In 1950, Enrico Fermi, best known as the creator of the first nuclear reactor, asked his colleagues during a lunchtime discussion of extraterrestrials, “But where is everybody?” Some new books take several different approaches to what has become known as “Fermi’s Paradox.”

In Extraterrestrial, Harvard astrophysicist Avi Loeb argues that Oumuamua, the mysterious interstellar object that passed through our solar system in 2017, represents the first sign of intelligent life beyond earth. The Zoologist’s Guide to the Galaxy prepares us for possible future encounters by considering what alien life must be like based on what we know of evolution and life on earth. Sarah Stewart Johnson examines humanity’s enduring fascination with the Red Planet and our current search for evidence of life there in The Sirens of Mars.

One of the first comprehensive scientific considerations of extraterrestrial life was Soviet astronomer I. S. Shklovskii’s 1963 Intelligent Life in the Universe. Carl Sagan was so moved by this work that he supervised the translation and provided an extensive commentary in which the two authors argued for the probability not just of life but intelligent life with which we may one day communicate. Carl Sagan’s own The Cosmic Connection (1973) inspired a generation of scientists and enthusiasts and further awakened a sense of wonder about the universe and the possibilities of more advanced extraterrestrial civilizations. Another SETI pioneer Jill Tarter was the inspiration for the main character of Sagan’s novel Contact (played by Jodie Foster in the film) and her life and work are explored in Making Contact.