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

Chapter 706: Group Photo of the Gods
It was obviously impossible for Dirac to complete his complicated theory in a short period of time. It would take at least next year for there to be some progress, including the famous Dirac equation and the astonishing solution obtained through the Dirac equation, namely the positron prediction.

Kapitsa is still not so interested in pure theory, he prefers to delve into experimental directions. In the past few days, Kapitsa's team has invited Li Yu to have several discussions, but the direction is clearly biased towards atomic physics and quantum mechanics.

During the chat, Kapitsa casually asked, "Mr. Bragg was also invited to attend the Solvay Conference in Brussels?"

Li Yu nodded and said, "Yes, Mr. Black and Mr. Compton, as representatives of experimental physicists, were both invited."

Kapitsa said: "They must think that you theoretical physicists are too slow. You haven't come up with a conclusion in such a long time. They want to go and see for themselves. Because all the experimentalists are waiting for the theoretical conclusions so that they can do experimental verification."

Li Yu laughed and said, "You really don't mind watching the fun."

Kapitsa lamented: "It's a pity that we can't go to the scene to watch the fun."

The Fifth Solvay Conference was known as the War of the Gods, and the participants were roughly divided into the following factions:

Copenhagen School: such as Bohr, Heisenberg, Pauli, Dirac; now we have to add Li Yu.

Anti-Copenhagen School: Einstein, Schrödinger, and de Broglie.

Experimentalists: Compton and Black. They are waiting for the two groups above to come to a conclusion so that they can conduct experiments.

There are also neutrals who are watching the show, including Marie Curie, Alan Foster, Debye, etc.

After giving a few lectures in Cambridge, Li Yu prepared to leave with Dirac. Before leaving, he went to say goodbye to Rutherford, Kapitsa and others.

When Rutherford arrived at the Cavendish Laboratory, he announced to a group of researchers: "I have applied for a research grant of 15000 pounds specifically for Kapitsa's low-temperature physics research."

Other researchers were immediately dissatisfied and could not help complaining to Rutherford: "Is Kapitsa really that great? His work has not made any progress. Don't you think he is wasting his time and equipment?"

Rutherford obviously had great confidence in Kapitsa: "This is a topic he chose himself. If this work is not successful, then I will guide him to another original topic. But as long as he perseveres and thinks independently, he will succeed."

The dissatisfied researcher said: "Everyone is holding on."

Rutherford was well aware that some people still did not like Kapitsa's Soviet identity. But in Cavendish, Rutherford's authority was unquestionable and his temper was quite bad. He immediately replied loudly: "I hate people who are busy all day, entangled in personal disputes or small circle factional activities. There is nothing more tragic than those who only care about the little things under their noses."

“But I went to work diligently every day and didn’t waste any time,” the researcher said.

Rutherford said sternly: "Some people seem to be busy all day long, going to work and leaving get off work on time, but in fact, they are busy with unnecessary things and have no meaning! In addition, in my opinion, there is only one person who can ruin a person's reputation, and that is himself."

Rutherford was clearly trying to clear the research obstacles for Kapitsa, so that no one would ridicule Kapitsa anymore. He walked out of the laboratory and saw Li Yu and Dirac who came to say goodbye.

Li Yu gave him a box of premium black tea and asked, "Professor, do you want to go to Brussels for a visit?"

"I'm not very keen on theoretical physics either," Rutherford said, "and I have more important things to do now, which is your prediction."

"Neutron?" Li Yu could basically guess it.

“Yes,” Rutherford said. “And your prediction about isotopes. If neutrons exist, then hydrogen is even more special, because all the other elements in the periodic table are made up of electrons, neutrons, and protons, but hydrogen is different. And the atomic weight is also a little more than 1, which is very puzzling to everyone.”

Li Yu smiled and said, "I am sure that hydrogen must have isotopes."

"Your prediction is very exciting, and there are a lot of labs looking for it now," Rutherford said.

The isotopes of hydrogen were discovered quite late, with deuterium with an atomic weight of 1932 being first discovered in 2.

At that time, there were still many voices that believed that deuterium was the first element and hydrogen was an isotope. Because of this, the scientific community experienced another fierce debate - between Soddy and Bohr, who won the Nobel Prize for isotopes.

