This view has been supported by the Astronomer Royal, Sir Martin Rees, who stated that he believes that if we receive communication from the stars, it will be from a machine civilization. These would be our descendents and would be the explorers of the galaxy. More recently, James Lovelock wrote that he believed that humans would be replaced by cyborgs, by which he meant not Martin Caidin’s Cyborg (AKA The Six-million Dollar Man) or Star Trek’s Borg, but intelligent robots. Sci-fi authors have explored these machine-centric futures, from the novel by Stephen Baxter and Alastair Reynolds The Medusa Chronicles, which extended the Arthur C Clarke novelette and has machines building a competing civilization to humans in the outer solar system, to Greg Benford’s Galactic Center novels, where sentient machines dominate the galaxy and humans have to survive like mice in a human world, while the mechs try to eliminate the humans just as we do for small rodents in our buildings. However, the rapid development of artificial intelligence (AI) since the middle of the 20th century, the continuing rapid performance improvement in computer systems, and the undeniable success and longevity of our robotic explorers in space should be an indication that we are in the throes of a rapid transition to true, artificial general intelligence (AGI) machines that are well adapted to inhospitable environments, especially space. Our conceit is that this will always remain so, as our technologies increase their capabilities, but always remain controlled by us. Our civilization has placed primacy on our cognitive level to ensure we are the prime agencies, using animals, and later machines, to displace physical labor. SETI assumed there would be some sort of galactic communication between biological species confined to their home systems due to the extreme difficulties of interstellar travel. SETI starts with the probability that life will appear, first unicellular then complex, leading on Earth led to hominid-level intelligence, which in turn eventually flowered culturally and created civilization and technological societies. Wells’ novel The War of the Worlds to recent movies like Independence Day and Arrival, technologically advanced ETI is depicted as biological. Until recently, most speculation about extraterrestrial intelligence (ETI) has assumed it will be biological. This essay similarly focuses on what a machine civilization would look for when searching for machine intelligence in space. For me, this story is memorable because it is one of so few stories that focuses on the viewpoint of aliens, and moreover, machine aliens. It remains one of the few stories where machine entities are dominant in the galaxy. The denouement is to erase the record of discovery from the survey report. Terry Bisson’s amusing short sci-fi story “They’re made Out of Meat”, is a communication between two individuals who express their disbelief that a biological species (detected on Earth by a galactic survey) can possibly be intelligent. But is there an equivalent in the machine world of a biosignature, and how would it be found? Interesting implications arise, some of them seemingly close to home. We are developing the tools to delve into planetary atmospheres in search of biosignatures, hoping to cull out ambiguities. If we ever make a SETI detection, will it be of biological beings or machine intelligence? As Alex Tolley explains in today’s essay, there are reasons for favoring the latter possibility, leading our author to compose what he calls a ‘light-hearted speculation’ about machines searching for other civilizations of their own kind.