Their father Mundilfari had two children so bright that he named the girl Sól, after the sun, and the boy Máni, after the moon. The gods heard arrogance in that and answered it with work. They set Sól to drive the two horses that pull the sun, Árvakr ('Early-waker') and Alsviðr ('Very-swift'), and to keep them from scorching she carries a shield called Svalinn ('Cooler') before the heat. Snorri adds a homely engineering detail: under the horses' shoulders the gods fixed bellows of iron to cool them on the road.
Máni governs the moon and reckons its waxing and waning. Grímnismál tells how he once lifted two children, Bil and Hjúki, off the earth as they carried a water-pail home from the well Byrgir, and Scandinavians long claimed to see the pair in the dark patches of the full moon. He rides the same sky as his sister and under the same threat.
Neither travels for pleasure. The wolves of the Ironwood run the chase, Sköll behind the sun and Hati before the moon, and the reason the two ride so hard is that they are prey. At Ragnarök the wolves close their jaws and the sky goes dark for the last battle. Vafþrúðnismál keeps back one line against that dark: before the wolf takes her, Sól bears a daughter as fair as herself, and it is the daughter who will drive her mother's road when a new world rises from the sea.