ABSTRACT
Figure 1.1: From the beginning of science, researchers tried to capture their observations by drawings. a With this famous sketch, Leonardo da Vinci [1452-1519] described turbulent flow of water. b In 1613, Galileo Galilei — at the same time as others — discovered the sun spots. His careful observations of the motion of the spots over an extended period led him to the conclusion that the sun is rotating around its axis.
