Chapter 51: Prime number

Late at night, the plant area.
Time is when most children are already in bed and ready to listen to bedtime stories.
There are almost some people on the slate road. The roadside is full of camphor and shrubs. In the shorter places, it is mint and geranium. The night wind is sloppy, and the fresh fragrance of the plants is faint in the air.
The street light sprinkled a soft glow. Lao Lin led the 12 children behind him and walked on this path where everything was peaceful and peaceful.
apart from……
"Master, no moon, where is the night?" Lin looked at him for a long time and finally asked.
"Yes, no moon."
"There is no star."
"It's so dark."
The children were screaming, and the adults standing at the front stopped to rest, and the quiet and peaceful atmosphere was instantly broken.
Lao Lin coughed a few times: "There is a month in the heart, it is such a good day..."
"You still talk about math." Hanaaki interrupted him.
"What is good about mathematics..." Lao Lin’s enthusiasm for poetry was once again hit. "What do you want to hear?"
"Application questions!"
"Yes, it’s going to be tested on Monday. The teacher talks about the application questions. What are the secrets?"
Lao Lin smiled and touched the child's head. He said very sadly: "So I want to learn the application questions. That's good. Let's talk about the number?"
"Ah~" The children dragged their tune. "That's super boring."
"Yes, especially what is the prime number, decompose the prime factor." A small boy in the sixth group said.
Wen Yan, Lao Lin’s eyes are bright:
No, you actually know so much!
He turned his head and clicked the loudest one:
What is a prime number?

"A natural number greater than 1, except for 1 and itself, a number that cannot be divisible by other natural numbers is called a prime number." The little boy's back is very smooth.
Thinking of a scene in front of the wooden door under the stars, Lin could not help but squeeze the sweat for this child.
"Yes, what is the natural number?"
Another child replied: "There is a lot of integers behind 123456789!"
Lao Lin: "How much is a lot?"
"Infinitely much!" The children raised their hands and opened their hands, and they seemed to fly under the night sky.
Time and space seem to have a short period of silence. Lao Lin stands under the street light, and the flying insects on the top of the head dance lightly. He smiles and smiles, and the corner of his eyes picks up the very light lines, but it is like shining.
It was also at that moment that Lin was very clear that Lao Lin was very happy. He liked to be with the children more than he was in the park, and he liked to feel close to mathematics again.
Lao Lin smiled for a while before slowly opening: "At the end of the 19th century, the Italian mathematician Piano proposed five axioms to define natural numbers. I will give you a back, one..."
One, two, three, four, five, he was very handsome to recite five axioms, all the children thought they had heard a foreign language, did not know what he was talking about.
Looking at this piece of Zhang completely licked a small face, Lao Lin asked: "Do you know what is a natural number?"
"I don't know!" The children shook their heads neatly.
"Because you recite these five sentences and know what it is, there is a world of difference."
The students nodded hard: "So endorsement is not important!"
Lao Lin smiled: "On the contrary, my point is that it is very important to understand. So, let us take a good look now, what is a natural number..."
Lao Lin pointed to the tree on the side of the road and began to tell the children, the most basic, what is the natural number.

The path of the botanical garden is very long, but it is also very short, so from the beginning to the end, the white small building standing under the mountain is already close at hand.
A group of children stood in the middle of the road and looked at the small dormitory, but no one was willing to leave.
"Go back to sleep early." Lao Lin broke the silence and turned to leave.
"I still don't want to sleep!"
"You haven't finished it yet, you haven't had time to learn tomorrow!"
"Quick exam, the topic has not been done, you have to give us a topic."
The students began to whisper again, the sound of 12 children screaming together, and the night was very penetrating.
Lao Lin did not care about them, said to leave and leave.
At this time, I don’t know which courage to say: "After we checked the house, we ran out again?"
"Yeah, anyway, I won't go to class tomorrow, and the aunt will not come to the second time. I was last discovered because the flashlight came out..."
Lin Zhaoxi followed the sound and found that Lu Zhihao said, she took a breath: "Lao Lu, your thoughts are too dangerous."
The last time I was caught by Vice President Zhang, then the person who was taught the lesson is clearly you.
But the children won't care so much. They talked for a while, considering that the hours are too tight. According to the current progress, they can't finish the exam before the mid-term exam. It is really a viable idea to run out at night.
"Teacher, is that good?"
I don't know who shouted a scorpion, and I don't know who started to rush. Lao Lin stood on the back of the downhill and was quickly surrounded by a group of students. Some people grab their clothes and have arms around them. In short, they just don't let them go.
Lin Chaoxi retracted his gaze and found that only she and Yu Zhi were still standing. They looked at each other and laughed at the same time.

