"Glass mirrors? At this time, it seems that the compound of ammonia has not yet been made, so it is naturally impossible to use the silver ammonia solution to make a silver mirror reaction. However, it seems that the process of dissolving tin foil with mercury is still possible. ”

Zhu Youzhen was thinking about his chemistry experiments in middle school and how to make mirrors that could be used.

After Luo Yagu and Tang Ruowang on the side glanced at each other, they stepped forward to Chongzhen and continued: "Actually, I want to create what Your Majesty said, to observe and measure the angle between two targets in the distance.

We also need to prove that the angle between the initial and final directions of the two reflected rays on the same plane is twice the angle between the two reflecting surfaces.

Of course, we have proved this mathematically, and if these two optical principles can be verified, then there will be no obstacle to making the sextant that His Majesty needs. ”

Zhu Youzhen immediately sobered up from his thoughts, and he said to the two of them: "I will hand over the matter of the glass mirror to the Wensi Academy to make it, and you should first prepare other work to prove these two optical principles."

The problem now is that once we have made a sextant, we assume that we can use it to measure the angle of the sun or other celestial body to the horizon or horizon at a given moment.

So how do we use this to determine the latitude and longitude of the observation point? ”

Roya Valley immediately replied: "The method of determining the dimensions is not difficult, in fact, the quadrant we have brought now is fully capable of measuring latitude.

His Majesty's proposal to make a sextant was only to improve the accuracy of the measurement. In order to measure longitude with a sextant, it is necessary to find a reference object for a celestial body.

In accordance with His Majesty's order, we discussed carefully with several officials of the Astronomical Section of the Qin Heavenly Prison and consulted the star map data recorded by the Astronomical Section.

We agreed that it was feasible to measure longitude using the lunar distance method. We find from the records of the Qin Tianjian that every 18 years, 10 days, or 12 days, the moon, the earth, and the sun return to the same position.

There were 43 solar eclipses and 28 lunar eclipses during this period, and the information preserved by the Qin Tianjian is so complete that we can even consult the astronomical records of the previous dynasty.

And these materials also just verify the astronomical periodic phenomena mentioned in Ptolemy's writings. Therefore, His Majesty thinks that it is perfectly feasible to measure the position of longitude by the position of the moon.

Now we only need to solve two problems, first, accurately predict where the moon will run; 2. There is a well-developed background star map that serves as a background reference for the Moon. In this way, no matter where we are, we can use a sextant to determine the latitude and longitude. ”

Zhu Youzhen suddenly smiled, and then he asked, "Then how long will it take for me to see that you confirm this theory?" ”

Zhu Youzhen's question silenced the missionaries who were still elated, and Luo Yagu said to the emperor with some regret: "We can barely use the star chart recorded by Qin Tianjian as a reference star map, but we haven't found a way to accurately calculate the movement of the moon. ”

Zhu Youzhen's heart was suddenly broken, and he said with some frustration: "In other words, we have found a solution to the problem of measuring longitude in theory, but in practice, it is not impossible to achieve, right?" ”

Luo Yagu nodded and said, "Yes, Your Majesty, there is also the star map recorded by Qin Tianjian is the star map of the northern hemisphere, and we still need the star map of the southern hemisphere." This ensures that the ship will not lose course anywhere. ”

Looking at the emperor's lost expression, Jinnige immediately stepped forward and said, "Father Deng Yuhan has written a letter to ask Mr. Galileo to solve the problem of calculating the trajectory of the moon. ”

Zhu Youzhen did not feel more comfortable with the comfort of Jinnige, although Galileo was an outstanding scientist, but in his memory, Galileo's outstanding talent lies in his contributions to physics.

And calculating the trajectory of the moon is obviously a mathematical problem. He didn't think Galileo would be able to solve the problem, and the distance between the Ming and Europe made him unsure when the problem would reach Galileo.

Speaking of which, in the end, we should still cultivate our own mathematicians, Zhu Youzhen couldn't help but have this enlightenment.

He finally perked up and said, "Anyway, we have finally proved that there is a way to determine the position of ships on the sea, and as long as we keep going, we will solve this problem after all."

Before we can solve these problems, we need more accurate star catalogs, and the observatories in Beijing and Nanjing need to be renovated and a unified standard for observing records will be developed.

Then find the most suitable area for observing the starry sky in the southern hemisphere, and prepare to send astronomers to build an observatory.

Li Zhizao and Wang Zheng, the two of you will take the lead in establishing the Daming School of Mathematics, select people with outstanding talents in mathematics, and enter the School of Mathematics to study how to calculate the trajectory of the moon..."

Although he learned that he could not promote the development of navigation technology in a short period of time, in view of the fact that the navigation industry of the Ming Dynasty was still in the stage of offshore navigation, Zhu Youzhen finally left this regret behind.

