"Was the Milky Way Galaxy an exception?"
William repeated in a whisper, his expression easing somewhat. He then asked Halsey again, "What about the number of Tier 4 Civilizations?"
"There are very, very few Tier 4 Civilizations. To use a Chinese idiom, they're as rare as phoenix feathers and unicorn horns."
Halsey replied without hesitation, then continued explaining to William:
"Based on our understanding as humans, we can only calculate civilization levels up to 'three' at most. Even now, there's no concrete explanation for Tier 4 Civilizations.
"But one thing I do know is that to develop into a civilization resembling true gods, they would have had to exist at least during the cooling period after the Big Bang."
"The cooling period after the Big Bang..." William pondered for a moment before suddenly realizing something. "Catherine, are you saying that those civilizations already existed in this world not long after the universe was born?"
"That's right." Halsey nodded lightly without denying it and said, "You have to understand, there are countless civilizations, but the number that still exists is far lower than what we calculate from our formulas.
"The universe also has a mechanism for filtering civilizations.
"That is, before a civilization can develop to the point of interstellar colonization, it may be destroyed by some major calamity.
"For example, asteroids, natural disasters on its home planet, or civil wars.
"Take us humans. If we hadn't had Project Heading Dawn, or if we hadn't suffered an invasion by the Reaper Civilization, we might very well have destroyed ourselves.
"It's not that the odds are nonexistent. They're actually very high. So the number of civilizations with technology equivalent to ours twenty years ago could be infinite.
"But civilizations with technology equivalent to that of our Human-Elite Alliance are already rare throughout