"You sound like you don't want Yang Dong to follow the path of physics."
David set down the photo album.
"Perhaps intellectuals are authorities in their own fields, but when facing the real world, they can also be weak," Ye Wenjie shook her head gently, her expression complex. "Compared to men, women exhibit this even more clearly. A woman should be like water, able to flow anywhere."
As she spoke, Ye Wenjie might have been thinking of her mother, or perhaps herself. But a knock at the door interrupted her reminiscence.
"They're here... it should be Yang Dong returning."
Ye Wenjie opened the door.
"Hello, Professor Ye!"
"Professor Ye!"
Seeing Luo Ji, who had returned with Yang Dong, carrying bags of gifts, David and Ding Yi exchanged a glance. They spread their hands simultaneously, a hint of embarrassment flashing in both their eyes.
"You're already here, why bring so many things?" Ye Wenjie cheerfully pulled Luo Ji and Ding Yi into the house.
"A small token for an unannounced visit," Luo Ji said as he followed Ye Wenjie inside to put the grains he brought into the kitchen.
"I don't know why, but there was a power circuit issue at the Peking University cafeteria today. Yang Dong suggested we all come here to eat," Ding Yi explained. After the initial awkwardness, he quickly adjusted his mindset.
As the "culprit" behind the power surge, David could only offer silent sympathy and understanding.
"I didn't know you were here before I came," Ding Yi whispered into David's ear as they sat on the sofa together, slicing a fruit platter.
"I actually just arrived myself," David explained, seeing that Ding Yi had misunderstood something. "Peking University cafeteria? Why, is the Liangxiang laboratory finished?"
"Not yet. There's been a small problem with the engineering."
Since this wasn't their first meeting and they were in Ye Wenjie's Beijing home, the relationship between Ding Yi and David warmed up quickly through small talk.
"There was a glitch in the processing of the liquid helium used as coolant for the last batch at the Western Nanopharmaceutical Base. All the original products were returned, and the industry needs to be restructured in a short time."
Ding Yi knew David was a student from Handong University's Physics Department, so he spoke without reservation.
Liquid helium, also known as LHe, is transparent, odorless, and tasteless. Under normal pressure, it never freezes into a solid. It has no triple point and only enters a solid phase when pressure exceeds 2.5 MPa. It exhibits a lambda transition, where specific heat and density change abruptly at the melting point (2.172K). It also possesses superfluidity, crawling film phenomena, and superconductivity, with a viscosity coefficient close to zero.
Elemental helium transitions from a gaseous to a liquid state at extremely low temperatures. Because the interaction between helium atoms (Van der Waals forces) and the atomic mass are both very small, it is difficult to liquefy and even harder to solidify, making it a primary low-temperature source in industry.
Seeing David frown, Ding Yi let out a sigh. Recently, theoretical physics had been filled with nothing but bad news. First, particle accelerators around the world had malfunctioned, then there were the mass suicides of astrophysicists, and now even the production sector was having problems—
"Have they found the cause?" David wondered if this was related to the Trisolarans.
But on second thought, the Trisolarans had only blockaded Earth's basic science. Although liquid helium is the most expensive refrigerant on the market, its preparation process is not that complex, and the raw materials aren't as rare as one might imagine. Essentially, the main method of producing liquid helium globally is as a byproduct extracted during the liquefaction of natural gas from gas or oil fields. Furthermore, due to its recyclability, the recovery efficiency of liquid helium can exceed 95%.
So what could be the reason? David shook his head. There was too little information now; drawing a hasty conclusion was pointless.
"This pharmaceutical base... is it in the Western Regions?" David raised an eyebrow.
"In Hotan," Ding Yi replied. After arranging the fruit platter, he handed the last apple to David.
David took it and nodded thoughtfully. Although the East relied heavily on natural gas imports, Xinjiang still possessed the country's richest natural gas reserves. Hotan was a vital hub for natural gas transit, housing pipelines that connected Central Asia and Siberia directly to the inland.
Based on the business trip route Shi Qiang had planned for two weeks later, David estimated that the convoy would likely pass through Hotan. If there was time, he would take a look to see what the actual cause was.
"Hmm? Why is it just the two of you?"
Yang Dong, having removed her coat and gloves, had changed into light blue loungewear. She looked at David and Ding Yi chatting on the sofa with a surprised expression.
"Luo Ji... he should be in the kitchen, right?" Ding Yi said uncertainly.
"I see," Yang Dong nodded.
Even though Yang Dong's gaze was calm, David felt an inexplicable sense of shame, as if he were being accused of being a "freeloader." However, this awkward atmosphere didn't last long. Soon, as Ye Wenjie and Luo Ji called them to eat, both David and Ding Yi felt a surge of relief.
"You guys eat first," Ye Wenjie said, a smile appearing on her face as she looked at David and Yang Dong sitting together naturally. She picked up a packed lunch box. "I'm going upstairs to deliver food to the children."
"By the way, don't you need to go to school?" Luo Ji asked as he scooped a bowl of rice for David.
"My unit granted me long-term leave," David replied calmly. The Earth Defense Security Department had already prepared for this.
"In what field?" Luo Ji was somewhat surprised.
"Geological prospecting, under the UN."
Nearly every member of the Earth Defense Security Department had a corresponding cover identity within the United Nations. Although this meaningless disguise would likely be revoked once the existence of Sophons was discovered, it was a very convincing identity for now.
"Impressive," Luo Ji commented. His words carried a double meaning; he likely didn't believe David's work was as simple as he claimed.
"Sorry to trouble you," Ding Yi said as he stood up after finishing the last grain of rice in his bowl. Unlike Luo Ji, he wasn't Yang Dong's classmate or Ye Wenjie's student. This time, Ding Yi had truly just come for a meal after the cafeteria shut down. He picked up his hat from the entryway. "I have arrangements at the lab this afternoon; I need to head back."
"I'll go with you," Luo Ji also stood up, tucking a book he hadn't finished reading under his arm as usual.
David looked closer. The spine of the book read The World of Ants.
Seeing both of them leave, David hesitated. He was thinking of a suitable reason to leave and was about to stand up when he was pressed down by Yang Dong's hand.
"Wait."
Yang Dong's eyes, more ethereal than in the photos, stared straight into David's. She pulled him toward the bedroom. After locking the door, she said seriously, "I have something to tell you."