In 1977, to take advantage of a rare alignment of Jupiter and Saturn, NASA launched two interplanetary probes: Voyager 1 and Voyager 2. The two spacecraft, each about the size of a school bus, were built by NASA’s Jet Propulsion Lab and launched separately toward the two gas giants. Both probes captured photographs of planets and their moons that were, at the time, the best taken of those objects. Once past Jupiter and Saturn, in 1981, Voyager 2 was given a new mission to study Uranus and Neptune, a first for any spacecraft. The Voyager probes continue to transmit data in 2022 from well beyond the orbits of Neptune and Pluto.

A section of Sagan’s book is dedicated to the findings of the Voyager missions, in which he was involved. He spearheaded a program to include information about Earth and human culture on the probes in the off chance they might be discovered by an alien civilization. As director of the Voyager Interstellar Record Committee, he helped decide the contents of the “golden record,” a series of phonograph discs that carried greetings in 55 languages, maps and images, sounds of human life, and music from multiple cultural traditions. Sagan also convinced NASA to turn Voyager 1 around and take a photo of Earth from the far side of Saturn.