Article/Document:

Resources on Interstellar Probes

Interstellar-probes.org

original source |  fair use notice

Summary: This page contains a guide to the resources needed to study interstellar probes, interstellar travel, interstellar propulsion systems, the search for robotic interstellar probes or ETI probe visitation, and information on earth's robotic probes. Abstracts for the papers or the introductory text from the book, or book chapter, will be given.

RESOURCES

This page contains a guide to the resources needed to study interstellar probes, interstellar travel, interstellar propulsion systems, the search for robotic interstellar probes or ETI probe visitation, and information on earth's robotic probes. Abstracts for the papers or the introductory text from the book, or book chapter, will be given. Online links will be given to complete online papers. You are encouraged to get copies of these documents for your research activites.

This resource page is divided up into sections. The sections are numbered and the subject matter is combined based on its associated relavence. The papers in each section are listed in alphabetical order by author name, and title.

 

Interstellar Travel Resources

Forward, Robert, L., Feasibility of Interstellar Travel: A Review,
Journal of the British Interplanetary Society, Vol. 39, pp. 379-384, 1986.

Abstract - Interstellar travel is difficult, but not impossible. This review paper discusses the relative feasibility of a number of different technologies that will allow travel to the stars. It gives examples of one-way and rendezvous unmanned interstellar probe vehicles that can return data on the number and nature of the planets around the target system within less than 50 years after launch. These initial exploration probe missions will be followed by manned or robotic exploration and colonisation missions. These can range from relatively feasible long slow missions using "world ships" propelled by existing nuclear pulse or nuclear electric technologies and carrying self-producing human crews, to high risk, high speed missions using beamed power, antimatter, or interstellar ramjet technology. For the nearer stellar system, speeds of 0.1 to 0.3 the speed of light will suffice to explore the 17 nearest stellar systems with 25 visible stars and hundreds of planets in trip times comparable to a human lifetime. Some emergent high energy density technologies that are under development for other purposes, such as laser and electron beam imploded fusion and solar powered lasers and masers, show promise of providing us with propulsion technologies that will make rapid interstellar travel feasible within the foreseeable future.

Interstellar Propulsion Resources

Probe Energy Systems Resources

Search for ETI Probes Resources

Abstract - A hypothesis concerning the nature of extraterrestrial messages to the earth is proposed. The hypothesis is based on the following assumptions about (1) that they exist in abundance in the Galaxy; (2) that they are benevolent toward earth-based life forms, and (3) that the lack of any human detection of extraterrestrials is due to an embargo assigned to prevent any premature disclosure of their existence. It is argued that any embargo not involving alien force must be a leaky one designed to allow a gradual disclosure of the alien message and its gradual acceptance on the part of the general public over a very long time-scale. The communication may take the form of what is now considered magic, and may therefore be misinterpreted as 'magic' by or a hoax by contemporary governments and scientists.

Abstract - The problem of how to communicate with the members of an alien society has been discussed by many authors but only one, Freudenthal, has constructed a language for this purpose. Freudenthal assumes nothing other than the ability to reason as humans do and, because he assumes so little, it is necessary to communicate a great deal about the language itself before being able to communicate any interesting information. The problem is here approached differently. Since it is likely that contact between the civilization and an alien one would be via radio, potential correspondents would have a basic knowledge of science. Such beings should therefore be able to learn a language based on fundamental science. It is assumed, more specifically, that the correspondents can count, understand chemical elements, are familiar with the melting and boiling behavior of a pure substance and understand the properties of the gaseous state. All this should be known to any society capable of developing the radio telescope. By systematically using this common knowledge one can communicate notation for numbers and chemical elements and then communicate the basic physical units; i.e., the gram, the calorie, the degree (Kelvin), etc. Once this is done more interesting information can be exchanged.

Abstract - Present SETI projects are described, emphasizing search methods alternative to investigations in the radio range. The possibility that the human race is being studied by alien presences within the solar system is addressed in the context of the 'zoo hypothesis' and the 'leaky embargo' hypothesis. In the former, the aliens prevent any contact with humans, while in the latter occasional contact is permitted.

