Chapter 439 The whole audience was shocked! Explaining the transparency of glass requires quantum theory? !
When Li Qiwei asked "Why is glass transparent?", the venue fell into silence for an instant.
Everyone seemed to have stopped in time, with their eyes wide open and their mouths wide open.
I seem to have heard something incredible.
After more than ten seconds, the atmosphere in the venue exploded.
There were countless sounds of surprise.
Many people were shocked by Li Qiwei's question.
“Oh! God! What’s the problem?”
“Isn’t glass inherently transparent? What else could be the reason?”
“It’s like Stone and metal are all opaque.”
"I feel like there's nothing worth discussing."
There are many non-science and engineering students in the venue today.
In their opinion, Professor Bruce's question is too strange.
Normal people would never think about why glass is transparent.
But for those students and teachers majoring in physics, this question is very interesting.
"Oh my god! It seems that I have never thought about this problem."
"Except for diamonds, ice, crystals and other countless substances in nature, most substances are opaque."
"Transparency should be a very rare property, but no one seems to have studied the transparency of glass."
"I have to say that Professor Bruce is too 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 another expansion of the boundaries of human knowledge.
If there is some kind of "ultimate problem" in this world, then human beings will definitely be ecstatic.
Faced with this problem, most ordinary students can only watch the excitement.
Geniuses such as Wu Youxun, Compton, and Hubble frowned and began to think deeply about this issue.
They knew that the question raised by Professor Bruce was definitely not as simple as it seemed.
Such as:
"Glass is inherently transparent."
"The light passes through, so it becomes transparent."
These There is certainly no point in talking nonsense.
It must be explained from a more essential theoretical perspective.
Even not only explain glass, but also explain why other substances are opaque.
But what theory would it be?
Haier in the front row looked confused at the moment.
He has been in the field of astronomy for decades and is an internationally renowned astronomy expert.
But he was ashamed that he had never thought about this issue.
He spends more time with the telescope than he does with his wife.
As for why glass is transparent, he has always ignored it.
“Is it enough if it can be used?”
Haier is sure that many astronomers present today have the same idea as himself.
"Professor Bruce, you are here to teach us a lesson."
Millikan next to him had a penetrating gaze.
As a big boss in the American physics community, he has met Professor Bruce a lot.
So, he knows that man very well.
He said to Haier:
"This is the magic of Professor Bruce."
"He can always make people interested in science from very small things, from small things to big things."
"Don't look at it. The question is very simple, but the theory contained in it is definitely very difficult.”
“I even guessed that no one here could answer this question.”
Haier was surprised when he heard this.
"Oh! That's impossible!"
"Can't you even answer Professor Millikan?"
"That's incredible."
Millikan smiled bitterly. A sound:
“At least I don’t know.”
Although he is a leader in the field of physics in the United States, compared to the rest of the world, he can only be regarded as a T4-level physicist.
What’s more, you can tell at a glance that this question is related to theory.
Theory is the weakness of experimental physicists like Millikan.
Haier was really shocked now.
Originally, he thought that this problem should be solved in the world of physics or materials science.
It’s just that because it’s too cutting-edge or the theory is too partial, laymen rarely hear it.
But for a physics master like Millikan, it is certainly not difficult.
Unexpectedly now, I don’t even know the other party.
This is a bit scary.
After Li Qiwei finished asking the question, he looked at the people in the audience quietly.
He was waiting for someone to answer the question.
Millikan was not wrong. This question is indeed difficult.
Therefore, many students did not dare to stand up, but scratched their heads or thought silently.
There are so many big guys at the venue today. It would be embarrassing if you gave the wrong answer.
And most people never think about this problem.
You can imagine how difficult it is to think of answers and organize language in such a short time.
Although science in Europe and the United States is developed, it does not mean that students in their countries must be awesome.
Most people are just ordinary students.
Just as Li Qiwei scanned the entire venue.
Suddenly.
