On a clear spring day, my mother and I hiked an unmarked spur trail to Subway Cave, in Boynton Canyon, near Sedona, Arizona. As we scrambled up a cliff to the cave’s opening, we heard a little boy ask his father, “Do you think moons could be spaceships? We’re always finding more of them.” I turned to my mom, who looked at me with wide eyes. “That kid gets it,” she said, impressed.