Abstract - Photographs in the vicinity of the Earth-Moon triangular libration points L4 and L5, and of the solar-synchronized positions in the associated halo orbits (A. A. Kamel, 1969, Ph.D. dissertation, Stanford University), were made during August-September 1979, using the 30-in Cassegrain telescope at Leuschner Observatory, Lafayette, California. An effective 2° square field was covered at each position. No discrete objects, either natural or artificial, were found. The detection limit was about 14th magnitude. The present work extends traditional SETI observations to include the search for interstellar probes.

Abstract - Abstract - A photographic search of the five Earth-Moon Lagrangian positions included the solar-synchro-nized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near L1/L2, Earth-Moon L3, and also L2 in the Sun-Earth system. Observations using the 61-cm Burrell Schmidt telescope at the Warner and Swasey Observatory, Kitt Peak Station, spanned 60° along the lunar orbital plane x 5° around Earth-Moon L5, 48" x 5° around L4, 25° x 13° around L3, 15° x 24° around the Moon (LI/L2). and 14° x 14° around Sun-Earth L2. Limiting magnitude for the detection of libration objects near L3, L4, and L5 was 17-19th magnitude, 10-18th magnitude for L!/L2 plates, and 14-16th magnitude for Sun-Earth L2. No natural or artificial objects were found. An automated search of selected priority plates was attempted using the Faint Object Classification and Analysis System (FOCAS) software package.

Abstract - Bracewell and Frietas have discussed the possible superiority of interstellar probes in missions of galactic exploration and recently Calder and Boyce have raised the issue of self-organizing machines in related contexts. In this paper a preliminary sketch of a self-reproducing starprobe is presented, with generation time ~103 years given a ~10-fold improvement in current human space/manufacturing technology.

Abstract - Bracewell has suggested the use if nonreproducing messenger probes for interstellar exploration, and Freitas has examined the feasibility of self-reproducing automated devices in the same context. The present paper compares reproducing and nonreproducing strategies for missions of interstellar and galactic discovery. Self-reproducing probes are found to be the method of choice for active exploration programs lasting >106 years, involving searches of >106 target stars to distances > 1000 light-years in the Galactic Disk, and are superior to one-shot "Bracewell Probes" for searches of >103 stars to distances > 100 light-years in the Galactic Disk. Any nonreproducing alien probes discovered in the Solar System during the normal course of future SETI research would most likely have been sent by extraterrestrial civilizations located within a approx. 1000 light-year radius of the Sun, whereas any self-reproducing devices similarly detected probably originated far outside the exploration sphere.

Abstract - The assertion that extraterrestrial intelligences (ETI) do not exist based on the apparent contradictions inherent in the Fermi Paradox, rests upon an unproven and untenable presumption: That ETI are not now present in the Solar System. Most advanced civilisations also would be either invisible or unrecognisable using current human observational methods, so millions of advanced societies may exist and still not be directly detectable by us. Thus the Fermi Paradox cannot logically be raised as an objection to the existence of ETI until these major observational deficiencies have been corrected.

Abstract - This paper discusses observational considerations in a search for extraterrestrial intelligence (SETI) program to detect extraterrestrial messenger probes in the solar system. Observable artifacts will most likely be found in a search space consisting of geocentric, selenocentric, Earth-Moon Libration, and Earth-Moon Halo orbits, which may be searched to a limiting artifact size of 110 m (pv = 0.1) using existing or foreseeable instrumentation.

Abstract --Interstellar transmissions via energy-markers (photons) or matter-markers (probes) appear to be energetically indistinguishable alternatives for advanced technical societies. Since only Type II and Type III civilizations realistically can afford beacons or starprobe technology, alternative distinguishability criteria suggest the possible superiority of intelligent artifacts for contact and communication missions among extraterrestrial cultures. A balanced, more cost-effective Search for ExtraTerrestrial Intelligence (SETI) strategy is proposed.

