1900: A physics genius wandering around Europe

Chapter 440 A piece of glass crushes the gang! Everyone is shocked! Li Qiwei finally takes action!

A small glass problem brought a big shock to everyone.

After all, Yu Qingsong is just an undergraduate student, so it is understandable that he could not give an answer.

Then Compton is a rising physicist, a superstar who proved the wave-particle duality of light.

But even his answer was wrong.

At this moment, everyone in the conference hall realized how extraordinary the question raised by Professor Bruce was.

“It’s so down-to-earth, yet so difficult.”

The magic of physics is once again displayed before everyone's eyes.

Now everyone can only place their hopes on the big guys in the front row.

Only they may know the answer.

Expectant and burning eyes are focused ahead.

Even though Hai'er couldn't see behind him, he could still feel the pricking pain in his back.

This astronomy expert could only smile bitterly to himself:
"The point is, I don't know how to do it either."

Many American teachers and students feel sad.

Is this the current state of American science?

"In such a big country, there is no one who can withstand Professor Bruce's attack."

"The United States has a long way to go in the field of science."

In this situation, Millikan stood up.

It immediately caused a cry of surprise!
"Oh! My God! It's Professor Millikan!"

"I didn't expect that Professor Bruce would call out Professor Millikan for just a random question."

"He is the banner of American physics!"

"I believe Professor Millikan can do it!"

At this moment, most people present were excited.

If it was Yu Qingsong’s answer just now that excited the Chinese international students.

Now, the emergence of Millikan is to save the face of the United States in the physics community.

Although today is just a lecture by Professor Bruce.

He himself had no intention of attacking anyone.

But in the eyes of these young students, this is a battle, a battle in the field of science.

Millikan instantly felt everyone's emotions.

Only at this moment did he realize how heavy the burden he had inherited from Professor Michelson was.

He must not fall!

So, Millikan smiled lightly and said firmly:

"Professor Bruce, I have an immature idea."

Seeing this, Li Qiwei smiled and said, "Please go ahead, Professor Millikan."

Millikan sorted out his thoughts and said:
"The perspective that Compton just answered is the probability of a photon encountering an electron."

"The greater the probability, the more photons are absorbed."

"He believed that in metals, since electrons can move freely, the probability of photons encountering electrons is high."

"But in a crystal, because the electrons are bound, the probability of encountering a photon is low."

"I think the explanation itself is logical."

"But the problem is that glass is not a crystal, so the crystal theory cannot explain the situation where the electrons are bound."

“So, I wanted to propose a new model.”

"Professor Bruce, do you remember the lecture you gave twenty years ago on the photoelectric effect?"

Li Qiwei was slightly stunned.

He didn't know why Millikan suddenly mentioned this matter.

At that time, he and Planck had just proposed quantum theory and encountered opposition from many physicists.

So, at the quantum theory conference, he used quantum concepts on the spot to explain the principle of the photoelectric effect, thus vindicating quantum theory in one fell swoop.

Millikan became famous as a famous experimental physicist because he proved the theory through experiments.

And Li Qiwei started his road to rise.

Those were passionate years.

When Li Qiwei thinks back on it now, he is still filled with nostalgia.

"Of course I remember, Professor Millikan."

"I wonder if it has anything to do with my problem?"

Millikan said:
"Of course."

"According to quantum theory, for a single electron."

"An electron will absorb a photon only if the energy of the photon is exactly equal to the energy level difference of the electron's transition."

"Otherwise, the electron would not absorb the photon."

"But in the photoelectric effect, as long as the energy of the incident photon is higher than a certain fixed value."

"The electrons on the metal surface absorb the energy of the photon, gain enough kinetic energy, and escape from the surface."

"It's like there's a threshold for metal electrons to absorb photons."

"Above this threshold, the electron will absorb the photon, no matter what its energy is."

"This phenomenon shows that quantum theory has certain limitations when dealing with the massive atoms in macroscopic matter."

"So, we can assume."

"For all macroscopic matter, electrons absorb photons to make transitions, and no longer need light of a specific energy."

"It's just energy above a certain threshold."

“Metal has a very low threshold, while glass has a very high threshold.”

"In this way, when the same beam of light shines on the metal, the electrons can make transitions, so more light is absorbed."

"And the electrons in the glass can't absorb the light and make transitions, so the light passes through the glass."

"That's my answer."

Wow!
Millikan's explanation is obviously a level more difficult than Compton's.