The biggest gain of this trip is the final completion plan of the Latin alphabet pinyin presented to Chongzhen by Jinnige, and with the simplified characters that Zhu Youzhen has completed, he can now finally edit a simple literacy textbook and a primary school dictionary.

Zhu Youzhen smiled and flipped through the pinyin plan, then said to Jinnige: "Thank you very much for your contribution to the Ming Dynasty, and then I will set up a normal school, I hope that the priest and the relevant personnel who edit this plan can become teachers in this school." ”

Fr. Kinneko replied with a smile on his face: "Although it is an honor for us Jesuits, Mr. Wan, Huang and Mr. Zhao of the Hanlin Monastery have also made outstanding contributions to the formulation of the plan. ”

Zhu Youjian nodded and said, "That's better, I hope that in the normal school, you will cooperate more happily." ”

When Zhu Youzhen said goodbye to Jinnige and the others, as soon as he walked out of the courtyard of the chapel, he saw two guards entangled with a scholar.

If it was the people of the capital, seeing these guards guarding the door, they would probably take a detour. But this scholar was about the first to come to the capital, and he regarded these brocade guards as ordinary sergeants.

He shouted with the two guards to enter the courtyard. The two brocade guards were afraid of the scholar's clothes he was wearing, and they didn't dare to be too rude.

The Emperor's visit to the Chapel was not public, so the two guards could not reveal the Emperor's presence in the courtyard.

Therefore, the scholar thought that the two sergeants were deliberately obstructing, but he was really in a hurry to enter the chapel to do business, so he resolutely refused to go, so the three of them stalemate at the gate of the courtyard.

But when Zhu Youzhen and the others came out of the courtyard, the scholar understood, and immediately knelt on the ground with the two guards.

Looking at the somewhat whitish blue robe washed on this scholar's body, Zhu Youzhen felt that he was really in a hurry, so he didn't want to ask him about the crime, so he couldn't help but say casually: "Forget it, those who don't know are not guilty, and he doesn't know that I am inside." If you have anything, go in and do it, and you don't have to dwell on it again. ”

Wan Hongsheng, who had escaped, had just breathed a sigh of relief, but suddenly thought that this was not his chance to gain the emperor's favor.

He hurriedly said, "Your Majesty, please stay, the students want to present a strange weapon to Your Majesty." ”

Zhu Youzhen stopped, turned to look at his side, and then said with some curiosity: "What kind of strange weapon, how do you know that I need a strange weapon?" ”

Wan Hongsheng hurriedly took out a newspaper from his arms, raised his hands above his head and said: "Your Majesty said in this newspaper that as long as someone can offer a tool that will not lose its way in the sea, or a tool to determine the direction of the ship, and explain the principle of manufacturing, he will receive a reward of 10,000 taels of silver. ”

Zhu Youzhen nodded and said, "That's true, did you invent the principle of this instrument?" ”

Zhu Youzhen, who had just experienced the blow, didn't think that this scholar could make a sailing clock. In his memory, the method of determining longitude at sea was the method of lunar distance and the method of clocks, which was proved by the history of navigation.

If this person wanted to fool himself with some strange theories such as the Induction School, Zhu Youzhen thought that he would definitely let him taste the consequences of deceiving himself.

Wan Hongsheng didn't hear the indifference in the emperor's words, he slammed up, and the two guards immediately went up and held him down.

"The students just wanted to get the utensils, and they had no other intentions." Wan Hongsheng hurriedly defended himself.

Zhu Youzhen nodded at the two guards, and the two guards immediately let go of their hands, but they were still staring at Wan Hongsheng nervously.

Seeing Wan Hongsheng take a lantern without skin from the corner of the wall, Zhu Youzhen said with a smile: "This is the strange weapon you want to show me?" ”

Wan Hongsheng took out a candle head from his arms and pressed it into the lantern, then took out the fire sickle and tried to light the candle, and explained: "Your Majesty, please wait a moment, the student just wants to demonstrate the principle of this instrument to Your Majesty, and the real strange weapon can be made by imitating this lantern." ”

The lantern with the candle rolled on the road, but the position of the candle remained the same.

Lian Shanxiang, who was behind Zhu Youjian, whispered to the emperor and said, "Isn't this the rolling lantern of the Lantern Festival?" Your Majesty, this is just a whimsical fool, let's let him go. ”

Zhu Youzhen didn't make a sound, he looked at the rolling lamp blankly, Wan Hongsheng said at this time: "As long as such a device is set up on the ship, and the direction is set when sailing, no matter how the ship rolls, the pointer will not move like this candle, then the ship will not lose its way?" ”

"Was it a gyroscope?" Zhu Youzhen finally remembered something similar, but he still doubted whether this primitive gyroscope could indicate direction at sea.

Looking at Wan Hongsheng's expectant appearance, Zhu Youzhen said quietly: "Your idea is very good, but whether it can be realized or not still needs to be verified, at least you have to complete a usable instrument first." If you're willing to develop this device, I can provide some funding. ”