Within his society of followers, Pythagoras spread knowledge of secret theorems like that of irrational numbers. To a wider general public, he spread many other ideas and educated many people. He also is credited with inventing the words “philosophy” and “mathematics,” as well as “calculus,” which came from the Greek word for pebble, which the Pythagoreans used for counting. He also discovered the ratio of string lengths to make pleasing chords (these were the whole numbers). Also, Pythagoras was interested in astronomy and was the first to call the Earth a sphere and discover the 24 hour day. However, he thought the universe was geocentric.