Under the surprised looks of Wu Youxun and others, Yu Qingsong stood up.
When Li Qiwei saw a Chinese face standing up on his own initiative.
His eyes immediately burst into light, a smile appeared on his face involuntarily, and he was very happy in his heart.
Since ancient times, China has emphasized the so-called moderation, balance, shooting the first bird, etc.
Neither too high-profile nor too low-key.
You can neither be too pushy nor too cowardly.
Especially after experiencing the ravages of the West, this concept has developed to a more negative side.
Without Li Qiwei, China’s right to speak in the field of science can be said to be completely equal to zero.
This will cause international students to have low self-esteem.
They are afraid to express their scientific opinions in front of a group of Westerners.
Because they feel in their hearts that they are inferior to others, and they will be laughed at if they speak out.
However, now, Li Qiwei is standing on the high platform, and he is the anchor of stability in the hearts of all Chinese students studying abroad.
His brilliance and aura made the Chinese people talk about him with disgrace, and foreigners did not dare to look directly at him.
His wisdom and achievements have crushed all the smart people in the world.
On today's occasion, young people like Yu Qingsong have already become excited.
A fire rose up in their hearts, burning away all the previous humiliation, fear, negativity and other emotions!
At least in the field of science, he, Yu Qingsong, must set an example.
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 mind 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.
This is a talent 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, he seemed to have an invisible power injected into his body.
Let him calm down slowly.
With Li Qiwei's encouragement, he said firmly:
"Professor, I took several optical courses during my undergraduate period."
"I want to try to answer this question."
Wu Youxun and others looked at Yu Qingsong with admiration and gave a thumbs up secretly.
“Well done, Qingsong!”
People from other countries in the venue were extremely emotional at this moment.
“Chinese people are different from before!”
Many older professors have even taught foreign students from the Qing Dynasty.
In their opinion, Yu Qingsong is full of vitality now and does not have the smell of decay.
And it can be seen from the purity in the other person's eyes 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 by this thing is absorbed by our eyes.”
“And the object’s Color depends on the color of the light it reflects. "When a beam of light interacts with an object, three situations occur: reflection, Absorption, transmission.”
"The more light an object reflects or absorbs, the less light is transmitted, making the object more opaque."
"For example, many metals sparkle because they reflect a lot of light."
“Mirrors use this principle of metal to coat the surface with a layer of light. After smooth metal, a mirror is formed that can reflect the picture. ”
“But objects such as stone and wood do not have a bright luster.”
“This shows that they reflect. There is very little light, and most of it is absorbed, so it is also opaque.”
"In addition, metal not only reflects light, it also absorbs light."
"Professor, your photoelectric effect is a good proof of this."
"As mentioned in the review, due to Any object will reflect part of the light, so we only need to consider the absorption of light."< br>
“The core of the question now becomes: Why do atoms in glass not absorb light, while atoms in metal, stone, wood and other substances absorb light better.”
“If it can be explained If you understand this problem, you will know the essence of why glass is transparent. ”
Wow!
Yu Qingsong’s rigorous logical analysis surprised everyone present.
The depth of this kind of analysis is nothing to the big guys in physics.
But for a sophomore, it is very rare.
Especially because the other party is an astronomy major, not a physics major specializing in optics.
This shows how solid the basic knowledge is.
Everyone stared at Yu Qingsong curiously, making him feel nervous again after just relaxing.
After hearing this, Li Qiwei was very satisfied.
Considering the average level of this era, Yu Qingsong’s answer can already be regarded as excellent.
Although it cannot be compared with the peerless geniuses such as 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 of glass are so special and do not absorb light?"
Yu Qingsong's brain was running wildly, but in the end he said honestly:< br>
“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."
Yu Qingsong just finished speaking. , there were sounds of regret in the venue.
Everyone thought he could solve this problem.
Unexpectedly, it failed in the end.
But no one laughed at him.
