The sound of cicadas chirped outside the window, the scorching sun cast bright spots of light on the ground, the fan above my head was creaking, and the tepid heat waves made the textbooks on the desk rustle.

The summer of 1991 was also exceptionally hot.

Le Jing was sitting in the first row, very close to the old man who was standing on the podium giving a lecture. The distance between them was no more than one meter.

This is a solid state physics class at Tsinghua University Graduate School. There are only about thirty people sitting in the huge lecture hall. Le Jing is here to attend the class.

The old woman on the stage is very old, with completely white hair, and her back is a little hunched due to long hours of desk work, but her eyes are still clear and moving, and her voice is still full of energy.

The classroom was very hot and there was not even a fan on the podium. The old man was sweating profusely, but he still tried to stand with his back straight and taught them in a loud voice.

Once, a student couldn't bear to see her standing for hours in class at her old age, so he brought her a stool to sit on, but she declined.

At that time, the old lady waved her hand, with a smile that carried the stubbornness of an old-school scholar. "When I was in school, the teacher stood in class. What would it be like to sit in class?"

At that time, Le Jing was sitting in the last row, looking at her quietly.

The old woman standing on the stage is 79 years old, with snow-white hair. Her name is Li Shuran. She is Li Jingran’s sister, but also not Li Jingran’s sister.

In this life, his name is Chang Jingchen, and he is a student who comes to attend classes for free.

He came here to take classes two months ago.

In fact, he had already grasped everything that Li Shuran said.

For this, we have to thank the black technology from the future.

In the distant 26th century, brain implantable learning chips have become popular. This means that people in the future do not need to study and memorize knowledge in shifts. They only need to implant relevant chips in the hippocampus area of the brain to read relevant knowledge.

If the human brain is regarded as a computer host, the learning chip is equivalent to a built-in storage card, which will undoubtedly greatly shorten the learning time of future people.

But this does not mean that people in the future will not need to learn. They just remember the knowledge, but if they cannot understand it, they cannot use it. Just like a person who does not seek to understand everything will only become a memorizing machine with an empty brain even if he memorizes the entire encyclopedia.

Therefore, the role of the learning chip is to shorten the memory process of the human brain. And its amazing function is that it is a permanent memory, which means that people in the future will never forget the knowledge in their brains.

Therefore, even though the system has implanted a learning chip into Le Jing's brain and he has the knowledge of related subjects in his brain, he still needs to learn and understand so that he can apply the knowledge.

Moreover, human energy is limited after all, and Le Jing cannot learn all the knowledge in all subjects. Although he has a high IQ, he is not an omnipotent superman. Therefore, after careful consideration, Le Jing decided to focus his research on the development of rocket engines for manned spacecraft.

Fortunately, Le Jing is not stupid and can work hard, so after two years of systematic study, he has initially mastered the relevant theoretical knowledge.

Logically speaking, Le Jing's major had nothing to do with the materials science courses taught by Li Shuran, but he still came to attend the class on time every week.

As for the reason, Le Jing thought, he probably just wanted to see an old friend.

Even though he knew that this Li Shuran was not the Li Shuran in his memory, he still wanted to come and see her.

He wanted to see for himself what his once shy little sister had become.

Thinking about Li Shuran's life experience, Le Jing couldn't help but feel deeply moved.

Although he died, he left Li Shuran a considerable amount of royalties as an inheritance, and the copyright of his books will also be inherited by Li Shuran, and the royalties from future reprints of the books will also be given to Li Shuran.

In other words, even if Li Shuran didn't work or get married, she could still live a rich and stable life relying only on his inheritance.

But Li Shuran didn't.

She studied very hard. Seven years after his death, at the age of 21, she was admitted to the Department of Physics at Tsinghua University, and three years later, she went to study abroad at Princeton University in the United States.

She was 24 years old at the time, and her graduate and doctoral research areas were materials science in physics.

When the People's Republic of China was founded, she was 37 years old. She was already a PhD student in materials science and a professor's assistant at Princeton University. Her mentor was planning to recommend her to be a lecturer. She was also married in the United States. Her husband was a classmate who shared the same ideals as her, and they had two lovely children.

Without much hesitation, she and her husband returned to China with their children. They abandoned all the favorable treatment in the United States and returned to the then impoverished New China to start from scratch.

In the 1950s and 1960s, the country began to conduct secret nuclear bomb research. At that time, the country lacked top physics talents and many important equipment. Researchers could only use an abacus to perform calculations.

After careful consideration, Li Shuran resolutely chose to change her career from the Institute of Materials Science to the Institute of Atomic Energy, and at the age of 48, she started from scratch to learn the relevant theoretical knowledge of controlled nuclear fusion. Li Shuran's choice was not uncommon at the time, and many of her colleagues changed their careers to meet the needs of the country. Because the needs of the country are their expertise.

Later, she went to the Northwest, where she stayed for nearly ten years.

After the two bombs came out one after another, Li Shuran, who was 55 years old at the time, did not sit idle. She regrouped and re-entered the field of materials science that she loved, and made outstanding contributions to the subsequent launch of Dongfanghong-1.

Now, Li Shuran is 79 years old. At this age, she should be enjoying the company of her grandchildren and the happiness of family life. But if Li Shuran did that, she would not be the Li Shuran who started studying nuclear physics at the age of 48.

