"There are still many important problems in high-energy physics that have not been solved, and there are some wonderful mathematical structures in superstring theory, so if you are interested in it, you might as well learn more about differential geometry and topology."

When talking to the masters of contemporary theoretical physics, the topic will inevitably involve the string theory, which is the hottest and most likely to become the grand unified theory of physics.

Although Yang Lao is now 95 years old, he is still full of energy when he talks about the field he is familiar with, and several points of view occasionally mentioned make Wu Bin very teachable.

"You seem interested?" Yang Lao looked at Wu Bin and smiled slightly, as if he saw the flame of interest in his eyes.

"I'm interested in the unknown."

As an ordinary teacher, when I meet someone like Wu Bin who does some research on everything, I usually sigh, thinking that he can't make things with a hammer in the east and a stick in the west.

But Yang Zhenning in front of him is different, he himself is the kind of person who has made great contributions to innovation in many fields, how can he narrowly think that scholars should spend their lives in a specialized field?

So Yang Zhenning was very happy to hear Wu Bin's answer, and continued: "If you think this direction is right, then you may be disappointed in the future, because the idea of superstrings and the actual physical contact are too little. ”

"It seems more like a math problem now." Wu Bin thought for a while and said.

"Yes, but in my academic career, I have seen too many theories that have little contact with actual physics and will not succeed in the end."

Taking a sip of hot tea, Yang Zhenning continued: "However, the number structure of superstrings is very wonderful, if you can absorb the subtleties in it, maybe it will be helpful for you to develop some real problem solving ideas in the future, from this standpoint, I suggest you can do superstrings." ”

Yang Lao said unhurriedly, but his tone still revealed a slight disagreement with the superstring theory.

"I'll give it a try." Wu Bin nodded seriously.

Yang Zhenning nodded slightly after listening: "There are very few examples of insights that can be greatly successful in physics later from the insights that come up with abstract mathematics, and I hope you can understand this before researching." ”

From Yang Lao's words, Wu Bin read that he was afraid that he would be disappointed if he had nothing to gain after studying superstrings, so he replied directly:

"Actually, I'm not very obsessed with the right or wrong results, I'm just looking for the fun of participating."

"Hah...... Ha...... Ha. ”

There was a burst of rhythmic laughter, and the expression on Yang Zhenning's face revealed some satisfaction.

After laughing, Yang Zhenning picked up a notebook on the coffee table, and then took out a pen inserted in his jacket pocket and wrote on it.

[Mathematics (1)] - [Theoretical Structure of Physics (2)] - [Combination of Theory and Experiment (3)] - [Experiment (4)]

Pushing the notebook in front of Wu Bin, Yang Zhenning continued: "This is the relationship between mathematics, theoretical physics and experiments, and the combination of 2 and 3 is theoretical physics, and a theoretical pure structure is connected by the second part and experiments. ”

Hearing this, Wu Bin couldn't help but pick up the conversation, "But if pure structure can't be connected with experiments for a long time, it will inevitably lose its position in physics......

Yang Zhenning nodded with a smile after hearing this: "That's right, the values in physics still have to come from experiments in the end, and the reason why superstrings are so controversial is because it has not been linked to experiments through the second part." ”

Looking at Wu Bin's thoughtful expression, Yang Zhenning continued: "When I was in the United States, there were students who debated with me, and they said that when I did gauge field theory in 1954, wasn't it also a pure structure that had nothing to do with experiments? ”

After changing his posture, Yang Zhenning continued: "It is true that it did not have much to do with experiments at that time, but if they had read my article carefully, they would have found that at that time it was closely related to two theoretical structures that already had a solid experimental foundation, and they were ......."

"Conservation of isospin and Maxwell's equations?" Wu Bin couldn't help but rush to answer.

"Hah...... Ha...... Ha. ”

After listening to Wu Bin's "rush answer", Yang Zhenning burst out into a burst of rhythmic laughter, and looked at Wu Bin happily and said, "I really wish you were sitting down when I talked about this topic in class last time." ”

After being praised, Wu Bin smiled shyly and said, "I also hope to have the honor to listen to Professor Yang's class once." ”

"Alas......" sighed lightly, Yang Zhenning shook his head and said: "In the past few years, I was able to take a group of students to class, but now I don't have the physical strength." ”

After speaking, looking at Wu Bin, who was about to speak, Yang Zhenning waved his hand: "Don't say anything about the polite words that I look young, I can't understand my own body anymore, tell me about you, I heard that you have finished learning the content of the four major mechanics in college?" ”

Wu Bin shook his head and replied: "I can only say that I have a superficial understanding, and I dare not say that I have finished learning." ”

"Very modest." Yang Zhenning took a sip of tea, and then said: "At that time in 71 years, I returned to China many times, and I found that the so-called "four major mechanics" in the physics department pressed the students to the breath, of course, I do not deny the importance of the four major mechanics, they are the backbone of physics, but only the backbone of physics is just a skeleton, and it has to be flesh and blood, it is living physics. ”

"And what is the flesh and blood of physics?" Wu Bin asked curiously.

"New things, living things, things that are closely related to phenomena, in the vernacular, it is to pay more attention to the frontiers of research, and in my eyes, now you are a flesh-and-blood physical person."

Faced with this sudden high evaluation, Wu Bin was a little stunned.

Without giving Wu Bin a chance to reply, Yang Zhenning continued: "In your paper, I read the spirit of innovation that is not afraid of heaven and earth, you dare to break through, and you are willing to make breakthroughs, and make drastic revisions on the basis of previous research, I like this spirit very much." ”

Wu Bin: "I am very happy to receive your affirmation, Professor Yang. ”

"It's time to eat."

Hearing the voice from the kitchen, Yang Zhenning took the opportunity to say to Wu Bin: "Let's eat first." ”

Wu Bin: "Okay. ”

However, for the two who were talking, sitting at the dinner table was just a change of place for conversation, and after three hours had passed, the topics of conversation between the two had changed several times, but the rice in the bowl was almost unchanged.

It wasn't until Weng Fan brought the reheated pork rib soup to the table for the third time that Yang Zhenning looked at Wu Bin with a smile and said, "Let's eat first, it won't taste right if it's hot." ”

"Okay." After hearing this, Wu Bin immediately moved the chopsticks in his hand, swept around the dining table, and did not forget to say a few words to Weng Fang's side: "Your craftsmanship is really good." ”