Plants with leaves no more efficient than today's solar cells could out-compete real plants, crowding the biosphere with an inedible foliage. Tough omnivorous bacteria could out-compete real bacteria: They could spread like blowing pollen, replicate swiftly, and reduce the biosphere to dust in a matter of days. Dangerous replicators could easily be too tough, small, and rapidly spreading to stop - at least if we make no preparation. We have trouble enough controlling viruses and fruit flies.

My work at MIT had focused on what we could build in space once we had inexpensive space transportation and industrial facilities in orbit. And this led to various sorts of work in space development.

Any powerful technology can be abused.

Nature draws no line between living and nonliving.

The basic parts, the start-up molecules, can be supplied in abundance and don't have to be made by some elaborate process. That immediately makes things simpler.

And that because the moving parts are a million times smaller than the ones we're familiar with, they move a million times faster, just as a smaller tuning fork produces a higher pitch than a large one.

Likewise nanotechnology will, once it gets under way, depend on the tools we have then and our ability to use them, and not on the steps that got us there.