The 20th century master of weird fiction, H. P. Lovecraft, once said that the "oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown." The creator of the extraterrestrial sea-demon Cthulhu knew what he was saying when he recognized the existential power of fear and its primary source: a lack of knowledge. Things are immediately less frightening when we understand their dimensions - their...