Accompanied by this classmate, Xu Mang came to a classroom in the physics department building, and he found a problem, this guy didn't bring any books, and there were more than a dozen people in the entire classroom who had no books.

What's going on?

Is this major a scumbag?

"Brother?"

"Why didn't these people bring books?" asked Xu Mang curiously.

"Auditors. The little brother said indifferently: "It's about the same as you." ”

“...”

"What about you?" asked Xu Mang with a black line on his face.

"Me?"

"Of course, I was also an observer. The little brother smiled: "But I am a little better than those of them, including you, in astrophysics and physics." ”

it!

Run into a pretending criminal!

Boy... Dare to pretend to be forced in front of me Xu Mang?

Xu Mang is so angry, he has always been tricked by himself, but today he was tricked by others, the problem is that he was tricked by a graduate student, which is the biggest stain in the history of his routine.

"Alas!"

"Does your family know that you are so awesome?" Xu Mang asked helplessly, "Good guy... Obviously, you're an auditor like me, how did you pretend to be an astrophysics major?"

“...”

"Can't say that. The brother smiled bitterly, "I may be a little better than you, of course... I mean, maybe. ”

"Dare to ask where the brother is sacred?" asked Xu Mang.

"Du Yuan. ”

"Oh..."Xu Mang nodded and said silently, "Do you know who I am?"

Du Yuan was stunned for a moment, and said indifferently: "It has nothing to do with me who you are, it's just that you just meet in Pingshui, maybe after tomorrow, we won't have any intersection, so I don't know the name, it's okay, less worry, more obsession." ”

Xu Mang: (°ー°〃)

Hell yes!

Run into an opponent who is evenly matched.

It feels like he's the one who's crazy.

soon

A rather dignified professor walked in, didn't name him or anything, and went straight to class.

"Today we will mainly explain the physical properties of neutron stars. "Although this professor is an acute child, he has a lot of knowledge, which can be inferred from his hairstyle and volume, after all, he is extremely intelligent.

"When massive stars reach an advanced stage of evolution, a huge iron core will accumulate through nuclear combustion, and when this iron core reaches a certain mass, it collapses due to excessive pressure, producing violent gamma-ray bursts and supernova explosions, so that a neutron star is born. ”

"Actually, a neutron star is a superdense star composed of neutron matter, and how dense is a neutron star? Give you five minutes to estimate the density of a neutron star, first of all, the mass of a neutron star is about the same as that of the sun, with a radius of ten kilometers. ”

"The radius of the Sun is 700,000 kilometers and the density is (1.4g/cm^3). ”

Words fall,

The professor said solemnly, "Let's start the math, it's five minutes." ”

Soon everyone began to calculate, and of course there were a dozen or so auditors who belonged to Bai Zhishi, sitting silently in their seats, waiting for the answer to be announced.

Xu Mang watched the students present making nervous calculations, and couldn't help but feel a little confused, and asked curiously: "Alas... It's a freshman, right?"

"How do you know?" Du Yuan said in surprise: "It's indeed a freshman." ”

“...”

"I don't even know the rapid conversion of two stars of the same mass, what do you say is not a new birth?" Xu Mang said helplessly: "When two stars with the same mass, their density is inversely proportional to the cubic of the radius. ”

Du Yuan was stunned for a moment, and said with a skeptical expression: "Are you sure?"

“...”

"Are you doing research in the astrophysics group?" Xu Mang asked, "Don't tell me, you are simply in charge of calculations?"

Du Yuan nodded awkwardly: "Then do you know this density?"

"Do you have a pen and paper?"

"Yes!"

I don't know where Du Yuan took out the pen and paper and handed them to Xu Mang.

In less than ten seconds,

Xu Mang completed the calculation of neutron star density, Pns=(R/Rns)^3xP≈(700000/10)^3x1.4≈10^14(gcm^-3)

"Give!"

After Du Yuan got the answer, he looked at Xu Mang with a frightened expression, and asked cautiously, "Brother... Isn't that right?"

"You give it a try. Xu Mang shrugged his shoulders and said indifferently.

The reason why Xu Mang gave up the answer was that he didn't want to bear the title of autism maker anymore, and he wanted to give this title to Du Yuan.

Du Yuan thought for a while, hurriedly raised his hand, and shouted at the professor: "Professor, I'm done!"

As soon as the voice fell,

It caused an uproar.

"You are..."

"Auditor?" the professor saw Du Yuan and saw that there were no textbooks on his desk, so he understood that this person had come to audit.

"Hmm!" Du Yuan nodded.

forthwith

The professor came to Du Yuan's side, glanced at his answer, and couldn't help but praise: "Which department are you from?"

"The Department of Mathematics..."

"I'm a graduate student, and I happen to be in the astrophysics research group, where I'm in charge of the calculation program. Du Yuan said seriously: "In order to strengthen my business ability, I came to listen to the class, I have been listening to your class, and I have kept in mind some of the knowledge points you taught." ”

Xu Mang:( ̄△ ̄;)

Talent!

No

It's a wolf extermination.

"Not bad!"

"It's good to be self-motivated, keep up the good work. The astrophysics professor nodded repeatedly.

Followed by

The professor returned to the podium and began to continue his lecture.

“...”

“...”

Xu Mang looked at Du Yuan, Du Yuan looked at Xu Mang, and neither of them spoke.

