In the university of the Duchy of Padua, to which the Republic of Venice belongs, Xu Xiake and his entourage found traces of Galileo, a professor at this university, a very famous professor. In this team, except for Xu Xiake, Li Zubai is the oldest, and he is also an academician of the Daming Academy of Sciences, and the most important thing is that he is a Catholic, a disciple of the German missionary John Tang, who can speak fluent Italian, and now the popular Italian language in the Republic of Venice is just his strength, and Li Zubai, who has official experience, is better at dealing with strangers.

Galileo Galileo is known as the "father of modern observational astronomy", "the father of modern physics", "the father of science" and "the father of modern science". He was both a diligent scientist and a devout Catholic, convinced that the task of scientists was to explore the laws of nature, and that the function of the Church was to manage people's souls. Zhu Youxiao knew Galileo's character, and he also knew that people who engaged in scientific research hated being disturbed innocently, and he told Li Zubai about this, so Li Zubai's visit gift for Galileo was very special, a pair of binoculars carefully made by the Daming Academy of Sciences, an abacus, a delicate "Nine Chapters of Arithmetic", and a pack of precious black tea, which neither looked chilling nor too expensive, this was a decent gift.

When Galileo saw this gift, he was extremely surprised, he was very familiar with the telescope, but he had never seen such a delicate one, and after a brief trial, he found that the telescope was much better than the one he had made himself, which he liked very much. When he saw the abacus, he thought it was very strange, he had heard of this thing, but he had not seen it, and he did not know how the abacus was used, this abacus made him very interested. However, when he saw "Nine Chapters of Arithmetic", his eyes revealed a fine light, this should be the first time he saw a book on the mathematical research of the Oriental people, this booklet with only 246 arithmetic problems made him like a treasure, but this is an unannotated original, the purpose is to study with him, to see the difference between Eastern and Western thinking, which is also Zhu Youxiao's purpose.

After waiting for nearly an hour, Galileo finally came back to his senses and looked at everyone with some embarrassment, so everyone sat down. Everyone understands this attitude very well, after all, these people are engaged in research, but when they enter the state, they will forget everything, which is not rude, it can only be said that they are too concentrated.

Then he officially entered the state of conversation, Li Zubai gave a brief introduction to Galileo and his party, and then said: "Under Li Zubai, from the distant ancient Eastern Ming Empire, where he was taught by the German missionary Mr. John Ton, and converted to Christ under the teaching of Mr. John Thompson, he was his student, and he had a lot of contact with the famous Italian missionary and scholar Mr. Matteo Ricci, and was a friend, and he kept hearing the name of Mr. Galileo from Mr. Matteo and other Italian priests. I have been envious for a long time, and I have not traveled thousands of miles to visit. ”

Galileo listened to Li Zubai's humble words, surprised by Li Zubai's fluent Italian, and was very happy in his heart. No matter who it is, it is very pleasant to be revered by others, especially a scholar thousands of miles away, and it is even more pleasant, even a great man like Galileo is not exempt from vulgarity, and naturally he will leave a good impression.

Galileo said happily: "I am very happy to meet all the scholars of the Ming Empire, and it is also my honor. I like the gifts you have brought very much, thank you very much, and I hope that we can have a pleasant exchange in the future, and jointly contribute to the progress of science and improve our knowledge. ”

Li Zubai said: "Mr. Galileo is polite, the purpose of our visit this time is to learn from you, we know that you are a famous astronomer, physicist, our Ming Empire does not have too much knowledge in these aspects, I hope you can explain to us, let us have a long insight, I don't know if you are willing?" ”

Galileo smiled and said: "Mr. Li is too polite, the knowledge of the Orient is broad and profound, all-encompassing, as far as the information I have seen, your country has a long time ago about the observation of celestial phenomena data records, as early as more than a thousand years ago there was an armillary sphere, even earlier there was a special calendar research, the formulation of the 'twenty-four solar terms' and other astronomical knowledge, do not need to be too modest, we can discuss these knowledge." ”

Galileo led Xu Xiake and his entourage into his astronomical observation laboratory, and introduced the observation and research instruments here, the main facility is an astronomical telescope, although it is very simple, but his use effect is very good. Galileo told Li Zubai and others about the history of European astronomical research and various theories, as well as how he used this telescope to observe the sky, how to record and divide various celestial bodies and celestial phenomena, and how he was most proud of discovering the moons of Jupiter.

