 Why is the Earth worse than the aliens imagine?
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. 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." 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. "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? They went much closer to Earth, not intending to commit themselves. For a day they circled the planet, avoiding radar detection, which for them was not difficult, testing, and sampling. Atmospheric analysis showed that as far away as we were." "What's worse is that I now find they also have missiles, range one thousand miles and upward. They either have or are near a primitive form of space travel."
 The Earth has missiles and is close to space travel.
 The Earth has missiles and is close to space travel.  The humans are rough and desperate.  A meteor shower could be interpreted as an enemy attack by the humans' clumsy instruments.  The humans don't like aliens.