"Contemplating it (the universe) we are invited to read something profound into it: the wisdom of the creator, the inexhaustible creativity of God," he said in a sermon to some 10,000 people in St Peter's Basilica on the feast day.
Some atheists say science can prove that God does not exist, but Benedict said that some scientific theories were "mind limiting" because "they only arrive at a certain point ... and do not manage to explain the ultimate sense of reality ..."
He said scientific theories on the origin and development of the universe and humans, while not in conflict with faith, left many questions unanswered.
"In the beauty of the world, in its mystery, in its greatness and in its rationality ... we can only let ourselves be guided toward God, creator of heaven and earth," he said.