Aliens invaded my life one Sunday night in 1957 when I was 6 years old. As I pulled close to watch Walt Disney's "Wonderful World of Color," the screen of our old black-and-white Admiral TV seemed to bleed into rainbow hues. Disney introduced the evening's program: "Mars and Beyond," a meditation—in retrospect, an entertainment—on the possibility of life on other worlds. "Will we find planets with only a low form of vegetable life?" Disney wondered, then nodded genially toward his towering, metallic co-host. "Or will there be mechanical robots controlled by super-intelligent beings?" To my juvenile...