Gray goo

Grey goo (alternatively spelled gray goo) is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves, a scenario known as ecophagy ("eating the environment").

Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines. The term grey goo was coined by nanotechnology pioneer Eric Drexler in his 1986 book Engines of Creation, stating that "we cannot afford certain types of accidents." In 2004 he stated "I wish I had never used the term 'grey goo'."

Definition

The term was first used by molecular nanotechnology pioneer Eric Drexler in his book Engines of Creation (1986). In Chapter 4, Engines Of Abundance, Drexler illustrates both exponential growth and inherent limits by describing nanomachines that can function only if given special raw materials:

Imagine such a replicator floating in a bottle of chemicals, making copies of itself…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; in another four hours, they would exceed the mass of the Sun and all the planets combined — if the bottle of chemicals hadn't run dry long before.

In a History Channel broadcast, grey goo is referred to in a futuristic doomsday scenario: "In a common practice, billions of nanobots are released to clean up an oil spill off the coast of Louisiana. However, due to a programming error, the nanobots devour all carbon based objects, instead of just the hydrocarbons of the oil. The nanobots destroy everything, all the while, replicating themselves. Within days, the planet is turned to dust."

Drexler describes grey goo in Chapter 11 of Engines Of Creation:

early assembler-based replicators could beat the most advanced modern organisms. '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 made no preparation. We have trouble enough controlling viruses and fruit flies.

Drexler notes that the geometric growth made possible by self-replication is inherently limited by the availability of suitable raw materials.

Drexler used the term "grey goo" not to indicate color or texture, but to emphasize the difference between "superiority" in terms of human values and "superiority" in terms of competitive success:

Though masses of uncontrolled replicators need not be grey or gooey, the term "grey goo" emphasizes that replicators able to obliterate life might be less inspiring than a single species of crabgrass. They might be "superior" in an evolutionary sense, but this need not make them valuable.

Bill Joy, one of the founders of Sun Microsystems, discussed some of the problems with pursuing this technology in his now-famous 2000 article in Wired magazine, titled "Why the Future Doesn't Need Us". In direct response to Joy's concerns, the first quantitative technical analysis of the ecophagy scenario was published in 2000 by nanomedicine pioneer Robert Freitas.

Risks and precautions

Drexler more recently conceded that there is no need to build anything that even resembles a potential runaway replicator. This would avoid the problem entirely. In a paper in the journal Nanotechnology, he argues that self-replicating machines are needlessly complex and inefficient. His 1992 technical book on advanced nanotechnologies Nanosystems: Molecular Machinery, Manufacturing, and Computation describes manufacturing systems that are desktop-scale factories with specialized machines in fixed locations and conveyor belts to move parts from place to place. Popular culture, however, remains focused on imagined scenarios derived from his older ideas. None of these measures would prevent a party creating a weaponized grey goo, were such a thing possible.

In Britain, Prince Charles called upon the Royal Society to investigate the "enormous environmental and social risks" of nanotechnology in a planned report, leading to much delighted media commentary on grey goo. The Royal Society's report on nanoscience was released on 29 July 2004, and dismisses the idea as impossible.

More recent analysis has shown that the danger of grey goo is far less likely than originally thought. However, other long-term major risks to society and the environment from nanotechnology have been identified. Drexler has made a somewhat public effort to retract his grey goo hypothesis, in an effort to focus the debate on more realistic threats associated with knowledge-enabled Template:Noredlink and other misuses.

Popular culture

Fiction

The term grey goo is often used in a futuristic or science fiction context, as the required technologies do not yet exist. In the worst postulated scenarios (requiring large, space-capable machines), matter beyond Earth would also be turned into goo (with goo meaning a large mass of replicating nanomachines lacking large-scale structure, which may or may not actually appear goo-like). The disaster is posited to result from a deliberate doomsday device, or from an accidental mutation in a self-replicating nanomachine used only for other purposes, but designed to operate in a natural environment.

In the manga Battle Angel Alita the planet Mercury has been been classified as a no-go zone after a scientist turned the planet into an invincible ball of grey goo that engulfs anything that goes near it, like space probes and other machines.

Notable examples of such a work can be found in the novel Blood Music by Greg Bear (1985), the 2002 Michael Crichton novel Prey and Wil McCarthy's novel Bloom. The remake of The Day the Earth Stood Still (2008 film) features a grey goo nanoattack on human civilization.

In the video game Deus Ex: Invisible War, a limited form of "grey goo" has been weaponized to create so-called Nanite Detonators, a potent weapon which uses self-replicating nanites to consume an entire city, yet which is not capable of running amok across the Earth's surface.

Broken Angels, the third novel in sci-fi author Richard Morgan's Altered Carbon trilogy, features an encounter with an evolving, self-replicating colony of nano-machines.

In the Thursday Next novel Lost in a Good Book by English author Jasper Fforde, the main character is warned of an impending apocalypse where all life on Earth had been converted into strawberry-flavoured Dream Topping, in a botched attempt to end world hunger. This was described as an example of a "pink goo" scenario.

In the novel Aristoi by author Walter Jon Williams, the original Earth was destroyed by "Mataglap Nano", a grey goo disaster which originated in Indonesia (thus the name, which means berserk in Indonesian).

Computing

Denial-of-service attacks in the virtual world Second Life which work by continually replicating objects until the server crashes are referred to as grey goo attacks. This reference refers to the self-replicating aspects of grey goo. It is one example of the widespread convention of drawing analogies between certain Second Life concepts and the theories of radical nanotechnology.

See also

• Self-reconfiguring modular robot

Further reading

• Lynn Margulis and Dorion Sagan—What Is Life? (1995). Simon & Schuster. ISBN 0-684-81087-5
• Bill Bryson A Short History of Nearly Everything (2003)
• Green Goo—Life in the Era of Humane Genocide by Nick Szabo
• Green Goo: Nanotechnology Comes Alive!
• Green Goo: The New Nanothreat from Wired

External links

• Some Limits to Global Ecophagy by Biovorous Nanoreplicators, with Public Policy Recommendations
• Nanotechnology pioneer slays "grey goo" myths Paper critical of "grey goo"
• Online edition of the Royal Society's report Nanoscience and nanotechnologies: opportunities and uncertainties
• Goo and Paste Directory
• UK Government & Royal Society commission on Nanotechnology and Nanoscience