Abstract - The rationale for the use of interstellar artifacts by intelligent life in the universe is described. The advantages of using interstellar probes as a means of exploration and communication are presented and shown to be significant enough to counter the time, energy, and technology arguments generally raised against contact via extraterrestrial artifacts. Four classes of artifacts are defined: Those seeking contact, those seeking to avoid contact, those intended to provide a passive technological threshold for detection, and those for which detection is irrelevant. The Search for Extraterrestrial Artifacts (SETA) is based on the latter two classes. Under the assumption that an extraterrestrial probe will be interested in life in our solar system, a near-Earth search space is defined. This search space is accessible to us now with ground and satellite observing facilities. The current observational status of SETA is reviewed and contrasted with the achievable detection limits for the different parts of the search space.

Abstract - The Artifact Hypothesis states that an advanced extraterrestrial intelligence has undertaken a long-term programme of galactic exploration via the transmission of material artifacts. An attempt to verify this hypothesis experimentally, the search for extraterrestrial artifacts (SETA), is proposed to detect such evidence in the Solar system by telescopic, radar, infrared, direct probe, or other available means.

Abstract - Interstellar spacecraft are superior to electromagnetic wave propagation for extrasolar exploration and communication. The search for extraterrestrial intelligence (SETI) should include a search for extraterrestrial probes. Arguments favouring, and various traditional objections to, interstellar communications via messenger probe are critically reviewed.

Abstract - The "Fermi Paradox," an argument that extraterrestrial intelligence cannot exist because it has not yet been observed, is a logical fallacy. This "paradox" is a formally invalid inference, both because it requires modal operators lying outside the first-order propositional calculus and because it is unsupported by the observational record.

Abstract - Four categories of facts are explored for explaining the lack of observable extraterrestrial beings (ETs) on earth. The physical reasons are suggested to be the long travel times required by sublight-velocity spaceships, a problem that may be overcome by beings that live several millennia or that can be stored and reproduced from zygotes on arrival. Also, the energy requirements for interstellar travel, though large, are not an insurmountable difficulty. Sociologically, it is suggested that ETs have no interest in space travel, or they may have destroyed themselves with atomic wars, or the earth is being used as a wildlife preserve. No procedures exist to test these hypotheses, however. The consideration that ETs have not yet had time to find earth is discounted by calculations that show that another intelligent species in the Galaxy would have found earth if their space exploration efforts began at least 2,000,000 yr ago. It is concluded that if the earth has not yet been visited, then colonization of the Galaxy will most probably be done by humans, who may have the first advanced civilization in the Galaxy.

Abstract - The discussion deals with two questions: assuming a signal has been detected, does the signal contain a message. If so, how can it be deciphered. The concept of the message as a statistical variate is explained. When the suspected sequence of elements is examined for randomness, if any departure from randomness is found, the presence of a message is indicated. Detection of several independent organizations approaches proof of the existence of a message. In answer to the second question, some linguistic concepts are brought forward. A common experience and accord on a symbol for that experience are required for communications. Interspecies experiential differences make the first condition difficult to meet. It is argued that the frequency of the hydrogen line would constitute such a commonality. A search for a beacon frequency could commence not at integral multiples of this frequency, but at multiples by some universal constant, such as pi or e. A hypothetical interstellar message is given which first gives the code, i.e., Morse, in terms of number symbols, a likely common ground; then transmits the number pi in those symbols; then repeats the message.

Abstract - Over a period of years, diverse aerial sightings of an unusual character have been reported. On the assumption that the majority of these reports, often made in concert, come from reputable persons, and in the absence of any universal hypotheses for the phenomena which stimulated the reports, it becomes a matter of scientific obligation and responsibility to examine the reported phenomena seriously despite their seemingly fanciful character. Accordingly, several hundred serious reports of "unidentified aerial objects" have been studied in detail in an attempt to get a pattern classification. It appears that those reported phenomena which do not admit of a ready and obvious explanation exhibit fairly well-defined patterns and that these are worthy of further study. One pattern in particular, that of a hovering nocturnal light, does not appear to be readily explainable on an astronomical basis or by mirages balloons or by conventional aircraft.

