Old ghost's words left me shaken.
It could be said that what he had said completely overturned everything I thought I knew.
What was this? This was science. No wonder the Doctor had written that in his letter.
Seeing that I seemed to understand, old ghost sighed. "So Old Madman must have gone to seek the truth."
Seek the truth? The truth behind the returnees?
Old ghost said flatly, "Since the return was fake, they must have come from spacetime adjacent to ours. Yet we have never discovered these neighboring spacetimes. Old Madman told me there might be an enormous secret hidden within this. Actually, if you think it through, you can understand it. Just as we once had no idea the Three Great Ancient Clans existed, nor did we know of the Hollow Earth people. All we could focus on was our own world. But only as our civilization continued to advance did we come into contact with them. The outsiders are the same. Only when our civilization reaches a new height can we gain a deeper understanding of them. Old Madman said that perhaps the returnees were not lying. Perhaps there is another pseudo-universe within our Solar System, and they came from that pseudo-universe. Even they believe that pseudo-universe is real, believing that they truly left the Solar System and settled in outer space. Have you read Journey to the West?"
I nodded. Of course I had.
Old ghost smiled. "The Great Sage Sun never actually flew out of Buddha Tathagata's palm, yet he believed he had reached the end of the heavens."
His words made my eyes widen. The analogy was truly fitting.
"There is no denying that those Ancient Humans who managed to leave Earth possessed a highly advanced civilization. Perhaps they built extremely fast aircraft.