Seven young people from the two houses, plus Sun Yunqiu, who was called to accompany them, gathered together in a clear way during the break.

There are four Hanlin Courtyards in a bunch, and four Qintian Courtyards in a bunch.

Li Quan, a sunny boy, sat on the ground and asked, "Brother Yuan Jing, hasn't your navigation clock been made yet?" ”

Wang Su, Zi Yuanjing, is a graduate student of Jinling University and a disciple of Fang Yizhi of Qintian Academy. Major in physics, minor in astronomy, proficient in mechanics, his appearance is not good.

Their appearance is not good-looking, at their age, even if they are not married, they already have a marriage contract, and it is really difficult to find those who meet the emperor's requirements, so Wang Su, who is relatively ugly, was also pulled to fill the number.

Wang Su cried bitterly: "Brother Yuheng, the precision you require is too high, where can I make it?" It's been more than three months of tossing, and the error value of the clock has only been reduced by 3%-8%, and it is estimated that when I die of old age, I will not be able to make a marine clock for you. ”

"Try again, haha, you'll definitely be able to." Li Quan was not discouraged, and smiled and gave Wang Su chicken blood.

Tian Yang said: "Brother Yuheng, if you want to measure longitude at sea, why do you have to use the idea of clockwork? Isn't it okay to use the moon distance method? ”

Li Quan shook his head: "The shortcomings of the moon distance method are too obvious. First, it cannot be used on rainy days, and it cannot be used during the day; Second, there are always a few days in each month when measuring longitude with the lunar distance method will produce deviations; Third, the calculation of the lunar distance method is too large, and it may be difficult for the star pullers on the ship to master. ”

Tian Yang was stuffy in front of the princess, but he spoke very neatly at the moment: "The ocean voyage has been going on for a year and a half, and the first and second shortcomings you said are completely negligible. As for the amount of computation, we can make a monthly distance table and get a lot of data out in advance. The calculation of the star puller against the table can greatly reduce the amount of calculation, and only secondary school graduates will be able to do it. ”

Sun Yunqiu listened to it for a while, and said curiously: "Are you talking about sailing?" ”

Sun Yunqiu is a master of Qintian Academy, while the other three are not even bachelors, they are just graduate students affiliated with Qintian Academy.

Li Quan was still sitting on the ground, and arched his hand and said, "I want to teach Master Sun to know that the three of us are discussing how to solve the longitude measurement during navigation." Today's maritime latitude measurement technology has been very mature, but longitude measurement has not been solved. If the ship is unable to dock for a long time, the longitude must be measured, otherwise it will have to try its luck and sail forward. ”

"Tell me what you think." Sun Yunqiu became interested.

Li Quan said in detail: "Now there are two theories, one is the clock method, and the other is the moon distance method. Let's start with the clocking method, according to the earth's orbit around the sun, the time is different at different degrees of longitude. The Qintianyuan Planetarium has set the longitude of Nanjing at 0 degrees. The time of the ship's location, by calculating the time difference with Nanjing, the specific longitude of the ship can be calculated. ”

Sun Yunqiu can also make clocks, and immediately shook his head when he heard it: "The clocking method is impossible to achieve for the time being, the error is too big, and the current clocks and clocks are not accurate enough." ”

Li Quan said: "My idea is to try to improve the accuracy of the clock and make more marine clocks. One or twenty nautical clocks are placed on the ship, and the longitude is measured by averaging these bells. ”

"No, no, you're trying your luck." Sun Yunqiu shook his head.

Li Quan said: "Then you can only use the moon distance method." Take advantage of the position of the moon in the starry sky, use the starry sky as a clock face, and the moon as a pointer. Then, through the calculation, the position of the moon is converted into the time where the ship is located. In this method, it is necessary to refer to the star catalog and rely on the long-term observation data of the observatory. The starry sky observation data is our strength, and the data of Nanjing and Beijing for hundreds of years are available. But the disadvantages are also obvious, rainy days cannot be measured, and there are a few days a month when the error is very large. The main thing is that the amount of calculation is too large, and it is difficult for ordinary nautical star pullers to complete. ”

Wang Su added: "The shaking of the hull also interferes greatly with the lunar distance method. ”

"It's not very big, it's very big, so I'm more inclined to the horological method." Li Quan said.

Wang Su said: "We plan to improve the measuring ruler and cross instrument to make more sophisticated nautical instruments. But no matter how you improve, if you want to measure longitude, you have to know where the ship is. ”

Longitude is measured with a sextant only if the local time is known.

The European side was also thinking about using the horological method for a long time because they did not have enough astronomical observations. Since the error of the marine clock is too large, then bring more marine clocks.

But marine clocks are precision instruments, and even in a few decades, each marine clock will cost more than £500. Twenty HNA clocks, 10,000 pounds are gone.

So after the astronomical data in Europe matured, with the invention of the sextant, the companion "lunar distance table" obsolete the marine clock - even then, it took several hours to calculate the longitude. It was not until 1766 that Mascalin hired a large number of "human computers" to list the relationship between lunar distance and longitude, and shortened the longitude measurement time to 30 minutes.

"You're going on an ocean expedition?" Sun Yunqiu asked.

Tian Yang pointed at Li Quan: "I don't want to go, it's he who wants to go." ”

Li Quan smiled: "I can't be idle, I'm ready to sail around the world." ”

Even if it is a circumnavigation of the world, there are now mature routes, and it is not necessary to calculate longitude. Only on circumnavigation expeditions, in order to cope with the unexpected, it is necessary to calculate the longitude.