Introductory paragraph -One of the fundamental questions in the Search for Extraterrestrial Intelligence (SETI) is the deceptively simple-worded "Where are they?". In certain respects it is an even more pertinent query than "What are they?" For SETI to succeed, we first need to know where alien intelligence exists in the Milky Way galaxy and the locations of their signals and artifacts-which may or may not be in the same places. Pondering the makeup of extraterrestrial beings is important, but until we actually detect them, the true constitution of alien life forms will remain only speculation.

A concerted, national, and perhaps international, effort to find radio signals from extraterrestrial civilizations (ETC's) will probably be started within the next few years. It will be the outcome of nearly 20 years of smaller searches at various radio observatories (1) and about a decade of preliminary planning for a dedicated facility (2). One major study conducted by Stanford University and NASA Ames Research Center (3) resulted in the design for an array of up to 1000 antennas of 100-meter aperture. The search for extraterrestrial intelligence (SETI) has bee identified in "Outlook for Space" (4) as one of the possible future tasks for the National Aeronautics and Space Administration (objective 125) and the large receiving array as one of the prerequisites (system 4010).
1. For a review of various search programs that have been conducted, see C.Sagan and F. Drake, Sci. Am. 233, 83 (May 15)
2. Final Report of the Science Workshop on Interstellar Communication, NASA Spec. Publ., in preparation.
3. Project Cyclops (Report CR114445, NASA Ames Research Center, Moffett Field, Calif., 1971)
4. "Outlook for Space," NASA Spec. Publ. SP-386 1976.

Abstract - This resource letter provides a guide to the literature about intelligent life beyond the human sphere of exploration. It offers a starting point for professionals and academics interested in participating in the debate about the existence of other technological civilizations or in SETI.

Abstract - If even a very small fraction of the hundred billion stars in the galaxy are home to technological civilizations which colonize over interstellar distances, the entire galaxy could be completely colonized in a few million years. The absence of such extraterrestrial civilizations visiting Earth is the Fermi paradox.

A model for interstellar colonization is proposed using the assumption that there is a maximum distance over which direct interstellar colonization is feasable. Due to the time lag involved in interstellar communications, it is assumed that an interstellar colony will rapidly develop a culture independent of the civilization that originally settled it.

Any given colony will have a probability P of developing a colonizing civilization, and a probability (1-P) that it will develop a non-colonizing civilization. These assumptions lead to the colonization of the galaxy occuring as a percolation problem. In a percolation problem, there will be a critical value of the percolation probability, Pc. For P < Pc, colonization will always terminate after a finite number of colonies. Growth will occur in "clusters," with the outside of each cluster consisting of non-colonizing civilizations. For P > Pc, small uncolonized voids will exist, bounded by non-colonizing civilizations. When P is on the order of Pc, arbitrarily large filled regions exist, and also arbitrarily large empty regions.

Introductory paragraphs - If intelligent life is a common occurrence in the Galaxy, then many civilizations should have arisen which by now are far in excess of mankind in both their age and their capabilities. It is to be expected on technical grounds that some of these should have crossed the threshold of their home planetary system and ventured out into interstellar space. In a time that is short when measured against astronomical timescales such civilizations could have colonized the planets orbiting every suitable star in the Galaxy.

As the Solar System is relatively young in the Galaxy, there should never have been a time in our history when mankind was not aware of the presence of such civilizations. And yet, we apparently see no signs of intelligent life in the Galaxy other than ourselves.

This paradox, now well known, was first expressed by Enrico Fermi 40 years ago, and today is still as relevant to discussions on the possible existence of intelligent life in the Universe and the methods of searching for signs of such life as it was then.

The authors have reviewed the many aspects of the Fermi Paradox for the last decade, and have recently entered the debating chamber. This present paper is an attempt to further contribute to that debate by exploring some of the arguments prompted by the Paradox in more detail than we have previously commented on. We emphasize that we are participating in a debate which has been underway for several years now, and which has well-developed arguments covered in depth in the literature. It is our hope that, by elaborating some of the key concepts which we find persuasive, we will cause the debate to refocus on the Paradox that Fermi identified so many years ago.

