Humans have always been fascinated by the possibility of extraterrestrial life, often wondering if we are alone in the universe. Drawing on nearly fifty years as a leader in planetary exploration, 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.

Friedman argues that intelligent life is probably rare in the universe (maybe even uniquely on Earth) but that simple life is likely abundant on millions or billions of planets waiting now to be discovered. He asserts that studying and searching for extraterrestrial life cannot be done by interstellar probes—due to the vastness of space and the comparative brevity of human lifespans—but it can be done remotely by a new technique involving the solar gravity lens that can magnify exoplanets by tens of billions. This technique will allow humankind to explore exoplanets and open up an exciting new field of comparative astrobiology.

Wide-ranging in scope, this book discusses the history of searching for extraterrestrial life, the scientific evidence thereof, and finally his own conclusions on what's next. Included in the book are three appendices: an explanation of interstellar messaging, a reprint of a debate between Carl Sagan and Ernst Mayr on extraterrestrial intelligence, and an opinion essay on the search for extraterrestrial intelligence.