Aristotle accepted the ideas of fire, air, earth, and water. He claimed them to be terrestrial elements due to their variable nature. These elements could be broken down into properties of hot, cold, dry, wet, light, and heavy, and by changing one or more of these properties, the elements themselves would change. This was his explanation for changes of state. But Aristotle also believed in a constant celestial region consisting of unchanging cycles of star movement. To explain this behavior he added a fifth element to the mix, aether. This element was unchanging and indivisible.