Introduction to the content of commodity information "Looking at the starry sky (1): how humans begin to understand the solar system" is one of the series of mathematical culture. The series "Mathematical Culture" has selected themes that have played an important role in the development of human civilization, deepened human understanding of the world or promoted human transformation of the world, and introduced the rich connotation of mathematical culture, some important chapters in the history of mathematical development, and the historical achievements and excellent qualities of some famous mathematicians in a simple way. The editor recommended "Looking at the Starry Sky (1)": How did humans begin to understand the solar system, which is suitable for readers including middle school students. Author's brief introduction Qi Youmin, professor of School of Mathematics and Statistics, Wuhan University. The main direction is partial differential equations. He used to be a member of Mathematics Group of the State Council Academic Degrees Committee, president of Wuhan University and vice chairman of chinese mathematical society. Chairman of Hubei Mathematical Society. Vice Chairman of Hubei Science and Technology Association. He has published several professional papers, written some textbooks and popular science books, such as Revisiting Calculus, and translated some foreign works, such as Philosophy of Mathematics and Natural Science by H.Weyl. Directory 1, Introduction 2, Ancient Universe Scenery-Geocentric Aristotle and Geocentric Ptolemy's Geocentrism and Christianity 3, Copernicus's Revolution, the Rise of Modern Science 4, Copernicus and his Heliocentrism's Mars Retrograde 4, the great pioneer of modern science-Galileo Galileo's life and mechanics Galileo and his telescope Galileo and the Inquisition 5, Conclusion Introduction The development history of mathematics is integrated with the development history of human material civilization and spiritual civilization. Mathematics is not only an accurate language and tool, but also a profound and widely used science and an advanced culture. It has been playing an active role in the process of human civilization and is an important pillar of human civilization. Learning mathematics well does not mean doing problems and memorizing formulas, but focusing on understanding the thinking method and spiritual essence of mathematics, understanding the key role of mathematics in the development of human civilization, and consciously accepting the influence of mathematical culture. Only in this way can we fundamentally reflect the requirements of quality education and lay a solid foundation for the improvement of the ideological and cultural quality of the whole nation. Postscript After one or two thousand years of hard work, mankind finally realized the law of motion of the solar system. Think of them as Kepler's three laws. However, why are there these three laws? Aristotle pays attention to the "why" of things, and his answer is metaphysical speculation. Catholicism is concerned with establishing the authority of God, and it can answer that all this is God's will. But after one or two thousand years of exploration, especially in Galileo's place, it is more clear that we should explore deeper laws. Compared with this deeper discussion, Kepler's three laws are just "phenomenological laws". This deep-seated law must be a mathematical law. At that time, mathematics represented by Euclidean geometry was far from enough. Galileo's life is hard to find such an original and prolific person in the history of science. His life is really magnificent. On the basis of Copernicus and Kepler, he established the basic framework of modern physics and deprived Aristotle of his supreme "authority". Like Copernicus and Kepler, he thinks that the laws of the universe are mathematical laws; He clearly pointed out that experiment is a basic scientific method. To this day, his thoughts are still full of vitality. Galileo loved mathematics, astronomy and physics since childhood. However, his father ordered him to study medicine. When he was studying at the University of Pisa, even his math teacher came to his house to plead for him and asked his father to allow him to study math. In this way, he was allowed to study the works of Euclid and Archimedes and Ptolemy's astronomy. After many efforts, Galileo finally began to teach mathematics at the University of Pisa from 1589. During his three-year teaching career, he wrote a book "De Motu". This is an anthology, but it has never been published, because Galileo is not satisfied with it, and there are indeed mistakes in it. The so-called two new sciences, one refers to mechanics and the other refers to the science of materials and structures mentioned by Galileo. However, unlike our understanding of material science, the book sometimes talks about the strength of trees, so it is actually close to what we call material mechanics. Galileo also has another important book, Two World Systems, whose full name is Dialogue between Two World Systems. Many foreign documents are often abbreviated as CDialog, which is well known to the world and has Chinese translation. It is different from the "task" of this book, which we will explain below. In "Theory of Motion" and "Two New Sciences", Galileo elaborated his research achievements in mechanics in great detail, especially the theory of inclined plane, which was a very important research for Galileo, because Galileo got the law of free fall from it. More importantly, however, Galileo explicitly opposed Aristotle when he wrote The Theory of Motion. In methodology, On Physical Education puts forward a revolutionary new idea: all kinds of scientific laws should be verified by experiments, and an inclined plane experiment is designed to verify the law of free pension. This idea is, of course, completely opposite to Aristotle. 