"Brother!"

"You're so awesome!" Du Yuan said to Xu Mang with a look of admiration: "Don't say anything, I'll treat you at noon." ”

Xu Mang smiled bitterly: "You... How did you get into NTU?"

"I'm good at math, but I don't know anything about astronomy. Du Yuan sighed: "If it weren't for the sake of mixing up a paper, what kind of astrophysics would the ghost learn." ”

“...”

"Good work. ”

At this point,

The professor threw another conundrum.

"Pulsars are neutron stars that rotate at high speed, and the rotation speed of pulsars is very fast, some can even reach more than 1,000 revolutions per second, such rapid rotation, coupled with magnetic fields and extreme conditions, will cause the poles of the pulsar to produce collimated electromagnetic radiation. ”

"Here's a question for you, who can prove that pulsars are neutron stars by means of numerical calculations?" the professor asked, "Think about it." ”

Xu Mang sat in the last row, witnessing everyone's bewildered looks, as if he had passed by.

In fact

Astrophysics is a completely new major, which can only be accessed in college, and it is also available at top universities, and these students are also unlucky... These things were never taught in high school.

It means that everyone is starting from scratch, and in addition to the professor's teaching, they also need another channel to acquire knowledge, otherwise they will definitely be eliminated.

"Paper and pen!" Xu said.

"Oh..."

Du Yuan hurriedly handed it to Xu Mang.

soon

Xu Mang used a simple Newton's law of universal gravitation and the formula of centrifugal force to give a calculation proof that a pulsar is a neutron star, in fact, you only need to grasp a concept, and the centrifugal force of the pulsar is less than the gravitational force, otherwise the pulsar will disintegrate.

Following this concept, it is possible to make very detailed calculations using the law of gravitation and the formula of centrifugal force.

The relationship between the pulsar density (p) and the period (P) is p>3π/P^2xG, and G is the gravitational constant.

The pulsar period in the Crab Nebula is 33 milliseconds, and the density is 10^11g/cm^3, which is greater than that of the white dwarf, and the density is 10^13g/cm^3, based on the current fastest rotating pulsar period of 1 millisecond.

Approximate density estimates for neutron stars.

"Give!"

"It's done. Xu Mang handed the answer to Du Yuan.

Du Yuan: Σ(っ°Д°;) っ

Oh, my God!

Is he really the reincarnation of Albert Einstein?

"Ahem!"

"Professor!" Du Yuan took Xu Mang's answer and shouted at the professor, "I'm done proof." ”

“？？？”

“？？？”

“？？？”

it!

Who is this guy?

Is it really an auditor?

Everyone stared at Du Yuan, only Xu Mang looked at the incandescent lamp on the ceiling with a cute face.

The professor hurriedly came to Du Yuan's side, looked at the answer in his hand, looked at it carefully for more than thirty seconds, and said solemnly: "Classmate... Are you sure you're in the math department? Are you in the math department? Are you amnesiac in the physics department?"

“...”

"Professor, I'm really here to sit in. Du Yuan said helplessly: "Is it right to prove the result?"

"Perfect!"

The professor smiled: "I didn't expect that there was a genius among the auditors." ”

In addition to emotion,

The professor returned to the podium and continued his lecture.

"Neutron stars are not only dense, but also have very strong magnetic fields, and let's take the sun as an example, compress the sun into a neutron star, of course... Naturally, this may not be true, because when the sun collapses, only white dwarfs can form. ”

"If the Sun compresses a neutron star, then its magnetic field will be..."

When the professor said this, he suddenly remembered that there was a genius in his class, and said with a smile: "The genius sitting in the last row, you go to the blackboard and calculate for everyone the magnetic field conversion between the sun and the neutron star." ”

Du Yuan was already confused, he didn't even know the strength of the surface magnetic field of the sun, how could he calculate the magnetic field conversion between the sun and the neutron star.

The previous two pretenses relied entirely on the answers provided by Xu Mang.

Right now...

Calculate in front of everyone, isn't this forcing people to hang themselves!

Sure enough, pretending to be forced is risky!

"I..."

"This..."Du Yuan, a fake astrophysics genius, no longer knew what to do.

"Classmates!"

"Everyone is waiting for you, please hurry up and don't waste everyone's time. The professor smiled and said, "It's not too difficult for you." ”

Xu Mang glanced at the poor man beside him who was forced to hang himself, and said helplessly: "Remember... Conservation of magnetic flux means that the magnetic field lines on the surface of the star are compressed, and the calculation is carried out according to this concept. ”

Hearing Xu Mang's words,

Du Yuan was even more desperate.

Eldest brother!

I don't understand!

"Classmates!"

"Don't be struggling, come up quickly!" the professor urged.

No way

Du Yuan could only get up silently, but his heart was tormented.

Just about to take this difficult step, Du Yuan suddenly woke up, instead of being exposed on the spot, it was better to reveal the truth now, and then pointed at Xu Mang, and said with shame on his face: "Professor... I confess... The previous two answers were given to me by this person, but I don't know anything. ”

_(°Д°)/Professor, I report, he did it!

Σ('д′*ノ)ノ Sleeper, you two or five boys?!

Words fall,

There was another uproar in the classroom.

What's the situation?

Twists and turns!

This plot is confusing... I can't even read it.

......