Galileo Galilei

Public-record biography

Galileo Galilei was born in Pisa on 15 February 1564 and died at his villa in Arcetri, outside Florence, on 8 January 1642. He held the chair of mathematics at Pisa from 1589, at Padua from 1592, and from 1610 served as Mathematician and Philosopher to the Grand Duke of Tuscany.

His telescopic discoveries of 1609–1610 — the moons of Jupiter, the phases of Venus, the resolution of the Milky Way into individual stars, the topography of the Moon — and his subsequent observations of sunspots constituted the first sustained body of telescopic observational evidence consistent with the Copernican heliocentric model of the solar system.

The 1616 injunction and the 1633 trial

In 1616, the Roman Inquisition, on the advice of a theological commission convened by Pope Paul V, declared the proposition that the Sun is stationary at the centre of the universe "formally heretical." Cardinal Robert Bellarmine personally instructed Galileo not to hold or defend the Copernican view; Galileo agreed.

In 1632, Galileo published Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo), which presented arguments for both the geocentric and the heliocentric models in dialogue form. The work received a Catholic imprimatur but was withdrawn from sale by Vatican order within months of publication.

The Roman Inquisition opened formal proceedings in April 1633. On 22 June 1633 the tribunal found Galileo "vehemently suspect of heresy"; required him to abjure, curse, and detest the Copernican view in a public ceremony; sentenced him to indefinite imprisonment (immediately commuted to house arrest); and placed Dialogue on the Index Librorum Prohibitorum, where it remained until 1835.

Galileo spent the remaining nine years of his life under house arrest at the archbishop's residence in Siena and at his villa at Arcetri. He continued to publish during this period, completing the Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638), the foundational text of classical mechanics. He remained a believing Catholic throughout.

Catholic Church rehabilitation

The institutional rehabilitation proceeded across centuries. Dialogue was removed from the Index in 1835. Pope Leo XIII opened the Vatican Secret Archives to scholars in 1881, making the trial documents publicly available. Pope John Paul II established a papal commission in 1981 to re-examine the case, and in an address to the Pontifical Academy of Sciences on 31 October 1992 formally acknowledged the error of the 1633 verdict.

Sources

• Maurice A. Finocchiaro, The Galileo Affair: A Documentary History (University of California Press, 1989).
• Maurice A. Finocchiaro, Retrying Galileo, 1633–1992 (University of California Press, 2005).
• Annibale Fantoli, Galileo: For Copernicanism and for the Church (Vatican Observatory / Notre Dame, 1996).
• John Paul II, address to the Pontifical Academy of Sciences, 31 October 1992.