“there are many things that we concede exist; what their qualities are we do not know. … Why, then, are we surprised that comets, such a rare spectacle in the universe, are not yet grasped by fixed laws and that their beginning and end are not known, when their return is at vast intervals? … The time will come when diligent research over very long periods will bring to light things which now lie hidden. A single lifetime, even though entirely devoted to the sky, would not be enough for the investigation of so vast a subject. … There will come a time when our descendants will be amazed that we did not know things that are so plain to them. … Some day there will be a man who will show in what regions comets have their orbit, why they travel so remote from other celestial bodies, how large they are and what sort they are. Let us be satisfied with what we have found out, and let out descendants also contribute something to the truth” — Seneca in Natural Questions VII, 25.