Galileo Galilei Publishes The Two Chief World Systems

Today on February 22, 1632, Galileo published his most influential book — A Dialogue Concerning the Two Chief World Systems.

Galileo Galilei was an Italian born polymath with interests spanning many disciplines. While most famous for his contributions to astronomy, Galileo also worked as a physicist, engineer, philosopher, and mathematician. Some historians have dubbed him as the Father of Modern Science for his impact on observational astronomy and physics. Galileo studied many fields within physics, including speed, velocity, gravity, inertia, motion, and early forms of relativity. The Italian polymath invented the thermoscope (an early type of the thermometer) as well as various compasses for military purposes. Galileo eventually became the first person to use a telescope for observing celestial objects.

Galileo spent much of his career championing Copernicanism. Over a century earlier, the Polish astronomer Nicolaus Copernicus published the world’s first book suggesting a heliocentric universe. But at the time, little evidence existed to support the theories of Copernicus. So Galileo took the reigns and committed to proving how the universe worked. In his book, known as the Two Chief World Systems, he outlined that the universe follows a system in which the Earth and all other planets orbit around the sun. The challenge was heliocentrism contradicted the commonly held theory of a geocentric universe.

The Catholic Church was steadfast in maintaining that the Earth stood still. The Bible even states that everything revolves around it. In 1615, the Roman Inquisition found the heliocentrism was “foolish and absurd” and defied the Holy Scripture. Under an exclusive license from the Vatican, he managed to release the Two Chief World Systems, comparing the Copernican system with the traditional Ptolemaic system. Galileo dedicated the work to his chief patron, Ferdinando II de Medici, the Grand Duke of Tuscany. On February 22, 1632, Ferdinando received the first copy.

In the following year, the Roman Inquisition suddenly found Galileo to be “vehemently suspect of heresy.” Pope Urban VIII insisted on having a trial to force him into recanting his beliefs. On June 22, 1633, Galileo formally recanted before the church. The Two Chief World Systems was immediately placed on the Index of Forbidden Books. It remained banned from the public domain for more than two hundred years. As punishment, Galileo lived out his remaining days under house arrest. During this time, he wrote another well-known book called the Two New Sciences, examining kinematics (a branch of mechanics and motion) and the strength of materials. The Father of Modern Science died eight years later at the age of 77.

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