You All Feel the Fun Yet?

A professor from the School of the Big Mathematics Department, who teaches undergraduate students, said to Shen Qi, "Why are you still coming to class?"

Princeton is still far from being finalized, and Shen Qi's current situation is somewhat awkward. He has obtained his undergraduate degree in mathematics, but he cannot immediately pursue graduate studies.

Life seems to be lacking a little bit of passion.

To be fair, purely theoretical academic research is a tedious task, a tedious task that continues year after year, until death.

Shen Qi also wanted to know how to find some stimulation and fresh vitality in his long-term theoretical research.

Shen Qi needs to take the initiative and seek passion in the mundane.

"Li Zhenqiang!" Suddenly, a professor on the podium roared, sternly reprimanding, "What's wrong with you, student? You've been sleeping through my physics class all the time?"

Li Zhenqiang suddenly woke up, his eyes still sleepy. "I'm sorry, Teacher Sun, I was wrong!"

The old professor's face darkened. "My surname is Ren, not Sun! The one with the surname Sun teaches your Advanced Algebra!"

After the Advanced Algebra, first-year Mathematics Department students took University Physics class in the same classroom, taught by Ren Buqi.

Professor Ren, nearing retirement age, still has a very fiery temper. "You can't even remember the lecturer's surname, Li Zhenqiang, your participation grade is 0!"

Li Zhenqiang's name sounds domineering, but his personality isn't assertive; he backed down.

University Physics is a required course for the Mathematics Department. Mathematics and physics are intertwined, and it is difficult to completely draw a line between them. A love-hate relationship is the norm.

Ren Buqi is a professor in the School of Physics, where he teaches University Physics courses to students who are not majoring in physics.

Professors in the mathematics department also teach Advanced Mathematics courses to students who are not majoring in mathematics.

"The final exams are next month, and this year's Mathematics Department students are the worst I've ever taught!" Ren Buqi fury. The School of Physics at Peking University was very strong, and the professors there had a completely different style from those in the Mathematics Department.

Shen Qi was heartbroken. "Professor Ren, your reasoning is too biased. The average grades of our Mathematics Department students this year are absolutely crushing your Physics Department. A quarter of the Physics Department in our year failed Advanced Mathematics. Don't ask me how I know, I have an informant."

"And you, Shen Qi." After scolding Li Zhenqiang, Ren Buqi continued to Ren Buqi Shen Qi, "As the class monitor, your attendance rate in Physics class is less than 50%. What kind of class monitor are you? Just dismiss him." The mathematics department teachers didn't care much about Shen Qi anymore, but the physics department teachers paid a lot of attention to him.

"I really didn't set a good example," Shen Qi apologized. He admitted that he had been busy writing his math thesis and defending his degree this semester and hadn't paid much attention to physics.

Now that he has his Bachelor of Science degree in Mathematics, Shen Qi has made a plan to put a lot of effort into physics and seek a breakthrough in the branch of Mathematical Physics.

"There are about thirty people in your Mathematics Department, and only 15 people attended this class." Professor Ren's eyes flashed with murderous intent. "Shen Qi, what do you suggest we do?"

"Should I call them back to class?" Shen Qi asked tentatively.

"No need," Ren Buqi said coldly.

No need. Just three simple words, a mere ten strokes.

The students present understood the meaning behind it.

"Alright, let's not waste everyone's study time, let's continue the lesson." Ren Buqi paced back and forth on the podium, seemingly deep in thought.

After we stood still, Ren Buqi immediately came up with a problem. "If we remove all the desks, chairs, the podium, and everything else from this classroom, leaving only me and you, what is the ratio of our total mass to the air mass in the classroom? Just estimate it. This is a guaranteed question on the test."

Estimation is a commonly used technique in physics. Generally, the estimated result does not need to be very precise; it is sufficient if the difference in magnitude is not significant.

There is often more than one method for estimation. Mastering the methods is simple and fun, but if you can't think of them, you'll be at a loss.

The estimation problem that Professor Ren just created does not provide any specific data; it asks for the ratio of the mass of people in the classroom to the mass of the air.

"That's interesting." Shen Qi writes papers every day, but he gets irritable from writing too many papers. Doing some practice problems occasionally is a way to relax and unwind.

Shen Qi quickly scanned the classroom. There were 16 people in total: one teacher and 15 students. There was one woman and 15 men.

The classroom height is approximately twice the height of a person, and the width of the classroom can be estimated to be approximately 10 times the width of a person based on the number of rows of desks and chairs.

Based on the number of rows of seats in the classroom, including the additional rows calculated from the podium area, the length of the classroom can be estimated to be approximately 45 times the thickness of a human body.

Therefore, the volume of space occupied by a classroom is approximately 900 times the volume of a person.

Theoretically, this small classroom can hold 900 people at a time, stacked like building blocks until it's full.

By taking a ratio of 16 to 900, we obtain an estimated value for the ratio of human volume to air volume in the classroom.

The volume ratio has been estimated; to obtain the mass ratio, we need a set of density data.

The question then becomes: what is the appropriate density value for the human body?

The fact that humans can swim in water indicates that the density of the human body is similar to that of water.

The molar mass of water is 18, and the average molar mass of air can be approximated as 30.

Considering the close packing of water molecules, the spacing between air molecules is approximately several tens of times the size of an air molecule.

Shen Qi finally estimated a value of 10.

It can be approximated that the total mass of the 16 people in the classroom is 10 times the mass of the air in the classroom.

This estimate surprised Shen Qi slightly. Was it that humans were too light or that air was too heavy?

All of these observations and calculations were completed in Shen Qi's mind, taking about 15 seconds.

"How much?" Shen Qi asked Ou Ye beside him.

"10." Ou Ye also relied on mental calculation to arrive at the estimated value.

"That should be correct," Shen Qi said to Ou Ye. "You answer Professor Ren's question."

Ou Ye raised her hand.

Professor Ren: "Ou Ye, you've already estimated it? So fast? How much?"

Ou Ye: "10."

Snap!

Ren Buqi snapped his fingers, "Ou Ye is quick-witted and has a near 100% attendance rate; you should all learn from her. That's right, the answer is 10. The combined mass of everyone in this classroom is approximately 10 times the mass of the air. We only need to estimate the approximate order of magnitude; we don't need to worry about precision. This is different from your studies in Advanced Algebra and mathematical analysis. Physics is profound, all-encompassing, flexible, and full of fun. Have you felt the fun in learning physics?"

Shen Qi noticed that physics teachers seemed to all like to snap their fingers. His high school Physics Competition Team teacher did it, and his University Physics teacher did it too.

During the break, Professor Ren spoke to Shen Qi privately, "I know you've already received your bachelor's degree, and you don't have to come to my physics class, but shouldn't you urge the other students to attend?"

"It's my fault for not supervising them properly. Physics is very important for the Mathematics Department students. I will make sure they attend classes and improve the overall attendance rate," Shen Qi said.

"I heard you won a gold medal at the CPhO when you were in high school?" Ren Buqi asked.

Shen Qi nodded. "Yes, I did. My high school Physics Competition Team coach was a graduate of Peking University's School of Physics, a PhD in astrophysics."

"Oh, what's your name?"

"Teacher Mu Rong."

"So it's Xiao Mu, my student," Ren Buqi said calmly, exuding the air of a renowned teacher.

Shen Qi shuddered. "I am Teacher Mu's student, Teacher Mu is Professor Ren's student. So, according to the generational naming system, Professor Ren is my grandmaster!"