Sun Yunqiu said: "I really can't help with other things." But to improve the cross, I have an idea, which is to install a clairvoyant mirror on the cross. Well, if you want to calculate more accurately, the cross meter definitely can't. If the lunar distance method is also to be used, the range of the instrument must be more than 90 degrees. Then make the instrument 60 degrees, the range is 120 degrees, it is better to call it 'sextant'. ”

Li Quan was very interested and asked, "What is the use of installing the clairvoyant mirror on the instrument?" ”

Sun Yunqiu said: "My idea is to use a clairvoyant mirror instead of visual observation, and then make a translucent mirror to make it a fixed horizon mirror, and then make a moving mirror. Turn the mirror so that the celestial object coincides with the horizon or sea horizon. In this way, the angle of the mirror can read the altitude angle of the celestial body......"

As soon as these words came out, the three of them suddenly heard it.

Tian Yang exclaimed: "Why can Master Sun have such a wonderful idea? ”

Sun Yunqiu said: "I often use a clairvoyant mirror to watch the stars, and many times I don't want to make calculations too troublesome, so I think about what instruments can simplify it. ”

The sextant was not originally intended for navigation, but for observance at the observatories, and the concept was proposed by Hooke and Newton. Because it was so easy to use, it was shrunk by the navigators and taken to the ship.

Li Quan belongs to that kind of action faction, and he has to do whatever he thinks, so he even assigned tasks on the spot: "In this way, I worked with Brother Ang Qi (Tian Yang) to calculate and make a finer moon distance table." Master Sun and Brother Yuan Jing (Wang Su) were in a group to invent and make that sextant. With the moon distance meter and sextant, the ocean expedition is bound to be invincible! ”

"Okay, I'll do it with you." Sun Yunqiu said with a smile.

Zhao Han and Li Zicheng did not go hunting, but rode horses in the horse farm.

Coming back at this moment, Zhao Han smiled and asked, "What are you talking about?" ”

The crowd stood up and saluted.

Feng Qizhi took the lead and said: "Back to Your Majesty, the students and colleagues of the Hanlin Academy are discussing the doubts of the oracle bone inscription. I deeply feel that my generation is not knowledgeable, and we need to be more sophisticated. ”

Zhao Han looked at the ground in front of them, and sure enough, he saw a few oracle bone inscriptions, as well as changes in the golden inscription and seal inscription, and immediately nodded in approval: "Yes, keep up the good work." ”

"Thank you, Your Majesty, for your encouragement!"

The four young people of the Hanlin Academy saluted excitedly and inexplicably.

Zhao Han asked Qintianyuan again: "What about you?" ”

Li Quan replied, "Back to Your Majesty, the students are discussing navigational matters. It has been agreed that the students and Tian Yang will improve the lunar distance table, and Master Sun and Wang Su will make a sextant. As long as these two things are done well, you will be in the vast ocean, and you can quickly measure the latitude and longitude. ”

"Sextant?" Zhao Han smiled and nodded, "Very good, Dashan!" ”

Li Quan suddenly knelt down: "Your Majesty, the student has a reluctant request." ”

Zhao Han said: "Let's talk about it." ”

Li Quan said: "The minister was in the Qintian Academy, and from the Taixi scholars, he learned the story of Magellan and other navigators. We are the same as China, and so far there are no navigators, let alone circumnavigators. Huanghuang Celestial Empire, how can it lag behind the Taixi barbarians? Your Majesty is to give your retainers five ships, with experienced captains, star pullers, sailors, and soldiers. The minister wants to take Shandong as a starting point, cross the ocean to the east, and explore the Americas for my Celestial Empire first! ”

At this time, the Pacific route started in Asia at the Balintang Strait, between Taiwan and Luzon. Even after a few hundred years, it is the most important shipping route for Japan, and there is no one.

Given the level of development of the South Seas in the 17th century, the starting point of the best Pacific route should be in the northern part of Taiwan.

Therefore, Spain went to colonize Keelung in the first place. As long as the port of Keelung is developed, it can obtain Chinese goods nearby and ship them directly to the American colonies, and at that time, Spain can even abandon Manila.

However, the Spaniards thought too simply, and there were too many maneuvers.

First, the Han people were not allowed to help develop Keelung, the port and the city never prospered, and the grain needed for Keelung had to be transported from Manila. Second, due to the lack of Spanish troops, they were bullied by the Taiwanese natives very badly, and even the castle was once breached.

In desperation, Spain had no choice but to give up the colony of Keelung.

Spain's Pacific route now sails from the South Philippine Islands to the Balintang Strait via Manila. Then, along the Ryukyu Islands, from the southern waters of Japan to the east, the ocean currents continue to the Americas. In the Americas, it follows the ocean current, returns straight to the Balintang Strait, and then goes south through Manila to the South Philippine Islands.

Luzon, Taiwan, and the Ryukyu Islands have all been controlled by China, and the Balintang Strait has almost become China's inland sea, directly cutting off the Asian starting point of the Pacific shipping route.

In such a situation, Spain did not dare to conflict with China at all. If a war really starts, the Chinese navy will not need to do anything else, just block the Balintang Strait, and the Spanish galleon trade will be declared over.

Li Quan's idea is to start from Shandong, use Japan as a springboard to the Americas, and open up a "Shandong-America" route.

This route is useless now, but in the future, if Chinese maritime merchants want to do business in the Americas, they will have two routes to choose from: one is Taipei-America, and the other is Shandong-America.

Zhao Han showed a relieved expression and asked, "Walking thousands of miles in the sea, nine deaths and one life, do you know the danger?" ”

Li Quan replied categorically: "Although I have died nine times, I have no regrets!" ”

This person definitely can't be a colt, Zhao Han doesn't want his daughter to be a widow.

(Thank you for the magic cultivation strategy, the alliance leader who has entered the nickname is already rewarding, and thank you to the two brothers.) ）

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