Free Astronomy Magazine March-April 2023

MARCH-APRIL 2023 ASTRO PUBLISHING derstanding at what evolution- ary stage it is. That civilization would have to be on a planet no more than 100-200 light- years from Earth to suspect that a species here has begun to modify its habitat heavily by starting industrial processes. Even so, anyone observing our atmosphere would still not be sure that we know of or could produce radio waves, nor that we have developed telecommu- nications to the point of being able to receive and interpret an unnatural signal from space. Only a civilization located less than 100 light-years from Earth could perhaps intercept radio signals from our planet. 100 light-years is the radius of the so-called “radiosphere,” the vol- ume of space around our planet where the first radio, radar, tel- evision and similar signals, more or less involuntarily launched into the cosmos by human ac- tivities, could have possibly reached. Even admitting that, incredibly, there may exist two technological civilizations capa- ble of communicating less than 100 light-years away from each other, hoping that “the others” may have picked up a signal of ours and recognized it as artifi- cial is a demonstration of con- siderable optimism. We know, in fact, that the intensity of an electromagnetic signal de- creases with the square of the distance, and by applying this physical law to signals of vari- ous kinds radiated from the Earth, we obtain that almost all of them, after traveling just one light year, are so degraded as to be indistinguishable from back- ground noise. Already at Pluto’s distance, even the largest ter- restrial radio telescopes would have many difficulties in picking 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 extra- terrestrials, 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 vis- itor 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 challenges readers to aim for the stars-and to think critically about what's out there, no matter how strange it seems.