Because no one knows how to do it themselves
Li Qiwei was not surprised when he heard this.
Yu Qingsong does not yet have the knowledge base to answer this question.
But his performance just now deserves praise.
Under Li Qiwei's approving gaze, Yu Qingsong slowly exhaled and sat down on his seat.
At this time, Li Qiwei continued: "The answer just given by classmate Yu Qingsong is actually the answer to the first level."
"But at this level, for physics For scientists, it is far from enough.”
“So, we must go deep into the level of microscopic particles.”
"So, can anyone continue to answer this question based on what Yu said?"
The answer on the first level is the limit that most people present can know.
After all, Yu Qingsong is just an undergraduate 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 it.
Compton is one of them.
I saw him suddenly stand up and said confidently:
"Professor Bruce, I have some ideas."
Compton had wanted to see Ridgway again since his last departure in Borneo.
It was precisely because of the other party's encouragement that he was able to persist in his project and finally succeeded.
So Compton was very grateful to Li Qiwei in his heart.
At the same time, he is also grateful to Wu Youxun. Without him, there would be no Wu-Compton effect.
Now, he can be regarded as entering the circle of physicists for the first time.
Only after entering this world did he realize how broad the scientific sky is.
How incredible is Professor Bruce’s strength?
So, Compton, who has become famous, has not stopped. He is still chasing the peak of physics.
In real history, Compton later, like Millikan, devoted himself to the study of cosmic rays.
And the [Inverse Compton Effect] was also discovered.
That is, after the photon and electron collide, the wavelength of the photon does not become longer, but becomes shorter.
It can be seen that cosmic rays are really a good thing.
Actually, there are deep-seated reasons for this.
In the later stages of modern physics, almost all of it was about the study of elementary particles.
But with the current technical conditions, it is simply impossible to build a large particle accelerator.
So it cannot be studied.
Fortunately, the universe itself is a natural particle accelerator.
The vast universe is filled with all kinds of celestial bodies and extreme environments.
High temperature, high pressure, and super strong magnetic field.
A variety of microscopic particles can naturally be born.
These particles are emitted in the form of cosmic rays and are eventually received by humans.
So, physicists can discover the mystery of elementary particles from cosmic rays.
But this kind of research is highly accidental and uncontrollable.
After all, no one knows what is in the ray.
It was not until the advent of particle accelerators that physicists could study microscopic particles more accurately and quantitatively.
In short, early cosmic rays played an important role in promoting the development of physics.
At this moment, under Ridgway’s signal, Compton said:
“The electrons inside the metal can move freely throughout the whole piece of metal.”
“So the shot Photons traveling toward metals 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 jump from a low energy level to a high energy level. ”
"This is why metals easily absorb electrons and appear opaque."
"But for crystal materials such as crystals and diamonds."
"Their structures are very neat, and the electrons are fixed in There is no random movement around the nucleus. "
"So the probability of photons encountering electrons is very low, so the electrons absorb fewer photons and transmit more photons."
" This creates a transparent effect.”
"Therefore, the crystal of glass is the same as crystal, that is, it is transparent."
Wow!
Compton’s explanation made everyone present suddenly realize.
It turns out that quantum theory is used to explain the light transmittance of glass.
"Oh God! No wonder Professor Bruce said that quantum theory is one of the two pillars of modern physics."
“Even glass is related to quantum theory.”
“That was something invented by humans thousands of years ago.”
“This sense of interlacing time and space that spans thousands of years , It’s really shocking.”
Everyone was shocked by the fact that quantum theory can be applied to glass.
One is a lofty physical theory, and the other is ordinary glass.
There is actually a connection between them.
The mystery and fun of science are materialized at this moment.
At this time, everyone suddenly thought.
"Does that mean the problem has been solved?"
"Is Professor Bruce wrong this time?"
Listening to the comments from people around him, Compton seemed to be confident.
In his opinion, his explanation is logically perfect and should be the answer.
