The University of Arizona Press

September 18, 2023

Humans have always been fascinated by the possibility of extraterrestrial life, often wondering if we are alone in the universe. Alone but Not Lonely, Exploring for Extraterrestrial Life answers those questions. Drawing on nearly fifty years as a leader in planetary exploration, author Louis Friedman brings into focus the subject of extraterrestrial life, separating knowledge from conjecture, fact from fiction, to draw scientific and technical conclusions that answer this enduring question.

What first sparked your interest to write this book?

I was motivated to write this book by the work I was doing with colleagues at the NASA Jet Propulsion Laboratory about using the solar gravity lens to image exoplanets. Magnifying light by 100 billion times with the solar gravity lens would give us the ability to see life on other worlds throughout the galaxy!  The challenge of designing a mission to reach the focus of the solar gravity lens is an exciting one to be working on. It’s hard, but we can do it; as opposed to interstellar flight which is not practical.

Why do you think people are so interested in life beyond planet Earth?

For the whole of human history we have wondered about the nature of life and our place in the Universe.  We wandered through religion and folklore, myths and stories—but now we wonder through science and exploration.  As Carl Sagan used to say, if you are not interested in the question of “are we alone and the nature of life in the Universe,” you must be made of wood. 

Why are you excited about comparative astrobiology? 

Comparative astrobiology will teach us about ourselves and our place in the Universe.  When we eventually find and compare life on other worlds to what has happened here, it will give us insights just as did the discovery of the nature of gravity and that the Earth was not the center of the Universe, but one object among billions of other—that we compare our planet to.  

Why did you, Carl Sagan, and Bruce Murray start the Planetary Society?

In the late 1970s NASA was planning to cease planetary exploration entirely, despite the enormous success and public interest from the Viking and Voyager missions. Sagan and Murray recognized that public interest needed to be expressed and thus we began the development of The Planetary Society as a citizens-based advocacy group promoting exploration of other worlds and the search for extraterrestrial life.  

What is your next research project?

I am following up the subject in this book of exploring exoplanets remotely by use of the solar gravity lens.  I hope to contribute to making a mission to the foci of habitable exoplanets possible in the next decade.  

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Louis Friedman co-founded the Planetary Society with Carl Sagan and Bruce Murray and was its executive director for thirty years. He has contributed to numerous journals and is the author of Starsailing: Solar Sails and Interstellar Travel, Human Spaceflight: From Mars to the Stars, and Planetary Adventures: From Moscow to Mars.