Two scientists were working on the Manhattan Project back during WW2. Now, everyone knows that many different approaches were tried because no one was certain what would eventually work. These two were working on a circular radio wave.

After toiling for months in a tiny, hot, shack in New Mexico one finally jumped up and yelled "Eureka!" He ran to his partner and showed him -- the diagram of a circular radio wave!

"You fool!" said the scientist. "This is not a circular radio wave! This is a naught, a nothing, a zero!" And with that he took the drawing of the circular radio wave, rolled it into a tube and ran it through the pencil sharpener, letting the shards fall to the floor.

They were immediately surrounded by a crowd of carping janitors complaining about the litter. And then, suddenly, there was a blinding flash and the whole area vanished in white heat and a mushroom-shaped cloud!

That's what you get when you have a critical mass at ground zero.