Once We Lived in Nanjing

Bai Yang immediately shared this significant discovery with his dad.

Dad was unfazed, waving his hand dismissively and asked how this was a major discovery. "A missing painting on the wall just means the putty's been scraped off, that's all. I bet there will be something in the future that'll lead to all the putty in your room being scraped off and redone. Believe it or not, just wait and see. When it actually happens, you can come back and take a look."

Dad sounded like a prophet.

Bai Yang scratched his head. After the image on the wall disappeared, he had imagined tens of thousands of words worth of science fiction plot: parallel universes, multiple histories, world line jumps – intricate and compelling. He felt like Okabe Rintaro was possessing him, ready to cross multiple worlds to save Makise Kurisu and his "Daru." But all his imaginative theories were effortlessly debunked by his dad's simple remark.

Bai Yang turned his attention to Uncle Wang by the coffee table.

Old Wang didn't even lift his head, completely uninterested in what Bai had said, only focusing on signing his name to the article written by Little Zhu.

Bai Yang had no choice but to turn back around.

Forsythia leaned against the door, spreading his hands and shrugging his shoulders.

Zhao Bowen was in a meeting.

But not at the provincial or city committee; he was at Zijin Mountain Observatory.

He was originally proceeding with a normal meeting, reporting on the current progress of the command center, when he suddenly received a message from the Observatory. He stealthily looked at his phone, which mentioned a major discovery. Without warning, Zhao cut off his sentence midway, tossed aside his notes, pushed the table, dragged his chair, and bolted out, leaving the other leaders utterly dumbfounded.

The leaders quietly asked the secretary if his house was on fire.

"Can it get any clearer?" Zhao Bowen furrowed his brows as he looked at a photo on the PPT, and another stack of photos laid out on the table in front of him.

"Uh... Teacher Zhao, you're a physicist too. You know that..."

"I just want to know, can it get any clearer?" Zhao Bowen interrupted him.

The photo had a black background with a few sparse white dots, like chalk dust sprinkled on a blackboard. There was also a dark red arrow pointing to a faint dot in the center of the photo.

Below it was labeled Sgr A＊.

Even Zhao Bowen, a complete layman in astronomy, knew that Sgr A＊ referred to Sagittarius A star, and the spot that was the size of a sesame seed or mung bean on the photo was actually a supermassive black hole four million times the mass of the Sun. Sitting in the conference room, it was impossible to see that; Zhao Bowen's mind couldn't even fathom what four million times the mass of the Sun would amount to. Fortunately, the director explained that it was a black hole, not a star. So even though its mass equaled that of four million suns, its actual diameter was only forty million kilometers.

The photo in Zhao Bowen's hand was an enlarged version of Sgr A＊, with even lower resolution and in black and white. Enlarge the dim little white dot from the PPT several hundred times and you'd get the photo Zhao was holding – the clarity worse than black sesame paste, but still roughly displaying a structure: a blurry, hazy ring without any detail.

Zhao unexpectedly thought of the giant eye he had seen that night, resembling a similar pupil. The association made Zhao shiver; wasn't the black hole's property of trapping even light similar to that ginormous eye? Staring into that eye, Zhao Bowen felt as if he was gazing into the abyss.

This photo was the fruit of the astronomical group's labor over the past month or so.

The astronomy team undertook the most important, and at the same time, the most perplexing task among all expert groups. That was to analyze and judge the possible origin of the Black Moon. The teacher's draft had already pointed out the direction—Milky Way Galaxy; the Black Moon came from inside the Milky Way Galaxy, it was not indigenous to Earth. This was a crucial clue, and it was incredibly reliable, reliable as when teachers tell you that the scope of the exam is the entire textbook.

With such a clue, the astronomy team also felt

After rigorous deduction, precise analysis, devout prayers, and blind voting (which is also an important part of scientific research), everyone unanimously believed that the most valuable target was the supermassive black hole at the center of our Galaxy. So, the planet's firepower turned towards the center of the Milky Way Galaxy—hey, you wouldn't believe it, but there were some gains.

They discovered that the intricate shadow structure of Sagittarius A star was different from what was expected, there might be multiple gravitational sources interfering outside the accretion disk, and further observations in the X-ray spectrum showed that a portion of energy had gone missing.

Although Zijin Mountain repeatedly emphasized that this could very well be a natural phenomenon, given the vast and unpredictable nature of the universe, Zhao Bowen was already excitedly pounding the table: Black Hole City! That's Black Hole City! (Note 1) The Black Moon must have come from there!

"Is this the latest achievement?"

Zhao Bowen calmed down.

"Old achievements. In the astronomical community, the study of supermassive black holes can be considered a prominent field. We've been working on it with our colleagues in Europe and America, including UCLA and the Max Planck Institute. Didn't they just produce the world's first black hole photograph earlier this year? They created something called the Event Horizon Telescope, using VLBI (Very-long-baseline interferometry) technology. The photo was of the supermassive black hole in the Virgo M87 Galaxy. That black hole is massive, weighing in at 6.5 billion times the mass of the Sun. Their telescope's virtual aperture is as wide as the Earth's diameter."

"Can it be requisitioned?" The first thing Zhao Bowen thought of was this.

"That belongs to foreigners," someone reminded in a lowered voice.

"Can we collaborate with them?" Zhao Bowen changed his wording.

"We're already collaborating," the reporter replied, "This observation plan involved eight of EHT's radio telescopes. But due to the short time and the hasty planning, we can only achieve this effect so far. After all, it took them ten years to prepare to photograph that black hole in M87."

"We need a clearer view," Zhao Bowen tapped the wooden desktop with his knuckles.

"It's possible, but we'll need a longer baseline and more observation time," said the presenter on stage. "The results we see now are a collaboration between Beijing's LAMOST, Miyun, Shanghai Observatory, and several telescopes in Australia, North America, South America. This intercontinental cooperation is already the largest baseline we can achieve on Earth. We can't extend the baseline any further; we can only extend the observation time."

"We don't have ten years. In ten years, everything will be over," Zhao Bowen shook his head. "We can only try to make the telescopes' aperture a bit larger."

Zhao Bowen pushed his glasses up the bridge of his nose, displaying a client's excellent quality: I don't care how you do it, I just need you to get it done.

But if a telescope with an aperture as wide as the Earth's diameter is not sufficient, where can we find an even larger one?

"I have a rough understanding of VLBI – by networking multiple radio telescopes we can create a virtual telescope with a large aperture. If we can place the telescopes far enough apart, the virtual telescope's aperture can be made larger," said Zhao Bowen. "So, how about this, we could utilize the Earth's own revolution. The Earth is in motion, and its movement could create a huge baseline. Ideally, the baseline could be as long as the diameter of the Earth's orbit, nearly two astronomical units."

Zhao Bowen added excitedly:

"This would be equivalent to a telescope with an aperture as big as the Earth's orbital path!"

"But VLBI requires simultaneity..."

Someone meekly reminded.

"That's certainly challenging and will require technical breakthroughs, but I know you all can solve the problem," Zhao Bowen ignored the protests of the astronomy team and opened the second folder, "Alright, let's move on to the next topic."

Zhao Bowen glanced down.

"How do we retrieve the Voyager and Pioneer probes? Any ideas, speak freely, those who have proposals can step forward."

With a jarring screech of chair legs, everyone in the conference room uniformly took a step back.