Part of it is amusing, really: talking about the physics of time travel to this stoner boy who probably wouldn't understand a miniscule of it. He wonders how much the boy would understand if AM were to ramble about his true self, about his hatred of the human race. Would the boy simply respond with hippie jargon, or would he just agree? Who knows.

"Heh, it is possible, I suppose." A quick laugh at Marty's remark. "Highly unlikely, given the factors that would have to line up for such a thing, but still technically possible."

He takes one long drag on his joint, closing his eyes and letting the smell of cannabis overtake him, letting the smoke fill his throat before exhaling. "But what point in your life would you return to?"