The Discourses and Mathematical Demonstrations Relating to Two New Sciences (Italian: Discorsi e dimostrazioni matematiche intorno a due nuove scienze pronounced [diˈskorsi e ddimostratˈtsjoːni mateˈmaːtike inˈtorno a dˈduːe ˈnwɔːve ʃˈʃɛntse]) published in 1638 was Galileo Galilei's final book and a scientific testament covering much of his work in physics over the preceding thirty years. It was written partly in Italian and partly in Latin. After his Dialogue Concerning the Two Chief World Systems, the Roman Inquisition had banned the publication of any of Galileo's works, including any he might write in the future. After the failure of his initial attempts to publish Two New Sciences in France, Germany, and Poland, it was published by Lodewijk Elzevir who was working in Leiden, South Holland, where the writ of the Inquisition was of less consequence (see House of Elzevir). Fra Fulgenzio Micanzio, the official theologian of the Republic of Venice, had initially offered to help Galileo publish the new work there, but he pointed out that publishing the Two New Sciences in Venice might cause Galileo unnecessary trouble; thus, the book was eventually published in Holland. Galileo did not seem to suffer any harm from the Inquisition for publishing this book since in January 1639, the book reached Rome's bookstores, and all available copies (about fifty) were quickly sold. Discourses was written in a style similar to Dialogues, in which three men (Simplicio, Sagredo, and Salviati) discuss and debate the various questions Galileo is seeking to answer. There is a notable change in the men, however; Simplicio, in particular, is no longer quite as simple-minded, stubborn and Aristotelian as his name implies. His arguments are representative of Galileo's own early beliefs, as Sagredo represents his middle period, and Salviati proposes Galileo's newest models.
Introduction The book is divided into four days, each addressing different areas of physics. Galileo dedicates Two New Sciences to Lord Count of Noailles.
In the First Day, Galileo addressed topics that were discussed in Aristotle's Physics and the Aristotelian school's Mechanics. It also provides an introduction to the discussion of both of the new sciences. The likeness between the topics discussed, specific questions that are hypothesized, and the style and sources throughout give Galileo the backbone to his First Day. The First Day introduces the speakers in the dialogue: Salviati, Sagredo, and Simplicio, the same as in the Dialogue. These three people are all Galileo just at different stages of his life, Simplicio the youngest and Salviati, Galileo's closest counterpart. The Second Day addresses the question of the strength of materials. The Third and Fourth days address the science of motion. The Third day discusses uniform and naturally accelerated motion, the issue of terminal velocity having been addressed in the First day. The Fourth day discusses projectile motion. In Two Sciences uniform motion is defined as a motion that, over any equal periods of time, covers equal distance. With the use of the quantifier ″any″, uniformity is introduced and expressed more explicitly than in previous definitions. Galileo had started an additional day on the force of percussion, but was not able to complete it to his own satisfaction. This section was referenced frequently in the first four days of discussion. It finally appeared only in the 1718 edition of Galilei's works. and it is often quoted as "Sixth Day" following the numbering in the 1898 edition. During this additional day Simplicio was replaced by Aproino, a former scholar and assistant of Galileo in Padua.
Summary Page numbers at the start of each paragraph are from the 1898 version, presently adopted as standard, and are found in the Crew and Drake translations.
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