The interests of Galileo Galilei radiated throughout every area of scientific knowledge. In particular, he studied bodies in equilibrium, moving bodies, and the forces producing both equilibrium and motion. His last book, Discourses and Mathematical Demonstrations about Two New Sciences (1638), was probably the most important of his scientific career, and marked the foundation of classic dynamics.
Galileo's astronomical work had a different and peculiar relevance. He conceived no new World system, or any new planetary computational model. From the conceptual point of view, he simply adhered to the Copernican doctrine of On the Revolutions. Nevertheless, the astronomical use of the telescope gave Galileo the possibility of adding a new meaning to the word "observation'. He added to the traditional measurement of precise angular data the observation of physical aspects of celestial bodies. Galileo's ecclesiastic accusation, trial and condemnation for the heretical defence of the reality of the Copernican system did not stop this new observational work.