Cabrol, the Director of the Carl Sagan Center at the SETI Institute, has written a fascinating story of her search for life on the exoplanets, asteroids, and dwarf planets that inhabit our universe in the millions if not trillions. This book would have been deemed science fiction as recently as the 1990’s but interstellar explorations from the Viking and Mariner probes of the 1970’s through the most recent orbiting telescope, the James Webb Space Telescope launched in 2021, have provided scientists with photographs of and biochemical and geological information about planets ( Mars, Venus, Neptune, Jupiter, Saturn) and their moons (Saturn’s moons Encaladus, Ganymede, and Titan), dwarf planets (Ceres, Pluto), and stars whose exoplanets orbit them as our Earth orbits the sun but millions of miles across outer space.

These telescopes on land and in space and the complex mathematics and physics that are deployed in examining their chemical structure and their distance from their suns are all attempting to answer the existential questions: Are we alone and if not, who or what is out there and what are they doing?  Cabrol makes a spirited attempt to address these questions, but gets bogged down in the excruciating acronyms and details about individual probes, their launch dates, their trajectories, the scientists, and their findings.  This is a good example of a science book that shortened and scrubbed of all these details would have made a terrific magazine article in ‘Scientific American’, ‘National Geographic’, or even ‘The New Yorker’.  As it stands, however, even this scientist and obsessive reader couldn’t manage to maintain my interest after the twentieth detailed description of the possible ocean in the interior of Ganymede.

On the other hand, I learned many fascinating facts, terms, and concepts and after finishing the book, I did have a better and more complete overall view of the ‘Are we alone’ story than I had before. The short answer is that we might be, but it would be incredibly unlikely and perhaps even scary to think that among the 125 billion galaxies in our universe and their uncountable stars many of which have exoplanets orbiting within a habitable zone we are the only place where life (whatever that is!!!) has originated.  Cabrol does a good job exploring what life actually is arriving at a definition which includes elements of self-reproduction, variation, and complexity.  The likelihood that life will emerge and reach stages of a technologically advanced civilization that would enable that life to communicate with us or travel in space to Earth is expressed in the Drake Equation, created in 1961.  The equation solves for the number of civilizations in our Milky Way galaxy, “N”.  It includes seven terms such as the rate of formation of stars suitable for the development of intelligent life and the fraction of those stars that have planetary systems.  These and the remaining terms are now within our reach of determining, and hence so is the value of N.  The Drake Equation, Fermi’s Paradox (if there are millions of potential planets where life might have begun, why haven’t we heard from anyone?), the Great Filter, and the Dark Forest concepts are all explored in detail; hence, my exhaustion with the whole book.

What is clear is that the science of astrobiology and its sisters that are addressing the big questions (What is life?  Are we Alone?  If not, what would life elsewhere look like and would we recognize it? and finally, If they’re out there, are they going to kill us?) is moving at an incredible pace.  Information will continue to accumulate at an every faster pace as AI is wielded and sometime after I’m gone, we will have a clearer idea of what’s out there. At the present time, however, it appears that we’re alone.  Enjoy the quiet as long as it lasts.