The old lady has a dream, or you could say an obsession, in her mind - manned space flight.

If the Soviets and Americans can do it, why can't the Chinese do it? One day, the Chinese will also be able to step into the stars of the universe.

So over the past decade or so, the old lady has been conducting research on manned space flight.

In her limited remaining free time, she would return to her alma mater, Tsinghua University, to teach graduate students, hoping to cultivate more pillars of talent for the motherland.

But the old lady probably doesn’t know that Le Jing can actually be considered her colleague.

The ding-ling-ling bell interrupted Le Jing's thoughts. Li Shuran put down her textbook and said with a kind smile, "Classmates, get out of class is over. See you next week."

Le Jing took a deep look at the smiling old lady on the podium and suddenly laughed.

He thought that he didn't need to come again.

His little sister has become a remarkable person. She has not wasted her life, she has been living a shining and shining life.

He put away his textbooks, put on his backpack, and whispered to her like any ordinary student: "Goodbye, teacher."

Li Shuran was stunned for a few seconds, and when she saw the boy's gentle smile, a familiar feeling suddenly emerged in her heart.

"Wait a minute..." She couldn't help but ask, "Classmate, I've seen you a lot recently. Are you also a student at Tsinghua University?"

Le Jing shook his head and said, "No, I'm a student at USTC."

Li Shuran said earnestly: "My courses are quite advanced and not suitable for undergraduates. I recommend you to take Professor Cheng Fang's courses at your school."

Le Jing was stunned, knowing that she had misunderstood, but he did not explain.

After thinking for a while, he finally asked the last question: "Have you been living well these years? Are you happy?"

This sentence was quite nonsensical, and the question the boy asked was also quite strange. Li Shuran stared at the boy's eyes, which were as clear and gentle as spring water. For some reason, her nose suddenly felt sour. This feeling came inexplicably, driving Li Shuran to give a serious and honest answer to the boy's question:

"I'm living a good life. I've lived a good life." She said to the boy with inexplicable urgency: "I have devoted my entire life to communism, the most magnificent cause in the world. I have also witnessed the rise of this country with my own eyes. I firmly believe that this country will have a bright future. In the future, I will continue to fight for the future and happiness of this country and nation. So I am very happy."

The young man smiled and nodded, and the look in his eyes was so gentle and warm that made her feel warm all over. He looked so familiar, just like the beauty from the past.

Li Shuran was in a trance, as if she had traveled through decades of vicissitudes and returned to that cool and gloomy autumn, where she saw the young boy again.

August 24, 1926, she will always remember that day.

That morning, my brother, who had been bedridden for a long time, suddenly got up, changed into new clothes, and said he was going out to visit a friend.

At that time, my brother's health was very poor and he spent most of his time sleeping every day.

But that day, her brother was in an abnormally good mood. He talked to her a lot and laughed happily.

She was really happy at that time. She thought her brother was going to get better.

Before leaving, her brother smiled and told her, "I'm going out. After I leave, go to my study. I left a letter for you on the desk."

She felt uneasy at the time, and asked with a forced smile: "Brother, can't you just say it directly? Why do you still need to write to me?"

Her brother rubbed her head vigorously. She couldn't see his expression, but she heard him chuckle and answer, "Because I'm very shy, there are some things I can only tell you in a letter."

She was too young at that time.

She ignored all the signs of danger, naively thinking that her brother would recover soon and they would continue their warm and ordinary happy life as mortals.

Then she watched her brother's back as he walked away step by step. At that moment, she suddenly felt a great sense of uneasiness, as if her brother was about to walk out of her world step by step.

She couldn't help but shouted: "Brother, come back early, I'll wait for you at home."

Her brother did not answer her. He just turned sideways, waved to her with a gentle smile on his lips, and left without looking back. He walked hurriedly and firmly, as if he was rushing to a battlefield of iron and fire.

…It was as if his back was telling her that there was no need to chase her.

This was the last time she saw her brother, clean and refreshed, with a gentle smile.

From then on, she would always dream of her brother's horrific appearance, covered in blood and with a festering body, every time she woke up in the middle of the night.

The suicide note on the desk became her inner demon. Whenever she thought about it, she was always heartbroken and could not sleep.

The unknown boy from another school turned and left. Looking at his back, Li Shuran suddenly felt a familiar panic and fear in her heart for some reason.

She asked loudly, "What's your name?!"

The young man paused, turned sideways, and said with a gentle smile, "My name is Chang Jingchen."

He waved at her and said, "Goodbye, teacher."

Chang Jingchen...ah.

Li Shuran didn't know what kind of answer she was expecting. She smiled bitterly and shook her head, waved back at the boy, and whispered to the boy and to the determined figure in her memory: "...Goodbye."

The author has something to say:

I will meet my sister!

I promise!

Sorry for being stuck today, the update is half an hour late. I wanted to update more... but it's a pity that today is too slow, I promise to update more tomorrow!!! If I don't update more, I'll be a dog!

Also, the prototype of Li Shuran's experience after returning to China is Mr. Wang Chengshu. This female gentleman changed her career twice for the needs of the country and re-learned nuclear physics knowledge when she was over 50 years old. She is a very great person. Those who are interested can search Baidu for the old gentleman's life. The old gentleman lived a long life and died at the age of 82.

ps I feel that people who study physics live a long life 23333