Galileo Galilei Biography

Galileo moves with his family from Pisa to Florence, where his early education continues.

Galileo enrolls in the Faculty of Arts at the University of Pisa.

Galileo observes the regularity of a swinging cathedral lamp, an episode later associated with his investigations of pendulum motion.

Galileo begins serious study of Euclid under Ostilio Ricci, strengthening the mathematical foundation of his later scientific work.

Galileo is appointed to the chair of mathematics at the University of Pisa.

Galileo delivers his inaugural university lecture before beginning regular mathematics teaching at Pisa.

The Venetian Senate appoints Galileo professor of mathematics at the University of Padua.

Galileo gives his inaugural lecture at Padua, beginning eighteen productive years in the Venetian Republic.

Galileo develops a sophisticated geometric and military compass for practical mathematical calculations.

Galileo writes to Johannes Kepler describing himself as a long-standing supporter of the Copernican system.

In the same letter, Galileo formulates the law of chords concerning descent times along chords of a vertical circle.

Galileo writes to Guidobaldo del Monte describing his principle that pendulums of equal length have approximately equal periods.

Galileo is thought to co-author a satirical dialogue attacking Aristotelian interpretations of the new star.

Galileo publishes instructions explaining the mathematical and practical uses of his geometric and military compass.

Galileo publishes a defence of his geometric compass against claims that Baldassarre Capra had originated the instrument.

After learning of the Dutch telescope, Galileo rapidly improves the design until his best instruments exceed twenty-power magnification.

Galileo becomes mathematician and philosopher to Grand Duke Cosimo II, allowing his return from Padua to Tuscany.

Galileo names Jupiter's newly discovered satellites the Medicean Stars in honour of the ruling Medici family.

Galileo reports that telescopic observation resolves the Milky Way into a vast multitude of individual stars.

Observes three points of light close to Jupiter, beginning the discovery of its major moons.

Observes the fourth Galilean moon, later named Callisto.

Concludes that four observed bodies orbit Jupiter rather than the Earth.

Publishes telescopic observations of Jupiter's satellites in Sidereus Nuncius.

Galileo begins systematic study of the orbital periods of Jupiter's four large moons.

Galileo proposes using predicted eclipses of Jupiter's moons as a celestial clock for determining longitude.

Galileo develops a micrometer to improve measurements of the apparent separations of Jupiter's moons.

Galileo demonstrates telescopic observations in Rome, strengthening recognition of the instrument's astronomical value.

Galileo publishes a discourse defending Archimedean hydrostatics against Aristotelian explanations of why bodies float or sink.

Galileo writes to Benedetto Castelli arguing that scriptural interpretation should not override demonstrated conclusions about the natural world.

Galileo becomes the target of a public sermon by Tommaso Caccini attacking Copernican astronomy and mathematicians.

Galileo completes a major letter discussing the proper relationship between scientific inquiry and interpretation of Scripture.

Galileo writes to Piero Dini defending Copernican astronomy and arguing that it need not conflict with Scripture.

Galileo sends another letter to Piero Dini continuing his defence of Copernican astronomy.

Cardinal Bellarmino formally admonishes Galileo not to hold or defend the Copernican doctrine.

Galileo publishes The Assayer, presenting influential arguments about mathematical description and the investigation of natural phenomena.

Galileo reports experiments in which an iron armature greatly increases the lifting strength of a magnet.

Galileo rents the villa Il Gioiello at Arcetri, near the convent where his daughters live.

Galileo presents his newly published Dialogue Concerning the Two Chief World Systems to Grand Duke Ferdinando II.

The Florentine Inquisitor orders Galileo to appear before the Holy Office in Rome over the Dialogue.

Galileo is formally condemned and required to sign an abjuration of the Copernican position.

The Holy Office permits Galileo to return to his villa at Arcetri while maintaining restrictions on his contacts and scientific discussion.

Publishes mathematical treatment of falling bodies later absorbed into gravitational physics.

Printing is completed for Galileo's Two New Sciences, a foundational work on strength of materials and mathematical treatment of motion.