known as the "steady gait" theory, is that he/she came from nowhere and is going to keep swimming through space to nowhere forever. Eric shows Great A'Tuin being made instantly from nothing, seemingly in support of the "steady gait" theory; however, the events in The Light Fantastic, in which the Great A'Tuin attended the hatching of eight baby turtles, each with four baby elephants and a tiny discworld of their own, would seem to support the Big Bang hypothesis. The little turtles have since gone off on their own journeys. Whether this was the event the Great A'Tuin was looking forward to or merely one step towards its ultimate goal is not mentioned. Great A'Tuin has been mentioned to frequently roll on its belly to avoid asteroid and comet collisions, or even to snatch these projectiles out of the sky which might otherwise destroy the Disc. These stunts do not affect the Disc's population, other than to induce severe seasickness on anyone who happens to be looking at the night sky at that time. A'Tuin has been known to do more complex rolls and corkscrews, but these are rarer. This is similar to real-world sea turtles' habit of rolling over with their shell down to protect themselves from sharks. Due to the Great A'Tuin's travelling through the universe, the night sky of the Discworld changes markedly over the course of decades, as the turtle departs older constellations and enters new ones. This means that astrologers must constantly update and alter their horoscopes to incorporate all-new zodiacs. A tiny sun and moon orbit the Great A'Tuin, both about in diameter when described at the start of the series, but the description of their diameter is increased to at least later in the chronicles. The moon is slightly closer to the Disc than the sun. One half is covered with silvery glowing plants, which feed the lunar dragons. The other half is burnt black by the sun. The moon rotates and completes a full revolution in about a month; the full moon occurs when the luminescent side is completely visible from the Disc; the new moon when the dark side is shown. The sun's orbit is so complex that one of the elephants has to cock its leg to allow the sun to continue on its orbit. According to the wizards of Unseen University, Chelys galactica, and thus Great A'Tuin, are composed