Abstract - Fermi's Paradox is set out, and related to Drake's Equation for the probability of communicating Extraterrestrial civilizations. The terms are described, leaving the lifespan of a technological civilization as the most important. Factors affecting this term (V) are outlined, with reference to asteroid impacts. The asteroid impact threat is discussed in terms of its nature, and implications for Space development. Survival strategies for particular cultures here on Earth are described. Two extreme cases - one of isolation - the aboriginals of Australia, and the other, one of dispersal, dynamism, and belief in future Destiny - Judaism - are contrasted. It is shown that, for advanced liberal human civilization, Diaspora works and is most likely to ensure development. A proposed solution to the threat from Fermi's Paradox for our emerging civilization is dispersal backed by belief in a Cosmic Destiny for Humankind. If we are alone in the Galaxy, this is necessary for further Evolution; if not, Humanity's contribution to an overall future Galactic civilization requires expansion into Space. This rationale for space development should be adopted by the Space community. Outreach efforts by the author and associates are described.

Abstract - In order to increase the probability of contact in the search for extraterrestrial intelligence (SETI) it has been proposed to search more intensively in certain regions of the electromagnetic spectrum ("the water hole"). The present paper describes a similar narrowing of the search in the time domain. Application of this strategy results in the SETI experiment of searching for signals from the Tau Ceti system late in 1986 and early in 1987 and the Epsilon Eridani system in mid 1988.

Abstract - The observations that life has a natural tendency to expand into all available space, that advanced technological civilizations should be able to engage with relative ease in interstellar travelling, and that once this threshold is crossed the complete colonization of the entire Galaxy will be accomplished in a very short interval relative to the age of the Galaxy, lead us to the following dilemma: either the entire Galaxy is teeming with intelligent life and hence our solar system must have been colonized hundreds of millions of years ago, or there are no other inhabitants in our solar system and hence most probably neither any-where else in the Galaxy. Before accepting, however, the bleak verdict that we are all alone in the Galaxy, we must search carefully throughout the solar system for any signs of other technological civilizations. The most logical place to look for them seems to be the asteroid belt because of the many advantages it offers to a galactic society living in space colonies.

Abstract - Scientific and philosophical issues related to the search for extraterrestrial intelligence (ETI) are examined. The possible existence and nature of ETI, extraterrestrial epistemology, and a solipsist approach to ETI are discussed. Consideration is given to the detectability and decipherability of extraterrestrial communications, the design of a language for cosmic communication, and the meaning and consequences of contact.

Abstract -The mechanistic interpretation of the communication process between cognitive hierarchical systems as an iterated pair of convolutions between the incoming discrete time series signals and the chaotic dynamics (CD) at the nm-scale of the perception (energy) wetware level, with the consequent feeding of the resulting collective properties to the CD software (symbolic) level, shows that the category of quality, largely present in Galilean quantitative-minded science, is to be increasingly made into quantity for finding optimum common codes for communication between different intelligent beings. The problem is similar to that solved by biological evolution, of communication between the conscious logic brain and the underlying unfelt ultimate extralogical processes, as well as to the problem of the mind-body or the structure-function dichotomies. Perspective cybernated nanotechnological and/or nanobiological interfaces, and time evolution of the 'contact language' (the iterated dialogic process) as a self-organising system might improve human-alien understanding.

Abstract - Considerations in the design of receivers for the detection and recognition of artificial microwave signals of extraterrestrial origin are discussed. Following a review of the objectives of SETI and the probable reception and detection characteristics of extraterrestrial signals, means for the improvement of the sensitivity, signal-to-noise ratios and on-line data processing capabilities of SETI receivers are indicated. The characteristics of the signals likely to be present at the output of an ultra-low-noise microwave receiver are then examined, including the system background noise, terrestrial radiations, astrophysical radiations, accidental artificial radiations of terrestrial origin, and intentional radiations produced by humans and by extraterrestrial intelligence. The classes of extraterrestrial signals likely to be detected, beacons and leakage signals, are considered, and options in the specification of gating and thresholding for a high-spectral resolution, high-time-resolution signal discriminator are indicated. Possible tests for the nonhuman origin of a received signal are also pointed out.

