And Yet It Moves: The Story of Galileo Galilei, Part 2 of 2

Beyond stargazing, Galileo also developed a variety of scientific inventions during his lifetime that not only advanced the study of physics, mathematics, and astronomy but also laid the groundwork for modern science. He proposed the use of the “bilancetta” – a balance for weighing objects directly in water – to reveal differences in specific weight. Mechanical clocks had been in use since the late 14th century, around 1386. Although Galileo did not invent the clock, he laid the theoretical foundation for using a pendulum as a timekeeping element. Galileo studied the motion of falling bodies using inclined planes. Through this method, Galileo tested and ultimately refuted several Aristotelian ideas about motion. More than three centuries later, American astronaut David Scott famously demonstrated Galileo’s principle on the Moon during the Apollo 15 mission in 1971. Standing on the lunar surface, he dropped a hammer and a feather at the same time. Galileo supported the Copernican system, which created controversy because the Ptolemaic view, rooted in Aristotle’s philosophy, had been endorsed by the Catholic Church for centuries.

In 1616, Pope Paul V ordered the Sacred Congregation of the Index to examine the Copernican theory. Believing that the new pope would be more tolerant, Galileo began writing “Dialogue Concerning the Two Chief World Systems — Ptolemaic and Copernican.” In 1633, the Inquisition banned the book for its pro-Copernican stance. Galileo was found “vehemently suspected of heresy” for violating the 1616 injunction. He was forced to recant his views and sentenced to house arrest for the rest of his life.

His final work, “Discourses and Mathematical Demonstrations Relating to Two New Sciences,” completed in his 70s and published in Leiden, the Netherlands, explored motion, strength of materials, and the principles of mechanics. Allegedly spoken by Galileo after he was forced to recant heliocentrism in 1633, the famous phrase “E pur si muove” (“And yet it moves”) did not appear in print until more than a century later, in 1757, when Giuseppe Baretti recorded it in his book “The Italian Library.”