Problem: Imagine yourself at a turning point in the history of science in the 17th century. You are a student of Galileo and he has just shown you his telescope and asked you to observe four moons circling the planet Jupiter. He suggests that the earth must orbit the sun like these moons orbit Jupiter, but your fellow students argue that the earth could not be moving because if it were, everything on it would fly off into space. What do you decide? Does the earth move or not? What reasons would you give if you lived in the 17th century? Would your choice be rational? Why or why not?