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We consider the problem of detectability of macro-engineering projects over interstellar distances, in the context of Search for ExtraTerrestrial Intelligence (SETI). Freeman J. Dyson and his imaginative precursors, like Konstantin Tsiolkovsky, Olaf Stapledon or John B. S. Haldane, suggested macro-engineering projects as focal points in the context of extrapolations about the future of humanity and, by analogy, other intelligent species in the Milky Way. We emphasize that the search for signposts of extraterrestrial macro-engineering projects is not an optional pursuit within the family of ongoing and planned SETI projects; inter alia, the failure of the orthodox SETI thus far clearly indicates this. Instead, this approach (for which we suggest a name of ‘‘Dysonian’’) should be the front-line and mainstay of any cogent SETI strategy in future, being significantly more promising than searches for directed, intentional radio or microwave emissions. This is in accord with our improved astrophysical understanding of the structure and evolution of the Galactic Habitable Zone, as well as with the recent wake-up call of Steven J. Dick to investigate consequences of postbiological evolution for astrobiology in general and SETI programs in particular. The benefits this multidisciplinary approach may bear for macro-engineers are also briefly highlighted

Motivated by recent developments impacting our view of Fermi's paradox (absence of extraterrestrials and their manifestations from our past light cone), we suggest a reassessment of the problem itself, as well as of strategies employed by SETI projects so far. The need for such reevaluation is fueled not only by the failure of searches thus far, but also by great advances recently made in astrophysics, astrobiology, computer science and future studies, which have remained largely ignored in SETI practice. As an example of the new approach, we consider the effects of the observed metallicity and temperature gradients in the Milky Way on the spatial distribution of hypothetical advanced extraterrestrial intelligent communities. While, obviously, properties of such communities and their sociological and technological preferences are entirely unknown, we assume that (1) they operate in agreement with the known laws of physics, and (2) that at some point they typically become motivated by a meta-principle embodying the central role of information-processing; a prototype of the latter is the recently suggested Intelligence Principle of Steven J. Dick. There are specific conclusions of practical interest to be drawn from coupling of these reasonable assumptions with the astrophysical and astrochemical structure of the Galaxy. In particular, we suggest that the outer regions of the Galactic disk are most likely locations for advanced SETI targets, and that intelligent communities will tend to migrate outward through the Galaxy as their capacities of information-processing increase, for both thermodynamical and astrochemical reasons. This can also be regarded as a possible generalization of the Galactic Habitable Zone, concept currently much investigated in astrobiology., 30 pages, 2 figures

An interesting consequence of the modern cosmological paradigm is the spatial infinity of the universe. When coupled with naturalistic understanding of the origin of life and intelligence, which follows the basic tenets of astrobiology, and with some fairly incontroversial assumptions in the theory of observation selection effects, this infinity leads, as Ken Olum has recently shown, to a paradoxical conclusion. Olum's paradox is related, to the famous Fermi's paradox in astrobiology and SETI studies. We, hereby, present an evolutionary argument countering the apparent inconsistency, and show how, in the framework of a simplified model, deeper picture of the coupling between histories of intelligent/technological civilizations and astrophysical evolution of the Galaxy, can be achieved. This strategy has consequences of importance for both astrobiological studies and philosophy., 14 pages, no figures

It is argued that the tight interconnection between biological, climatological, and geophysical factors in the history of the terrestrial biosphere can teach us something of wider importance regarding the general astrobiological evolution of planets in the Galactic habitable zone of the Milky Way. Motivated by a recent debate on the future of Earth's biosphere, we suggest an additional reason why the impact of plate tectonics on the biological evolution is significant on the global Galactic level., 5 pages, no figures; Precambrian Research, submitted

Ancient origins of a modern anthropic argument against cosmologies involving infinite series of past events are considered. It is shown that this argument - which in modern times has been put forward by distinguished cosmologists like Paul C. W. Davies and Frank J. Tipler - originates in pre-Socratic times and is implicitly present in the cyclical cosmology of Empedocles. There are traces of the same line of reasoning throughout the ancient history of ideas, and the case of a provocative statement of Thucydides is briefly analyzed. Moreover, the anthropic argument has been fully formulated in the epic of Lucretius, confirming it as the summit of ancient cosmology. This is not only of historical significance but presents an important topic for the philosophy of cosmology provided some of the contemporary inflationary models, particularly Linde's chaotic inflation, turn out to be correct., Comment: 11 pages, no figures; Astronomical and Astrophysical Transactions, accepted

We investigate the rate of operation of quantum "black boxes" ("oracles") and point out the possibility of performing an operation by a quantum "oracle" whose average energy equals zero. This counterintuitive result not only presents a generalization of the recent results of Margolus and Levitin, but might also sharpen the conceptual distinction between the "classical" and the "quantum" information., a new form of quant-ph/0103150; Journal Ref. Phys. Lett. A 302 (2002) 291

Cosmology seems extremely remote from everyday human practice and experience. It is usually taken for granted that cosmological data cannot rationally influence our beliefs about the fate of humanity -- and possible other intelligent species -- except perhaps in the extremely distant future, when the question of heat death (in an ever-expanding universe) becomes actual. Here, an attempt is made to show that it may become a practical issue much sooner, if an intelligent community wishes to maximize its creative potential. New developments in the fields of anthropic self-selection and physical eschatology give solid foundations to such a conclusion. This may open some new (and possibly urgent) issues in the areas of future policy making and transhumanist studies generally. It may also give us a slightly better perspective on the SETI endeavor., Comment: 18 pages, expanded and modified version of the paper published in "Journal of Evolution and Technology" (http://www.jetpress.org), vol. 12 (2002)

We investigate the impact of the non-zero cosmological constant on the classical decaying dark matter theory developed by the late Dennis Sciama. In particular, we concentrate on the change in relevant values of cosmological parameters in comparison to the high-precision estimates given by Sciama (1997). It is shown that the appropriate changes in resulting parameter values are such to make the DDM concept less plausible. This is in complete agreement with recently reported observational results detrimental to this theory., 4 pages, 2 eps figures, uses AA latex style

An estimate of the maximal informational content available to advanced extraterrestrial or future (post)human civilizations is presented. It is shown that the fundamental thermodynamical considerations may lead to a quantitative estimate of the largest quantity of information to be processed by conceivable computing devices. This issue is interesting from the point of view of physical eschatology, as well as general futurological topics, like the degree of confidence in long-term physical predictions or viability of the large-scale simulations of complex systems., Comment: 6 pages, no figures