A Man of Science and Engineering in Troubled Times Wandering in the Late Qing Dynasty

Berlin two months ago.

Einstein got off the train alone and took a taxi to his mother's house.

He hadn't been back for a long time. Einstein's mother was very happy and called her sister and family to celebrate him.

Einstein's cousin Elsa helped him take off his coat and said, "Oh my gosh, you look in great spirits right now."

The two have known each other since childhood. To be precise, Elsa is not only Einstein's cousin, but also a cousin, because their mothers are biological sisters.

Einstein said: "It's because the atmosphere in Zurich is far less depressing than in Berlin. Moreover, the water in Berlin is harmful to the body, the air is full of soot; and there is a class hierarchy that makes me very unhappy - you know, I hate this! Hate the drunken waiter nodding his head and saying, 'Your most humble servant.'"

Einstein's mother said: "After all, you grew up here."

Einstein shrugged: "Mom, you should remember that I have hated Germanic military parades since I was a child and have avoided them at all costs, not to mention the rigid and rigid German education model that started in elementary school."

Elsa asked again: "Where is your wife? Why didn't she come with you?"

Einstein said: "Mileva is a Slav and she hates everything Germanic. And I don't want to carry this heavy and painful cross forever."

Elsa was very smart, and she immediately heard that there was a huge rift in the relationship between Einstein and Mileva.

She gently took a cup of hot tea and a comb: "Drink a cup of tea quickly, and then take care of your fluffy hair."

"Thank you," Einstein took it, a different emotion suddenly rose in his heart, and said, "With this comb, I will definitely make great progress in personal grooming."

Elsa pursed her lips and smiled: "I heard such words many years ago, but it won't be long before you will return to your old sloppy self."

Einstein paused and said: "That is to guard against vulgarity and petty bourgeoisie! Just like the streets of Berlin, one side is a horrifying scene of misery, and the other side is a show off luxury."

Elsa continued: "No matter how bad Berlin is, why don't you come?"

Einstein suddenly said: "Because now there is such a person in Berlin, the thought of her can bring real pleasure, and I live for her."

Of course Elsa understood Einstein's flirtation, and joy arose in her heart. However, in front of so many family members, she did not show it. She just took out a newspaper and said: "I heard that you have A Chinese friend, the newspaper said that there was a great revolution in China and the emperor was overthrown."

"Like France?" Einstein's mother asked.

"It doesn't seem to be the same, but I don't know very well."

Einstein picked up the newspaper, which reprinted a British report titled "Western Civilization is Beating the Chains that Bind China."

"These British guys still like to talk about the politics of other countries and always think they are smart. It's really boring." Einstein said dissatisfiedly, and then threw down the newspaper.

Elsa asked: "Don't you men all like to talk about politics and war?"

Einstein said: "I don't like it. In my opinion, politics itself is full of wisdom, but politicians are often stupid. As for war, only fools like war."

Elsa asked: "Then what do you like?"

"Of course there are physical truths hidden in the universe." Einstein said.

In the current view of Einstein, physics is the highest crystallization of human wisdom, and mathematics is only for service. But it won't be long before he regrets it.

Elsa said: "I think I should also study physics."

Einstein said: "It makes sense. I can teach you. I am a very good college physics teacher."

"Great!" Elsa said, "When you return to Zurich, can I continue to write to you for advice?"

"Of course, beautiful Elsa." Einstein said solemnly.

-

This trip to Berlin was "full of gains" for Einstein. As soon as he returned to his office at the University of Zurich, he found a letter from Elsa in his mailbox.

Einstein thought to himself that his cousin was really smart and knew to send the letter to the office instead of home.

"When I saw your letter, I was so happy to learn that you had thought of a way for us to keep in touch with each other!" Einstein immediately wrote back, "I don't even know how to tell you that these days I have... How much I love you. … I have to love someone, otherwise life is miserable, and that someone is you.”

Einstein's ability to flirt was really strong, and his cousin quickly fell for him with his sweet words.

However, Elsa was very cautious and asked him to destroy the letter, which Einstein did.

And she kept Einstein's replies throughout her life, sealed them in a folder, and made an envelope for it, marked "Especially beautiful letters from better days."

Successfully circulated all the disgusting love stories of mankind's top scientists.

Not only was Einstein emotionally satisfied, Einstein was also busy studying the general theory of relativity recently, but it was just a little bit more difficult.

"Boom boom boom!"

"Please come in!"

"Oh, my old friend!" Einstein said as he came in. "It's such a pleasure to see you."

The person in the room was Grossmann, who was a classmate of Einstein's at ETH Zurich.

Grossman said: "There are not many theoretical physics professors at the University of Zurich. Even I am envious that you can get this position."

Einstein said: "Thanks to Mr. Planck and Li Yu's recommendation letters, otherwise not only the university president, but also the education officials in Zurich would not agree at all. Because in their view, the theoretical physics professor is a kind of An extravagant and wasteful position with little experimental capacity at all.”

"I guess they also thought you weren't a very good teacher," Grossman laughed.

"Oh!" Einstein said, covering his head, "Don't make fun of me anymore. I have improved a lot in my lectures."

Grossman said, "You should have something else to do with me today?"

"Yes!" Einstein sat down and said, "You must help me, otherwise I feel like I am going crazy."

Grossman wondered, "What could make you crazy?"

Einstein said helplessly: "Of course it is mathematics that I love and hate." As early as 1907, Einstein had already thought about the "equivalence principle" and was preparing to apply it to the theory of relativity to solve the fatal flaw of the special theory of relativity.

However, in the four or five years after proposing this principle, Einstein ignored it and turned to thinking about light quantum issues.

It wasn't until last year, when he was exhausted by quantum problems, that Einstein began to think again about how to use a gravitational field theory to generalize the theory of relativity.

