Among other things, he wondered what had happened to his future self.
She was in some way a rendering of his future self.
The song is about someone who travels ahead in time to visit his future self.
"I know all the arguments," my future self was saying.
"He wants to get back to Mars," his future self said.
But there was something about the cold desperation in his future self's face that haunted him still.
In the letter, he makes a small request for his future self to let him know if time travel exists.
He knows nothing, naturally, about this gift from his aged future self.
No one could ever recognize his own future self.
In some games, his future self appears as a playable character.