But Bohr had more important things to argue about right now.

Li Yu said, "See you later, Professor Rutherford."

“I regret that our meeting was so short,” Rutherford said, “and I wish you all the best in Brussels.”

Li Yu and Dirac first arrived in Leiden, the Netherlands, and visited Lorentz, who was the host of the Solvay Conference, mainly because he had a high enough prestige and was proficient in multiple languages.

"Mr. Li Yu, it's great that you're here," Lorenz said to Li Yu, "Could you please give the opening report for this meeting?"

Li Yu said: "I heard that you met with Mr. Einstein."

"That's because I wasn't sure at first whether you would come," Lorentz said, "and Mr. Einstein refused to give the opening speech."

"Is it because the theme of the conference is about quantum theory?" Li Yu asked.

"That should be it," Lorentz said. "Einstein told me that after long consideration, he was not able to report on the current situation of quantum theory. And he did not agree with the purely probabilistic approach of the new theory."

Li Yu smiled and said, "Einstein really doesn't like probability."

Lorentz said: "When statistics was introduced into physics, no one was overly opposed. Einstein also accepted the ideas of quantization and discontinuity, but he could never accept the probabilistic explanation and the ghost of uncertainty of Heisenberg."

Li Yu said: "If the public knew this now, they would probably stand on Einstein's side."

"It's too difficult," Dirac said, one of the rare times he said, "Quantum theory is too difficult to be understood by the general public."

Lorenz said calmly: "Maybe this is a good thing."

In fact, even after a few decades, the public will still know very little about quantum theory, mainly because quantum theory is still developing and it is difficult to keep up with the pace.

Many people oppose the theory of relativity with only a vague understanding of it, but few oppose quantum theory. After all, the learning threshold is higher and quantum mechanics is more abstract.

Lorenz added: "I will be leaving late, so you should go and see Ehrnfest first."

Ehrenfest was also in Leiden, and his home was a place where physics greats often stayed when they arrived in Leiden.

Ehrenfest was a student of Mr. Boltzmann, an Austrian who has now become a Dutch citizen.

His house was not small, and he warmly welcomed Li Yu and Dirac.

As soon as Li Yu entered the room, he noticed a wall with signatures of Einstein, Kapitsa, Dirac and others on it.

Allenfest had already taken out a pen: "Mr. Li Yu, please leave your signature as well."

This was Allenfest's custom, so Li Yu picked up the pen and wrote down his name.

Allenfest said happily: "These Chinese characters are amazing."

Li Yu and Dirac were going to stay at his house for one night. The bigwigs who signed on the wall had also stayed here, but Allenfest had a condition: they needed to tell some interesting stories to his three children (two daughters and a son).

In particular, Allenfest's son suffers from Down syndrome, which is a major shadow for him.

In 1933, Ehrenfest settled his two daughters first, then shot his son who had Down syndrome, and then committed suicide. Ehrenfest and his teacher Boltzmann unexpectedly came to the same end.

However, Boltzmann gave up suicide under Li Yu's intervention and lived for another seven or eight years before dying of natural causes.

Li Yu really doesn't want to see these scientific giants end their lives in this way.

Li Yu can tell many interesting stories, because these children don’t know much about China, and they like any story about China.

The two daughters were fascinated by what they heard, but the boy with Down syndrome just smiled foolishly.

Li Yu could see from the corner of his eye that Allenfest was very sad, so he said to him: "I have heard a proverb that every disabled child is an angel with broken wings."

Allenfest smiled helplessly: "Then God is really cruel."

Li Yu then said, "I think PhD students can study biology like Professor Schrödinger."

"It's no use," said Ehrnfest. "There's no cure for this disease. There's no hope."

Li Yu thought for a moment and said, "Doctor, don't you want to find the cause of this disease?"

Allenfest's eyes flashed: "I hate it! But I really don't even know what caused it."

Down syndrome was discovered as early as the 1860s by British doctor Don Langdon, hence the name Down syndrome.

But it was not until 1959 that geneticists determined that Down syndrome was caused by a trisomy of chromosome 21.

