the world > the universe > heavenly body > movement of heavenly bodies > move [verb (intransitive)] > travel west (2)
intransitive. Of the sun or other celestial object: to travel westward in its course; to decline towards the west. Also figurative.
intransitive. To move westwards, to turn to the west; (of the sun) to draw near to the west, to decline towards the west. Cf. wester, v.