"And your father found it somewhere in the Belt," the Major said softly. He looked at the weapon again, shaking his head. "There isn't any such gun," he said finally. "These things you say it could do ... they would require energy enough to break down the cohesive forces of molecules. There isn't any way we know of to harness that kind of energy and channel it in a hand weapon. Nobody on Earth...."
He broke off and stared at them.
"That's right," Johnny said. "Nobody on Earth."
"You mean ... extraterrestrial?"
"There isn't any other answer," Johnny said. "Look at the thing, Major. Feel it. Does it feel like it was made for a human hand? It doesn't fit, it doesn't balance, you have to hold it with both hands to aim it...."
"But where did it come from?" the Major said. "We've never had visitors from another star system ... not in the course of recorded history. And we know that Earthmen are the only intelligent creatures in our Solar System."
"You mean that they're the only ones now," Tom said.
"Or any other time."
"We don't know that, for sure," Tom said.
"Look, we've explored Venus, Mars, all the major satellites. If there had ever been intelligence on any of them, we'd have known it."