Through Galileo's explanation, Li Zubai was greatly inspired, and he finally knew the difference between the observation and research of astronomical knowledge in the East and the West. Unlike Europe, ancient astronomy in China, India, and the Arab world was based on the calendar. China, on the other hand, is different from India and Arabia, which is longer than calculating the positions of the planets, while China is longer than calculating the movements of the sun and moon.

Chinese astronomical research focused on practical applications to aid agricultural production, while Western astronomy focused on theoretical research to preserve Christian rule, but long-term observations revealed contradictory celestial phenomena that led to further theoretical development.

Based on Aristotle's geocentric theory, Europe believed that the heavens were the result of a multi-layered crystal ball, and that all the sun, moon and stars revolved around the earth. In ancient China, celestial models were established to simulate and study celestial phenomena. China's astronomical research is based on the state system, and the imperial court strictly prohibits private research on celestial phenomena, which restricts the popularization and improvement of astronomical research, after all, it is the patent of a few people. European studies were private, unfettered, free debate, and conducive to the popularization of astronomical knowledge, but unfortunately this freedom was guided by geocentrism, which led to Copernicus being considered a heretic and Bruno being burned at the stake.

After talking about these astronomical knowledge, the next step is to discuss the "Nine Chapters of Arithmetic", Galileo is very interested in this book, this time it is Li Ciyu who came forward, since Galileo explained his astronomical research to Xu Xiake and his party, in response, Li Ciyu should also explain to Galileo the Chinese "Nine Chapters of Arithmetic", which is an encyclopedia of ancient Chinese mathematical knowledge, an all-encompassing book.

Li Ciyu picked out a few questions with classic cases for Galileo to try, such as 1. Today, someone holds the meter out of the three levels, the outer pass three and takes one, the middle pass five and takes one, the inner pass seven and takes one, and the remaining meter five buckets, asking: This holds the meter geometry? 2. Today, there are seven days from the South China Sea to the North Sea, and the geese from the North Sea to the South China Sea for nine days. 3. A person uses a car to load rice, from A to B, the car loaded with rice is said to travel 25 kilometers, and the empty car without rice is said to travel 35 kilometers, three times in 5 days, ask how many kilometers are the distance between the two places? and some other math problems.

Galileo did not understand Chinese, so he changed to Italian under Li Zubai's explanation, although it is not very accurate, but it can still fully explain the meaning. Galileo was not pretentious, and began to calculate these questions, sometimes pondering, sometimes frowning, sometimes smiling, and in about half an hour worked them out, and then asked Li Ciyu's opinion to see if there were any problems.

Li Ciyu was very surprised by Galileo's calculation method, although some of the steps are more complicated, but each part has a strict explanation, in such a short period of time there is such a complex method to explain these topics, in the Ming Dynasty is not seen, it is difficult to say whether such a method is good or not, but such a calculation speed is definitely not as good as Mr. Bookkeeper.

Next, Li Ciyu used the abacus to demonstrate the Daming algorithm of these problems to Galileo, and the result made Galileo stunned, he only saw Li Ciyu's ten fingers flying, playing the piano on the abacus, and the result was that in a very short period of minutes, the results of these problems that had changed the numbers were calculated, and the results were the same as the results of his own calculations, or even more accurate.

See Galileo in astonishment. Li Zubai didn't hide his selfishness, so he told Galileo about his calculation method, only to hear Galileo nodding frequently, expressing his admiration. But the next sentence made Li Ciyu puzzled, because Galileo said "pentacimal".