Chapter 418

After listening to Zhang Yuan's story, Lin Xuanxuan was silent for a long time and suddenly said, "the feelings between you boys are often more pure. If I were you, I would have been crying... "

A star drifts from the light cluster behind, draws a complex curve, and moves to the light cluster ahead. This is because the ship is sailing at high speed.

"The relationship in our dormitory is not very harmonious. You know, there are always such and such frictions between girls. If a girl's private life is chaotic, the whole dormitory will be in a mess. Everyone forms their own small groups. I don't know how complicated it is. "

"I haven't heard you say that."

Lin Xuanxuan said: "in fact, it's nothing. It's all over Finally, as graduation approached, everyone had a meal and then dispersed, and all the old and new grudges disappeared. There's no more chance to get together. "

Zhang Yuandao: "it's no pity. In fact, the relationship between people is not as close as you think. Sometimes when you go to a party, you are too lazy to go. One or two friends is enough for a lifetime. "

Lin Xuanxuan thought for a while, "Oh, yes, I can't remember their names! What's more, I can't even remember what my mother looked like. "

"I can't remember what my father looked like You have to look at the pictures to remember. " Zhang Yuan sighed.

They were silent for a while.

Lin Xuanxuan asked again Would you cry if I died suddenly? "

"What are you crying for?" Zhang Yuan said with a smile: "death is a new beginning. This reincarnation is over, and a new life will start again. It's meaningless to miss the past. "

"I can only wish you happiness in the new world and live your next life!"

Lin Xuanxuan was surprised for a moment, and then she began to smile: "I wish you a bright future in the future world!"

……

In the last few years, Zhang Yuan has been working in the observatory, mainly responsible for teaching primary school students and junior high school students how to use astronomical telescopes, how to distinguish the planets in the universe, including the direction of the sun and glitzer 581. These are the places where the parent star was born, or where humans developed here.

"If one day you become captain, if you can't find your way home, it will be miserable!"

This job is very easy, there is not much workload, and every day is very full and happy.

A smart little girl asked: "grandfather Zhang, how should we position the navigation in the universe? The galaxy is in motion, and everything is in motion. How can we determine the position of our spaceship? "

"Even airplanes on the planet need navigation. How can a spaceship navigate? Long distance navigation must be accurate enough! "

In the face of this problem, Zhang Yuan pondered for some time, and drank a drink: "it's very simple, there are three good ways."

"First, use accelerometers and gyroscopes, or inertial navigation systems. By measuring the acceleration and angular velocity at each moment, the velocity and displacement of the aircraft can be calculated by integral. However, the disadvantages of inertial navigation are also obvious: the longer the time, the greater the error, so it is only suitable for short range and auxiliary positioning

"The second method uses the relative position of the known celestial body to locate, observe the surrounding stars, and establish simultaneous equations. But as you said, everything is moving, and the distance measured by the spectrum changes all the time, and it's difficult to measure it very accurately. "

"The third method, navigation through a fixed radio signal source, is also the method we use now. There are a large number of pulsars in the universe, which periodically emit electromagnetic pulses. As long as multiple pulsars are observed to form a pulsar timing array, it is a natural deep space network, also known as the "Galactic positioning system."

"If you think the pulsars inside the Milky way are moving, leading to a certain degree of error, you can even observe pulsars outside the Milky way, 100 million light-years away!"

"Such a distant planet, we can directly think that it is still."

Zhang Yuan played out several images of pulsars on the screen, and these pulsars are like satellites constantly sending signals to the outside world.

These students, in the face of real complex knowledge, are stunned.

The girl then asked, "if we go out of the galaxy and sail across the river system, how should we position ourselves?"

Zhang Yuan replied: "there is a phenomenon called rapid radio bursts. These high-energy millisecond flashes, it is speculated that the signal source is very huge, may come from outside the galaxy. Maybe one day, they will become lighthouses for human beings to travel across galaxies. These high-energy millisecond flashes, it is speculated that the signal source is very huge, may come from outside the galaxy. Maybe one day in the future, they will become a lighthouse for human beings to travel across rivers. "

"Across the river system?"

