A Bracewell probe is a hypothetical concept for an autonomous interstellar space probe dispatched for the express purpose of communication with one or more alien civilizations. It was proposed by Ronald N. Bracewell in a 1960 paper, as an alternative to interstellar radio communication between widely separated civilizations.
A Bracewell probe would be constructed as an autonomous robotic interstellar space probe with a high level of artificial intelligence, and all relevant information that its home civilization might wish to communicate to another culture. It would seek out technological civilizations—or alternatively, monitor worlds where there is a likelihood of technological civilizations arising—and communicate over "short" distances (compared to the interstellar distances between inhabited worlds) once it discovered a civilization that meets its contact criteria. It would make its presence known, carry out a dialogue with the contacted culture, and presumably communicate the results of its encounter to its place of origin. In essence, such probes would act as an autonomous local representative of their home civilization and would act as the point of contact between the cultures.
Since a Bracewell probe can communicate much faster over shorter distances, as well as being able to communicate over long timespans, it can thus communicate with alien cultures more efficiently than radio message exchange might. The disadvantage to this approach is that such probes cannot communicate anything not in their data storage, nor can their contact criteria or policies for communication be quickly updated by their "base of operations".
While a Bracewell probe need not be a von Neumann probe as well, the two concepts are compatible, and a self-replicating device as proposed by von Neumann would greatly speed up a Bracewell probe's search for alien civilizations.
It is also possible that such a probe (or system of probes if launched as a von Neumann–Bracewell probe) may outlive the civilization which created and launched it.
There have been some efforts under the SETA and SETV projects[ clarification needed ] to detect evidence for the visitation of the Solar System by such hypothetical probes, and to signal or activate such an alleged probe that may be lying dormant in local space.[ dubious ][ citation needed ] Variations in the echo delay times of radio transmissions, known as long delayed echoes, or LDEs, have also been interpreted in Professor Bracewell's 1960 paper as evidence for such probes.[ dubious ] [1] [2]
The near-Earth object 1991 VG was initially suggested as a candidate for a Bracewell probe due to its unusual characteristics. [3] In more recent years, however, additional discoveries have accounted for the characteristics of 1991 VG, and it is no longer regarded as anomalous. [4]
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other planets.
The concept of self-replicating spacecraft, as envisioned by mathematician John von Neumann, has been described by futurists and has been discussed across a wide breadth of hard science fiction novels and stories. Self-replicating probes are sometimes referred to as von Neumann probes. Self-replicating spacecraft would in some ways either mimic or echo the features of living organisms or viruses.
Xenoarchaeology, a branch of xenology dealing with extraterrestrial cultures, is a hypothetical form of archaeology that exists mainly in works of science fiction. The field is concerned with the study of the material remains to reconstruct and interpret past life-ways of alien civilizations. Xenoarchaeology is not currently practiced by mainstream archaeologists due to the current lack of any material for the discipline to study.
In astrobiology, Uniformity of Motive is an essential assumption of the Zoo Hypothesis explanation to Fermi’s Paradox. The Zoo Hypothesis states that alien civilizations refrain from contacting Earth, so as to not interfere in natural evolution and cultural development, or to minimize risk for themselves. Certain technological, political or ethical thresholds and standards could be implemented for other civilizations to pass, after which contact would be established.
The zoo hypothesis speculates on the assumed behavior and existence of technologically advanced extraterrestrial life and the reasons they refrain from contacting Earth. It is one of many theoretical explanations for the Fermi paradox. The hypothesis states that alien life intentionally avoids communication with Earth to allow for natural evolution and sociocultural development, and avoiding interplanetary contamination, similar to people observing animals at a zoo. The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence. A variant on the zoo hypothesis suggested by the former MIT Haystack Observatory scientist John Allen Ball is the "laboratory" hypothesis, in which humanity is being subjected to experiments, with Earth serving as a giant laboratory.
The Great Filter is the idea that in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
The communication with extraterrestrial intelligence (CETI) is a branch of the search for extraterrestrial intelligence (SETI) that focuses on composing and deciphering interstellar messages that theoretically could be understood by another technological civilization. The best-known CETI experiment of its kind was the 1974 Arecibo message composed by Frank Drake.
First contact is a common science fiction theme about the first meeting between humans and extraterrestrial life, or of any sentient species' first encounter with another one, given they are from different planets or natural satellites. The theme allows writers to explore such topics such as xenophobia, transcendentalism, and basic linguistics by adapting the anthropological topic of first contact to extraterrestrial cultures.
Active SETI is the attempt to send messages to intelligent extraterrestrial life. Active SETI messages are predominantly sent in the form of radio signals. Physical messages like that of the Pioneer plaque may also be considered an active SETI message. Active SETI is also known as METI.
