Moving in space, the atoms originally were individual units, but inevitable they began to collide with each other, and in cases where their shapes were such as to permit them to interlock, they began to form clusters. Water, air, fire, and earth, these are simply different clusters of the changeless atoms.
There are innumerable worlds of different sizes. In some there is neither sun not moon, in others they are larger than in ours and others have more than one. These worlds are at irregular distances, more in one direction and less in another, and some are flourishing, others declining. Here they come into being, there they die, and they are distroyed by collision with one another. Some of the worlds have no animal or vegetable life nor any water.