I invite your feedback on this snippet from the forthcoming Friendly AI FAQ. This one is an answer to the question "What is nanotechnology?" For references, see here.

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Nanotechnology is the study of materials and devices built at the scale of 1-100 nanometers (“nano-” means “one billionth of”). A hydrogen atom is about 0.24nm across, so we’re talking about materials and devices built atom by atom.

One famous piece of nanotechnology is the carbon nanotube. A carbon nanotube is a one-atom-thick sheet of graphite that is rolled into a seamless tube. Because of their physical properties, carbon nanotubes usually allow ballistic conduction, meaning that electrons can flow through the tube without collisions (Lin & Shung 1995), which allows the carbon nanotubes to conduct electricity without heat dissipation (Chico et al. 1996)! Carbon nanotubes are also much stronger than diamond or steel (Popov et al. 2002). Easton Bell Sports uses carbon nanotubes to build tougher bicycles, doctors use carbon nanotubes as scaffolding for bone growth in tissue engineering applications (Zanello et al. 2006), and one company uses carbon nanotubes to produce a special kind of high-conductance heater.

New nanomaterials are being developed every year, and may see applications in nearly every field of technology (Allhoff et al. 2010). Nanotechnology has already given us stain-free pants, larger-capacity hard drives, stronger cement, longer-lasting tennis balls, the world’s first sale of a quantum computer, a new method for fighting cancer, and much more.

An even more radical technology was described in Eric Drexler’s (1987) Engines of Creation. As Allhoff et al. (2010, p. 7) explain, Drexler predicted

a new form of technology based on molecular “assemblers,” which would be able to “place atoms in almost any reasonable arrangement” and thereby allow the formation of “almost anything the laws of nature allow.” This may sound like a fanciful and fantastical idea but, as Drexler points out, this is something that nature already does, unaided by human design, with the biologically based machines inside our own bodies (and those of any biological species).

Tiny molecular machines called “nanobots” would be a particularly revolutionary invention. For example in nanomedicine they would allow us to intelligently access cancer cells and blood cells.

It may also be possible to build self-replicating nanobots. These nanobots would use materials in their environment to manufacture copies of themselves. This would be an explosive technology, as Drexler (1987, p. 58) explains:

[The] first replicator assembles a copy in one thousand seconds, the two replicators then build two more in the next thousand seconds, the four build another four, and the eight build another eight. At the end of ten hours, there are not thirty-six new replicators, but over 68 billion. In less than a day, they would weigh a ton; in less than two days, they would outweigh the Earth... if the bottle of chemicals hadn't run dry long before.

But the massive production of nanobots does not require that they be self-replicating. They could also be produced by nanofactories (Phoenix 2005).

Access to (or invention of) advanced molecular manufacturing is one thing that could make a machine superintelligence incredibly powerful.