At the thought that there are so many natural lighthouses in the universe, all the students are yearning for them and can't help looking out of the window.It's too far to cross the river system!

"Grandfather Zhang, there is another question. Why are there as many integers as even numbers?"

After a while, a little fat man who just went to junior high school asked again.

His name is Wang Tiantian. I don't know where he heard about this knowledge. He asked about almost everything from astronomy, geography, mathematics and chemistry.

Children all worship power. Knowledge is power. In their eyes, Zhang Yuan is the most knowledgeable person. He is also an old captain and has a gentle temper. He can basically answer all the questions. We can even play computer games here, so there are always many children gathered at the observatory.

"That's a complicated question!" Zhang Yuan burst out laughing. It's still too difficult to talk about infinity with children of this age.

After pondering for a while, he said, "do you think there are more points on the 1cm line segment or the 2cm line segment?"

"Of course There are many points on the 2 cm line segment! 2 cm is longer than 1 cm. Shouldn't there be more points on it? " Little fat man looks nervous. It's not a very simple problem, is it

It's a shame to answer wrong.

The surrounding students also thought that, however, there are a few smart, crooked head did not speak.

Zhang Yuan said with a smile, "have you learned functions once?"

"Of course I did."

"So, can the image of y = √ 3x be drawn?"

This image is very simple. It's a straight line with an angle of 60 degrees to the x-axis.

Zhang Yuan intercepted one centimeter on the x-axis of the abscissa, and the corresponding oblique section is exactly two centimeters. He said with a smile: "according to this function image, the points on the abscissa and the points on the oblique line are not one-to-one corresponding, from (0,0) to (1, √ 3), they are exactly two centimeters. The coordinates of each X-axis can correspond to it one by one. "

"You say there are more points on the 2 cm line segment. Where are the more points?"

"If we can't find it, we can only think that there are as many points on the 1 cm line segment as there are on the 2 cm line segment, right?"

The little fat man looked unconvinced and went to look for those disappeared spots, but he couldn't find them

In the end, they launched a mass offensive and made some misconceptions, such as whether the "0.9 cycle equals 1" came out, but in the end, they could only be very unwilling to lose the battle.

"Can't find it, ha ha!"

In fact, according to our theory, one-to-one correspondence is a very important means. There are as many points on a one centimeter line segment as there are on a two centimeter line segment. In one way, there are as many points on a one centimeter line segment as there are on a piece of paper, that is, on a plane.

"Even a point of one centimeter, a point on such a large curved surface as the Kunlun Mountain spaceship, and even a point in the whole space Even any point in a high-dimensional space has the same number and can be corresponded one by one in some ways. "

"That is, there are as many points on a centimeter line as there are in the whole universe!"

"Ah?" Not only the little fat man, but also a large number of students were exclaiming.

They never thought that such a small section could be compared with the whole universe. Isn't it incredible?

Let these children show a surprised expression, exclamation of the mystery of the universe, has become a great pleasure of Zhang Yuan.

Zhang Yuan said with a smile: "but infinity can be divided into big and small. The set of natural numbers, mathematically known as alef0, is the smallest infinity."

"The smallest infinity?"

"The number of points on a line segment, that is, the infinite set formed by real numbers, is called alev 1."

“…… All possible mathematical functions: the number of continuous and discontinuous functions is called alev 2. "

"I see, and alev 3, alev 4, alev 5!" The little fat man yelled, as if he had found something full of power.

Students of this age are always second in secondary school. They get a little knowledge and can show off in front of their peers.

