The stars are an overarching motif that allows the authors to discuss the unknown aspects of the universe. The novel opens on a day when four of Kalgash’s six suns are in the sky, a detail that will resonate with the final chapter of the novel, when the presence of four suns signals the hope of a new beginning. Although the six suns are an everyday phenomenon to the people of Kalgash, Asimov and Silverberg rely on the reader’s basic knowledge of stars and the sun on Earth to better understand the psychological effect that they would have on the novel’s characters. For instance, the first time the Stars are referenced as an apocalyptic phenomenon, the scientists are unable to conceive of their six suns as stars. From their perspective, the Stars are a divine fire, associated with the gods in whom the Apostles of Flame believe.

The characters similarly find it difficult to fathom anything of the universe beyond the six suns. Sheerin speculates about the existence of a planet with only one sun, allowing for regular cycles of day and night. Beenay suggests that life would be impossible on such a planet. Asimov and Silverberg seem to suggest that the same could be said for the reader who might find it difficult to imagine a world that experiences near-perpetual daytime.