1900: A physics genius wandering around Europe

Chapter 439 Everyone is shocked! Quantum theory is needed to explain the transparency of glass? !
When Li Qiwei asked, "Why is glass transparent?", the conference hall fell into silence.

Everyone seemed to have stopped in time, with their eyes wide open and their mouths agape.

It seemed like I heard something incredible.

After more than ten seconds, the atmosphere in the venue exploded.

Countless voices of surprise were heard.

Many people were shocked by Li Qiwei's question.

"Oh! God! What's the question?"

"Isn't glass transparent? What other reasons could there be?"

“It’s like stone and metal are opaque.”

“I don’t think there’s anything worth discussing.”

There are still many non-science and engineering students in the venue today.

In their opinion, Professor Bruce's question was too strange.

No normal person would ever wonder why glass is transparent.

But for students and teachers of physics, this question is very interesting.

"Goodness! I never seem to have thought of that question."

"Except for a few substances such as diamonds, ice, and crystals, most substances in nature are opaque."

"Transparency should be a very rare property, but it seems that no one has studied the transparency of glass."

"I have to say, Professor Bruce is really good at asking questions."

For scientists, asking questions is as important as solving them.

Sometimes, the former is even more important than the latter.

Because every additional question raised represents the expansion of the boundaries of human knowledge.

If there were some "ultimate question" in this world, humans would be ecstatic.

Most ordinary students can only watch the fun when faced with this problem.

Geniuses such as Wu Youxun, Compton, and Hubble frowned and began to think deeply about this problem.

They knew that the question raised by Professor Bruce was definitely not as simple as it seemed.

What are:
"Glass is transparent."

"The light passes through, so it becomes transparent."

This nonsense is certainly meaningless.

It must be explained from a more fundamental theoretical perspective.

It even goes beyond explaining glass and explains why other substances are opaque.

But what theory would that be?

Haier in the front row looked confused at the moment.

He has been active in the field of astronomy for decades and is an internationally renowned astronomer.

But to his shame, he had never thought about this question.

He spends more time with the telescope than with his wife.

As to why glass is transparent, he always ignored it.

"Isn't it okay if it works?"

Haier was sure that many of the astronomers present today had the same idea as he did.

"Professor Bruce, this is going to teach us a lesson."

Millikan next to him had a deep look in his eyes.

As a big shot in the American physics community, he had met Professor Bruce many times.

So, he knew the man well.

He said to Haier:
“That’s the magic of Professor Bruce.”

"He always sees the big picture from the smallest details and makes people interested in science."

“Although the problem seems simple, the theory behind it is definitely very difficult.”

"I even guess that no one here can answer this question."

Hai Er was shocked when he heard this.

"Oh! Impossible!"

"Can't you even answer Professor Millikan?"

“That’s incredible.”

Millikan smiled bitterly:
"At least I don't know."

Although he is a leader in the field of physics in the United States, compared with the rest of the world, he can only be considered a T4-level physicist.

What's more, it is obvious at first glance that this question is related to theory.

Theory is the weak point of experimental physicists like Millikan.

Haier was really shocked this time.

He originally thought that this problem should have been solved in the field of physics or materials science.

It’s just that because it is too cutting-edge or the theory is too niche, laymen rarely hear about it.

But for a physics giant like Millikan, it is certainly not difficult.

Now I didn’t expect that even the other party didn’t know about it.

This is a bit scary.

After Li Qiwei asked the question, he looked at the people in the audience quietly.

He was waiting for someone to answer this question.

Millikan was not wrong; this question was indeed difficult.

Therefore, many students did not dare to stand up, but instead scratched their heads or thought silently.

There are so many big guys present at the meeting today. It would be embarrassing if I gave a wrong answer.

And most people don’t usually think about this kind of question.

You can imagine how difficult it is to think of the answer and organize the language in such a short time.

Although science in Europe and the United States is well developed, it does not mean that students in those countries are necessarily awesome.

Most of them are just ordinary students.

Just as Li Qiwei scanned the entire venue.

suddenly.

Under the surprised gazes of Wu Youxun and others, Yu Qingsong stood up.

When Li Qiwei saw that there were Chinese people who stood up on their own initiative.

His eyes immediately lit up, and a smile appeared on his face involuntarily, and he felt very relieved.

