Clearly, we didn’t get the message. Three decades on, our “pale blue dot” is riven by geopolitical turmoil, and the late 20th-century hope for an ascendent global liberalism has faded.

The obvious answer is “yes!” So then, how will we preserve it? In 1994, the astrophysicist, author, and TV presenter Carl Sagan wrote the “Pale Blue Dot,” a book inspired by and discussing the intense ...