Chapter 6672 Astronomical Geodesy

Chapter 6672 Astronomical Geodesy
The Gan and Shi families have accumulated thousands of years of experience in astronomy and climatology. Even if we don't count the period of the Ji clan before that, it has been more than 600 years since these two families produced the first astronomical work in human history.

Over the past six hundred years, the two families have accumulated a large amount of data on astronomy, hydrology, and climatology.

After being hit hard by several large-scale catastrophic climate events, the Gan and Shi families finally came to their senses - we need to create a big, accurate thing that integrates all the information in the family and can be passed down dynamically.

Of course, there is a very important point here. There is too much information left by the ancestors of these two families. Even if some of it was lost or damaged during the period, the number of bamboo slips is enough to crush a person to death.

So this group of people planned to classify and organize them, and during this process, the young man of the Shi family brought something to the two families. Wan Zhen listened to the young brother of the Shi family explain the astrology, and then he suddenly had an idea and pieced together the magical operation of planetary positioning.

As I said, Wan Zhen is a genius in the true sense. His spiritual talent of knowing everything can be used to great effect in his hands. For many things, he only needs to know the beginning to analyze a large number of magical uses.

Combined with the messy knowledge he had acquired before, giving you a new skill on the spot is like a piece of cake. Although theoretically, Wan Zhen's new skills do not contain any of his own developments, his skills are all messy stuff he picked up from other people, and then created with his amazing ability to piece together.

However, you have to admit that Wan Zhen is really the god of patchwork. He can always piece together some messy things to create a set of amazing things.

For example, he chatted with the kids of the Shi family and learned about astrology and sea navigation. Soon after he learned it, he combined his knowledge of mathematics, astrology, sea navigation and clocks to develop the technique of planetary positioning.

For example, in the official history, Wan Zhen had never been to the South, but what he wrote was very accurate and has great value for reference, quotation and learning.

For example, Wan Zhen has actually reached the fourth level of smelting now, and he has also combined his understanding of talents to create a talent smelting and transformation logic book, as well as talent structure combination optimization, successfully allowing himself to keep up with the combat effectiveness of the Iron Cavalry Headquarters.

He even learned a little about military command because he had experienced war. Then, combining Chen Xi's modular concept, some things taught by Huangfu Song, and the war experience of the Xiliang Iron Cavalry, he developed a set of military command techniques that he could use for himself without any problems. Apart from anything else, he had no problem commanding a legion.

This guy is a real god, but he doesn't want to be an official, nor does he want to stay at home. He also doesn't seem to want to have children, so he just wanders around the world all day long.

During the journey of thousands of miles, Wan Zhen also wrote a lot of useful things. This time, the two heads of the Gan and Shi families came together and read some of Wan Zhen's records before deciding to conduct astronomical and geodetic measurements in advance.

Chen Xi didn't know about these things, but since these two families wanted to do this, Chen Xi had a rough idea of ​​the level of this group of people.

"This is a big project." Chen Xi said with a serious look, "And since you want to test it, it will probably involve more than just a few things. Tell me what you found first, and then I'll see how much you want to invest."

Astronomical and geodetic surveys require a lot of manpower and material resources. During the first astronomical and geodetic survey during the reign of Emperor Xuanzong of Tang Dynasty, not to mention the manpower mobilized, the measured points alone, from 51 degrees north latitude (Ulaanbaatar, Mongolia) to 18 degrees north latitude (Vietnam), exceeded the current land territories of China in the north and south.

To be honest, this kind of actual measurement method could not be used in the feudal era unless the country reached its peak. Moreover, the territory was not large enough, and the control samples were not enough, so it was impossible to be accurate.

Chen Xi thought that this was indeed necessary. After all, the astronomical knowledge he mastered was not accurate in this era. The existence of precession and nutation caused errors in some of the astronomical knowledge Chen Xi used.

Of course, the law is the same, only the basic terms have changed. But to be honest, since the basis has changed, the results calculated by the law can only be used as a reference.

