Universo marzo-abril 2023

MARZO-ABRIL 2023 ASTRO PUBLISHING luz de la Tierra para sospechar que una especie de aquí ha empe- zado a modificar fuertemente su hábitat iniciando procesos indus- triales. Pero aun así, cualquiera que observara nuestra atmósfera seguiría sin estar seguro de que conocemos las ondas de radio y de que hemos desarrollado las te- lecomunicaciones hasta el punto de ser capaces de recibir e inter- pretar una señal no natural pro- cedente del espacio. Sólo una civi- lización situada a menos de 100 años-luz de la Tierra podría tal vez interceptar señales de radio pro- cedentes de nuestro planeta. 100 años-luz es el radio de la llamada “radiosfera”, es decir, el volumen de espacio alrededor de nuestro planeta donde podrían haber lle- gado las primeras señales de ra- dio, radar, televisión y similares, más o menos involuntariamente lanzadas al cosmos por las acti- vidades humanas. Incluso admi- tiendo que, increíblemente, pue- dan existir dos civilizaciones tec- nológicas capaces de comunicarse a menos de 100 años-luz de dis- tancia la una de la otra, esperar que “los otros” hayan podido cap- tar una señal nuestra y recono- cerla como artificial es una de- mostración de optimismo conside- rable. Sabemos, en efecto, que la intensidad de una señal electro- magnética disminuye con el cua- drado de la distancia, y aplicando esta ley física a las señales de di- versos tipos irradiadas desde la Tierra, obtenemos que casi todas ellas, tras viajar sólo un año luz, se degradan tanto que son indistin- guibles del ruido de fondo. Ya a la distancia de Plutón, incluso los mayores radiotelescopios terres- tres tendrían no pocas dificultades para captar nuestras transmisio- nes de radio y televisión. Las po- cas señales enviadas intenciona- damente a otras estrellas (a me- The Great Silence — Science and Philosophy of Fermi's Paradox This book explores the multifaceted problem named after the great Italian physicist Enrico Fermi and his legendary 1950 lunchtime question “Where is everybody?” In many respects, Fermi's paradox is the richest and the most challenging prob- lem for the entire field of astrobiology and SETI studies. The author shows how Fermi'’s paradox is intricately connected with many fields of learning, technology, arts, and even every- day life. It aims to establish the strongest possible version of the problem, to dispel many related confusions, obfuscations, and prejudices, as well as to offer a novel point of entry to the many solutions proposed in existing literature. The search for extraterrestrials — Intercepting alien signals Follow Monte Ross of the Laser Space Signal Observatory as he explores the challenges in searching for evidence of extrate- rrestrials, the programs that have failed, and those that con- tinue. The book circumvents the failure of searches at radio frequencies by being the first to explore electromagnetic fre- quencies besides RF and microwave as possible signal sources, taking into consideration all the ways that extraterrestrials might try to communicate with us. Throughout the presenta- tion, all the ideas, concepts, and approaches are explained clearly, without the use of complex math or physics. Light of the stars — Alien worlds and the fate of the Earth Adam Frank shows that not only is it likely that alien civiliza- tions have existed many times before, but also that many of them have driven their own worlds into dangerous eras of change. He explains how dust storms on Mars, the greenhouse effect on Venus, Gaia Theory, the threat of nuclear winter, and efforts to prove or disprove the plurality of worlds from Aristotle to Copernicus to Carl Sagan have contributed to our under- standing of our place in the universe. And he raises what may be the largest question of all: If there has been life on other worlds, what can its presence tell us about our own fate? Extraterrestrial — The First sign of intelligent life beyond Earth In Extraterrestrial, Avi Loeb (a Harvard University astrophysicist) takes readers inside the thrilling story of the first interstellar vi- sitor to be spotted in our solar system. He outlines his contro- versial hypothesis and its profound implications: for science, for religion, and for the future of our planet. A mind-bending jour- ney through the furthest reaches of science, space-time, and the human imagination, Extraterrestrial chal-lenges readers to aim for the stars-and to think critically about what's out there, no matter how strange it seems.