6 But what? Is there not cause to wonder when one looks at the constitution of the sun? For being to the sight as it were a small body he contains a mighty power; appearing from the East, and sending forth his light unto the West: whose rising at dawn the Psalmist described, saying: And he comes forth out of his chamber as a bridegroom. He was describing the brightness and moderation of his state on first becoming visible unto men: for when he rides at high noon, we often flee from his blaze: but at his rising he is welcome to all as a bridegroom to look on.
Observe also his arrangement (or rather not his, but the arrangement of Him who by an ordinance determined his course), how in summer he rises higher and makes the days longer, giving men good time for their works: but in winter contracts his course, that the period of cold may be increased, and that the nights becoming longer may contribute to men's rest, and contribute also to the fruitfulness of the products of the earth. See also how the days alternately respond each to other in due order, in summer increasing, and in winter diminishing; but in spring and autumn granting equal intervals one to another. And the nights again complete the like courses; so that the Psalmist also says of them, Day unto day utters speech, and night unto night proclaims knowledge. For to the heretics who have no ears, they all but cry aloud, and by their good order say, that there is none other God save the Creator who has set them their bounds, and laid out the order of the Universe.
Source: Catechetical Lectures (New Advent)