Because this requires not only understanding quantum theory, but also knowing the photoelectric effect.

Most of the people present simply couldn't understand.

"Ah? Can anyone tell me what Professor Millikan's answer means?"

"Isn't this quantum theory? Why is the photoelectric effect mentioned again?"

"Oh my God! A tiny piece of glass is actually related to so many cutting-edge physics. This is too exaggerated."

"."

The rookies were in a state of extreme confusion.

Only Wu Youxun, Hubble and others, as well as the physicists in the front row, could immediately understand the meaning.

Then, a look of realization appeared on their faces.

Because Millikan's analysis makes a lot of sense!
Starting directly from the electron transition threshold, the problem of glass being amorphous is avoided.

“It’s truly a genius idea!”

"Professor Millikan is indeed a physicist of the same generation as Professor Bruce."

"He saved the face of the American physics community."

"As the Chinese saying goes: Ginger is still spicy with age."

The bigwigs were full of praise for Millikan's answer.

Most people felt relieved when they saw the big guys’ voices and expressions when they were discussing.

"Professor Millikan did not disappoint us."

At the same time, everyone suddenly discovered an amazing coincidence.

Professor Bruce's speech twenty years ago actually solved a problem twenty years later.

I have to say, this kind of coincidence has a wonderful feeling of fate.

That man, his whole life, seemed to have some inexplicable relationship with physics.

A history of physics is half blues!

In modern physics, his name appears in every volume!
At this moment, Li Qiwei stood on the high platform, feeling emotional.

It turns out that we cannot underestimate the heroes of the world.

Millikan is not a very famous physicist in history.

But his contribution is also huge.

Even some of his research indirectly promoted the discovery of the fourth quantum number.

For such a big guy, it is inaccurate to use only T4 grading.

Li Qiwei's T series merely evaluates and divides the academic achievements of physicists.

However, there is no way to divide their IQ and level.

This too cannot be divided.

Therefore, even Millikan, who is at T4 level, will have many brilliant ideas.

His answer just now falls into this category.

Although this answer doesn't really solve the problem.

But at least the idea is right.

The reason why Li Qiwei dared to assert that no one can solve the problem of why glass is transparent is that

Because the theory that can explain it has not been published yet.

This theory is the [band theory].

In real history, Heisenberg's student, Swedish physicist Bloch, proposed the band theory of crystals in 1928.

Quantum mechanics had already matured by then.

But when physicists used it to study solids, they discovered a problem.

Existing quantum mechanics can only describe the state of a single microscopic particle.

Solids are made up of countless atoms, which form complex connections between them.

Quantum mechanics is somewhat helpless when it comes to macroscopic objects such as solids.

In particular, the movement laws of electrons in solids were the focus of research by physicists at that time.

Because it is related to the conductivity of the material.

Physicists hope to introduce quantum mechanics into the study of electrons in solids.

Against this background, Bloch first set his sights on a special type of solid substance: crystals.

Because the atoms in the crystal are arranged regularly and neatly, the difficulty is relatively small.

Bloch had a sudden idea and assumed that the atomic nuclei in the crystal were fixed and arranged in a certain periodicity.

In this way, countless atoms can actually be regarded as a whole.

The periodic potential field they form runs throughout the entire crystal.

It is like looking at the waves on the entire lake as a whole, then it is one big wave running across the entire lake.

He then went on to believe that electrons move in this potential field.

All electrons in a crystal are shared electrons that move throughout the crystal.

In this way, the multi-electron problem can be simplified into a single-electron problem.

(It doesn’t matter if you don’t understand, as long as you know it, it’s fine. This thing can’t be explained clearly without formulas and diagrams.)
Therefore, based on the deduction, Bloch can draw an important conclusion.

That is, in a crystal, electron transitions no longer require photons of a specific energy.

The conditions for electrons to absorb photons become a range, like an energy band.

For example, suppose the energy band width of a crystal is 10eV.

(【eV】is a unit of energy, pronounced as electron volt, which represents the kinetic energy gained by an electron after being accelerated by a potential difference of 1V.)
(1eV=1.6×10(negative th power) J)

Then, as long as the energy of the incident photons exceeds 10eV, whether it is 11eV or 12eV, the electrons can absorb these photons and undergo transitions.

When the photon energy is less than 10eV, the electrons will not absorb it and the photons will penetrate the crystal.

