Imagine a giant saucer hovering above Earth. Over every TV, aliens announce they’ll destroy our planet in one hour. When the time is up, they say, “Just kidding!” And then they fly off to mess with everyone’s head on some other world.
It does seem that one of nature’s traits is playfulness. Look at kittens or dolphins or some of your friends. They just want to fool around.Astronomy magazine subscribers can read the full column for free. Just make sure you're registered with the website.