Abstract - A ~ 10-metre object on a heliocentric orbit, now catalogued as 1991 VG, made a close approach to the Earth in 1991 December, and was discovered a month before perigee with the Spacewatch telescope at Kitt Peak. Its very Earth-like orbit and observations of rapid brightness fluctuations argue for it being an artificial body rather than an asteroid. None of the handful of man-made rocket bodies left in heliocentric orbits during the space age have purely gravitational orbits returning to the Earth at that time, and in any case the a priori probability of discovery for 1991 VG was very small, of order one in 100,000 per anmun. In addition, the small perigee distance observed might be interpreted as an indicator of a controlled rather than a random encounter with the Earth, and thus it might be argued that 1991 VG is a candidate as an alien probe observed in the vicinity of our planet.

Abstract
Technological advancements have allowed us to build robotic space probes to remotely explore the solar system. Interstellar robotic missions are under serious consideration. Advanced extant extraterrestrial civilizations within the galaxy, if they exist, are very likely exploring with robotic probes as well, some of which may have reached our solar system and taken an interest in life on Earth. Recent technological advances make it possible to conduct a scientific search for evidence of extraterrestrial interstellar robotic probes. Modern solid-state sensing devices and scientific instruments, combined with high-speed computer hardware, can be used in an effort to detect the physical presence of a probe. The SETV (Search for Extraterrestrial Visitation) model is new and an offspring of SETA (artifacts) and SETI. SETV includes the construction of passive autonomous data acquisition platforms using "commercial off-the-shelf" hardware, to collect reliable and unambiguous data on anomalous observational phenomena that may be ETI probes. The SETV hypothesis and experimental methods will be described. The SETV hypothesis can be experimentally tested and attempts to statistically reject a null hypothesis which states that ETI probes do not exist. SETV Pre and Post-detection protocols are necessary and will be examined. SETV is a timely, results-oriented, method worthy of serious consideration in our continuing desire to answer the question "Are we alone?"

Keywords: SETI, Interstellar robotic probes, SETV, SETA, COTS, Instruments, Sensors, Automated smart surveillance

Table of Contents
1. Introduction
2. Autonomous ETI Probes and their missions
     Figure 1. Russian Luna 1 Space Probe (circa 1959)
3. The SETV Experiment
    3.1 Placement of an Experimental Platform
    3.2 Description of an Experimental Platform
       Figure 2. ETP Scanning Polycamera System Block Diagram
    3.3 Related Observational Experiments, AOP and DATA Analysis
       Figure 3. Hypothetical Cladogram
    3.4 SETV Protocols
4. Conclusion
5. Acknowledgements
References

Abstract -Arguments that even a single extraterrestrial civilization would have long ago colonized the Galaxy are not compelling. Many factors, including intraspecific competition, could prevent complete colonization, except, perhaps, on time scales much greater than 1010 years. It follows that the fact that extraterrestrial civilizations do not appear to be represented on Earth is irrelevant to the formulation of plans to search for them.

Introductory paragraph - It appears that the search for extraterrestrial intelligence (ETI) is now a legitimate activity for astronomers and other scientists. This topic was recently reviewed on behalf of NASA by a panel of distinguished scientists led by professor Philip Morrison. Their primary conclusion is that, 'It is both timely and feasible to begin a serious search for intelligent extraterrestrial radio signals and also outline possible techniques for searching for planets associated with nearby stars (1).
1. Morrison, P., Billingham, J. & Wolfe, J. (eds), 1977. The Search for Extraterrestrial Intelligence, SETI, NASA SP-419, National Aeronautics and Space Administration, Washington, DC.

Abstract - Estimation of the number N of communicative civilizations by means of Drake's formula involves the combination of several quantities, each of which is to some extent uncertain. The uncertainty in any quantity may be represented by a probability distribution function, even if that quantity is itself a probability. The uncertainty of current estimates of N is derived principally from uncertainty in estimates of the lifetime of advanced civilizations. It is argued that this is due primarily to uncertainty concerning the existence of a "Galactic Federation" which is in turn contingent upon uncertainty about whether the limitations of present-day physics are absolute or (in the event that there exists a yet-undiscovered "hyperphysics") transient. It is further argued that it is advantageous to consider explicitly these underlying assumptions in order to compare the probable numbers of civilizations operating radio beacons, permitting radio leakage, dispatching probes for radio surveillance or dispatching vehicles for manned surveillance.

