The royal officials left satisfied.

Handing over his prince to Xu He was the right decision.

Zhang Rong led Xu He to his study.

As soon as he sat down, Zhang Zheng smiled bitterly: "Brother-in-law, don't tell me those big truths, I really want to know how much distance there is between heaven and earth!" ”

Xu He thought about it and asked a question: "Your Highness, what do you think it looks like to be stepping on under our feet?" ”

"Of course it's flat!" Zhang drew two lines on the paper.

He dotted the line with his pen: "It's the sky!" ”

Then he clicked the line below with a pen: "This is the ground!" ”

Came to him, took the pen from his hand, and drew a circle on the paper, and then a person at the bottom of the circle.

"This is where we stand, and the place where we live is actually a sphere called the Earth!"

"Earth?" Zhang Zhen shook his head: "Your statement is too strange, it's impossible, what I'm obviously stepping on is the ground of a flat river." ”

"The earth is so big, with the naked eye, it is a plane as far as the eye can see!"

"Has Your Highness ever seen the sea?"

"Nope!"

"If you have a chance, Your Highness will go down and look at the sea, a ship on the sea will sail like you, and the first thing you see is definitely the sails, not the whole of the ship!"

"Why is this happening? If, according to His Highness, we are on a plane, then we should see the whole ship, right? ”

One question, Zhang Hao was completely speechless.

He still needs to find a chance to verify this matter.

But: "But, brother-in-law, this little man you painted is head-down, so he doesn't fall into the sky?" ”

"Come, let me tell you what the rotation and revolution of the earth are, and then tell you what atmospheric pressure and gravity are!"

……

It took more than an hour for Xu He to teach Zhang Huang some basic knowledge of astronomy.

"It's incredible!" Zhang Zheng shook his head and said, "Brother-in-law, what you said is too ......."

The first time I heard that I was standing on a ball, even if the ball was reversed, it couldn't fall, and it was really hard to understand and shocking.

But doesn't anyone know the world itself?

No.

"Your Highness, do you know Zhao Youqin?"

"Who is he?" Zhang Rong wondered.

Xu He smiled: "The eleventh grandson of Song Taizong, a person from the former Yuan Dynasty. He wrote a book called "The New Book of Leather Elephants"! ”

Zhang Lian may really be an astronomy enthusiast and listens very attentively.

According to Zhao Youqin's "New Book of Leather Elephants": Although the earth is round, it is not round for hundreds of miles and tens of miles, and people pay direct attention to it, and it cannot be curved. Try to go boating in the rivers and lakes, but see the boat bulge everywhere it goes, and the water does not see its head, and the water goes without its tail. The width of the cave, if the sun and the moon haunt it, the distant mountains are all under the loop, not as an obstacle. Measure the height of the North Pole and the time of the lunar eclipse in the east and west, sooner or later, the earth is round, and the earth should be the proof of the heavens! ”

What does that mean? Roughly translates to ......

The earth we live on is round, so why can't we see that the earth is round even if we look at it for a hundred or dozens of miles?

The answer is: because our human vision is straight, not curved.

Therefore, the ground we see can only be flat, just as we row on the lake, where the boat goes, the water will rise, but we can't see the movement of the water.

For example, we seem to see that the sun and moon rise and fall on the surface of Dongting Lake, but in fact the sun and moon do not fall into Dongting Lake, and the mountains in the distance do not block the sun and moon.

Because the earth is round, the flat ground we see is just an illusion. I have observed the visual differences between the north and south poles of the earth, as well as the changes in the east and west of the lunar eclipse, which irrefutably prove:

The earth is round!

Interestingly, however, Zhao Youqin was not the only one among the ancient Chinese who knew that the earth was round. There are also people. Who? Zhang heng.

That's right, it's the Zhang Heng who invented the legendary kinetic instrument (note: it's legendary). Zhang Heng also believed that the earth was round, he wrote in his Notes on the Armillary Sphere

"The sky is like a chicken, the earth is like an egg in the yellow, living alone, the sky is big and the earth is small"

Translated into human words, that's what it means

"The universe is an egg, our earth is like the yolk, alone in this egg, the universe is big, the earth is small"

Look, Zhang Heng also said it very clearly, and what he said is generally in line with the facts.

It can be seen that Zhang Heng is also very smart.

In fact, the ancestors of our Chinese, there are really many smart people! There is another person, Zeng Zi, a figure in the Spring and Autumn Period, although Zeng Zi did not explicitly put forward that "the earth is round", but Zeng Zi raised a strong question about the statement that "the sky is round and the place is round", he said in "Zeng Zi Tianyuan":

"If the sky is round and the place is round, it is the four corners of the world!"

Translated into human words, it means this:

"If the sky is a round cover, and the big one is a square piece of bread, then how does this big round cover cover the square earth? The four corners of the earth, it can't cover them! ”

"Look, our ancestor Zengzi is also a very wise man."

Sheet? Blinded.

Zengzi he knew, [If the sky is round and the place is round, it is the four corners of the world] He has also seen this sentence, but he has never thought about it.

But the person in front of him, who was about to become his brother-in-law, not only rang, but also found ancient books to prove the existence of the [earth].

That's ...... It's admirable!

Sheet? Xin Yue sincerely sighed: "I have seen a lot of champions, but it is the first time I have seen a champion like my brother-in-law!" ”

Xu He said with a smile: "It is rare to see a prince like His Royal Highness who is interested in astronomy!" ”

The two looked at each other and smiled, and Xu He said at this time: "Since Your Highness knows the atmosphere, then I can tell you how much the distance between heaven and earth is!" ”

"The sky, in fact, is two concepts, one is the sky, the other is the sky, the ground we are standing on is up, the place two hundred miles from the ground is the boundary of the sky, more than two hundred miles is empty, I call him space!"

"Why two hundred miles?"

Don't ask, ask is another time and space, defined by the International Aviation Federation!

"This question, for the current Highness, you can't understand it!"

"Ah, that's it!" Sheet? With a look of shame, he said, "My brother-in-law's knowledge makes me feel like a mountain!" What a shame! ”

Xu He smiled: "Your Highness is interested, in the future, we can also talk about what physics is and what chemistry is!" Inglesi can also be discussed! ”

Sheet? His eyes lit up and he said excitedly: "My brother-in-law knows so many things, I want to learn them all!" ”

Hehe, young people don't know the sky and the earth is thick, and they want to learn? For the sake of you being so studious, let's let you feel the power of the doomsday junior high school.

I hope that in the future, you can still keep your original intention and want to learn, not cry!