Robert J. Bradbury wrote: So we could in general "lighten up" about
> things. It might be much better if we explored the realms of
> our inquiries with the perspective of Zen masters rather than
> that of primitive mercenaries.
Which brings me to *my* retraction {8-[ blush {8^D: Just yesterday, I *almost* posted the notion that a nanobot would be unable to tell the difference between a desireable carbon 12 atom and an explosive carbon 14. You said it could "weigh" the carbon, throw out the bad guys, etc, and my reply could be summarized as: "huh?"
This morning I realized you are right: a nanobot *could* mass a carbon atom, and heres how: it could make a short carbon nanotube, hemispherical on either end to make a closed cylindrical capsule, with only the candidate carbon atom *inside* the tube. Then it could place a positively charged atom on either end of the tube. A halogen such as potassium might do the trick, because it would be likely to maintain a positive charge. Then if the candidate carbon atom inside the tube were to get ionized (1+), it would repel the ends of the tube. The ionization process would give it some momentum, so the carbon atom should bounce back and forth from one end of the tube to the other. Right?
Now, the *chemical* properties of a 14C are identical to a 13C or a 12C, but the mass is higher, so looks to me like the frequency at which the atom bounces from end to end of the tube would be proportional to the inverse square root of the atom's mass, so the carbon 14 should bounce back and forth about 8% slower than a carbon 12 atom. Some nanoexpert could jump in any time here and help me out {8-]. A nanobot *can* filter out the bad guys! Using this simple nanoslinky.