Since ancient times, China has emphasized the so-called moderation, balance, and the principle of shooting the first tree to stick its head out.

Neither too high-profile nor too low-profile.

You can't be too showy, nor too cowardly.

Especially after being ravaged by the West, this idea has developed in a more negative direction.

If there were no Li Qiwei, China's voice in the field of science would be almost zero.

This will cause international students to feel inferior as well.

They were afraid to express their scientific insights in front of a group of Westerners.

Because they feel in their hearts that they are inferior to others, and if they say it out loud they will be laughed at.

However, now, Li Qiwei is standing on the high platform, and he is the stabilizing force in the hearts of all Chinese international students.

His brilliance and aura made even foreigners, who were afraid of Chinese people, dare not look at him directly.

His wisdom and achievements crush all the smart people in the world.

On an occasion like today, young people like Yu Qingsong are already excited.

A fire started in their hearts, ready to burn away all the previous humiliation, fear, negativity and other emotions!

At least in the field of science, Yu Qingsong wants to set an example.

The Chinese people can bravely make their voices heard!

"Hello, professor. My name is Yu Qingsong."

“Currently studying astronomy at the University of Pittsburgh.”

When Li Qiwei heard the name, his heart moved.

It turned out to be Yu Qingsong.

Gao Lu once mentioned this young man to him.

After meeting today, he knew the other party's information.

These are talents that can be vigorously cultivated.

At this moment, he was in a better mood and the smile on his face became brighter.

"Qingsong, can you explain the answer to this question?"

Yu Qingsong was a little nervous at first.

But when he saw Li Qiwei's eyes, it seemed as if an invisible force was injected into his body.

Let him calm down slowly.

Encouraged by Li Qiwei, he said firmly:

"Professor, I took several optics courses during my undergraduate studies."

“I want to try to answer this question.”

Wu Youxun and others all looked at Yu Qingsong with admiration and secretly gave him a thumbs up.

"Good job, Qingsong!"

People from other countries in the conference hall were all deeply moved at this moment.

"The Chinese are different now!"

Many older professors have even taught international students from the Qing Dynasty.

In their opinion, Yu Qingsong is now full of vitality and does not have that smell of decay.

And from the purity in the other person's eyes, it can be seen that this is a young man who truly loves science.

Under the gaze of everyone, Yu Qingsong said:
"We can see something because the light reflected from that object is absorbed by our eyes."

"And the color of an object depends on the color of the light it reflects."

"When a beam of light interacts with an object, three things happen."

"They are reflection, absorption, and transmission."

"The more light an object reflects or absorbs, the less light it transmits, making the object more opaque."

"For example, many metals have a sheen and shimmer because they reflect a lot of light."

"Mirrors use this principle of metal. After a layer of smooth metal is coated on the surface, a mirror that can reflect images is formed."

"But objects like stone and wood don't have a bright sheen."

"This means that they reflect very little light and most of it is absorbed, so they are also opaque."

"In addition, metal not only reflects light, it also absorbs it."

"Professor, your photoelectric effect is a great example of this."

"In summary, since any object will reflect some light, we only need to consider the absorption of light."

"The core of the question now becomes: why do atoms in glass not absorb light, while atoms in metals, stones, wood, etc. absorb light more."

"If we can explain this problem, we can understand the essence of why glass is transparent."

Wow!
Yu Qingsong's logically rigorous analysis surprised everyone present.

The depth of this analysis is nothing to the big names in physics.

But for a sophomore, it is very commendable.

Especially since the other party is majoring in astronomy, not a physics major specializing in optics.

This shows how solid their basic knowledge is.

Everyone stared at Yu Qingsong curiously, making him feel tense again after just relaxing.

After hearing this, Li Qiwei was very satisfied.

Considering the average level of this era, Yu Qingsong's answer can be considered excellent.

Although he cannot be compared with those geniuses like Pauli and Heisenberg.

But it also surpassed many people.

However, Li Qiwei still wanted to test the opponent's limits.

"So Qingsong, can you continue to explain why the atoms in glass are so special and don't absorb light?"

Yu Qingsong's brain was working frantically, but in the end he said honestly:
"Professor, I don't know about that."

"But I guess there are two reasons."

"One is the difference in the atoms themselves, and the other is the difference in the structure of the atoms."

As soon as Yu Qingsong finished speaking, voices of regret were heard in the conference hall.

