This recent article in The Scientist describes the daily dilemma facing scientists and science journalists: How do you describe what can't be seen? Well, thank goodness for the marvelous metaphor. If you took all the metaphors I've used over the years and stacked them up end to end, they would reach from Earth to the far side of Uranus and back. But all the good metaphors I've used could dance on the head of pin, their substance a thousand times thinner than the width of a human hair.

Which takes me back to nanotechnology. It's suffering from a chronic case of misleading metaphor. It's actually no joke, since much of the gooey fear surrounding the concept of self-replicating nanosystems stems from the use of a bad biotech analogy.

A few weeks ago, nanotechnology and cryptography poo-bah Ralph Merkle sat down with me to talk about a number of issues, including the need to alter the analogy.

"I think one of the fundamental things which is not understood at this point is that artificial replicating systems, manufacturing systems, are going to bear about as much resemblance to the biological variety as, say, a 747 bears to a duck," Merkle said.

For the complete story, please see Howard Lovy's NanoBot.