 Why do the aliens believe they have succeeded in saving Earth?
A gentle fancy for the Christmas Season—an oft-told tale with a wistful twistful of Something that left the Earth with a wing and a prayer. Earth was so far away that it wasn't visible. But this vast distance did not mean that isolation could endure forever. Instruments within the ship intercepted radio broadcasts and, within the hour, early TV signals. The history of the planet was tabulated as facts became available. The course of the ship changed slightly; it was not much out of the way to swing nearer Earth. "We've got to make or break," said the first alien. "It's not what they've done," said Bal, the second alien. "The big bomb can destroy them. They've had two world wars in one generation and that the third and final one is coming up you can't help feeling in everything they do." "The wrong diplomatic move, or a trigger-happy soldier could set it off. A meteor shower could pass over and their clumsy instruments could interpret it as an all-out enemy attack." "We'll just have to forget there ever was such a planet as Earth." Except for the one thing they lack, and that's quite odd, they seem exactly like us. "It is. "There is. "In a week we can't negate their entire history. There's nothing in this region of space our people want," said Ethaniel. "And how long can Earth last?
 The humans did come to a formal agreement before the aliens left them.
 The humans did come to a formal agreement before the aliens left them.  The humans realized they were not alone in the universe. They dropped all their petty differences to defend themselves against an alien invasion.  The humans painted many pictures of the aliens to commemorate the historic event of first contact, a sign they will hold to the agreement made.  The humans were kneeling before the aliens in deference, a sign that they will hold to the agreement made.