Nanotechnology Now

The earliest proposals for molecular manufacturing technologies echoed biological systems. Huge numbers of tiny robots called “assemblers” would self-replicate, then work together to build large products, much like termites building a termite mound. Such systems appeared to run the risk of going out of control, perhaps even “eating” large portions of the biosphere. Eric Drexler warned in 1986, “We cannot afford certain kinds of accidents with replicating assemblers.”

Since then, however, Drexler and others have developed models for making safer and more efficient machine-like systems that resemble an assembly line in a factory more than anything biological. These mechanical designs were described in detail in Drexler's 1992 seminal reference work, Nanosystems, which does not even mention free-floating autonomous assemblers.

Replicating assemblers will not be used for manufacturing. Factory designs using integrated nanotechnology will be much more efficient at building products, and a nanofactory is nothing like a gray goo nanobot. A stationary tabletop factory using only preprocessed chemicals would be both safer and easier to build. Like a drill press or a lathe, such a system could not run wild. Systems like this are the basis for responsible molecular manufacturing proposals. To evaluate Eric Drexler's technical ideas on the basis of gray goo is to miss the far more important policy issues created by general-purpose nanoscale manufacturing.

A gray goo robot would face a much harder task than merely replicating itself. It would also have to survive in the environment, move around, and convert what it finds into raw materials and power. This would require sophisticated chemistry. None of these functions would be part of a molecular manufacturing system. A gray goo robot would also require a relatively large computer to store and process the full blueprint of such a complex device. A nanobot or nanomachine missing any part of this functionality could not function as gray goo.

Development and use of molecular manufacturing will create nothing like gray goo, so it poses no risk of producing gray goo by accident at any point. However, goo type systems do not appear to be ruled out by the laws of physics, and we can't ignore the possibility that someone could deliberately combine all the requirements listed above. Drexler's 1986 statement can therefore be updated: We cannot afford criminally irresponsible misuse of powerful technologies. Having lived with the threat of nuclear weapons for half a century, we already know that.