Everyone thought he could solve this problem.

Unexpectedly, it failed in the end.

But no one laughed at him.

Because everyone themselves can't do it.
Li Qiwei was not surprised to hear this.

Yu Qingsong does not yet have the knowledge to answer this question.

But his performance just now deserves praise.

Under Li Qiwei's approving gaze, Yu Qingsong slowly exhaled and sat down in his seat.

At this time, Li Qiwei continued, "Yu Qingsong's answer just now is actually the answer to the first level."

"But this level is far from enough for physicists."

"So, we have to go down to the level of microscopic particles."

"So is there anyone who can continue to answer this question based on what Mr. Yu said?"

The answer to the first level is the limit of what most people here know.

After all, Yu Qingsong is just an undergraduate student majoring in astronomy.

So there are many physical theories that he has not understood.

For example, quantum theory.

Since it involves the level of microscopic particles, quantum theory needs to be used.

Obviously, many people present had thought of this as well.

Compton is one of them.

He suddenly stood up and said confidently:
"Professor Bruce, I have an idea."

Compton has always wanted to see Ridgeway again since their last meeting in Borneo.

It was because of the other party's encouragement that he was able to persist in his project and finally succeed.

So Compton was very grateful to Li Qiwei in his heart.

At the same time, he was also grateful to Wu Youxun. Without him, there would be no Wu-Compton effect.

Now he can be considered to have just entered the circle of physicists.

Only after entering this world did he realize how broad the sky of science is.

How powerful is Professor Bruce?

Therefore, the successful Compton did not stop his steps, he still wanted to pursue the pinnacle of physics.

In real history, Compton, like Millikan, later devoted himself to the study of cosmic rays.

And as a result, the [reverse Compton effect] was discovered.

That is, after the photon collides with the electron, the wavelength of the photon does not become longer, but shorter.

This shows that cosmic rays are really good things.

In fact, there are deep-seated reasons behind this.

In its later stages, modern physics is almost entirely concerned with the study of elementary particles.

However, with current technological conditions, it is impossible to build a large-scale particle accelerator.

So it cannot be studied.

Fortunately, the universe itself is a natural particle accelerator.

The vast universe is filled with various celestial bodies and extreme environments.

High temperature, high pressure, and ultra-strong magnetic field.
Various microscopic particles will naturally be born.

These particles are then emitted in the form of cosmic rays and are eventually received by humans.

Therefore, physicists can discover the mysteries of elementary particles from cosmic rays.

However, this kind of research is highly accidental and uncontrollable.

After all, no one knows what is in the rays.

It was not until the advent of particle accelerators that physicists were able to study microscopic particles more accurately and quantitatively.

In short, early cosmic rays played an important role in the development of physics.

At this moment, at Li Qiwei's suggestion, Compton said:
"The electrons inside the metal can move freely throughout the entire piece of metal."

"So photons shot at the metal can easily encounter electrons running around."

"According to the transition theory in quantum theory, these photons will be absorbed by electrons, causing the electrons to transition from a low energy level to a high energy level."

"That's why metals tend to absorb electrons and appear opaque."

"But for crystalline substances such as crystals and diamonds."

"Their structure is very neat, and the electrons are fixed around the nucleus and do not move around randomly."

"So the probability of a photon encountering an electron is very low, so fewer photons are absorbed by the electron and more photons are transmitted."

“Thereby creating a transparent effect.”

"So, glass is like crystal, which is transparent."

Wow!
Compton's explanation made everyone present suddenly realize.

It turns out that quantum theory is required to explain the light transmittance of glass.

"Oh my God! No wonder Professor Bruce said that quantum theory is one of the two pillars of modern physics."

“It turns out that even glass is related to quantum theory.”

"That's something humans invented thousands of years ago."

"This feeling of time and space interweaving across thousands of years is truly astonishing."

Everyone was amazed that quantum theory could be applied to glass.

One is a sophisticated physical theory, the other is ordinary glass.

There is actually a connection between them.

The mystery and fun of science are embodied at this moment.

At this moment, everyone suddenly thought of it.

"Doesn't that mean the problem has been solved?"

"Is Professor Bruce wrong this time?"

Listening to the discussions around him, Compton seemed to be confident.

In his opinion, his explanation was logically perfect and should be the answer.

