A von Neumann probe is a hypothetical spacefaring probe designed to self-replicate using raw materials found in any star system. The probe is named after John von Neumann, a mathematician who made many important contributions to science. One of his contributions was the first rigorous study of self-replicating machines. Though von Neumann himself never discussed the idea of using self-replicating machines to explore space, shortly after his death in 1957 the concept began to enter science fiction and futurism.
Packed with advanced artificial intelligence and nanotechnology, a fleet of these probes could conceivably help colonize the entire galaxy or even universe. They could carry human zygotes, or the information required to create them, to populate new-found worlds without the hassle of human interstellar spaceflight. A von Neumann probe could even contain emulations of human beings, assisting with decision-making and data analysis.
If the speed of a von Neumann probe and its ability to self-replicate is fast enough, the probes could enable the creation of a colonization wavefront of exponentially self-replicating probes, expanding outwards at an appreciable fraction of the speed of light. Probes could be programmed to terraform planets upon arrival, preparing worlds for future inhabitants.
The best-known appearance of a von Neumann probe in fiction was in Stanley Kubrick's 1968 film, "2001: A Space Odyssey," which portrayed this probe as a black monolith. Since then, the concept has appeared in many sci-fi novels and futurist works.
Oxford philosopher Nick Bostrom has argued that a von Neumann probe should be dispatched from Earth as soon as possible, due to the huge opportunity cost of delaying space colonization, a concept he calls "astronomical waste." The resources of the galaxy could be used to sustain massive numbers of people living happy, fulfilling lives, but now those resources are simply sitting idle, being wasted. Others believe this viewpoint to be idealistic and egocentric; and point to the dangers of self-replicating machines turning the universe into real 'astronomical waste.' One hypothetical alternate form of the probe, referred to as the berserker probe, could theoretically use the same technology to make life impossible on all worlds by sterilizing every world it touches--even wiping out existing life. This scenario might unfold via unforeseen malfunctions of the probe, or through purposeful apocalyptic technology.
Whether the von Neumann probe is realized or not, the notion of spacefaring self-replicating machines clearing the way for humankind remains a very real future possibility.