Abstract - Progress in science depends on the appraisal of hypotheses by reference to observational data. This procedure is formalized in such a way that judgments made by the theorists and judgments made by the observers may be combined to yield probabilities for the considered hypotheses.

Origins of Life, Vol. 6, pp. 459-470, July 1975.

Abstract - Unexplained plasma-like atmospheric "light balls" are observed at very low altitudes during alternate phases of maximum and minimum in the essdalen area, located in central Norway. Several theories are presented in order to explain the observed phenomenon; among these: piezo-electricity from rocks, atmospheric ionization triggered by solar activity, cosmic rays and extraterrestrial visitation. The presented study is aimed at proposing the use of a dedicated instrumental set-up, research experimental procedures and methods in order to prove or disprove every single theory: in this context several kinds of observational techniques, measurement strategies and physical tests of tactical relevance are discussed in detail. An introduction on any considered theory is presented together with a detailed discussion regarding the subsequent experimental phase. For each specific theory brief descriptions of the observable parameters and of the essential instrumental choices and a detailed discussion of measurement procedures coupled with suitable flow-charts, are presented.

Abstract - Possible forms of energy conversion, technologies, and interstellar projects on which advanced extraterrestrial civilizations may be occupied are discussed. It is suggested that if life began evolving in the Universe 8-10 billion years ago, then some alien civilizations may be presently reshaping and building galaxies by now, although no astronomical evidence for such feats is presently available. Limiting factors for civilizations are light speed and dependence for thermal conditions on the distance to the home star. Energy limitations will encourage continual reconfiguring of a civilization's energy usage until the prime energy source is the home star, around which city-worlds could be built. The techniques would eventually lead to star travel because of the ability to reform and use energy. However, if life came into existence everywhere in the Universe simultaneously at the phase change after the Big Bang, then even millions of years could transpire before initial attempts to colonize the galaxy are enacted. The limitations on terrestrial technology and energy supplies would then be the equivalent of those in other civilizations, indicating that millimeter wave transmissions would have a chance at establishing contact.

Abstract - Humanity is making rapid progress in computers, robotics, nanotechnology and space exploration. Consequently, within 200 years, we will be likely to launch small interstellar probes containing highly advanced computers. Perhaps other civilizations, more advanced than ours, launched intelligent machines long ago to explore parts of our galaxy. One of their tiny probes may have already reached our planet in order to observe or monitor us. Our current scientific search for extraterrestrial intelligence should be expanded by adding a sophisticated search for such a probe. Two SETI "declarations of principles" have been developed to cover the search for radio and laser signals originating many light-years away. Some SETI scientists have assumed that these two declarations also apply to the scenario of discovering a nearby probe but, in fact, the fit is not very good. A separate set of "Procedures Following Detection of An Interstellar Probe" has been drafted.

Abstract - Because their capacities are probably highly advanced, some extraterrestrial species may be using unobtrusive methods of observing humankind and other fledgling civilisations in the Galaxy. The amount of help they want to give to such civilisations is probably quite significant. Their help could be of three types: instant intervention to avoid a nuclear holocaust or other imminent catastrophe; long-term help in reducing grave dangers; and help in improving nondangerous spheres of life. Sooner of later, unless we extinguish ourselves first, advanced extraterrestrials will have an enormous impact on humankind. Even during the next 30 years, the probability of contact or interaction may be one in four. Given these conclusions, what should we do next? Thirteen possible strategies are outlined. The likelihood and benefits of success are estimated for each strategy; then its overall priority is rated. At present, seven of the eight highest priority strategies remain neglected and unfunded.

Chapter 7. Interstellar Propulsion Systems

Author: Freeman Dyson

Chapter Introductory Statement:

Chapter 8. Interstellar Travel: A Review

Author: Ian A. Crawford

Chapter 9. Settlements in Space, and Interstellar Travel

Author: Cliff Singer

Read more articles on this topic:

Interstellar Probes / SETV