Before the emergence of quantum theory, humans really knew nothing about glass.

But now, with a little light transmittance, it is easily achieved.

Even the many bigwigs in the front row nodded slightly.

They found Compton's explanation to be correct.

But is it really that easy?
That was the question Professor Bruce asked.

Only Millikan frowned, as if he always felt something was wrong.

Because Compton's answer is a bit too simple.

If Planck, Bohr, Rutherford and others were here, they would probably be able to think of the answer immediately.

and.

Millikan looked at Li Qiwei on the stage, who always had a faint smile on his face.

There was no emotional fluctuation due to Compton's answer.

This is unusual.

So, there must be a problem.

This is the intuition of the physics masters.

Millikan suddenly said:

"Bruce, there should be something wrong with Compton's answer."

Wow!
Millikan's words shocked everyone.

"How can such a perfect explanation be wrong?"

"We've already used such a sophisticated theory as quantum theory."

Even Compton thought it impossible.

But what a man Millikan was.

He is not only his mentor, but also a representative of the American physics community.

The other party's words definitely carry weight.

Compton suddenly felt a little unsure.

He looked at Millikan and then at Ridgway.

Finally it freezes on the stage.

Because Li Qiwei spoke.

"Yes, Compton's answer is wrong."

boom!
Li Qiwei's words were like a bomb dropped into the water.

Everyone present was stunned.

Even Compton was wrong!
Although the other party is young, he is also a well-known physicist.

As a doctoral graduate, he has a deep understanding of modern physics.

Otherwise, it would not be possible to think of using quantum theory to explain it so quickly.

However, Professor Bruce still said that the other party was wrong.

At this moment, everyone was a little confused.

Only Millikan showed an expression of "as expected".

At this moment, everyone was waiting for Professor Bruce's explanation.

Li Qiwei smiled and said:

"Laue used the regular arrangement of atoms in crystals to prove the wave nature of X-rays."

"Based on his work, the Bragg father and son developed crystal diffraction."

"Using X-rays, we can [see] the internal structure of the crystal."

"Calculate parameters such as the distance between atoms in the crystal."

“Crystal structure analysis has advanced by leaps and bounds.”

"When I visited Professor Prague's laboratory before, he introduced his latest research results to me."

"One of the conclusions was that the X-ray diffraction data showed that glass was not a crystal."

"Its main components are silicates formed by silicon dioxide and other oxides."

"Glass is an amorphous solid with no regular structure."

"So, Compton's explanation just now doesn't hold."

"Since glass is not a crystal, the atoms inside it are arranged randomly."

"The probability of a photon encountering an electron is greatly increased, so the probability of absorption is also greatly increased."

"Logically, glass should also be opaque."

“In other words, even if there is transparency, it should be very low.”

boom!
Everyone was shocked!

After all this fuss, it turns out that the glass that was sparkling was not crystal!

"Oh my God! This is the first time I know that glass is not a crystal?"

"How can this be?"

"Glass looks like crystal, so how can it not be a crystal?"

“It’s unbelievable.”

Compton was speechless.

If glass were not a crystal, then his answer would be the other way around.

But the fact is that glass is both amorphous and transparent.

This is a bit weird.

Yu Qingsong and others were stunned.

Is this the academic exchange between physicists?
It's absolutely wonderful.

Professor Li's knowledge made Yu Qingsong climax.

So handsome!

Astronomers such as Hale were already beginning to get confused.

He could still understand it at first, but now it has gradually gone beyond his knowledge.

Just because Ridgwell could make the jump from physics to astronomy doesn’t mean they can make the jump from astronomy to physics.

A small piece of glass is a watershed like a natural moat.

Millikan took a deep breath.

"Sure enough, I knew it wasn't that simple."

He was well aware that crystallography had been developing rapidly recently.

Every day, various new substances have their structures determined.

So it is not difficult to measure the structure of glass.

But the key point is that few physicists pay attention to this kind of knowledge.

Not to mention Bruce, the best in the world.

I can only say that the other party's knowledge reserves are too exaggerated.

suddenly.

Millikan thought back to the morning twenty years ago when he first heard Ridgway explain the photoelectric effect.

"what?"

“Perhaps it can be explained from this perspective.”

He smiled brightly.

"Bruce, I still have to look to you for inspiration."

So Millikan stood up.

(End of this chapter)