"I only said a little." Lao Lin sat on the mat cross-legged. "Be caught, don't give me out."
There is light and smog in the room, and the air is mosquito-scented, but when you are quiet, you can hear the sound of insects and frogs outside the house.
At night, they still quietly came to the temporary dormitory of Laolin.
Oasis base has no other advantage, that is, there are many houses, so Laolin, a temporary worker's dormitory, is also a rare single room.
The place is big, but there are not so many tables and chairs, so the little girls have towed the ground diligently, and they sit on the floor tiles.
Lao Lin is sitting next to the mosquito-repellent incense, and the whole person is set off with a scent.
"I remember that you just didn't like to do topics related to number theory?"
"Yes, I just think it's useless to learn!" The student said, began to slap the book, "just like this topic - there are 30 2 cent coins and 8 5 cent coins, and there are 49 different kinds within 5 angles. Currency value, which currency value cannot be composed of the above 38 coins"
"Really." Lao Lin laughed: "What is not boring?"
"I... I think the application question is a bit interesting!"
Lao Lin smiled: "I think the chicken and the rabbit are also very boring. Is it really a few rabbits when buying food?"
When the students saw that the teacher himself said that the things he taught were boring, they began to be speechless.
"There must be a lot of people telling you that mathematics is beautiful and beautiful. They have a wide range of applications in life, but we look down and see what is obviously a very boring topic."
"Yes, right!" The children should be harmonious.
Lao Lin: "So, adults are lie to you, don't believe them."
Lin Zhaoxi: "..."
"It is still the same sentence, most mathematicians study mathematics because..."
"They are very bored~" Hanamaki answered very well.
"Yes, but if there are not so many people who are very boring, our current world is definitely not what you see." Lao Lin is sitting upright and spirited.
He said: "You mentioned the prime number just now. The research on the prime number can be traced back to more than 2,000 years ago or even earlier. You have also done quite a lot of questions related to the prime number, and the definition is also well-recognized, but for What is the prime number, why do we have to learn it, still feel very confused, right?"
"Yes, yes."
The children are quickly becoming the response of the old forest.
"Do you have to know what it means to be boring?" Lao Lin said intriguingly. "I can probably say that there are two kinds of necessity for qualitative research. Do you need to listen?"
"I want it!"
"primesarebuildingblocksallnumbers." Lao Lin said, "This is one of the arguments."
The children looked up at him, like a small goldfish that was only blinking, very aggressive.
"Ah, what did you say to the teacher?" Finally someone reacted.
"Can you speak Chinese?" Chen Chengcheng asked weakly.
Lao Lin "Children, it is very important to learn a foreign language."
Lin Zhaoxi: ...
Lao Lin: "Come, I roughly translate it like this. The prime number is the basic element that constitutes a natural number. For example, scientists are always exploring what constitutes matter, molecule, atom, and atom. What is it?"
"what is it?"
Lao Lin: "I don't know, is there a saying "string"?"
"Does the prime number be like a string to matter for a natural number?" asked a child who responded quickly.
"Because the prime number is indivisible except for 1 and itself, it is super important for natural numbers!" Ambebe also shouted.
"I know that blocks are bricks. You just said this, prime numbers are the bricks that make up the natural numbers!" said another child.
The surprise smile on Lao Lin’s face is getting stronger and stronger:
English is really good, kids!

The children are talking about their own opinions one by one, and the sounds of the ones in the dormitory are heard. Lao Lin just listened patiently and nodded his approval for each child’s answer. On the topic of light, they discussed the small half hour.
Starting from the most obvious qualitative topics, Lao Lin explained the different kinds of prime numbers to the children in a simple way, and expanded from the prime number to the number theory. It seems that because of the discussion just now, the purely mathematical boring stuff of the number theory has become instantly important. stand up.
I don't know how long it took, suddenly what the child thought of, and asked: "What is the second meaning of the prime number?"
Lao Lin smiled, as if they had asked this question for a long time: "On the prime number, the mathematician bored and studied for more than two thousand years. You can imagine that for two thousand years, some particularly boring mathematicians started to get angry. The distribution of prime numbers, how many prime numbers are calculated within a certain range..."
"How long does it take?"
"I don't know how long it takes, it may be the life of some people." Lao Lin laughed. "In short, they are dead with these boring numbers. For more than two thousand years, mathematicians have been doing this. I can't find anything that is practical."
The children were silent and looked at Lao Lin quietly.
"What do you mean, I don't think they have any meaning, they are just looking for some fun."
"Poor life, find some fun." Lao Lin smiled. "Until two thousand years later, human beings entered the information age, and the prime number revealed its role. It was applied to the public key cryptosystem, which decided The current information security."
Lao Lin said that here, it stopped. The children seem to understand and nod.
Lin Zhaoxi looked at his father's face waiting for a smile. She actually knew that Lao Lin wanted to say - no need to find so much meaning, mathematics research itself is the meaning.
But he didn't say that, he probably wants the children to experience this.
Plant a small seed in your heart, and perhaps one day, it will grow into a towering tree.
Lao Lin probably hopes so.

The study of the day was late, and it could even be said very early.
When they secretly left the Laolin dormitory, the children were not tired. They walked quietly at night, chatting freely, telling no questions, telling what they learned today, and telling where to go tomorrow...
Lao Lin followed in the end, Lin Chaoxi walked beside him.
Lin Xiangxi looked up and looked at the dark night sky, the air was moist, the fragrance of flowers and plants, um... is the fragrance of knowledge. She found a metaphysical metaphor.
"Taro." Suddenly, Lao Lin called her, "Will you go home tomorrow?" Lao Lin asked.
Lin slammed his head and looked up at Lao Lin: "Big... probably not going back..."
"That's good." Lao Lin turned to ask, "What about you, kid?"
He turned to look at him, very simply: "Do not return."
"That's good, Lao Lin laughs," will you take you to the wilderness tomorrow?

Lin Chaoxi was flattered and nodded hard. She was very happy to turn her head and look at her, but found her little classmate, looking at her with thoughtful thoughts.
As if to say, can you really be tomorrow?
Lin Zhaoxi suddenly remembered the phone call, the dean’s mother said... weekend... Professor Shen and his wife...
When Lao Lin asked, he walked away with his hands and pretended that nothing happened.
Lin Daixi has a scalp numbness. What if the Professor Shen and his wife take Lin Aimin’s children to see her tomorrow?
The author has something to say: When is tomorrow more, not sure, now to write tomorrow's update...