The piece of white that Li Jiancheng was referring to was Antarctica.

Ye Jinyu shook his head and said: "This is not a good place, the Antarctic continent is the southernmost point of the world, where it is covered with ice and snow all year round, and the temperature is extremely low. ”

Li Yuanji said in surprise: "Isn't it the hotter you go south?" Why is it covered with ice and snow when the south reaches the extreme? Could it be that the extremes of things must be opposed? ”

Ye Jinyu then remembered that it is difficult for people in these years to go far away, and it is even more difficult to go to the sea; It seems that the Song Dynasty, where the maritime trade was developed, went to the South Seas was the limit, and the officials sent to Hainan Island was considered the end of the world, not to mention that it was now the Tang Dynasty; The southern hemisphere is probably not conceptual in the eyes of these people here.

"Guys, look at these three lines." As he spoke, Ye Jinyu pointed to the three horizontal lines on the map and said, "These three are the Tropic of Cancer, the Equator, and the Tropic of Capricorn." "When you say a thread, you mean a thread.

"Bounded by the equator, to the north, is the northern hemisphere, and to the south is the southern hemisphere; This line of the equator is the hottest place, and it slowly gets colder to the north and south. All the way to the South Pole and the North Pole, it's the coldest place. ”

After explaining the role of the equator, he pointed to the two lines of Tropic of Cancer and said:

"The four seasons change throughout the year because the sun moves back and forth between the Tropic of Cancer and the Tropic of Capricorn, and when the sun is at the equator, one in the southern and northern hemispheres is in the vernal equinox and the other in the autumn wind; As the sun moves toward the Tropic of Capricorn, the Northern Hemisphere slowly heats up and becomes summer; In the Southern Hemisphere, on the other hand, it slowly cools into winter. ”

"When the sun reaches the Tropic of Capricorn, it is the summer solstice of Datang, the longest day of the year, and it should also be the hottest day; Switching to the Southern Hemisphere is the opposite, the winter solstice, which should theoretically be the coldest day. After a day's pause here, the sun begins to return south; When it reaches the equator again, the autumn equinox will be on the Datang side, and the southern hemisphere will enter spring. ”

The map is drawn very clearly, although Ye Jinyu speaks more verbosely, but at least he explains things clearly;

"I see, the world is so big, it's really strange, I never thought of going south The season is actually the opposite of my Datang, so didn't I go to this Tuzhou, and the New Year is the scorching summer?"

Li Jiancheng shook his head and said, then asked, "Godman, what do these lattice-like lines mean?" What is it for? ”

Ye Jinyu looked at it and explained:

"The horizontal line is the weft, and the vertical line is the warp."

The vertical line of the fabric is called "warp", and the horizontal line is called "weft", which is a metaphor for planning the world. Describe the talent of the world who governs the world. The word Jingtianwei and Earth appeared a long time ago, so as soon as Ye Jinyu said it, everyone could understand it.

"This warp and weft knot are intertwined to form a graticule, which can be used to determine every geographical location on the ground and on the sea. Like sailing, marching, etc., you can determine your location and know where you are, and with a map or nautical chart, you won't get lost! ”

Hearing that this latitude and longitude could be used to march and fight, he hurriedly asked, "Then how can this latitude and longitude be determined?" ”

Ye Jinyu heard this question from the geography teacher at the beginning, but it will almost be forgotten. I can only rely on my own reflections, and make up a rough compilation:

"The degree of latitude is easy to explain, but it is actually the co-angle of the angle between the sun and the ground; With the equator at zero degrees, north latitude and south latitude are south latitudes. However, the meridian is a bit more troublesome, because there is no clear geographical demarcation that can be used as a meridian, and we need to assume a vertical line as a zero meridian first. ”

Originally, the meridian used on this map was the prime meridian of London, England, as the zero degree meridian; Although Ye Jinyu does not know exactly what year the British set this line, it must have been after the Age of Discovery, and there is no such British standard zero longitude now. So he thought that he had even changed the names of the continents, so why not simply change the zero meridian to China?

"For example, taking the center of the Xuanwu Gate of Chang'an City as the zero degree longitude, just like the equator divides the north and south, take this zero degree longitude as the benchmark and set it as the east longitude and west longitude. The east of the Xuanwu Gate is the east longitude, and the west is the west longitude, so that we only need to know the latitude of the Xuanwu Gate, and we can get the accurate geographical location of the Xuanwu Gate. But I haven't learned how to measure it, so I'll get an instrument when I have a chance in the future, and you'll know if you try it. ”

The establishment of the zero meridian, that is, the prime meridian, is a very serious issue, once it is determined as a benchmark, the future geographical parameters are subject to this, once extended, as long as the Tang people do not die, it will always be used.

Ye Jinyu didn't quite understand the importance of this matter, but several natives in the Tang Dynasty felt that the Tang Dynasty, as the upper kingdom of the Celestial Empire, took it for granted that the zero degree warp was repaired at their doorstep, so they didn't mention it.

