What does Galileo's discovery of Jupiter's moons tell us about the process of scientific discovery?

In 1610, Galileo Galilei discovered Jupiter's moons with the aid of a new more powerful telescope of his invention. Analysis of his report reveals that his discovery involved the use of at least three cycles of hypothetico-deductive reasoning. Galileo first used hypothetico-deductive reasoning to generate and reject a fixed star hypothesis. He then generated and rejected an ad hoc astronomers-made-a-mistake hypothesis. Finally, he generated, tested, and accepted a moon hypothesis. Galileo's reasoning is modeled in terms of Piaget's equilibration theory, Grossberg's theory of neurological activity, a neural network model proposed by Levine & Prueitt, and another proposed by Kosslyn & Koenig. Given that hypothetico-deductive reasoning has played a role in other important scientific discoveries, the question is asked whether it plays a role in all important scientific discoveries. In other words, is hypothetico-deductive reasoning the essence of the scientific method? Possible alternative scientific methods, such as Baconian induction and combinatorial analysis, are explored and rejected as viable alternatives. Educational implications of this hypothetico-deductive view of science are discussed. © 2002 Kluwer Academic Publishers.