However, the Han Dynasty rarely touched upon things that were affected by precession and nutation, such as the true rotation axis, true celestial pole, true celestial equator, instantaneous true vernal equinox, and so on.

To be honest, these things have no effect on ordinary people.

Therefore, Chen Xi has been muddling along, but now it seems that the heads of the Gan and Shi families want to solve all these problems together. Come to think of it, if one wants to study the atmospheric circulation accurately, these things are necessary parameters.

After all, the true rotation axis affects the position of the poles, which will be offset by the combined effects of the sun's and moon's gravity and the earth's movement, which is why the poles move over time.

This thing is related to the exact position of the conceptual point of north and south, and is an indispensable parameter for the precise construction of a dynamic planet.

Of course, let's put this thing aside for now. In fact, as long as we understand the precession of the equinoxes and nutation, these things can be calculated by hard calculation. The so-called precession of the equinoxes is actually the time difference between the sidereal year and the tropical year.

The tropical year is simply the time it takes for the sun to pass through the vernal equinox twice, while the sidereal year is the time it takes for the earth to orbit the sun and return to the previous point. The difference between these two times is the precession of the equinoxes.

Of course, this is a concept in time. The real reason for the precession of the equinoxes is actually the change of the true rotation axis mentioned above. The change of the true rotation axis is the joint result of the gravity of the sun and the moon and the movement of the earth.

The logic of nutation is similar to that of precession, but nutation is caused by the change in the distance between the Earth and the Moon. We have learned about universal gravitation and we all know the orbits of the Earth and the Moon, so it should not be a problem to understand the impact of the moon's perigee and apogee on the Earth.

This gravitational pull causes the Earth's rotation on the great circle of the star's orbit to not be completely smooth, but to have peaks and troughs, which is called nutation.

These two things affect a lot of things at the same time, and are the basis for astronomy to consider.

Therefore, Chen Xi must understand what the Gan and Shi families want to achieve. If it is just the level of the Tang Dynasty, Chen Xi will provide three to five hundred professionals and hundreds of millions of dollars. If they have already realized the influence of the gravity of the sun and the moon on the true rotation axis, and consciously adjusted the true rotation axis and even determined the earth's pole, then Chen Xi can invest more.

"First, there is the issue of solar phenomena. There is a large amount of data in the family to prove that the time of the solar eclipse and the eclipse phenomena seen will be different in different observation locations. The same is true for the length of the sun's shadow and the division of day and night in each solar term." Gan Bao saw Chen Xi asking and knew that every word of his current answer was related to the subsequent funding and manpower.

Of course, funding is not important. If you don't have money, you can go to other families to beg. Anyway, the Yuan family of Runan still has hundreds of gold bricks. You can grab them to increase the funding. At most, you will be scolded by the Yuan family, which is not a big deal at all.

The real problem is manpower. If Chen Xi agrees, the number of professional personnel that can be transferred will increase significantly. For example, even gods like Wan Zhen and Zhao Shuang can be brought back to work, which is very important for the Gan and Shi families.

"Well, this is a problem of latitude and longitude. This is relatively easy to do. I can approve 200 million yuan for you to conduct actual measurements at different latitudes and the same longitude, and then calculate the length of the meridian based on the angle difference." Chen Xi nodded. This can be done as long as you pay the money, and it is very meaningful.

As for why it is called the meridian, it is because the Zi in the Earthly Branches represents due north and Wu represents due south. The original meaning of the meridian is the line from due south to due north. Once this thing is calculated and combined with the circumference of the earth, you will realize that the earth is an ellipsoid. The ellipsoid has some characteristics. As long as you realize that the earth is an ellipsoid, many things can be inferred.

"You guys don't even care about the connection between heaven and man. This is a solar eclipse, the bright and shining sun, and you don't respect it at all." After Chen Xi finished speaking, he asked in a teasing tone.

