Gray goo

Gray goo (also spelled as grey goo) is a hypothetical global catastrophic scenario involving molecular nanotechnology in which out-of-control self-replicating machines consume all biomass (and perhaps also everything else) on Earth while building many more of themselves,^[1][2] a scenario that has been called ecophagy (the literal consumption of the ecosystem).^[3] The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.

Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines or clanking replicators. The term gray goo was coined by nanotechnology pioneer K. Eric Drexler in his 1986 book Engines of Creation.^[4] In 2004, he stated "I wish I had never used the term 'gray goo'."^[5] Engines of Creation mentions "gray goo" as a thought experiment in two paragraphs and a note, while the popularized idea of gray goo was first publicized in a mass-circulation magazine, Omni, in November 1986.^[6]