The river of time flows back to the summer of 1995.

“Ding-ling, ding-ling-ling-”

The evening self-study bell rings from the bottom floor of the teaching building. Students from Class Three of ninth grade come into the second-floor classroom one by one.

The graduation entrance exam is approaching, and students from the countryside bring their mats and quilts into the school dormitory, immersing themselves in the sea of books day and night…

On a cool and quiet summer night, the stars filled the sky.

Gang Chen stood on the corridor outside the classroom, looking up at the vast sky above the rooftop. The Big Dipper was clearly visible, like a huge question mark hanging high up in the sky. Sirius star kept flashing, like a dazzling diamond, shining bright and splendidly.

Observant Gang Chen accidentally noticed a strange star hidden behind the bright halo of Sirius. It sometimes stood still, and sometimes moved quickly. Too far away to judge, Gang Chen couldn’t decide whether it was an unscrupulous star or an unidentified flying object with a mysterious trajectory.

Under the dim starlight, Qingchun Huang walked from the playground.
Several old locust trees were full of pure white flowers, swaying in the wind, with a fragrant aroma. Qingchun Huang wore a light yellow shirt and plastic sandals. She picked up a bunch of fallen locust flowers by the playground, fragrant, delicate, and white as snow. She intended to bring the flowers into the classroom and let her deskmate Gang Chen smell them. But seeing Gang Chen standing alone in the corridor, gazing at the stars, she felt too shy to give him the flowers and just passed by with a blush.

Jie Dong , the physics teacher, was the patrol officer for evening self-study. Jie Dong  was always well-dressed and charming. He was a teacher who didn’t stick to the textbook and often taught his students some cutting-edge physics theories. In addition, Jie Dong  liked to ask random questions and wander around with his imagination.

At this moment, Jie Dong  wrote a question on the blackboard with chalk - “How were you born?”

Liang Ma  was called upon, he looked around and didn’t answer for a while. Just now, he seemed to be taking notes attentively, but in fact, he was drawing a funny cartoon for Jie Dong .

“How were you born?” Jie Dong  repeated, laughing at Liang Ma .

Liang Ma  felt a bit embarrassed. This question seemed simple, but actually quite tricky. If he didn’t answer well, he would be laughed at.

The students below chuckled…There was a course called “Physiology and Hygiene”, and the teacher’s explanation was so vague that everyone had already understood.

Liang Ma  scratched his hair and answered seriously, “I was born by my parents!”

Jie Dong  laughed heartily, “You got half of it right. From ancient times to the present, every one of us, including all animals, plants, mountains, and rivers, was born from a ‘singularity’ that was infinitely small in size, infinite in density, and infinite in temperature, 13.8 billion years ago. Our universe was gradually formed from the expansion of space-time after the singularity’s big bang, and underwent a series of physical and chemical reactions.”

Gang Chen raised his hand to ask, “Will our universe keep expanding forever?”

Faced with this question, Jie Dong  hesitated a bit. “Hopefully…It’s like a balloon, the more you blow it up, the bigger it gets, and then it will pop back to the singularity.”

The students were horrified. Does this mean our universe is doomed?

After explaining the birth of the universe, Jie Dong  took a sip of tea and then, holding his teacup, loudly asked, “There is a saying that goes, ‘tea gets cold when men abandon it’. In fact, whether people walk away or not, the tea will still get cold. Can anyone explain it?”

Gang Chen raised his hand to answer, “Because the heat of the tea will gradually transmit and diffuse into the surrounding space.”

Jie Dong  nodded. “This cup of tea is a miniature of the entire universe. If you don’t heat up the cup, the tea will naturally get cold. Your dormitory will get messier and messier, like a doghouse, if you don’t keep it tidy. And inevitably, you, who have been classmates for three years, will go your separate ways. This is the law of the increase of entropy - any open system will inevitably go from order to disorder. Currently, the observable diameter range of the universe is 93 billion light-years. But no matter how big the universe is, it cannot escape the law of entropy increase.”
Facing the group of teenage elites in the audience, Jie Dong  lectured fluently on the profound theories of advanced physics. He tried to make it easier to understand, but most of the students were still confused and unable to understand.

The night wind was strong, pouring in through the window in the corridor. A large group of moths fluttered towards the fluorescent tube on the ceiling of the classroom, burning themselves and flying around the room.

Jia Xu sat in the back row with Liang Ma , who had short hair and was a smart and competent girl. She quietly threw a small piece of paper to Liang Ma . But with too much force, the paper went over the desk and landed in the aisle.

This scene happened to be noticed by Jie Dong .

