On this day, 98 years ago, October 24, 1927 (September 29, 1927 in the lunar calendar), the fifth Solvay Conference. The 5th Solvay Conference. Physics masters gathered together and passed down this century photo of the "Physics All-Star Dream Team" that made future generations sigh. This meeting was like a boxing championship. Einstein and Bohr had a fierce "duel" on quantum mechanics. It is almost certain that there is no second photo in the world that can gather so many and high-level human elites in one picture like this one. The meeting lasted for 6 days from October 24 to 29, 1927. The theme is "Electrons and Photons", and we still remember that "photon" is a new term, which was just proposed by American Lewis in 1926.) The agenda of the meeting is as follows: First Lawrence Bragg will give a report on X-rays, and then Compton will report on the Compton experiment and its inconsistency with classical electromagnetic theory. Next, de Broglie gave a lecture on quantum new mechanics, mainly about de Broglie waves of particles. Bonn and Heisenberg then introduced matrix theory of quantum mechanics, while Schrödinger introduced wave mechanics. Finally, Bohr gave the report on quantum postulates and the new theory of atoms based on Como's speech again, further summarizing the complementarity principle and laying the entire philosophical foundation for quantum theory. The agenda itself is a miniature history of quantum theory, from which it can be clearly divided into three schools: the experimental school, which cares only about experimental results: Prague and Compton; the Copenhagen school: Bohr, Bonn and Heisenberg; and the Copenhagen school's mortal enemies: de Broglie, Schrödinger, and Einstein sitting down the stage. The atmosphere of the meeting was fiery from the beginning. Like the championship championship, there was a series of pre-emptions before the main event came: everyone first discussed Compton's experiment, and then everyone divided into distinct camps and bombarded each other. De Broglie took the lead in speaking. He tried to incorporate particles into the image of waves and proposed a theory of "guided waves" that believed that particles were a singularity in the wave equation and must be controlled and guided by waves. Pauli stood up and criticized the theory severely. First, he could not tolerate the wheel of history turning back into a traditional image, and then he cited a series of experimental results to refute de Broglie. As we all know, Pauli is the world's number one sniper. Anyone who is targeted by him will probably come to a bad end. De Broglie finally had to publicly declare that he would abandon his views. Fortunately, Schrödinger came to help on a large scale, but he still insisted on a very traditional explanation, which even the allied forces de Broglie were not satisfied. Pauli had long ridiculed Schrödinger as "childish." Bonn and Heisenberg, who were hiding behind a bunker in Copenhagen and fired at it, concluded their report: "We maintain that quantum mechanics is a complete theory whose basic physical and mathematical assumptions cannot be further modified." They also concentrated their firepower on Schrödinger's "electron cloud", which believed that electrons did actually spread out like waves in space. Heisenberg commented: "I don't see anything in Schrödinger's calculations that proves that the facts are as he hoped. Schrödinger admitted that his calculations were indeed not very satisfactory, but he still insisted that talking about the orbits of electrons was "nonsense"(it should be the superposition of wave eigenstates), and Bonn replied: "No, it's not nonsense at all." Amid the smoke, the veteran organizer of the meeting, Lorenz, also expressed some conservative views, and soon... Einstein did not move at first and maintained a terrible silence, but when Bonn mentioned his name, he finally couldn't help but attack. He proposed a model: an electron passes through a small hole to obtain a diffraction image. Einstein pointed out that there are currently two views. The first is that there is no "electron" here, only a "cloud of electrons", which is a reality in space described by the de Broglie-Schrödinger wave. The second is that there is indeed an electron, and ¦× is its "probability distribution". The electron itself does not diffuse into the air, but its probability wave. Einstein admitted that View II is more complete than View I because it contains View I in its entirety. Still, Einstein said he had to oppose View II. Because this randomness suggests that the same process can produce many different results, and as a result, many areas on the sensing screen have to respond to observations of electrons at the same time, this seems to imply a far-distance action, thus violating the theory of relativity. The situation has changed, and the dragon and the tiger have crossed each other. Now the behind-the-scenes leaders of the two camps have finally come to the stage and begin a fateful one-on-one fight. Unfortunately, no official data has been preserved in the original discussion records of Bohr and others, and the reconstruction of the scene at that time mainly relies on the memories of several parties involved. Among them are the long article "A Discussion with Einstein on Epistemological Issues in Atomic Physics" that Bohr himself was invited to write in 1949 to celebrate