Galileo often expressed sharp objections and was discriminated and rejected by the school. 159 1 year, his father died of illness and the family burden increased, so he decided to leave Pisa. During the Padua period, Galileo transferred to the University of Padua to teach at 1592. Padua belongs to the principality of Venice, far from Rome, not directly controlled by the Vatican, and his academic thoughts are relatively free. In this good atmosphere, he often participates in various academic and cultural activities inside and outside the school, arguing with colleagues with various ideas and opinions. At this time, while absorbing the research results of mathematics and mechanics of N.F. tartaglia, G.B. Benedetti, F. Comentino and others, he often inspected factories, workshops, mines and various military and civil projects, made extensive friends with technicians in various industries, helped them solve technical problems, and learned production technical knowledge and various new experiences from them, which was inspired.
During this period, he deeply and systematically studied the falling body, projectile motion, statics, hydraulics and some civil and military buildings. Discovered the principle of inertia, invented the thermometer and telescope.
1597, he received a book "The Mysterious Universe" by J Kepler, and began to believe in Heliocentrism, acknowledging that the earth has two movements: revolution and rotation. But at this time, he was deeply impressed by Plato's most natural and perfect circular motion thought, and was not interested in Kepler's theory of planetary elliptical orbit. 1604 A supernova appeared in the sky, and the light lasted for 18 months. He took the opportunity to make several popular science speeches in Venice to promote Copernicus' theory. Because of the wonderful speech, the audience gradually increased and finally reached more than 1000 people.
1609 In July, it was rumored that a Dutch glasses worker invented a telescope for people to enjoy. He didn't see the real thing, so he thought of making a telescope with organ tube and convex-concave lens in the future. The magnification was 3, and then it was raised to 9. He invited Senator Venice to the top floor of the tower and looked at the distant view through a telescope, which surprised all the spectators. The Senate then decided that he was a tenured professor at the University of Padua. At the beginning of 16 10, he increased the magnification of the telescope to 33 times to observe the moon, the sun and the stars, and found many new discoveries, such as the uneven surface of the moon, the light emitted by the moon and other planets is the reflection of the sun, Mercury has four satellites, the Milky Way was originally a confluence of countless luminous bodies, Saturn has a changeable ellipse and so on, which opened up a new world of astronomy. In March of that year, he published the book Star Messenger, which shocked all of Europe. Later, it was discovered that Venus changed in profit and loss and size, which was a strong support for Heliocentrism. Galileo later looked back on his 18 years in Padua and thought it was the most productive and spiritual period in his life. In fact, this is also the greatest academic achievement in his life.
Galileo's fruitful achievements in physics and astronomy during his 20 years in Tuscany aroused his greater academic ambition. In order to get enough time to devote himself to scientific research, in the spring of 16 10, he resigned from the university and accepted the appointment of the Grand Duke of Tuscany as the chief mathematician and philosopher of the court and the honorary position of the chief professor of mathematics at the University of Pisa.
In order to protect science from church interference, Galileo went to Rome many times. 16 1 1 year, in order to win the recognition of his discoveries in astronomy from religious, political and academic circles, he went to Rome for the second time. In Rome, he was warmly received by elites including Pope Paul V and some senior bishops, and was accepted as an academician by the Lindsay Institute. At that time, the Jesuit priest acknowledged his observation, but disagreed with his explanation. In May this year, at the meeting of the University of Rome, several senior priests publicly announced Galileo's astronomical achievements. In the same year, he observed sunspots and their movements, compared the movement law of sunspots with the projection principle of circular motion, and proved that sunspots are on the surface of the sun; He also found that the sun rotates. 16 13 published three communication articles about sunspots. In addition, in 16 12, the book "floating body dialogue in water" was published.
16 15 A perfidious cleric group and many people in the church who were hostile to Galileo jointly attacked Galileo's argument of defending Copernicus and accused him of violating Christianity. After learning the news, he went to Rome for the third time in the winter of, trying to save his reputation, pleading with the Vatican not to be punished for keeping Copernicus' views, and not to publicly suppress him and publicize Copernicus' theory. The Vatican acquiesced in the former request, but rejected the latter. In 16 16, Pope Paul V issued the famous "16 16 ban", forbidding him to reserve, teach or defend Heliocentrism orally or in writing.
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 emerging science. He had six audiences, trying to explain that Heliocentrism could be in harmony with Christian teachings, saying that "the Bible teaches people how to enter the kingdom of heaven, not how celestial bodies work"; And tried to convince some archbishops, but to no avail. Urbon VIII insists on "16 16 ban" unchanged; He is only allowed to write a book introducing Heliocentrism and geocentric theory at the same time, but his attitude towards these two theories must not be biased, and both should be written as mathematical hypotheses. In this year's efforts, he developed a microscope, "which can enlarge flies into hens."
In the following six years, he wrote a book "Dialogue between Ptolemy and Copernicus". 1630, he went to Rome for the fifth time and obtained the "publishing license" of this book. The book was finally published in 1632. This book is neutral on the surface, but actually defends the Copernican system, and in many places implicitly ridicules the Pope and the Bishop, which goes far beyond the scope of discussing only mathematical assumptions. The book has a humorous style and is listed as a literary masterpiece in the history of Italian literature.