Picking up from the automatic computer in the previous segment, we go to a modern planetarium in order to get into the models of the universe as they were understood by the ancients. The end of the Crusades led to the recovery of old books by Ptolemy and other classical thinkers. One side effect was the need for telling time better, and from there a series of innovations that resulted in the mechanical clock. The Germans took their skill in making clocks and other mechanisms and applied it to scientific instruments like telescopes and navigation sights. Modern astronomy emerges (in a lot of content also covered in THE DAY THE UNIVERSE CHANGED) . The search for a reliable navigation chronometer went through new metal smelting techniques, new methods of cutting and marking metal, and the assembly line method of assembly. From there work itself evolved, from the field to the factory.