In Egyptian mythology, the sun's emergence from the horizon each morning is likened to Ra's birth, an event that revitalizes him and the order of the cosmos. Ra emerges from the body of a goddess who represents the sky—usually Nut. Depictions of the rising sun often show Ra as a child contained within the solar disk. In this context, the Egyptologist Lana Troy suggests, the disk may represent the womb from which he is born or the placenta that emerges with him. The Eye of Ra can also take the form of a goddess, which according to Troy is both the mother who brings Ra forth from her womb and a sister who is born alongside him like a placenta. Ra was sometimes said to enter the body of the sky goddess at sunset, impregnating her and setting the stage for his rebirth at sunrise. Consequently, the Eye, as womb and mother of the child form of Ra, is also the consort of the adult Ra. The adult Ra, likewise, is the father of the Eye who is born at sunrise. The Eye is thus a feminine counterpart to Ra's masculine creative power, part of a broader Egyptian tendency to express creation and renewal through the metaphor of sexual reproduction. Ra gives rise to his daughter, the Eye, who in turn gives rise to him, her son, in a cycle of constant regeneration.