94: From Technological Warfare to Space Empire

Chapter 117 Who in the world does not know you?

Besides Professor Wang, there were several other faces that looked familiar, but whose names I couldn't recall.

Some middle-aged and young scholars also came to the second and third rows.

By 9 o'clock, the entire venue was packed.

Academician Wang stood up and, without using a microphone, spoke with a strong and resonant voice.

"Please be quiet. I don't need to introduce our guest today."

"The extraction of titanium from steel slag caused quite a stir in Beijing a while ago."

"You've all seen the news about what happened on the 315 Gala not long ago; I bet no one doesn't know him."

"Extracting titanium from steel slag and making unleaded gasoline are just side projects that people do on the side."

"Today he's going to talk about something really big."

"Absolute zero and Bose-Einstein condensates!"

The room fell silent for a moment, then a hushed murmur arose.

Absolute zero?

Isn't that part of the third law of thermodynamics?

What new tricks can you possibly come up with if you keep talking about this?

Lin Yu stood up as Academician Wang introduced him, and greeted everyone again.

He then stood in front of the podium.

He placed the few sheets of paper he was holding on the table.

This is a draft he wrote a couple of days ago.

But he didn't actually need to look at it; some of the things were already etched into his mind.

He looked up and glanced at the curious, scrutinizing, and critical gazes from below the stage before speaking.

"Dear teachers and students."

Lin Yu spoke, his voice steady.

"Today I want to talk to you about cold, not the kind of cold that comes with winter."

"It's cold in a physical sense. That is, absolute zero!"

He turned around and wrote a few numbers on the blackboard:

-273.15℃

0 K

"This temperature exists in theory, but it can never be truly reached."

Lin Yu tapped the blackboard: "The third law of thermodynamics states it very clearly: it is impossible to cool any system to absolute zero through a finite number of operations."

"This is not a technical problem, it's a problem of principle."

Some people in the audience nodded in agreement; this is common sense.

"but..."

Lin Yu changed the subject.

"We can actually get infinitely close to it."

"Do you know what happens when you get infinitely close?"

Lin Yu drew a simple diagram on the blackboard.

A simple coordinate axis, with temperature on the horizontal axis and a certain physical quantity on the vertical axis.

"As we all know, temperature is essentially the intensity of the thermal motion of particles."

"The higher the temperature, the more energetically the particles move; the lower the temperature, the quieter they are."

"When the temperature drops low enough, the quantum properties of the particles will become apparent."

Lin Yu drew several small balls and some wavy lines on the blackboard.

"What is temperature? We all learned about it in junior high school. Temperature is a measure of how hot or cold an object is. The more vigorous the molecular motion, the higher the temperature."

"So here's the question..."

He paused, then wrote another word on the blackboard: limit.

Is there an upper limit to the temperature?

"Theoretically, no. The interior of a star can reach tens of millions of degrees, while a nuclear explosion can reach hundreds of millions of degrees in an instant."

"But is there a lower limit to the temperature?"

There was a moment of silence in the audience, then someone whispered, "Absolute zero."

"Yes, absolute zero!"

Lin Yu nodded. "Minus 273.15 degrees Celsius, the zero point on the thermodynamic temperature scale."

"At this temperature, molecular motion ceases, and the internal energy of the object reaches its minimum. But then another question arises..."

He turned around and glanced at the audience.

"What would matter look like at this temperature?"

The classroom fell silent.

Everyone present could answer this question: when molecules stop moving, matter solidifies and becomes a solid.

But everyone knows that the answer is not that simple.

Lin Yu picked up the chalk and drew a simple diagram on the blackboard.

According to classical physics, at absolute zero, matter should be in its lowest energy state, with atoms arranged in a perfect crystal, completely still.

"But quantum mechanics tells us that things are not that simple."

"The so-called uncertainty principle."

"The position and momentum at maximum speed cannot be determined simultaneously."

"If an atom is completely fixed at a certain point, its momentum will be infinitely uncertain, which means it has infinite kinetic energy."

Therefore, even at absolute zero, atoms cannot be completely stationary.

People in the audience started whispering among themselves.

They knew this statement, but Lin Yu's next words stunned them.

"So, what exactly do atoms do at absolute zero?"

Lin Yu paused, then said, word by word, "They will lose their individual identities and all become the same thing."

The classroom fell silent instantly; you could hear someone breathing.

Lin Yu turned around and wrote a few large characters on the blackboard: Bose-Einstein Condensate.

Lin Yu continued, "Classical physics tells us that particles are particles."

Quantum physics tells us that particles are also waves.

"At room temperature, we only observe particle-like properties."

"But at extremely low temperatures, volatility will dominate."

"At this point, the form of matter will change."

Lin Yu paused, then emphasized his words.

"It's not a solid-liquid-gas change. It's a more fundamental change, a reorganization of quantum states."

The lecture hall fell silent as people began to take notes.

Quantum mechanics is not something everyone can delve into; there are few books and few teachers these days.

They are extremely rare.

Lin Yu continued speaking.

From Kelvin's absolute temperature scale to Nernst's heat theorem, and the law that specific heat capacity decreases with the cube of temperature in the Debye model.

These are the theoretical framework, the foundation. If he doesn't explain these, the students probably won't be able to keep up.

He deliberately controlled the pace, narrating slowly and deliberately, like paving a path, so that the truly important things that followed could be steadily conveyed to everyone's hearts.

At this moment, the scrutinizing gazes from the audience subsided considerably.

The fact that he could explain all these things so clearly and eloquently made most of the students present feel ashamed of their own abilities.

But at this point...

For Lin Yu, knowledge was just beginning!

"So, here's the question."

Lin Yu put down the chalk and dusted off his hands.

"What happens when we lower the temperature low enough, say below one millionth of a Kelvin?"

His gaze swept across the audience, finally settling on the elderly gentlemen in the front row.

"In 1924, Bose sent Einstein a paper."

"Einstein realized the importance of this paper, personally translated it into German and published it, and did something even more important."

"He extended Bose's statistical methods to particles with mass."

Lin Yu turned around and wrote a formula on the blackboard.

He wrote down a formula: △.·△p≥h/2.

"Then Einstein predicted a phenomenon: when the temperature drops below a certain critical value, a large number of bosons will suddenly condense into the same quantum state."

"This is not partial condensation, but a macroscopic number of particles, millions, tens of millions! All of them are in the exact same state."

"Macroscopic matter will directly exhibit a quantum state!"

After saying this, Lin Yu paused slightly, letting his words echo in the air.

Let people digest this statement.