Zhang Yuan said with a smile: "yes, it can be extended infinitely upward However, it is very difficult for you to find the specific meaning of infinity in higher dimensions in reality, and it can only become a string of symbols on paper. Moreover, the difficulty in mathematics is whether there is an infinity whose number is larger than alev 0 and smaller than alev 1? This problem is called the continuum hypothesis

"Although the continuum hypothesis is a hypothesis, it can never be proved or denied. It has been put there alone for nearly 4000 years and has not been solved yet."

"Why?" Wang Tiantian asks again, this world is also too strange.

A problem has not been solved for four thousand years. His heart was a little ready to move

Zhang Yuan laughed again: "that's Another story is called Godel's incompleteness theorem! The history of mathematics is a magnificent course. There are so many problems that can't be solved in the world! "……

Time passes day by day. As aging continues, the body is getting worse day by day.

Even on the way to the observatory, he would feel very tired, but he still insisted on working to answer the children's doubts, which can be said to be the greatest joy after friends withered.

On this day, the doctor who specially examined him showed a very sorry look. She said very carefully: "old captain, your physical condition has reached the standard of entering the virtual world."

"I'll type a report for you, and your wife is up to standard. At the end of this month, if you like... "

"So I've really lived long enough Zhang Yuan nodded and sighed, "there's nothing I don't want. Let me say goodbye to this era."

On August 29, 5812, Zhang Yuan, the first captain of the Kunlun fleet, was about to leave the world.

The salute lit up briefly in the starry sky and disappeared silently.

At present, 90% of the population is in hibernation, there is no need to wake up. The remaining 10% of the sober population spontaneously carried out this farewell ceremony.

Many production activities in the Kunlun Mountains have also stopped, and the school has a day's holiday, and Zhang Yuan deserves such an honor.

"Do you have anything else to say?" Said the doctor.

Countless posterity seeing him off are watching him, expecting him to say something, or encourage him, or something else. There are also some old people who are constantly wiping their tears. This time, he is not the last one to leave.

"No, everyone is fine. Let's move on." Zhang Yuan said with a smile: "the future still depends on you."

Several staff members helped him up from his wheelchair and lay down.

Hibernation warehouse is like a soft Simmons, lying very comfortable, Zhang Yuan turned his head, looking around.

A former friend, a colleague, is saying goodbye to him.

It seems that there are few.

This kind of feeling is very delicate. Zhang Yuan is not a person who is afraid of death, but at this moment, there is still a feeling of breathlessness.

He suddenly recalled -

when he was very young and understood what death was all about, he squatted in the corner and wailed.

"Can I not die?" Zhang Yuan asked with tears in his eyes.

"What does immortality mean?" His father, Zhang Qiming, replied.

"That is Always alive. "

"Oh, you mean You want to live forever. " Facing this problem, Zhang Qiming pondered for a long time and said solemnly: "I think it's better to die. You can't live forever. "

Young Zhang Yuan couldn't accept the answer for a while, although many of his father's answers were puzzling.

Zhang Qiming said: "I think it is very likely that you will live forever for a short time. Immortality means infinity, one hundred years, ten thousand years, one hundred million years, even ten billion years. Compared with infinity, it is no different from zero. "

"In the eyes of the real immortal, the universe may be hot in a second, that is, you feel all the happiness on earth for a very short time. Next is the long, lonely existence time in the vast and empty universe. There's no substance, no company. "

"Until we wait for the little big bang in the quantum ocean to restart a new era. But how long does it take? "

"Human beings may not be able to endure this loneliness, or their thinking form may become another species, or they may stop thinking I think it's better to stop thinking and choose to die. " Zhang Qiming looked at the blue sky, touched Zhang Yuan's head and said solemnly.

Even though young Zhang Yuan didn't understand what his father was saying

I don't know why, Zhang Yuan thought of this dialogue before he left the world.

Maybe, a dead hero is a good hero.

It's just How lonely

Among the flowers, Zhang Yuan vaguely heard bursts of crying. I don't know who is crying.

In a daze, he soon lost consciousness.

……

One era is over, and another era begins.

Human beings will not stop because of this. This great journey is still going on

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