Before the advent of quantum theory, humans knew nothing about glass.
But now, with its small translucency, it can be easily removed.
Even the many big guys in the front row nodded slightly.
They found nothing wrong with Compton's explanation.
But is it really that easy?
That is the question raised by Professor Bruce.
Only Millikan frowned. He always felt that something was wrong.
Because Compton's answer is a bit too simplistic.
If Planck, Bohr, Rutherford and others were here, I am afraid they would have thought of this answer immediately.
And.
Millikan looked at Li Qiwei on the stage, who always had a faint smile on his face.
There were no mood swings because of Compton's answer.
This is abnormal.
So, there must be something wrong.
This is the intuition of the physics master.
Millikan suddenly said:
"Bruce, there must be something wrong with Compton's answer."
Wow!
Millikan's words shocked everyone.
“How can such a perfect explanation be wrong?”
“We have already used such a high-level theory as quantum theory.”
Even Compton It seems impossible.
But what a character Millikan was.
Not only is he a great leader, he is also a representative of the American physics community.
The other party’s words definitely carry weight.
Compton suddenly felt a little unconfident.
He looked at Millikan and then at Li Qiwei.
Finally settled 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 still a well-known physicist.
He graduated with a Ph.D. and has a deep understanding of modern physics.
Otherwise, it would be impossible 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 that was indeed the case.
At this moment, everyone is waiting for Professor Bruce’s explanation.
Li Qiwei said with a smile:
"Laue used the regular arrangement of atoms in crystals to prove the wave nature of X-rays."
"The Braggs developed crystal diffraction based on his work."
"Using X-rays, we can [see] the internal structure of the crystal."
"Calculate the crystal The distance between atoms, etc. Parameters."
"Crystal structure analysis has developed by leaps and bounds."
"When I visited Professor Bragg's laboratory before, he introduced his latest research results to me."
“One conclusion is that according to X-ray diffraction data, glass is not a crystal.”
“Its main component is silicate formed from silicon dioxide and other oxides.”
“Glass is an amorphous solid with an irregular structure.”
“So, Compton’s explanation just now is not valid.”
“Since glass is not a crystal, Then the atoms inside it are arranged chaotically.”
"The probability of photons encountering electrons is greatly increased, so the probability of absorption is also greatly increased."
"Logically speaking, glass should also be opaque."
"Or even if If there is transparency, it should be very low.”
Boom!
Everyone was shocked!
After fussing for a long time, Bulingbuling’s glass turned out not to be crystal!
"Oh God! This is the first time I know that glass is not a crystal?"
"How is this possible?"
"Glass looks like crystal, how can it be? Not a crystal?”
“It’s incredible.”
Compton was speechless.
If glass is not a crystal, then his answer should 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 an academic exchange between physicists?
It’s really wonderful.
The various knowledge that Professor Li had at his fingertips made Yu Qingsong climax directly.
So handsome!
Haier and other astronomers have begun to be confused.
He could still understand it at first, but now it has gradually fallen out of the scope of his knowledge.
Li Qiwei can cross from physics to astronomy, but it does not mean that they can cross from astronomy to physics.
A small piece of glass is a watershed like a chasm.
Millikan took a deep breath.
"Sure enough, I knew things were not that simple."
He was well aware that crystallography was developing at a rapid pace recently.
Every day, various new substances have their structures measured.
So it is not difficult to measure the structure of glass.
But the key is that few physicists pay attention to this kind of knowledge point.
Not to mention Bruce, the number one person in the world.
It can only be said that the other party's knowledge reserve is too exaggerated.
Suddenly.
Millikan thought again about the morning twenty years ago when he first heard Li Qiwei explain the photoelectric effect.
“Huh?”
“Maybe it can be explained from this perspective.”
He smiled brightly.
"Bruce, I still have to look for inspiration from you."
So, Millikan stood up.
(End of this chapter)