Li Qingsong was somewhat surprised by that answer.
"What observation methods did your Lantu Ke Civilization use?"
Momo Lansi replied weakly, "Planetary Atmosphere Spectrum Determination Technology.
We built a massive Space Telescope Array and observed the planets throughout this star system. We found that the third planet was located right within the Habitable Zone, with temperatures sufficient to support the existence of liquid water.
We determined the elemental composition of the planet's atmosphere and confirmed that life existed on it. We then tested for Industrial Markers in the atmosphere, as well as changes in Carbon Dioxide concentration, and confirmed that there was no intelligent life on the planet. So... so we chose it as our migration destination..."
Li Qingsong knew that so-called Industrial Markers were gases that could not form naturally and could only be produced through the industrial processes of intelligent life.
Freon, the refrigerant commonly used in refrigerators and air conditioners, was a typical Industrial Marker.
After such substances were released into the atmosphere, when the planet passed between a distant observer and the sun, those substances in the planetary atmosphere would cause corresponding changes in the sunlight.
By observing whether sunlight displayed those changes, a distant observer could determine whether Industrial Markers existed in the atmosphere of a faraway planet.
If Industrial Markers were present, it could clearly prove that an intelligent civilization existed on that planet and had reached a certain level of development—at the very least, the industrial age.
But... this alien was saying there were no Industrial Markers in Earth's atmosphere?
How was that possible?
Human Civilization had developed within the Solar System to the point where it could build the Deep Space spacecraft, and yet he was claiming there were no Industrial Markers in Earth's atmosphere?
"You're still lying."
Li Qingsong sneered and