**"Citizens of Human Union's 1183rd Underground City, according to the latest observations, the Sun will undergo a helium flash in 30 minutes."**
**"Human civilization has entered its final 30-minute countdown."**
**"We... have failed."**
Within the 500-meter-deep underground city, a somber female voice echoed through ubiquitous speakers. An indescribable suffocation gripped everyone who heard the broadcast.
Lv Yongchang sat expressionlessly before a holographic projection. The image displayed a massive fireball burning quietly in the cosmic void—a live feed of the Sun at this moment.
Taking a deep breath, Lv Yongchang waved his right hand. The hologram abruptly scaled down, revealing the entire solar system. Unlike its former self, two planets had vanished: Venus and Mercury had been devoured by the Sun, which now loomed as a crimson behemoth—a red giant.
"Yongchang... Is this truly the end for humanity?" A faint, helpless voice sounded beside him.
Turning, Lv Yongchang saw Su Yutong, a woman in a white lab coat, staring blankly at the hologram. As the chief scientist of the Human Union Academy and his longtime partner, her normally sharp eyes now held only resignation.
"Yes. We're finished." Lv Yongchang sighed. "There's still over 20 minutes. Would you like to see the surface one last time?"
Su Yutong's eyes flickered. She stood, releasing her neatly coiled raven hair, and smiled radiantly at him.
"Absolutely."
In the elevator ascending from 1183rd City, the pair donned heavy protective suits in silence. The screen displayed their depth decreasing: **518℃**—the current surface temperature.
Memories flooded Lv Yongchang's mind. In 2045 AD, the Sun inexplicably accelerated its aging process, entering the red giant phase within five years. Humanity united into the Human Union, constructing underground cities and interstellar arks under his leadership. But his calculations had erred catastrophically—the Sun's evolution skipped billions of years. Now, Earth would soon become a molten sphere.
*Ding.*
"May your surface research succeed, Chief Scientist."
The elevator doors slid open, unleashing searing heat and distorted air. Even through their suits, Lv Yongchang felt the inferno radiating from the swollen red Sun.
"One minute until the helium flash," Su Yutong's voice crackled over the radio.
He stared upward, unflinching. *I refuse to yield.*
"Do you know why I fought so hard to become your assistant?" she asked softly. "Because... I love you."
Lv Yongchang froze.
The helium flash erupted—a searing white brilliance swallowed the Sun. Consciousness slipped away.
Everything glowed neon green. A white line stretched upward, forming a tree diagram against the luminescent void. Lv Yongchang felt disoriented.
*What is this?*
A faint flicker ignited at the diagram's base: **Nuclear Energy Mastery: Controlled Fission**. The text brightened, then advanced upward—**Controlled Fusion**. Symbols and equations inundated his mind.
"Lv Yongchang! Lv Yongchang!"
"Professor Guan is calling you!"
Groggily, Lv Yongchang opened his eyes. He was in a classroom.