Jie Dong  walked down from the podium, picked up the small piece of paper from the ground, and watched it with interest.

Liang Ma  was nervous and curious, wondering what secret was hidden in the small piece of paper Jia Xu threw to him.

Jia Xu, however, remained indifferent and looked at Jie Dong  calmly, as if daring to do anything, righteous and resolute.

The eyes of the whole class were focused on the small piece of paper in Jie Dong ’s hand, waiting for the moment when the secret would be revealed.

Jie Dong  glanced at Jia Xu and Liang Ma  but remained silent. He then threw the small piece of paper out the window and into the enclosed wilderness between buildings, as if nothing had happened.

Jia Xu was a little disappointed and almost confessed that there was a piece of chocolate truffle inside!

Jie Dong  returned to the podium, picked up a chalk, and tapped on the blackboard. As everyone knew, he was going to call someone’s name to answer a question.
As expected, Jie Dong  sighed heavily and said, “You little kids have been influenced by Hong Kong and Taiwan dramas, what’s with all this puppy love? Do any of you know what the most faithful love in the world is like?”

Qingchun Huang was afraid that Jie Dong  would call her out, so she quickly hid the locust flowers in the bottom drawer and felt a little guilty. Her secret crush was Lambert, the boy who sat next to her.

Jie Dong  directly called out, “Jia Xu, why don’t you share your thoughts?”

Jia Xu was amazed and thrilled. She didn’t have good grades and was rarely called on by the teacher. She stood up, fixed her hair, and said without hesitation, “Love is mutual. When there’s candy, we share it. We face challenges together!”

The classmates burst into laughter.

Jie Dong  didn’t laugh. He signaled for Jia Xu to sit down, then picked up a chalk, snapped it in half, and held each piece in his hands. He spread his arms and said, “Let me give you an example. These are two subatomic particles. If we set them to be in a quantum entangled state, and then separate them; no matter how far apart they are in the universe, if one particle’s state changes, the other particle will also change correspondingly. True love is like quantum entanglement: not only do hearts connect, but it can also transcend time and space!”

The classmates were confused again. Jie Dong  actually explained love with unproven quantum mechanics theory. Away from worldly tumult, and reaching the edge of the universe…

Qingchun Huang listened attentively, imagining the mysterious “quantum entangled state”. She turned her head and stole a glance at Lambert, blushing secretly. Meanwhile, Gang Chen was totally unaware and focused on the lecture.

The weather on a summer night was unpredictable.

A fine rain began to drift outside the window. Qingchun Huang quietly played with the locust flowers in the drawer but still didn’t have the courage to give the petals to Lambert. The thoughts of a sixteen-year-old girl were like the drizzle in spring, gentle and charming, inexpressible, sweet yet melancholic…

As expected, Jie Dong  sighed heavily and said, “You little kids have been influenced by Hong Kong and Taiwan dramas, what’s with all this puppy love? Do any of you know what the most faithful love in the world is like?”

Qingchun Huang was afraid that Jie Dong  would call her out, so she quickly hid the locust flowers in the bottom drawer and felt a little guilty. Her secret crush was Lambert, the boy who sat next to her.

Jie Dong  directly called out, “Jia Xu, why don’t you share your thoughts?”

Jia Xu was amazed and thrilled. She didn’t have good grades and was rarely called on by the teacher. She stood up, fixed her hair, and said without hesitation, “Love is mutual. When there’s candy, we share it. We face challenges together!”

The classmates burst into laughter.

Jie Dong  didn’t laugh. He signaled for Jia Xu to sit down, then picked up a chalk, snapped it in half, and held each piece in his hands. He spread his arms and said, “Let me give you an example. These are two subatomic particles. If we set them to be in a quantum entangled state, and then separate them; no matter how far apart they are in the universe, if one particle’s state changes, the other particle will also change correspondingly. True love is like quantum entanglement: not only do hearts connect, but it can also transcend time and space!”

The classmates were confused again. Jie Dong  actually explained love with unproven quantum mechanics theory. Away from worldly tumult, and reaching the edge of the universe…

Qingchun Huang listened attentively, imagining the mysterious “quantum entangled state”. She turned her head and stole a glance at Lambert, blushing secretly. Meanwhile, Gang Chen was totally unaware and focused on the lecture.

The weather on summer nights is capricious.

Fine rain drifted outside the window. Qingchun Huang quietly fiddled with the locust flowers in the drawer but never had the courage to give the petals to Lambert.The thoughts of a sixteen-year-old girl were like the spring rain, affectionate and tender, but she couldn’t express them, sweet and sorrowful…