Marvin realizes why his father has brought him “outside” “for the first time in his life.” After hours of driving in a scout car with balloon tires, they reach a place in their lunar outpost from where Marvin can have a glimpse of the earth. Vaguely though, he can read the topography of the earth:

…he could discern the outlines of continents, the hazy border of the atmosphere, and the white islands of cloud. And even at this distance, he could see the glitter of sunlight on the polar ice.

The darker half of the “shining crescent” too glows because of the “evil” nuclear radiation. Despite his desire to go to the earth, he can’t do so because the atomic war has rendered the earth uninhabitable.

The earth burns in its “funeral pyre.” It may take several centuries for the earth to overcome the poisonous effects of radioactivity. The extant human race will have to wait for centuries to reclaim their planet.

It would be centuries yet before that deadly glow died from the rocks and life could return again to fill that silent, empty world.

Neither Marvin had ever been to the earth nor would he be there in his entire lifetime, he realizes. However, his father gives him the objective of his survival by showing him his original home. The purpose of his survival is revealed to him. 

The sole objective of Marvin and the other human survivors is to pass on this goal to their successors that someday in the distant future when the earth will have cleansed itself of the toxicity of nuclear radiation, they could go back home.

“That was the dream: and one day, Marvin knew with a sudden flash of insight, he would pass it on to his own son, here at this same spot with the mountains behind him and the silver light from the sky streaming into his face.”