Seriously, sir? You can even pursue a professor?

Tang Zheng took the book back to the sofa, found a comfortable position, and began to study it.

Gamow truly deserves his reputation as a master; he writes in a way that is both profound and easy to understand, making complex mathematical and physical concepts vivid and interesting. Tang Zheng originally just wanted to flip through it casually, but before he knew it, he was engrossed in reading it.

The living room fell silent again, with only the occasional soft rustling of the two turning pages and the gradually fading chirping of cicadas outside the window.

Tang Zheng found the part explaining infinite sets and the concepts of countable and uncountable a bit convoluted. He didn't have a deep understanding of this part in his previous life, and now he only vaguely understood it.

He glanced at Ruan Hongzhuang across from him. She was still engrossed in that thick book, her expression focused, her profile softened in the dimming light.

"Aunt Ruan, this place... the set of all integers and the set of all even numbers can be matched one-to-one, so they are the same size... How do you understand this same size? It feels a bit counterintuitive."

Upon hearing this, Ruan Hongzhuang looked up from her book and gazed at the passage he was pointing to. She didn't answer immediately, but instead closed her book, placed it on the coffee table, and then got up and sat down next to Tang Zheng, about half an arm's length away from him.

The sofa sank slightly, and a very faint, fresh fragrance wafted over, like a shampoo mixed with her own clean scent, somewhat like grass after the rain, with a crisp soapy feel, which smelled especially good in the twilight air.

Tang Zheng's breathing paused slightly, and his attention was involuntarily drawn to this aura for a moment.

"This involves a definition and comparison method of infinity in set theory, proposed by Cantor," Ruan Hongzhuang's voice rang out nearby, seemingly clearer and gentler than usual.

She leaned slightly forward, her gaze falling on the pages of the book in Tang Zheng's hand. A few loose strands of hair fell down with her movement, swaying gently beside her fair cheeks.

Tang Zheng's gaze involuntarily followed those few strands of hair for a moment before quickly focusing back on the book.

"Look." Ruan Hongzhuang stretched out her hand and gently touched the sentence next to it in the book with the tip of her index finger.

Her fingers were beautiful, slender and long, with fair and delicate skin that seemed to glow warmly against the backdrop of the book pages. Her nails were neatly trimmed and clean, without any paint, and had a natural, healthy sheen.

"One-to-one correspondence is key. If we can find a way to ensure that every element in set A can be paired with a unique element in set B, and that every element in B is also paired, then we say that the two sets are equipotent, or that they have the same cardinality. In this sense, they are the same size."

As she spoke, her fingertips lightly traced the relevant words, guiding Tang Zheng's gaze. The trajectory of her fingertips was steady and clear.

"This is easy to understand for finite sets, but for infinite sets, some counterintuitive results emerge, such as..."

Her voice was soft and her pace was slow. She explained things very clearly. Tang Zheng listened, and his previous confusion seemed to be resolved to some extent, but new questions arose.

"Then...does that mean all infinite sets are the same size?" Tang Zheng turned to look at her and asked, the movement bringing him closer to her, making the light and pleasant fragrance seem even clearer.

Ruan Hongzhuang also turned her head slightly to look at him. The distance between the two was less than a foot. Tang Zheng could clearly see her long eyelashes that were clearly separated and her clear, watery eyes.

"No," she replied, her eyes still focused on the question. "Cantor also proved that the set of real numbers is larger than the set of integers because a one-to-one correspondence cannot be established. He used the famous diagonal proof method."

As she spoke, she casually took the book "From One to Infinity" from Tang Zheng's hand and quickly flipped to a later page. "Here, Gamow should be talking about it, you see..."

She spread the book out on the sofa between them, then moved closer, almost shoulder to shoulder, and the fresh scent lingered around Tang Zheng's nose even more noticeably.

Tang Zheng felt his heart skip a beat, so he quickly composed himself and looked at where she was pointing.

"Suppose we can list all the real numbers between 0 and 1 in a table..." Ruan Hongzhuang began to explain the idea of ​​the diagonal proof method. Her finger moved on the virtual table on the page, occasionally lightly tapping a key position. Her fingertip was rounded and left a very faint shadow on the paper.

Tang Zheng tried hard to concentrate on the lecture, but his eyes were always unconsciously drawn to the hand moving in front of him. The slender fingers made gestures with a unique rhythm, clean and neat, and with a kind of feminine gentleness.

"In this way, we can always construct a real number that isn't on the list, which creates a contradiction." After explaining, Ruan Hongzhuang looked up at Tang Zheng. "Therefore, the infinity of real numbers is at a higher level than the infinity of integers, do you understand?"

Tang Zheng was still a little confused, but looking into Ruan Hongzhuang's calm, questioning eyes so close to him, he subconsciously nodded: "I think... I understand a little."

Ruan Hongzhuang looked at him for two seconds, seemingly noticing the lingering confusion in his eyes. "It might feel a bit confusing at first," she said calmly. "Think about it more, or find some concrete examples to help you understand. For instance, the one-to-one correspondence between integers and even numbers—you can try listing out the first few items yourself to get a feel for it."

"Hmm." Tang Zheng nodded, feeling a little hot, unsure whether it was because of the brain-burning questions, the close proximity between them, or the lingering, refreshing fragrance unique to the person beside him.

"Then I'll take a look and ask you again if there's anything I don't understand."

"Mm." Ruan Hongzhuang nodded, picked up the book, and continued reading.

Tang Zheng's gaze fell on the pages of the book, but he found it hard to focus. Out of the corner of his eye, he saw a strand of hair falling down, a delicate earlobe, and a fair and smooth neck...

The living room was so quiet that you could hear your own heartbeat and the two of you breathing softly, almost as one.