"We have already calculated this. One degree of the meridian is about 111 kilometers." Shi Tao waved his hand and said, they had already used other people's gold coins to calculate it, "As for the connection between heaven and man, our two families don't play this kind of thing very much. We just do it for fun, it's ok to fool others, but fool us? Oh, we don't have the money to fool those who play with the connection between heaven and man, let them fool others..."

Chen Xi was speechless after hearing this. He lowered his head and recalled the data he had read in the encyclopedia. The difference between the data and this data was very small. He then realized that the Gan and Shi families already had a very in-depth understanding in this regard.

"You have calculated the length of the meridian, and followed Jiang Dong to the equator and calculated the length of the equator. Haven't you found any problems?" Chen Xi asked curiously.

"Isn't it really not a perfect ball?" Gan Bao said uncomfortably while grabbing his head. For someone with obsessive-compulsive disorder, it is really uncomfortable to be so close to a perfect ball.

"So you know it, but you just don't want to accept it, right?" Chen Xi said with a smile. The earth is not a perfect sphere, but an ellipsoid. Although it is very close to a perfect sphere, some things are almost not.

"Forget it, let's continue talking about the problems we found after reading the data." Gan Bao said uncomfortably, "The orthographic sphere is only one aspect of the problem. In fact, after having the atmospheric circulation map and planetary positioning technology as a reference, we actually discovered a lot of things by comparing with the ancient records, such as tides, precession of the equinoxes, and the declination of the earth's poles."

"Hmm, the declination of the Earth's pole. You have already discovered the Earth's pole shift, right?" Chen Xi pondered for a moment and said thoughtfully, "That means you will have to measure the Earth's pole shift for a while. So how do you plan to measure it? Where do you plan to measure it?"

Shi Tao's mouth turned bitter when he heard this. He lost the game of rock-paper-scissors to Gan Bao. His family sent people to the Arctic Circle to measure the geographical poles and geomagnetic poles. Although they had been aware of this for a long time, it would be very difficult to actually measure them.

"When the time comes, I will lead the Shi family to the North Pole for actual measurements." Although it will be hard, Shi Tao must remain righteous at this time.

"I remember that the Yong family seems to be in the Arctic Circle. You can discuss with them and stay at the Yong family's place. It happens that there will be a grand court meeting this year, and the Yong family should be here. You can discuss it then." Chen Xi thought for a moment and suggested.

After all, if they want to measure this, they can only go to the Arctic Circle. After all, going to the Arctic Circle and experiencing the polar night will also help these guys understand the realistic concept of the ecliptic plane.

As for the troublesome Yong family, even if they are stay-at-home families, they still need a family like Ganshi that understands astrology, climate and calendar. In an agricultural society, this kind of family stands at the top of almost all families.

Even though they are not well-known and their official positions are not high, official positions will continue to be assigned to this family and there will be no political conflicts. As long as they do their job well, everything will be arranged from birth to death.

Therefore, even if the Yong family is a stay-at-home type, they have to give face to such a family when they go there for a field investigation. After all, if someone stays with you for a while and helps you write a local perpetual calendar, it will save you a lot of trouble in farming in the future.

"We have also considered the Yong family, but we don't know the situation with them and we can't contact them. We plan to contact the Yuan family first. The Yuan family said that they also have a base in the north of the Ural Mountains near the North Pole, and we can conduct research there first and they will provide us with protection." Shi Tao expressed his understanding after hearing this. They did consider the Yong family, but they couldn't find them.

"The Yuan family is also okay. But you better be careful. The Yuan family's sugar-coated offensive is very fierce." Chen Xi said casually.

"We know this too. We previously supported five astronomical figures of the Yuan family, and four of them have married and had children in Sizhao City." Gan Bao said helplessly, "Plus, when the other major families left, they married daughters from our family. Now, there are less than 120 people working in our two families. I am really impressed."

