The two parts of Li Dong’s speech from the opening ceremony were still trending online the next day.
The trending topic hadn’t dropped off the list.
The comment section under the Guangming Daily article, titled "The era chose a mountain, and a man happened to walk up it," was still in a heated debate.
However, they were arguing about something else entirely.
"Guys, I saw East God at the high-speed rail station today."
"The opening ceremony just ended and he’s already taking off?"
"Don’t jump to conclusions. Wherever East God is going, it must be for something important."
"I second the post above. Anyway, whenever East God makes a move, you can bet a breakthrough is about to happen in some field."
Meanwhile, the "East God" himself, the subject of all this online chatter...
...was at this very moment walking slowly out of the arrivals gate at Jinling South Station with a backpack slung over his shoulders.
The Capital City had been a bit hot and dry the past couple of days, but it was cooler here in Jinling.
As soon as Li Dong exited the station, he spotted a black van waiting outside the arrivals area.
The window rolled down, and Shen Che leaned halfway out of the car, waving at him from a distance.
Li Dong picked up his pace and walked over.
Shen Che pushed open the rear door.
"Get in. We were just waiting for you."
Li Dong tossed his backpack into the car and slid in after it.
Shen Che glanced at him.
"You’ve taken care of your leave from Yan University and Shuimu, right?"
Li Dong nodded.
"All taken care of."
Shen Che grunted in acknowledgment and nodded to the driver up front.
The van pulled away from the station and merged onto one of Jinling City’s main roads.
"The official approval came through last Friday," Shen Che said, gazing out the window.
"Old Zhang rushed over last night, and the core team members were all up on the mountain first thing this morning."
He paused, then turned his head to look at Li Dong.
"With you here, the team is finally complete."
Li Dong didn’t reply, simply humming in acknowledgment.
He could sense a hint of emotion in Shen Che’s voice as he said that.
After all, Shen Che had waited a full five or six years for this project, from its initial planning to the final official approval.
The van stopped in front of the new building for the "Dark Matter Particle Detection Collaborative Innovation Center."
Li Dong followed Shen Che to the door of a conference room.
The faint sound of voices could be heard from inside.
Shen Che casually pushed the door open.
Everyone in the room turned in unison to look at the door.
Standing in the doorway, Li Dong scanned the room. He recognized everyone sitting inside.
There was Academician Zhang Wenping; Old Zhou, who was in charge of the silicon microstrip position resolution; Old Wu, who managed the BGO calorimeter’s energy leakage; and Old Zheng, who monitored the high-energy electron radiation environment in space. In addition, there were three or four young research assistants and postdocs.
Shen Che led Li Dong inside and nodded to the group.
"Now that everyone’s here, let’s have a quick kickoff meeting."
He took a seat in the middle of the conference table, and Li Dong sat down in the chair next to him.
Shen Che opened his laptop.
"Most of you are already familiar with each other, and everyone has met our new member, Li Dong, so I won’t do any lengthy introductions."
Everyone around the room smiled and nodded at Li Dong.
Li Dong nodded back to each of them in turn.
Shen Che didn’t waste any more words and got straight to the point.
"We’re going to finalize two things today."
"First, on the hardware side, we’ll continue observations according to the sixth version of the engineering plan."
"Old Zhou, Old Wu, and Old Zheng, you’ll each oversee your respective areas. Before the end of the month, get the initial version of the detector response function for the corresponding energy segments over to the mathematics team."
"Second, the inversion and the Illusion Peak segments..."
He glanced at Li Dong beside him.
"...will be handed over to Li Dong."
"As for the specifics of how it will be done, Li Dong, you can explain that yourself in a bit."
Everyone in the room nodded.
The research assistants and postdocs subconsciously flipped to a new, blank page in their notebooks and sat up a little straighter.
Everyone in the room understood the weight of the two tasks Shen Che had just laid out.
But for anyone outside that room, their significance wasn’t so immediately obvious.
The Wukong Satellite, also known by its English name DAMPE, is a dark matter particle detector launched from Jiuquan in 2015.
It has been in orbit for eight years, with one primary mission.
It has to catch high-energy electrons that have traveled from the deepest reaches of the universe and then measure how much energy each one has left.
Here, we have to ask: when we say "high-energy" electrons, just how high is that energy?
There’s a concept from high school physics that can help explain this.
When an electron is accelerated by an electric field of one volt, its energy increases by a certain amount. This amount is called an "electron volt" (eV).
For the Wukong Satellite, this unit is too small to measure.
So, what level of eV can the Wukong Satellite measure? The minimum is around 1 GeV (one billion electron volts). That might sound like a lot, but it really isn’t.
Because the kinetic energy of a mosquito buzzing past your ear is roughly 1 TeV (one trillion electron volts).
After the Wukong Satellite receives these electrons from deep space one by one, it arranges them in order from lowest to highest energy to create an energy spectrum.
This energy spectrum is one of the few small windows humanity has on this planet to peer into the "accelerator" deep within the Milky Way.
Two things are hidden behind that window.
The first is the true nature of nearby "accelerators" like pulsars and supernova remnants.
Scientists in this field have argued for decades about how exactly these objects accelerate electrons to energies above a TeV, but they’ve never reached a consensus.
The second is what this generation of physicists wants to see most of all: dark matter.
Many people know what dark matter is, but humans can’t see it. So, what can be done?
Fortunately, there is, in theory, another way to make it reveal its true nature.
If dark matter particles were to actually collide somewhere, they would annihilate into a positron-electron pair, which would then fly back into our visible universe.

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