Dava Sobel came across the subject for her book "Galileo's Daughter" when researching what became her best-seller "Longtitude." She uncovered a letter to the 16th-century astronomer written by his daughter, a cloistered nun. Sobel discovered it was just one of a hundred letters written during one of the biggest battles between science and theology...the debate over whether Galileo's book proving Copernican theory that the earth revolves round the sun was heretical. She told Minnesota Public Radio's Euan Kerr the letters reveal Galileo, far from being an enemy of the church, was a devout Catholic who was trying to protect his religion.