On the moon, inside a classified base.
A square-faced, middle-aged man frowned deeply. He wore a crisp military uniform with three gold stars on his shoulders, and carried himself with grave composure.
Across from him sat an elderly man with graying temples and reading glasses.
"Chief Engineer Gu, after that anomalous gravitational signal was discovered, the Speaker flew out personally to investigate. Nearly half a month has passed, and he still hasn't returned. The director is deeply concerned and sent me to ask whether you've determined what's causing the signal."
Chief Engineer Gu looked troubled too. Adjusting his glasses, he said helplessly, "General Li, we've launched a probe toward the signal's coordinates, but the distance is too great. Even Insight One, the most advanced probe at this base, will need roughly twenty-six days to get close. So I can't give you a definite answer yet.
"Still, we have a few theories about the anomalous signal.
"First, an unknown boson star is rotating. You can think of it as a strange celestial body.
"Second, an electroweak phase transition is occurring in that region and continuously releasing gravitational waves. But that astronomical phenomenon is rare.
"Third, there's a small wormhole there.
"Fourth, an alien spacecraft happened to enter that region, and its propulsion system produced anomalous gravitational waves.
"There are other theories too. A few of our younger researchers think the waves might be ripples left by the Immortal Gods of legend walking through space. But we can disregard that possibility. After all,
"we've never seen the Immortal Gods, and we don't know whether their movements could generate gravitational disturbances on such a scale—"
"Which do you think is most likely?" General Li asked gravely.
Chief Engineer Gu fell silent for a moment before answering. "Personally, I lean toward the third or