In shaping his vision of Middle-earth, Tolkien sometimes ran into "difficulties" of a scientific nature. One he frankly and openly admitted was in the area of biology: "Elves and Men are evidently in biological terms one race, or they could not breed and produce fertile offspring – even as a rare event: there are two cases only in my legends of such unions, and they are merged in the descendents of Eärendil." Given his mindfulness of natural laws, one may ask did Tolkien incorporate astronomical lore and fact into his universe? The answer is, in far more ways than can possibly be explored in a talk of this length. Astronomy helped, and haunted, Tolkien as he set out to develop his universe – or Eä, as the Elves would say.
Dr. Kristine Larsen, Professor of Physics and Astronomy: Astronomy of Middle Earth