However, Ye Jinyu hasn't thought about it so much now, he only feels that his knowledge reserves in warp and weft have been hollowed out, and it will be embarrassing to continue talking, so he wants to change the topic. At this time, Li Shimin, who was looking at the Chang'an area and thinking about setting a zero degree meridian, suddenly said: "Godman, this is a little wrong!" There are still many mountains, rivers and forests around Chang'an, why is there all yellow sand on this map? ”

"Ugh!" Ye Jinyu never thought about this problem, so he had to tell the truth: "This is the topography and landform after more than a thousand years, after nearly 1,500 years of deforestation, at that time, the forests around Chang'an have been cut down, the desert invasion in the north, the north of Chang'an is full of yellow sand, even Chang'an City is often full of yellow sand!" ”

Fifteen hundred years later! Several natives were shocked, you look at me, I look at you. The gods suddenly broke out a shocking secret, and the natives were not easy to answer, how could they chat happily?

Li Jiancheng asked: "What can the gods do, don't let this great Chang'an City become a barren land!" "The capital city he wants to rule in the future will become a desert, although the time is still far away, Li Jiancheng still feels uncomfortable, and feels that he can rescue it before he takes over.

Haven't seen anything yet, but worry about it now? Although Ye Jinyu felt that Li Jiancheng was a little worried, but in line with the idea of having dates and not being able to hit a shot, he still popularized the knowledge of environmental protection to a few natives, what if it had any effect?

So he said, "This solution is very simple, isn't it just that the tree has been cut down?" In fact, as long as you keep planting trees while cutting down trees, especially planting more shelterbelts on the edge of the desert; But it's hard to do. As the largest city in the world and the political center of the next few hundred years, Chang'an City will live here with more than one million people; So many people eat, drink and keep warm, and they need firewood and charcoal for a year; It was only a matter of time before the surrounding trees were cut down. Unless we promote the use of coal or other fuels to make fires from now on, reduce the consumption of wood, and at the same time plan the interval between felling trees and replant saplings in time; This should solve most of the problems. ”

After talking for a long time, Ye Jinyu felt that his mouth was a little dry, and asked the person next to him: "Is there any tea?" Pour a glass to quench your thirst. ”

Li Yuan immediately said to Li Yuanji: "Go and pour a cup of tea for the gods!" ”

Li Yuanji was stunned for a moment, and asked in disbelief: "Me?" "As a prince, he usually serves others by others, but today he has to serve others for the first time.

"You're the youngest here, who are you going to if you don't go?"

He didn't dare to disobey his father's emperor's order, and he reflected that it was pouring tea for the gods, which was an opportunity to please the gods, so he hurriedly ran outside the hall and ordered people to pour tea.

While waiting for tea, Ye Jinyu asked the national teacher: "National teacher, what kind of fire talisman did you give me last time, I accidentally used it; The power was indeed extraordinary, and it actually burned the iron plate in one fell swoop, breaking such a big hole. But why didn't you tell me all the time, that charm was so dangerous, I kept it in my trouser pocket, so it hung and burned. ”

"Impossible!" The national teacher's eyes widened, and he said, "I don't know the talisman I drew myself?" At most, it takes two quarters of an hour to burn the wood and set the tree on fire, but it is impossible to melt gold and break iron! Don't fool me! ”

Suddenly, his eyes rolled, and he frowned and said, "It is not impossible to say that it is impossible to achieve the level you said, that is, to penetrate the incomparable mana in an instant, detonate the fire talisman with a huge amount of mana, and release the power of the fire talisman in the shortest possible time; But that possibility is too low, just ask who else in this world can do this level, unless it is a god ......" The immortal word of the god was not spoken, the national teacher was stunned, and the god in front of him seemed to say this possibility; His heart was filled with turbulent waves, he had cultivated to the point of being full of joy and anger, and he was already full of horror, and he looked at Ye Jinyu in horror, could it be ...... This is a man of God!

Ye Jinyu looked at the old Taoist priest with his eyes wide open, and said in his heart, how can this Taoist priest's eyes be so wide? However, the words of the Taoist priest revealed an important information, the fire talisman can burn for two quarters of an hour, a quarter of an hour is 15 minutes, and two quarters of an hour is not half an hour? This kind of charm can actually work continuously! So he asked, "National Teacher, didn't you consume this talisman at once?" Can you still burn two quarters of an hour? ”

The national teacher was a little absent-minded thinking about the gods and mana, and after listening to Ye Jinyu's question, he replied casually: "How long this talisman can be burned mainly depends on the material of the talisman, high-grade cinnabar; Add some other materials, carefully mix them, and draw them on the finest rune paper with real wolf hair. Drawing talismans is just a path, and using mana flexibly to dissolve them is the right way. ”

Ye Jinyu nodded as if he didn't understand, it seemed that the power input of the baton was too large in an instant, which made the fire talisman explode instantly. However, the national teacher answered him a question, which made him have more questions; How can the best cinnabar be considered high-quality? What are the bonuses of a real wolf? There is also a high-quality rune paper, can you draw runes with other materials besides rune paper? Paper is not burned!

Just as he was about to continue to ask the national teacher about the Fu, Li Yuanji respectfully handed over a sea bowl: "God, please taste tea!" ”

Ye Jinyu wanted to ask the national teacher about the role of the water talisman again, but now that the tea is here, drink the water first. He was about to pour the bowl into his mouth, but he was stupid when he saw the contents of the bowl, your sister, what is this? In addition to the suspected tea powder at the bottom of the bowl, the green onion floating on the tea water, and the ginger at the bottom of the bowl are what the situation is. This is a bowl of ginger soup with some tea foam in it!

It's miscellaneous, and I don't have an appetite to watch. Forget it, Ye Jinyu put the tea bowl on the table, and said in his heart that he would continue to talk about the map, find a place for Li Shimin, and his task will be completed!