Today is the end of the month, and there is only a shallow crescent moon in the sky, which is not the best time to observe the moon, but it is just right to observe the stars. Pen? Interesting? Pavilion wWw. ｂiquge。 info Wang Mai turned his lens on Jupiter, the big brother of the eight planets in the solar system.

"You see, this is the Tai Sui Star, which has just risen now, and the light on the surface is sufficient." Wang Mai grabbed the binoculars and said.

Several people curiously stepped forward to watch one by one, and they were all amazed.

"I can't imagine that the star has become so big under this telescope that even I, a person with eye disease, can see it clearly." Yuan Tiangang sighed.

"If we can build a better astronomical telescope, we can see even the stars beyond the galaxy." Wang Mai said.

"Is that true?" Yuan Tiangang asked.

"Of course." Wang Mai pointed to the roof of the observatory, "If you can make such a big lens, even the Milky Way will not be a problem." ”

"How do you know? Have you seen it? Yuan Tiangang squinted his eyes and asked.

"Nope." Wang Mai immediately denied it, "But I made this thing, so I naturally know the truth." ”

"If you can build a telescope like this, it doesn't matter what you ask of me." Yuan Tiangang opened his mouth and promised.

"Although I am very impressed by this condition you proposed, but unfortunately, I can't do this, with my knowledge, it is very good to be able to make a product of this size." Wang Mai said helplessly, "But if you use the method I gave you to study carefully, I believe that you will soon be able to make a much better telescope than this." ”

"I wonder what this telescope is?" Li Chunfeng asked.

"You want to hear it?" Wang Mai looked outside, "It's getting late now, if you don't go back, it's past the curfew time." ”

"It doesn't matter." Yuan Tiangang stroked his beard, "We have already obtained permission." ”

"That's good." Wang Mai took a pen and paper from the table on the side and began to explain to them the principle of refracting light through a lens.

Yuan Tiangang is a master of astronomical calendars who has been famous for many years, and it is not difficult to understand. Wang Mai didn't expect that the young Li Chunfeng and Si Swenwen's Yan Qinli were also proficient in arithmetic. Especially Li Chunfeng, every time Wang Mai said something, he could always understand it the fastest, and then said the truth to Yuan Tiangang and Yan Qinli. This is the real young genius, Wang Mai finally knows what a prodigy is.

"In this way, the magnification depends on the distance of the focal point, which in turn depends on the curvature of the mirror." Li Chunfeng pursed his lips, "I just don't know how to calculate this curvature?" ”

The three of them all looked at Wang Mai, expecting him to give an answer.

Wang Mai smiled bitterly, he was purely cocooned and self-bound, and the curvature solution was in the category of advanced mathematics. I only took a year of advanced math classes in college, and I had already returned the knowledge of differential calculus to my teacher, and I couldn't use it after work, so I basically didn't have anything left in my head.

When the three of them saw Wang Mai's expression, they knew that he couldn't do anything, but Rao was like this, and he was already amazed by his mathematical ability. Yuan Tiangang sighed: "Assistant Teacher Wang, it is really rare to be able to deduce this step. I'm afraid it's hard to get any more into this matter. ”

From the Eastern Han Dynasty to the Wei, Jin, Southern and Northern Dynasties, there were many mathematicians, among which the most famous three were Zhang Heng, Zu Chongzhi, and Liu Hui, the first two of whom were all astronomers, because arithmetic focused on practical application, especially in astronomical calendar calculation. Yuan Tiangang and Li Chunfeng in front of them are both masters of astronomical calendars, and they are also the highest level mathematicians in the world. However, Liu Hui was poor all his life, so he had to study mathematics and made remarkable achievements.

"Do you know about circumcision?" Wang Mai asked, thinking of Liu Hui, he couldn't help but mention his circumcision.

Circumcision is a method of finding pi by continuously doubling the number of sides of a circle with regular polygons, and the idea of this method is very close to the limit idea of calculus, but unfortunately after Liu Hui, there are not many people who are willing to spend their first years studying mathematics, otherwise, the people who eventually invented calculus will not be Newton and Leibniz.

The three of them were all erudite people, so they naturally knew that this circumcision technique was the method invented by Liu Hui to solve pi. Li Chunfeng's eyes lit up: "Assistant Teacher Wang is saying that the same way of thinking is used to solve the curvature of this mirror. ”

A genius is a genius, Wang Mai sighed in his heart. Before he could say anything about the limit thought, Li Chunfeng thought of it. He nodded immediately: "Yes, that's it." ”

This time it was finally Yuan Tiangang and Yan Qinli's turn not to understand, the two of them looked puzzled, and Yan Qinli asked: "What is the relationship between the circumcision technique and the solution of this curvature?" ”

Wang Mai shook his head: "Actually, I only know a little bit about it, but I can tell you about the principle." ”

"I want to hear about it."

Wang Mai drew a curve on the paper: "Look, everyone, I will draw a tangent straight line on this curve, and the tangent point is A; Take another position to get another tangent point, and the curve between the two tangent points can be supplemented into a complete circle......" as he said as he wrote and drew on the paper, "using this method to know the degree of curvature of the curve, which can be called curvature." ”

The three of them gathered around Wang Mai and watched his demonstration intently.

