BRIEFING DOCUMENT:  DECEMBER 14, 2003

Grey Goo is a Small Issue

Fear of runaway nanobots, or “grey goo”, is more of a public issue than a scientific problem. Grey goo as a result of out of control nanotechnology played a starring role in an article titled "The Grey Goo Problem" by Lawrence Osborne in today's New York Times Magazine. This article and other recent fictional portrayals of grey goo, as well as statements by scientists such as Richard Smalley, are signs of significant public concern. But although biosphere-eating goo is a gripping story, current molecular manufacturing proposals contain nothing even similar to grey goo. The idea that nanotechnology manufacturing systems could run amok is based on outdated information.

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 personal nanofactory is nothing like a grey 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 grey goo is to miss the far more important policy issues created by general-purpose nanoscale manufacturing.

A grey 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 grey 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 grey goo.

Development and use of molecular manufacturing will create nothing like grey goo, so it poses no risk of producing grey 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.

Grey goo eventually may become a concern requiring special policy. However, goo would be extremely difficult to design and build, and its replication would be inefficient. Worse and more imminent dangers may come from non-replicating nano-weaponry. Since there are numerous greater risks from molecular manufacturing that may happen almost immediately after the technology is developed, grey goo should not be a primary concern. Focusing on grey goo allows more urgent technology and security issues to remain unexplored.

UPDATE: The August 2004 issue of the Institute of Physics journal Nanotechnology includes an article on "Safe Exponential Manufacturing", co-authored by Chris Phoenix and Eric Drexler. They conclude that:

Nanotechnology-based fabrication can be thoroughly non-biological and inherently safe: such systems need have no ability to move about, use natural resources, or undergo incremental mutation. Moreover, self-replication is unnecessary: the development and use of highly productive systems of nanomachinery (nanofactories) need not involve the construction of autonomous self-replicating nanomachines. Accordingly, the construction of anything resembling a dangerous self-replicating nanomachine can and should be prohibited. Although advanced nanotechnologies could (with great difficulty and little incentive) be used to build such devices, other concerns present greater problems. Since weapon systems will be both easier to build and more likely to draw investment, the potential for dangerous systems is best considered in the context of military competition and arms control.

For more information, or to download a PDF of this important paper, click here.