This is of course a super difficult research and the most important achievement of Einstein's life.

Einstein took out a paper he wrote last year, "On the Influence of Gravity on the Propagation of Light," and told Grossman: "My research has found that if the propagation of light passes through a massive celestial body, it is likely to be a curve. If I want to continue to study in depth, it seems that I can only use non-Euclidean geometry, and this is not my strong point.”

Grossman knew his classmates well. When he was in college, Einstein often skipped math classes. Grossman helped him take notes. Einstein scored 4.25 in both geometry courses, while Grossman scored a perfect 6 in both.

Grossman knew that Einstein always believed that his scientific success was due to his amazing ability to reveal the physical principles behind nature.

He always asked others to help find the best mathematical expressions of these principles, such as the special theory of relativity. The mathematics relied on Minkovsky mathematics, with the help of Li Yu.

After listening to Einstein's words, Grossman immediately understood: "Do you need a mathematical system to express or even help you discover the laws governing the gravitational field?"

Einstein said happily: "That's it!"

Grossmann thought carefully for a long time, rummaging through the bookshelf from time to time, and then said to Einstein: "I think you can try to use Riemann's geometry."

Riemann cherished his ink like gold, and made great leaps. He seemed to think that readers all had his mathematical talent, which made it difficult to read his books.

On the other hand, a mathematician like Poincaré who could write literary works would feel more comfortable writing.

Einstein felt dizzy when he heard it: "Riemann? Okay, I will try."

Grossman also suggested: "This is just my suggestion as a mathematician. You can ask Li Yu, who is proficient in both mathematics and physics, and he may give a better answer."

Einstein said: "I was just thinking of asking him again after getting enough advice from people around me."

Einstein borrowed a few Riemann's works from the university library. After reading them for a few days, he realized that the difficulty level was off the charts. It seemed that he had to ask Li Yu to help him come up with an idea.

Otherwise, if he spends several years studying Riemannian geometry and finally finds that it is not applicable, the time cost will be too great.

Einstein unfolded the letter paper, took out a pen, filled it with ink, and began to write:
  "Dear Academician Li Yu, the giant of Eastern science, I haven't corresponded with you for several months.

"I read in the newspaper that your country has undergone tremendous changes, and even the supreme emperor has been overthrown. It reminds me of France back then. I wonder how you are doing recently?
  “If you can, you can even come and live in Switzerland for a while.

"Of course, this is also a selfish thing on my part, because I hope to study physics problems with you again.

"You are so smart that you must have guessed between the lines that I have a problem now.

"Actually, this problem is very difficult. In my previous paper "On the Effect of Gravity on the Propagation of Light," I discovered that the propagation of light may not be a straight line.

"It's a hard result for everyone to accept. But somehow I feel like you'll understand.

"In addition, I found that it is possible to verify my theory experimentally. The nearest massive celestial body to us is the sun. I preliminary estimated that when light passes near the sun, it will be deflected by about 0.83 degrees.

"This result can be observed since stars near the Sun are visible during a total solar eclipse.

"But I can only seek the help of astronomers for this. When I was thinking about this problem, I thought that you also have outstanding achievements in astronomy.

"It's just that total solar eclipses are rare. The most recent one seems to be two years away. The time span is too big, so I want to get some practical conclusions from you and solve the big problem that bothers me."

-

More than two months had passed when Li Yu received this letter. Due to major events such as the Revolution of [-] and the abdication of the Qing Emperor, many systems, including the postal service, had come to a standstill.

I also received letters from Planck, Rutherford and others.

Li Yu was really touched that these big guys cared about him so much.

Planck and Rutherford mainly asked about the current situation, and it was relatively easy to reply, so Li Yu wrote a reply to them first, and also sent a telegram to report that they were safe.

Einstein's letter is a large package, which also contains a typed paper by Einstein and many manuscripts.

Li Yu finally replied to him:

"Dear Mr. Einstein,

"First of all, thank you for your concern. I am in good condition now. This will be a bloodless super revolution that the whole world will remember.

"As for the question you asked. After careful reading and thinking, I can solemnly answer that Riemannian geometry is the most suitable for you.

"Because the core of your article, to summarize, is that gravity originates from the curvature of space and time. In this way, from a mathematical point of view, gravity becomes geometry.

"Of course, it is not easy to study and understand Riemannian geometry.

“But I firmly believe that mathematics is a tool for discovering—not just describing—the laws of nature.

“Mathematics is nature’s script!

"... When it comes to the total solar eclipse in two years' time, the best observation location should be in Crimea. Going to Russia for observation is no small task. At that time, you can try to contact the astronomical community and St. Petersburg to see if you can provide support.

"I think it's worth trying, and theoretical physics ultimately comes down to experimental physics anyway."

This correspondence took over three months back and forth.

During this period, Einstein wrote letters to many European scientists, such as Sommerfeld, the key figure in quantum mechanics.

Their answers more or less emphasized that Einstein should pay attention to mathematics. After all, he was a theoretical physicist. Experiments were no longer good, and the theory must be hard enough. If you want to go far enough in theory, you must have a very good mathematical foundation.

There are too many such examples, the most typical ones are Boltzmann, Maxwell, Lorenz and other super bosses.

After receiving Li Yu's letter, Einstein became even more convinced that he wanted to work harder on mathematics. He wrote down Li Yu's words: Mathematics is the script of nature.

Many years later, Einstein said frankly when recalling the process of his research on general relativity: "I concentrated on studying the problem of gravity. Li Yu and Grossman gave me great help, allowing me to overcome all difficulties. And the most important thing is , It was Li Yu who made me have great respect for mathematics. Before that, I had always foolishly believed that the more mysterious things in mathematics were just a kind of showmanship."