Women are also capable of working. These days, the internal blockade of family studies is not serious. In addition, due to staff shortages, women will also be pulled in to do odd jobs. After a long period of exposure, most of the women from the Gan and Shi families are reliable in hydrological and climate research. At the very least, they have no problem recording data and making judgments according to the tables step by step.

Earlier, the Gan and Shi families had nearly 200 workers, but now there are less than 120 left. Some of them got married, or they joined other families because other families offered higher prices, and considering that some old men and women are no longer able to undertake field investigation missions, the Gan and Shi families are even more short of manpower.

In addition, the current territory of the Han Dynasty has increased significantly, and the newly occupied territories must at least have a basic farming calendar, which has increased everyone's workload. This is also the reason why the older generation retired directly. They couldn't bear it anymore. They really couldn't bear it anymore.

"Where are the new people we trained?" Chen Xi asked curiously. If he remembered correctly, the Gan and Shi families had realized this problem five years ago and had been constantly training new people, but they had no products to sell, right?

"We have tried our best to recruit children under ten years old, but most of them have zero knowledge of astrology and climate." Gan Bao was speechless.

Chen Xi was helpless when he heard this. Nowadays, it would be a miracle if the children recruited here had any knowledge of astrology and climate, even if they were descendants of aristocratic families.

"Forget it, let's continue talking about the astronomical and geodetic surveying that you are going to do." Chen Xi sighed and said, there was no other way, there was no newbie to inherit, so he could only do it slowly, the popularization of such basic knowledge really takes time.

"We already have some understanding of the precession of the equinoxes, but the accuracy needs to be calculated. In addition, we have found evidence of the influence of the moon on tides and planetary rotation from data over the past few hundred years, but it all requires precise measurement and calculation." Shi Tao said with admiration for his ancestors.

Again, some ancestors of the Gan and Shi families did manually modify and adjust the records when they found that they were illogical, but there were also some who recorded honestly and then said that this is what I recorded, and the reality is not illogical. I think we may have made a mistake in the calculation. You later generations can calculate it when you have time.

Over the past 600 years, there have been many people who manually modified and adjusted the data to ensure that the differences were not too big compared to their own calculations. However, there were also many people who realized that there was a problem with their own calculation formulas but could not find the problem and recorded it truthfully.

In this era, with the knowledge that the earth is a sphere and the concept of atmospheric circulation, it is possible to verify and compare many recorded data and filter out the correct data.

Even though the screening conditions are extremely harsh, the accuracy of the records must be guaranteed. After looking through more than 600 years of archives, there are tens of thousands of entries, which are then verified and compared with each other. Under the concept of the planet, many things that were originally overlooked are naturally picked out.

Concepts such as precession of the equinoxes, nutation, geomagnetic poles, terrestrial poles, ellipsoids, angles of the ecliptic plane, etc. have all been forcibly deduced from these data, and even the concept of gravity has been forcibly pulled out and added in.

Although the constant has not been calculated, the concept has been introduced. The vacuum pendulum from the northern border to the equator is enough for Gan and Shi to calculate the range of gravitational acceleration. These are all very big improvements.

It’s just that this group of people just can’t figure out the thing called gravity. Lord Niu is indeed a true god to some extent. Fortunately, Chen Xi is not in a hurry.

After all, this group of people have deduced Kepler's three laws of motion based on their ancestors' data, and it seems that they are still one Lord Niu away from Lord Niu.

But it doesn't matter. Since they have achieved this level and introduced the concept of gravity, sooner or later a true god will come up with the law of universal gravitation. Now we have to see how the Gan and Shi families operate.

"Have you ever considered how long it will take to observe this thing?" Chen Xi asked with some curiosity.

"We estimate that the influence of the lunar phases and tides on the rotation of the earth will take a generation, the one in front..." Gan Bao looked at Chen Xi awkwardly. They didn't know how long it would take, but it would definitely be a long time.

"Where are the mathematical calculations?" Chen Xi looked at the two speechlessly.

Slipped, slipped, the author is really useless, sigh