Galileo Galilei biography timeline

Birth of Galilei Galileo

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.

Invents the Hydrostatic Balance

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

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

Invents the Open Thermometer

The Venetian senate examines Galileo's telescope. Demonstrates his first telescope to Venetian lawmakers, his work on the device made for a profitable sideline with merchants who found it useful for their shipping businesses and trading issues

Galileo along with Englishman Thomas Harriot and others are among the first to use a refracting telescope as an instrument to observe stars, planets or moons. Builds his own telescope, has 20x magnification

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

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

Publication of "The Starry Messenger", claims the Earth revolves around the Sun. Galileo's observations of the phases of Venus proved that it orbited the Sun and lent support to (but did not prove) the heliocentric model

Discovers Lunar Reflected Light

Uses the newly invented telescope to discover mountains & continents on the moon

The first observation of Saturn through a telescope is made by Galileo Galilei, his first telescope is so crude that he wasnt able to distinguish the planets rings; instead he thought the planet might have ears or two large moons on either side

Galileo's observations of the phases of Venus proved that it orbited the Sun and lent support to (but did not prove) the heliocentric model. Galileo observes that Venus exhibited a full set of phases similar to that of the Moon

Publishes his initial telescopic astronomical observations in March 1610 in a short treatise entitled Sidereus Nuncius (Starry Messenger)

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.

Publishes his initial telescopic astronomical observations in March 1610 in a short treatise entitled Sidereus Nuncius (Starry Messenger). Publication of "The Starry Messenger", claims the Earth revolves around the Sun

Discovers that Sunspots move across the surface of the sun

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 also observed the planet Neptune in 1612, but did not realize that it was a planet

Previous sunspot observations had been misinterpreted as planetary transits, until Galileo gave the correct explanation in 1612

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

Published in "letters on the solar spots". For Galileo, the tides were caused by the sloshing back and forth of water in the seas as a point on the Earths surface speeded up and slowed down because of the Earths rotation on its axis and revolution around the Sun. Attempts to show there is scriptural support for his beliefs but condemned by the Pope

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

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.

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

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

Galileo circulates his first account of the tides in 1616, addressed to Cardinal Orsini. Cardinal Bellarmine, acting on directives from the Inquisition, delivered an order not to "hold or defend" the idea that the Earth moves and the Sun stands still at the centre

Galileo revives his project of writing a book about heliocentrism, encouraged by the election of Cardinal Barberini as Pope Urban VIII in 1623

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.

Publication of "Two Chief World Systems", claims the Earth revolves around the Sun

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.

The book, Dialogue Concerning the Two Chief World Systems, is published in 1632, with formal authorization from the Inquisition and papal permission. By the inquisition, forced to deny his belief in the Copernican system

The book, Dialogue Concerning the Two Chief World Systems, is published in 1632, with formal authorization from the Inquisition and papal permission

By the inquisition, forced to deny his belief in the Copernican system

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.

Placed under House arrest

Sentenced to life imprisonment, commuted to house arrest

Discovers Lunar libration

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.

Death of Galilei Galileo

John Paul II orders an inquiry into the Church's treatment of Galileo

The Vatican admits that it was mistaken in its treatment of Galileo