St Thomas instances "the heavenly bodies, the movements of which ever proceed uniformly." So men from Plato's time to Newton's contrasted the vicissitudes of the sublunary world with the uniformity of the heavens above. Newton showed that the same forces are at work in the starry heavens as on this earth. In our day the spectroscope has shown that the materials of our earth, or sundry of them, enter into the composition of the stars. The same instrument reveals stars still in process of formation, stars even colliding and exploding. There is uniformity in the heavens above and on the earth beneath: not more in one than in the other. The ancients under-estimated the regularity and uniformity of nature on earth. Their gaze was fixed on catastrophes befalling living creatures and man in particular. Yet even in catastrophes nature is still uniform, although working to an effect which we had not expected. What crosses our expectations, that we call evil. But what right have we to expect? Man is not the measure of all things, nor is human expectation a law to nature.
The 'heavenly body,' corpus coeleste, built of matter fully actuated by its form, and therefore imperishable and unchangeable (B. II, Chap. XXX, n.1, with note: Sum. Theol. 2-2, q. 24, art. 11, corp.), played a great part in the metaphysics and psychology of the Middle Ages. See Chapp. LXXXII-LXXXVII of this Book. Little did St Thomas think that if he could have altered the point of view of his eye by some millions of miles, he would have beheld our planet Earth, the native region of generation and corruption, turned into a corpus coeleste, serenely resplendent as Venus and Mars, sweeping out in its orbit with the same accuracy, neither morning star nor evening star more wonderful. Yet the reader of St Thomas will find him not altogether credulous of the popular astronomy of his time. He attributes less to the corpus coeleste than many of his contemporaries.
Of God and His Creatures: 3.1