This is the band theory of crystals.

Using it, we can introduce quantum mechanics into the study of solid-state electronics.

Band theory plays an important role in explaining solid conductivity, semiconductors, etc.

According to band theory, the band width of a metal is obviously zero because its electrons can move freely.

That is, no matter what kind of incident light, the electrons in the metal can absorb it. (This question only considers the visible light range)

Glass also has its own energy band width, which is approximately 9eV.

But the photon energy range of visible light is between 1.6eV and 3.3eV.

Therefore, the electrons in the glass do not absorb any visible light, and thus become transparent.

Now comes the problem!

Glass is not a crystal!

Although energy bands can be measured in glass, you cannot apply the theory of crystals to it. There must be another theory for non-crystalline materials.

This question, even in Li Qiwei's previous life, still has no reasonable explanation and remains an unsolved mystery.

Therefore, there is currently no authoritative explanation as to why glass is transparent.

Doesn’t it feel incredible?

Humans have even landed on the moon, but they can’t even understand a piece of glass.

This is the charm of physics.

When individual particles combine to form macroscopic objects, it’s as if some kind of evolution occurs.

This is as amazing as how many quantum behaviors combine together to form "consciousness".

This boundary from quantitative change to qualitative change seems to involve something original.

Now, the theory proposed by Millikan is actually somewhat similar to the prototype of the band theory.

He's a bit of a rogue, though.

He directly said that the energy band widths of metal and glass are different.

But why it was different, he couldn't explain.

This is actually a variation of "metal electrons absorb photons better than glass."

It just looks more sophisticated after adding the threshold range.

Millikan himself didn't know, but he actually found the right direction by accident.

At this moment, his eyes were fixed on Li Qiwei, and the muscles on his face trembled slightly.

Obviously, he also knew the limitations of his theory.

Although the logic is perfect, there is still something wrong.

Under the gaze of everyone, Li Qiwei said:
"A very fascinating idea, Professor Millikan."

"Current quantum theory cannot be applied well to solids."

"The concept of transition threshold may be a supplement to quantum theory."

Hearing this, Millikan breathed a sigh of relief.

Li Qiwei's comment was his reassurance, enough to prove his status as a physics giant.

Even though one has reached Millikan's level, he no longer cares about the opinions of many people.

But he would never dare to ignore Li Qiwei's opinion.

However, he then heard:
"But, Professor Millikan, your answer still doesn't explain it clearly."

"According to your theory, why is the threshold of metal lower than that of glass?"

"Perhaps you would say that it is because their composition structures are different."

"But crystals, diamonds, etc. are also transparent."

"Their composition and structure are also different from glass."

"Then why is it different this time, causing both to be equally transparent?"

"So, I think there must be a deeper underlying reason."

Wow!
Li Qiwei's analysis surprised all the bigwigs present.

Just when they were still accepting Millikan's theory, Professor Bruce counterattacked and struck directly at the crux of the matter.

He pointed out the flaws of Millikan's theory in a very sharp way.

"Yes, Professor Bruce is right."

"Professor Millikan's theory is a bit like working backwards from the results to the causes."

“He didn’t explain what factors would affect the threshold.”

“Metal, diamond, and glass, these three different structures should be compared together.”

"Now Professor Millikan only says that the thresholds are different for metals and glasses."

"Then it stands to reason that the thresholds for diamonds and glass should also be different."

“But the two different results are completely different.”

"This is obviously illogical."

(Metals are actually crystals, but they are different from covalent bond crystals such as diamonds, so I won’t go into detail here.)
At this moment, everyone felt like the sky had fallen.

Even Professor Millikan failed.

Many geniuses and bigwigs were crushed by a piece of glass and lost their temper.

Before today, everyone would have thought it was impossible.

But the truth is so cruel.

Professor Bruce shocked everyone again.

“It turns out that we really know nothing about glass.”

"This is simply like the Arabian Nights."

"Without Professor Bruce, I would never have known this question."

Millikan showed a wry smile on his face.

He didn't expect that his theory would be so vulnerable in front of Professor Bruce.

He deeply felt the horror of Li Qiwei.

That man has become stronger again.

The questions that the other party casually asked now made him feel as difficult as climbing to the sky.

This feeling is indescribable for a big shot like Millikan.

It was as if he was standing at the very top, but when he looked up he found that he was only at the bottom of another mountain.

How sad!