1592, Galileo's father died. As the eldest son, Galileo took on the burden of supporting his family (and prepared a dowry for his two unmarried sisters), so he came to Padua. The university taught mathematics and Ptolemaic astronomy to medical students (because doctors used astrology to treat diseases at that time, they had to study astronomy). At this point, Galileo had believed in Copernicus' Heliocentrism, but he had not publicly expressed his views. The following excerpt is from 1597 Galileo's letter to Kepler: "... I accepted Copernicus' position several years ago, and like you, I found many reasons for natural effects, which cannot be explained by the current popular theory. I have written down the reasons for supporting and opposing this theme, but I have been afraid to make it public, because the fate of Copernicus warned me that our master (Copernicus) won an immortal reputation among a few people, but failed in a large group (because there are always many fools) and was laughed at and humiliated. If there are many people like you, of course I dare to open my heart, but because this is not the case, I have to endure. " We might as well read Kepler's reply again: "... since you have such profound insight, I hope you can adopt another attitude." Take yourself as an example. You advise us to act cautiously and secretly, take a step back in the face of general ignorance, and be careful when opposing the violent attacks of those scholars and thugs (you are imitating our real prophets here: Plato and Pythagoras). But in our time, a grand task has begun, first of all Copernicus, and many very knowledgeable mathematicians. Now, there is nothing new about the assertion that the earth is moving. Now that we have boarded the chariot, let's drive it hard together and gradually shout loudly to mortals. They didn't really grasp the power of our argument carefully. Wouldn't it be better to sail to the ultimate goal like this? In doing so, perhaps we can bring truth to mortals as long as we are careful. At the same time, you can also use your argument to help your like-minded people, who have suffered so many unfair judgments and will be comforted by your consent or the protection given to them by your influential position. Not only you Italians don't believe that the earth is moving, because you can't feel it, so can we Germans. In any case, we can't let them feel the kindness and nature of this idea. But we will always find a solution to these difficulties ... Galileo, cheer up and come to the public. If my judgment is right, there will always be a few mathematicians on our side in Europe, and the power of truth is enormous ... ". From this quotation, can't our readers feel the oppression of truth at that time? Can't you experience the friendship of these scientific giants? We will describe in detail the experience of fighting for Copernicus Heliocentrism and finally being persecuted by the Inquisition. Galileo was at the University of Padua around *** 18. Galileo himself said that this was the happiest period of his life. His research on mechanics such as inclined plane, projectile and pendulum is mainly the result of this period. It is worth mentioning that 1609, his friend Charpy in Venice told him that Venice was demonstrating a Dutch artificial telescope. It should be pointed out that Galileo was not only a theorist, but also an experimenter. You can not only design experiments, but also make experimental instruments. He has made many practical things. So he began to make his own telescope, and made great progress, and the magnification was increased to 10 times. Galileo began to observe the sky with a telescope. This is an epoch-making event in the history of human science. In just two months, some people say that its achievements are unprecedented. But it also made him more deeply involved in the struggle with the Catholic Church. Galileo left the University of Padua in 16 10. A far-reaching struggle has begun. Before introducing Galileo's various contributions, we must first answer a question: what is his most important contribution? It may surprise readers, especially in mathematics. But the following does not introduce what theorem Galileo proved. Why do you say that? In fact, this is his own opinion. Philosophers before him, mainly Aristotle, paid attention to the "ultimate reason" and "purpose of existence" of things and wanted to answer the question of "why", which was full of speculative color. Galileo focused on the question of "how", hoping to get a clear and quantitative result. Essentially, it is to seek mathematicization. He said: Philosophy is written in the great book of nature, and the book of nature is open to us. However, we can't understand it unless we first learn to understand its language and read the vocabulary used in this book. It is written in mathematical language, and its characters are geometric figures such as triangles and circles. Without it, mortals can't understand a word of this book. Without these, you will get lost in the dark abyss. Because this passage is very important, let's quote it again to explain its background. The change from "why" to "how" is a major change in scientific methods, and its founder is Galileo. Doing something is a necessary condition to become a master. What Galileo did not do was to speculate and demonstrate the abstract "why" problem. This is the watershed between Galileo and Aristotle. Seeing this, the following meaning is easy to understand.