"As for the curvature solution, a new concept needs to be introduced." Wang Mai explained the variables and functions to the three of them again, until the advanced functions, and now Yuan Tiangang and Yan Qinli couldn't keep up, only Li Chunfeng still listened carefully and carefully, with a surprised smile on his face from time to time.

Wang Mai was also very tired to speak, and a lot of the content was already unfamiliar, and in the end, even he himself was confused and didn't know what to say. It wasn't until I finished my last knowledge of high mathematics and wiped the sweat on my face that I breathed a sigh of relief. This Li Chunfeng is also too rebellious, and a lot of the content he has forgotten, after some deduction, he actually solved it, it is simply a demon.

After this explanation, it was until late at night, several people were yawning, and outside the wandering objects, only Li Chunfeng was calculating the functions he had just learned over and over again under the dim oil lamp, and he didn't show any tiredness.

"Poor Dao is old and lacks energy, and he is really not as good as you young people, so he will retire first." Yuan Tiangang couldn't hold on to his body after a long day of travel, and left first, Yan Qinli was also worried that he would not return overnight, afraid that his father and brother would worry, and he would go back together.

Wang Mai looked at Li Chunfeng, who was in a frenzy, this person didn't have the slightest intention of leaving, and couldn't bear him to be alone with a young man, so he said goodbye to the two: "There is still an hour before the Zhenxing is about to rise, I will wait here for a while, so I can exchange my experience with Li Daochang." ”

Seeing off the two, Wang Mai looked at Li Chunfeng, who was engrossed, and shook his head, once he entered the kingdom of mathematics, few people could come out, and the sense of accomplishment of overcoming difficulties was incomparable to anything.

After a long time, Li Chunfeng raised his head, the clothes on his body had already been soaked with sweat, but he didn't care at all, and kept a faint smile on his face: "I've figured it out, thank you Assistant Teacher Wang for your guidance." ”

Wang Mai waved his hand: "You are the most powerful mathematical genius I have ever seen, and I am just a person who has not even stepped into the gate, how can I be called a guide?" You're better than me now. ”

"If it weren't for Assistant Teacher Wang's inspiration, how could Chunfeng master such a mysterious method of counting overnight, no matter what, please be worshiped by Chunfeng." When he speaks, he is to the end.

Wang Mai hurriedly helped him up: "Where is the Taoist chief?" Your genius is simply rare in the world, and if you can study it diligently, you will definitely achieve extraordinary results. I just don't know why you became a Taoist monk at a young age? ”

"Actually, my father was obsessed with Taoism in his early years...... Li Chunfeng told Wang Mai in detail about his life experience.

It turned out that Li Chunfeng's father was also a highly talented person, who had been an official in the Sui Dynasty, but later because of unsatisfactory officialdom, he abandoned the official and concentrated on learning the Tao. Li Chunfeng was influenced by his father since he was a child, and he also preferred these astrological calendars, coupled with his talent, he soon became a well-known young genius in the local area. Yuan Shoucheng valued his talent very much, coupled with the influence of his father, so he entered this sect to learn the Tao. After entering the Daomen, he didn't like alchemy and taking medicine to pursue immortality, so he had to use magic to deduce the astrological calendar.

I see, but most of the mathematicians in ancient times were astronomers, and Daomen has always been an astronomer because of its emphasis on astrology, so this is easy to understand.

After another conversation, it was already the second half of the night, Wang Mai searched for a long time and finally found a trace of Saturn in the sky, beckoned to Li Chunfeng, and motioned for him to come and watch.

Li Chunfeng put his eyes on the lens tube, and the scene that appeared in front of him made him unbelievable, Saturn, which used to be just a point of light, was so bright and beautiful, especially with clear and distinguishable protrusions on both sides, as if it had two ears, and couldn't help exclaiming: "Why is this happening?" ”

"It's called the Star Ring." Wang Mai explained.

"It's a ring?"

"That's right, if you look around, you can see that there are more satellites revolving around it, more than one." Wang Mai said.

"Circling the stars?" Li Chunfeng was thoughtful. He turned his gaze to the armillary sphere not far away, got up and took two quick steps, and came to the side of the armillary sphere.

The heavenly sky is like a chicken, the celestial body is round like an egg ball, and the ground is like a chicken in the middle yellow, this is the heavenly theory. During the Eastern Han Dynasty, the armillary theory has overshadowed other views and become the first theory of people's understanding of the universe, and Zhang Heng improved the armillary sphere on the basis of his predecessors, and it became what it is today.

The armillary sphere is composed of two parts, the armillary sphere and the armillary sphere, the armillary sphere is to depict or inlay the stars, the equator, the ecliptic, etc. on a large sphere, the armillary sphere is a kind of observation of the stars, the measurement of dusk, dan and other functions of the instrument, the two are one, forming the armillary sphere.

There are many similarities between the armillary theory and the Ptolemaic geocentric theory, both of which believe that the earth is the center of the universe, and the sun, moon and stars revolve around the earth, which can be regarded as a kind of Chinese-style "geocentric theory".