A post-detection policy (PDP), also known as a post-detection protocol, is a set of structured rules, standards, guidelines, or actions that governmental or other organizational entities plan to follow for the "detection, analysis, verification, announcement, and response to" confirmed signals from extraterrestrial civilizations. Though no PDPs have been formally and openly adopted by any governmental entity, there is significant work being done by scientists and nongovernmental organizations to develop cohesive plans of action to utilize in the event of detection. The most popular and well known of these is the "Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence", which was developed by the International Academy of Astronautics (IAA), with the support of the International Institute of Space Law. The theories of PDPs constitute a distinct area of research but draw heavily from the fields of SETI, METI, and CETI.
The cultural impact of extraterrestrial contact is the corpus of changes to terrestrial science, technology, religion, politics, and ecosystems resulting from contact with an extraterrestrial civilization. This concept is closely related to the search for extraterrestrial intelligence (SETI), which attempts to locate intelligent life as opposed to analyzing the implications of contact with that life.
Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not. Some authors prefer to exclude radio transmissions from the definition, but such restrictive usage is not widespread. Jill Tarter has proposed that the search for extraterrestrial intelligence (SETI) be renamed "the search for technosignatures". Various types of technosignatures, such as radiation leakage from megascale astroengineering installations such as Dyson spheres, the light from an extraterrestrial ecumenopolis, or Shkadov thrusters with the power to alter the orbits of stars around the Galactic Center, may be detectable with hypertelescopes. Some examples of technosignatures are described in Paul Davies's 2010 book The Eerie Silence, although the terms "technosignature" and "technomarker" do not appear in the book.
Breakthrough Initiatives is a science-based program founded in 2015 and funded by Julia and Yuri Milner, also of Breakthrough Prize, to search for extraterrestrial intelligence over a span of at least 10 years. The program is divided into multiple projects. Breakthrough Listen will comprise an effort to search over 1,000,000 stars for artificial radio or laser signals. A parallel project called Breakthrough Message is an effort to create a message "representative of humanity and planet Earth". The project Breakthrough Starshot, co-founded with Mark Zuckerberg, aims to send a swarm of probes to the nearest star at about 20% the speed of light. The project Breakthrough Watch aims to identify and characterize Earth-sized, rocky planets around Alpha Centauri and other stars within 20 light years of Earth. Breakthrough plans to send a mission to Saturn's moon Enceladus, in search for life in its warm ocean, and in 2018 signed a partnership agreement with NASA for the project.
Douglas A. Vakoch is an American astrobiologist, search for extraterrestrial intelligence (SETI) researcher, psychologist, and president of METI International, a nonprofit research and educational organization devoted to transmitting intentional signals to extraterrestrial civilizations. Vakoch led METI's participation in Sónar Calling GJ 273b, which transmitted a series of interstellar messages to Luyten's Star, located 12.4 light years from Earth. Vakoch advocates ongoing transmission projects, arguing that this does not increase risks of an alien invasion as suggested by British cosmologist Stephen Hawking. He has participated in several SETI observation programs, and after sixteen years at the SETI Institute, where he was director of Interstellar Message Composition, Vakoch founded METI International. He has edited over a dozen books in SETI, astrobiology, the psychology of space exploration, and ecocriticism. He is general editor of two-book series in ecocriticism and in the intersection of space and society. Vakoch has appeared widely on television and radio as a commentator on SETI and astrobiology. He is an emeritus professor of clinical psychology at the California Institute of Integral Studies (CIIS).
Archaeology, Anthropology, and Interstellar Communication is a 2014 collection of essays edited by Douglas Vakoch and published by NASA. The book is focused on the role that the humanities and social sciences, in particular anthropology and archaeology, play in the search for extraterrestrial intelligence (SETI). The seventeen essays are gathered into four sections, which respectively explore the history of SETI as a field; archaeological comparisons for human-alien communication, such as the difficulties of translating ancient languages; the inferential gap between humans and aliens, and the consequences this would have for communication and trade; and the potential nature of alien intelligences.
The following outline is provided as an overview of and topical guide to extraterrestrial life:
The berserker hypothesis, also known as the deadly probes scenario, is the idea that humans have not yet detected intelligent alien life in the universe because it has been systematically destroyed by a series of lethal Von Neumann probes. The hypothesis is named after the Berserker series of novels (1963–2005) written by Fred Saberhagen.
The Hart–Tipler conjecture is the idea that an absence of detectable Von Neumann probes is contrapositive evidence that no intelligent life exists outside of the Solar System. This idea was first proposed in opposition to the Drake equation in a 1975 paper by Michael H. Hart titled "Explanation for the Absence of Extraterrestrials on Earth". Assuming that the probes traveled at 1/10 the speed of light and that no time was lost in building new ships upon arriving at the destination, Hart surmised that a wave of Von Neumann probes could cross the galaxy in approximately 650,000 years, a comparatively minimal span of time relative to the estimated age of the universe at 13.7 billion years. Hart’s argument was extended by cosmologist Frank Tipler in his 1981 paper entitled ‘Extraterrestrial intelligent beings do not exist’.
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