For millennia, humans have gazed at the sky and tried to make sense of what they saw there. Many of the men and women who puzzled over the dazzling displays and movements of the stars recorded their explanations in systematic ways—that is, they created models of the cosmos. Jump to: Background Suggestions for Teachers Additional Resources Background These models were small versions of large systems that astronomers could hold in their minds, and that they could then set down on paper to share wi