"PhD students may not pay much attention to biology, but this discipline actually has great development potential," Li Yu said firmly, holding up three fingers. "I estimate that in 30 years at most, we will know the cause of the disease."

Allenfest certainly didn't want to give up on his son, so he asked, "If we know the cause of the disease, is it possible to treat it?"

Li Yu could only comfort him: "It should be, just like diabetes and insulin not long ago."

"Thirty years," Allenfest thought for a while, "I can wait!"

As long as people have hope, they can persevere.

Li Yu smiled and said, "Maybe it will be earlier."

"But," Ehrnfest asked, "is Professor Schrödinger really so passionate about biology?"

"Of course. He has written many biology papers and almost gave up physics," Li Yu said. "You can ask him in person when you go to Brussels."

Allenfest was very interested: "It would be nice to study biology."

-

After leaving the Netherlands, Li Yu and his companions arrived in Brussels relatively early.

Bohr and Heisenberg were already gearing up for a fight, having just reached a consensus on some of their differences.

In the previous fierce debate between Heisenberg and Schrödinger, Bohr also stood in the middle, after all, Heisenberg spent most of his time in Copenhagen.

But Bohr attacked from both ends: he certainly opposed Schrödinger's view of continuity, but he also had disputes with Heisenberg.

This spring, Bohr, who had just returned from a skiing vacation, had an epiphany and proposed his most representative quantum theory: the principle of complementarity.

This principle was gradually formed in previous debates.

Bohr deeply realized the duality of wave and particle, and it is an inherent property of matter, that is, the nature of light has both particle and wave aspects. Based on the fact of wave-particle duality, Bohr proposed the "complementarity principle" to try to answer some problems encountered in physics and philosophy research.

Bohr's complementary view is based on the objective fact of wave-particle duality. Both light and particles have wave-particle duality, and wave properties and particle properties will not appear in the same measurement, which means that the two are mutually exclusive when explaining the properties of microscopic particles.

On the other hand, the wave-particle duality cannot be measured at the same time, which means that there will be no contradiction in the experiment; at the same time, the two are indispensable in explaining the properties of microscopic particles. Therefore, the two are complementary.

From this, Bohr abstracted a basic idea that everything has many different aspects. For the same research object, if some aspects are acknowledged, other aspects have to be abandoned, which means that they are "mutually exclusive"; while the other aspects cannot be completely abandoned because under certain conditions, they must exist. In this sense, the two are "complementary".

It’s a bit confusing, but it all comes down to the same thing - wave-particle duality is a natural law. Particle nature and wave nature will be observed in different situations, but they both exist.

Bohr explained quantum theory through the "complementarity principle", which together with the uncertainty principle, probability interpretation, etc., formed the "Copenhagen interpretation".

As for the disagreement with Heisenberg, it was because Bohr believed that complementarity provided a universal framework for the existence of uncertainty, and uncertainty provided the basis for the unified expression form of quantum mechanics.

Heisenberg's paper was based only on particles and discontinuities; it was too narrow and immature.

Anyway, the two have been arguing about this for several months, and the dispute came to an end in the summer. Now they are pointing their guns at the outside world.

That afternoon, all the participants arrived.

Lorenz first suggested: "There are so many people this year, why not take a photo as a souvenir."

Photos are taken every year, so naturally no one would refuse.

As the host, Lorenz had already thought of the seating order: "Then please sit down according to the order on this paper."

Lorentz placed Li Yu on the left of Einstein, and Langevin in the original photo moved one position to the left.

Li Yu smiled and said, "It's great that we took photos in advance. Otherwise, it would be too late to take photos after everyone is arguing with each other."

Einstein whispered to Li Yu: "I have decided to remain silent at this meeting, so I refused to make a proposal report."

Li Yu didn't believe it: "You can only remain silent for one day at most."

Einstein shrugged: "We'll see."

Ten minutes later, the photographer set up his camera:
"Please look at me here! Very good!"

"Crack"!
Just like that, Li Yu entered this photo of the gods.

But judging from the developed photos, the 30 participants still looked basically expressionless when taking the group photo.

In Dirac's words many years later:

“It’s like taking a collective passport.”

(End of this chapter)