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Under the hypothesis that self-reproducing probes have formed a galactic-scale communication network by direct Gravitationally-Lensed (GL) links between neighboring systems, we identify Wolf 359, the third nearest stellar system, as an…
The Kepler mission has shown that a significant fraction of all stars may have an Earth-size habitable planet. A dramatic support was the recent detection of Proxima Centauri b. Using a Drake-equation like formalism I derive an equation for…
We address the possibility that intelligent civilisations that destroy themselves could present signatures observable by humanity. Placing limits on the number of self-destroyed civilisations in the Milky Way has strong implications for the…
It has recently been suggested in this journal by Benford (2019) that "Lurkers" in the form of interstellar exploration probes could be present in the solar system. Similarly, extraterrestrial intelligence could send long-lived probes to…
The question of whether intelligent life exists elsewhere is one of the fundamental unknowns about our Universe. Over the past decade more than 200 extra-solar planets have been discovered, providing new urgency for addressing this question…
The METI risk problem refers to the uncertain outcome of sending transmissions into space with the intention of messaging to extraterrestrial intelligence (METI). Here, I demonstrate that this uncertainty is undecidable by proving that that…
We present a simplified description of expansionistic life in the standard relativistic cosmology. The resulting model is exactly integrable, yielding a simple set of predictive formulas. This allows one to quickly propose new scenarios for…
The concept of a rapid spread of self-replicating interstellar probes (SRPs) throughout the Milky Way adds considerable strength to Fermi's Paradox. A single civilisation creating a single SRP is sufficient for a fleet of SRPs to grow and…
Ours could realistically be the generation to discover evidence of life beyond Earth. With this privileged potential comes responsibility. The magnitude of the question, "are we alone?", and the public interest therein, opens the…
The data recently accumulated by the Kepler mission have demonstrated that small planets are quite common and that a significant fraction of all stars may have an Earth-like planet within their Habitable Zone. These results are combined…
First contact with another civilization, or simply another intelligence of some kind, will likely be quite different depending on whether that intelligence is more or less advanced than ourselves. If we assume that the lifetime distribution…
Hypothetical existence of other universes gives an opportunity not only to extend the scope of physics, but the scope of biology, SETI, and METI as well. Some steps of the development of alien life concept shall be briefly summarized, then…
An astrophysical model is proposed to answer Fermi's question. Gamma-ray bursts have the correct rates of occurrence and plausibly the correct energetics to have consequences for the evolution of life on a galactic scale. If one assumes…
We estimate the relative likelihood of success in the searches for primitive versus intelligent life on other planets. Taking into account the larger search volume for detectable artificial electromagnetic signals, we conclude that both…
One of the most interesting unsolved questions in science today is the question of life on other planets. At the present time it is safe to say that we do not have much of an idea as to whether life is common or exceedingly rare in the…
The Search for Extra-Terrestrial Intelligence (SETI) has been conducted for over sixty years, yet no technosignatures have been identified. Previous studies have focused on stars in our galaxy, with few searches in the extragalactic…
The Search for Extraterrestrial intelligence (SETI) is a scientific and cultural effort seeking evidence of intelligent life beyond earth. Radio SETI observes the radio spectrum for ''technosignatures" that could be produced by an advanced…
The search for extraterrestrial intelligence includes efforts to constrain populations of artificial broadcasts in other galaxies. Previous efforts use individualist methods, searching for single broadcasts with high signal-to-noise ratio.…
The number of people able to end Earth's technical civilization has heretofore been small. Emerging dual-use technologies, such as biotechnology, may give similar power to thousands or millions of individuals. To quantitatively investigate…
The theory of lithopanspermia proposes the natural exchange of organisms between solar system bodies through meteorites. The focus of this theory comprises three distinct stages: planetary ejection, interplanetary transit and planetary…