Einstein's 70th birthday, as well as Heisenberg, de Broglie and Ehrenfest's memories and letters, etc. Among the issues discussed in the fierce battle was the electron's dilemma in front of the double slit we have already described: how to choose its path and the impact on the electron of quickly closing/opening a slit. There are many other thought experiments. Ehrenfest described in a letter to his disciples who stayed in Leyden (Urenbet and Goodschmidt, etc.): Einstein was like a spring doll, popping out of the box every morning with new ideas, while Bohr found tools from the misty philosophy to crush all the other party's arguments one by one. Heisenberg recalled in 1967:"The discussion quickly turned into a duel between Einstein and Bohr: To what extent could the atomic theory of the time be regarded as the final answer to the difficulties that had been discussed for decades? We usually met over breakfast in the hotel, so Einstein described a thought experiment in which he believed the internal contradictions of Copenhagen's interpretation could be clearly seen. Then Einstein, Bohr and I walked to the venue together, so that I could listen to the discussions between these two people with very different philosophical attitudes. I myself often interjected a few words about the structure of mathematical expression. In the middle of meetings, especially during breaks between meetings, we young people-mostly Pauli and I-tried to analyze Einstein's experiments, and at lunch the discussion was between Bohr and other people from Copenhagen. Generally speaking, Bohr had a complete understanding of these ideal experiments in the evening, and he would analyze them to Einstein at dinner. Einstein could not refute these analyses, but in his heart he was not convinced." Einstein was certainly unconvinced. He believed so devoutly in the law of causality that he could never believe the cynical explanation of probability in Copenhagen. Bohr recalled that Einstein once mockingly asked him whether he really believed that God's power depended on rolling dice (obderliebe Gottwürfelt)? God does not play dice! This is not the first time Einstein has said this. In a letter to Bonn as early as 1926, he said: "Quantum mechanics is impressive, but an inner voice tells me it is not real. This theory has produced many good results, but it does not bring us closer to the mystery of the old man. I firmly believe that the 'old man' does not play dice." "Old Man" is Einstein's nickname for God. However, in the 1927 Huashan Sword Discussion, Einstein ultimately lost one move. It's not that swordsmanship is not good, but it's that internal force is insufficient. Faced with the mighty historical trend, he tenaciously bucked against the current, but as a result, he was washed away until he could stand unstable and struggled to support it. In 1927, the explosion of the quantum revolution had entered its third year and reached a final stage. The seeds planted back then are now bearing fruit, and the revolutionary trend of thought has swept across the entire physics community, pointing out the direction of the future without reservation. More and more people have finally understood the core meaning of the Copenhagen interpretation and sincerely believed in it, all of whom have fallen under the door of quantum. Not only did Einstein fail to persuade Bohr, he was often refuted and speechless. Moreover, his "reactionary" attitude caused many people to sigh. Back then, in 1905, Einstein was born and attacked six times in a year. Each battle was earth-shaking and shocking, and he created a vigorous career alone. At that time, the young man looked down on the heroes, raised his whip and rode his horse, and laughed proudly in the Jianghu. This legendary picture left an eternal fascination in the hearts of many people! However, Einstein, who was the most rebellious, revolutionary, informal, and contemptuous of authority back then, is now standing on the opposite side of the new quantum theory! "We have lost our leader," Bonn lamented. Erenfest was so angry that he said to Einstein,"Einstein, I feel ashamed for you! You have put yourself in the same position as those who seek in vain to overthrow the theory of relativity. Einstein lost the battle miserably, and Bohr seemed silent and dull, but his sword had no sharp edge and no great skills. He had hardly lost a serious debate in his life. The Copenhagen faction and its interpretation of quantum theory won a great victory. Heisenberg said in a letter to his family: "I am very satisfied with the results. Bohr and my views have been widely accepted. At least no one can provide a strict refutation, not even Einstein and Schrödinger." Many years later, he concluded: "At first, it was mainly Bohr, Pauli and I, and probably only the three of us, but it soon spread. "But Einstein was not the kind of person who was easily defeated. He stood against the wind, his messy hair could not hide the determination in his eyes. There were two others standing behind him, one was de Broglie and the other was Schrödinger. The three people, Wu Dai Ling Ling Feng, and their clothes fluttered in the wind. In the dawn of the quantum era, they had a solemn and tragic aura of long and cold forks, and vowed to live and die together with classic theories. A total of 17 of the 29 people who participated in the conference won the Nobel Prize.