 Why does the narrator say that the aliens' jokes are dangerous?
The most dangerous of weapons is the one you don't know is loaded. Illustrated by Schoenherr The wind howled out of the northwest, blind with snow and barbed with ice crystals. It screamed over the top, whirled snow in a dervish dance around the hollow there, piled snow into the long furrow plowed ruler-straight through streamlined hummocks of snow. It lit the snow slope to a frozen glare, penciled black shadow down the long furrow, and flashed at the furrow's end on a thing of metal and plastics, an artifact thrown down in the dead wilderness. When the movements stopped, there was a click and a strange sound began. Sure I'm a good astronomer but so are lots of other guys. If I were ten years older, it would have been an honor, being picked for the first long jump in the first starship ever. We got lined up between Earth and Mars, you'll remember, and James pushed the button marked 'Jump'. There was never anything wrong with the Whale till right at the end and even then I doubt if it was the ship itself that fouled things up. Walking, talking natives on a blue sky planet with 1.1 g gravity and a twenty per cent oxygen atmosphere at fifteen p.s.i. The odds against finding Chang on a six-sun survey on the first star jump ever must be up in the googols. We were able to show them our sun, in their telescopes. Look more like cats than people, but they're people all right.
 The wrong kind of joke could end in catastrophe
 The wrong kind of joke could end in catastrophe  It hurts the scientists' reputations to be beat at games like chess  Their practical jokes tend to meddle with spaceship parts  They like to play with weapons and people tend to die