However, this disease is easy to cure. You will get used to it by living in Chongqing, China for a few days.

Astronomy giants such as Haier were all shocked.

At this moment, they personally felt how terrifying Professor Bruce's strength was.

Any theory with the slightest loophole will be seized upon by the other party.

The most important thing is that the person being refuted cannot find any reason to refute back.

Hai Er sighed:

"I can't wait to see Professor Bruce's next impact on astronomy."

In his view, although general relativity has revolutionized astronomy.

But that was created unintentionally by the other party.

Professor Bruce's original intention was to study physics, but he shocked astronomy incidentally.

But now it's different.

Professor Bruce is about to publish a real astronomy paper.

These are completely two concepts.

"Oh my god, I'm not going to be debating with Professor Bruce from now on."

The Haier boss, who has always been extremely domineering and self-willed, is a little panicked at this moment.

He could look down on Dyson, and even Eddington was just a lucky young man in his eyes.

But facing Li Qiwei, he did not have this confidence.

That is absolute suppression in terms of strength.

Haier could even imagine a scene:
[Professor Bruce waved his right hand at the International Astronomy Conference and said:

"Regarding astronomy, there has been a very common phenomenon since ancient times."

“But in fact, we have never really understood it.”

"That is"

"Professor Haier, can you explain this problem?"

hiss!
Hai Er was suddenly startled and was almost frightened by his own imagination.

He muttered to himself: "I have to make up for some knowledge when I get back."

"Don't make a fool of yourself and bring shame to American astronomy."

Even the big guys were so shocked, not to mention the ordinary teachers and students present.

They are now in a completely dazed state.

I can’t imagine why the glass problem could be so difficult.

“I will never underestimate any research field again.”

"Even if you're studying pulleys and sliders, there might be something interesting in it."

"Professor Bruce is truly horrible."

"How on earth did he come up with such a question?"

Shapley and Curtis had remained silent since the question was raised.

They had only one thought in their minds: Fortunately, Professor Bruce did not attend the astronomy debate five days later.

Otherwise, they could surrender now.

The other party’s logical ability is too strong!
That powerful aura made it hard for everyone to breathe.

No matter how simple the problem is, in the other party's hands, it seems to be transformed into something magical, and even leads to profound scientific theories.

The two had no doubt that Professor Bruce must have his own ideas about the cosmic scale issue.

Under the opponent's offensive, Shapley and Curtis didn't think they could hold on.

But soon, they cheered up.

With such a good example in front of us, it would be a waste if we didn’t learn from it.

The two of them were in the crowd, their eyes met, and there was a strong sense of tension.

Yu Qingsong looked at the figure on the stage with admiration.

He had been completely conquered.

This was the first time he felt Professor Li's charm up close.

He studied in the United States and met many professors.

Every professor is like a mysterious dragon that is hard to find and is very arrogant.

But no one could give him this feeling of invincibility.

He was fascinated by the way he could easily suppress the big guys with just a few gestures.

Millikan, Compton, and Hale.
They are all well-known figures in the American scientific community.

But in front of Professor Li, he seemed like a child.

Yu Qingsong said with longing:

"When will I be able to reach that level?"

At this moment, everyone present was in shock.

They seemed to have forgotten that the speech had just begun.

At this moment, Millikan suddenly spoke again.

"Bruce, you said we knew nothing about glass."

"Don't you even know why glass is transparent?"

“Now that you’ve asked this question, do you have an answer?”

Wow!
Millikan's words instantly woke everyone up.

Yup!

Professor Bruce hasn't expressed his views yet?
In this world, even if no one can explain it, as long as the other person is still there, there is still hope.

This is the status of Li Qiwei in everyone's heart.

Li Qiwei smiled lightly upon hearing this, and said calmly:
"To be honest, I don't know either."

"This problem can only be solved with further developments in materials science, solid state science, and quantum theory."

After hearing this, everyone was even more shocked than before.

Even Professor Bruce couldn't explain it.

How appalling!

But the bosses were relatively calm and accepted it naturally.

There are too many unsolved mysteries in this world.

Even Professor Bruce cannot be omniscient and omnipotent.

The issue of glass is obviously closely related to the development of the discipline.

However, just when everyone thought that this problem had no solution for the time being.

Li Qiwei then said:

"But, just like Professor Millikan."

"I also have an immature idea."

"I can tell you this for your reference only."

Wow!
The whole audience was shocked!

(End of this chapter)