Shang Wen's speech at the last State of the Union address was quickly printed into newspapers and quickly spread to all parts of the country. The emergence of newspapers and other media is actually to make some affairs transparent and open. Shang Wen, who comes from the future society, certainly understands the role of the media. Before the others Shang Wen noticed this powerful weapon. Shangwen should give full play to its role. By creating an image of justice, you can gain the support of the people. Occupy a favorable position on the issue of popular support.

Shangwen's proposal requires a response from the other party before further action can be taken. But before waiting. Shangwen has one more important thing to do. Popularize a lot of astronomy, geography knowledge. Especially the map civilization that extends between the two.

"It's an astronomical telescope. He looked a little rough. But he was able to prove that what I saw was correct. Shang Wen faced the podium, and there was a crowd of all kinds. This group of people includes skilled craftsmen from the six countries, as well as representatives of various families. In short, there are all kinds of people. Even those Confucians who went to the school palace also participated.

In order to popularize this knowledge, Shang Wen announced the news in the newspaper in advance and wanted to give a lecture at Qinguo University. As soon as this news came out, many people came to visit. Fan Zeng also quietly walked into a large lecture hall that could accommodate three hundred people. There are just too many people. Many people sat on the stairs and listened to Shang Wen's explanation.

"This astronomical telescope is able to see our satellites. Moon. Actually, the moon is a spherical shape. In the same way, the land we are in. The Earth is also a sphere. It's like this one. Shang Wen said and pointed to the big iron ball on the podium. Shangwen was originally used to demonstrate the causes of lunar eclipses, solar eclipses. But apparently it has been impossible to finish. Because there are too many people. Shang Wen's doctrine is too advanced. Some people haven't understood it yet.

"This issue will be put aside for the time being. If you are interested, you can go and check it out at night. I welcome that. Shang Wen made a welcoming gesture.

"My theoretical foundation is to build on this theoretical foundation. Our planet is a star. And we live on top of the earth. How we observe it. Shang Wen said loudly.

"That's what we use." As he spoke, Shang Wen took out a sextant.

"It's a sextant. It is used to determine our latitude. I'll explain it to you later. But first, I'm going to explain to you why we were able to determine our latitude with a sextant. ”

"First of all, our earth, it does not revolve around the earth at a certain inclination. Like this. Look, everybody. Shang Wen said as he took a large stick and walked directly through the wooden star. That represents the earth.

"He's got a leaning angle. It is because of this inclination that the direct point of the sun rotates back and forth between the Tropic of Cancer. Shang Wen said as he demonstrated. Many people stared intently. They see. It is this oblique angle that causes the difference in the point of direct fire faced. Some of the quick reactions suddenly dawned on them. Open your mouth wide and can't speak.

"The orbital plane of the Earth's revolution we call it the ecliptic plane and the Earth's equatorial plane, we call it the equatorial plane. The angle between these two faces is the angle of yellow and red. Preliminary settlement. This angle is 23 degrees 26 minutes. It is precisely this angle that appears. Our Spring, Summer, Autumn and Winter. Shang Wen didn't know how to explain it, he was an expert in weapons, and he made a temporary cameo as an astronomer and geographer.

Some Qinguo University students even picked up pencils to take quick notes. And more people are paying full attention to this new knowledge. I didn't have this knowledge before.

"We call the two returning parallels where the sun shines directly on them the Tropic of Capricorn. If you're interested. I hope you can go to Chu to check it out on the spot. Shang Wen said.

"It's the sun that shines directly into different positions. So, we have spring, summer, autumn and winter, we have the spring equinox, summer solstice, autumn equinox, and east solstice. Shang Wen didn't know if there were these spring and autumn equinoxes, winter and summer solstices at this time. Whether there is or not, this knowledge must be universalized.

"At the time of the spring and autumn equinox. The direct point of the sun is at the equator. At the time of the winter and summer solstice, he was on the Tropic of Cancer. Shang Wen said.

"Since we know the date and angle of the point where the sun shines directly. Then we can use this to measure the height of the sun, and the angle between the horizontal lines. Convert through a certain formula. Shang Wen said as he wrote the formula on the blackboard. The blackboard is all black. Shang Wen himself didn't know, so his hands were all black.

cosz=sinφsinδ+cosφcosδcost" is the formula. Shang Wen wrote a few mathematical symbols on the blackboard. The people below were talking. They didn't understand why Shang Wen drew such a symbol. Do you want to exorcise evil spirits? Shang Wen didn't care about so much. Half an hour has passed. The big bell in the back has already struck.

"We can calculate the latitude φ of the place. where z is the 90 degrees distance of the celestial body from the horizon, δ is the declination of the celestial body, t is the time angle, which can be obtained by subtracting the local sidereal time from the right ascension of the celestial body, and the sidereal time can also be obtained by simple calculation. If the geographic latitude is calculated from the position of the sun, the easier algorithm is "Shang Wen said and picked up spherical chalk and wrote δ=z+δ.

"With this, we can calculate the latitude faster." Shang Wen said after writing.

"So let's explain, what latitude is." Shang Wen said as he took out a ball made of wire.

"It's like these wires woven horizontally. This is our latitude. He circled the earth. All the way to the apex. Shang Wen said.

"They go east and west, in a circle around the globe, called the parallel. All the parallels are parallel to each other and perpendicular to the meridians, which indicate the east-west direction. The size of the weft coil varies, with the equator being the largest weft coil, gradually shrinking from the equator to the poles, and then shrinking to the north and south poles to points. The meridians and parallels were drawn on globes and maps in order to determine the position and direction on the earth, and there were no latitude and longitude lines on the ground. However, it is not difficult for you to see the meridian of your place: stand a bamboo pole on the ground, and when the sun rises at noon, the shadow of the bamboo pole is the meridian of your place. Because the meridian indicates the north-south direction, the meridian is also called the meridian. The warp and weft are perpendicular to each other. ”

"Time is running out. There is still one last bit of time, and class is about to end. I can't afford to put it off. The significance of latitude and longitude is that we can determine our own location without relying on geographical things. By calculating the latitude coordinates, we can determine our position more precisely. If it is used on the map, then our civilization will take a big step forward. Shang Wen finished. The bell rings for the end of class.

"Oh. All right. Let's get out of class. Shang Wen shrugged and said.