Timeline of Galileo Galilei

February 15, 1564

Galileo is born to Vencenzo Galilei, a musician.


Galileo's family moves to Florence, and he starts to attend the monastery of Vallombrosa.


He enters the University of Pisa to study medicine. As the story goes, Galileo was in the cathedral at Vallombrosa when he observed a lamp hanging from the ceiling swaying with perfect rhythm. He was fascinated that the lamp took the same amount of time to swing no matter how large the range of swing. He later would apply his theories of pendulums to clocks.



Galileo, fascinated by mathematics and geometry, starts taking classes from Ostilio Ricci, a teacher in the Tuscan court.



Galileo, not completing his degree, is forced to leave the University because of lack of funds. He returns to Pisa.



He publishes an essay on the hydrostatic balance, a device to measure the mass of objects.



He publishes a paper on the center of gravity in solids and is awarded a position as lecturer at the University of Pisa.



Galileo works on his theory of motion. Aristotle had said that bodies of different weights fall at different rates, but Galileo did not believe this.



Galileo applies and is awarded the chair of mathematics at the University of Padua, where he remained until 1610. Padua is where Galileo did the majority of his work.



Galileo publishes his theories, now called the theory of uniform acceleration. He proved that all bodies, regardless of their weight, fall at an equal rate, in the absence of friction. Also in this paper he stated that a ball thrown in the air follows a parabolic path.



Galileo writes a letter to Johannes Kepler supporting his heliocentric universe theory over that of Aristotle. Galileo would have published, but he was afraid of ridicule.



Galileo learns of the recent invention, the telescope. He returned to Padua and is able to improve the magnification of the telescope he bought to 32 powers.



Galileo makes many different observations about the solar system, using his new telescope.

  • The moon is an irregular, rough body, not smooth as scientists thought.
  • The Milky Way is composed of many stars.
  • Jupiter has many small satellites that he named, "Sidera Medicea," after his favorite pupil.
  • He made observations about Saturn, sunspots, and the phases of Venus.

He publishes the results in the 1610 book, "Sidereus Nuncius." ("The Starry Messenger")


He leaves his position at Padua to become the first philosopher and mathematician to the grand duke of Tuscany. The Duke allowed Galileo more time to work on his projects.



He visits Rome to demonstrate the telescope.



After being so warmly accepted at Rome, Galileo writes three letters to formally take his position on the heliocentric theory of the universe. His main reason for believing Kepler and Copernicus were his observations of sunspots moving around the sun.



Rome and Galileo spend three long years in conflict. Because Galileo choose to write his 1613 letters in Italian, they enjoyed a larger audience than the religious and scientific communities. The Aristotelian Scholars saw the attacks on Aristotelian Philosophy to be attacks upon themselves. The Aristotelian Scholars united against Galileo. The Church, swayed by the Aristotelian Scholars declared that Galileo was contradicting scripture,


March 5, 1616

The Catholic Church formally declares the writings of Galileo banned, and warns Galileo not to "hold or defend his doctrines."



He retires to his home in Bellosguardo near Florence.



Galileo writes his "Assayer..." in which he debates the difference between primary properties, (measurable, quantative) and other properties (smell) and writes his famous quote, "The Book of Nature is written with Mathematical characters."



He again travels to Rome hoping to appeal the 1616 decree. The Pope does not repeal the decree, but he does allow Galileo to write on both sides of the issue, noncomentally, and equally supportive of both sides of the issue, and without making any definite conclusions.



Galileo publishes his great work, Dialogo sopra I due massimi sistemi del mondo, tolemaico e copernicano (Dialogue Concerning the Two Chief World Systems--Ptolemaic and Copernican) IN compliance with the Pope, the work is set as a conversation between two men discussing the Ptolemaic and Copernican systems.



Simply put, all hell brakes loose in Galileo's world. The Pope, infuriated at the content of "Dialogo," places him on trial for one thing after another.


February 1633

Galileo is eventually placed on trial and at his old age, is forced to make the journey to Rome. He is under suspicion of "vehement suspicion of heresy," but is convicted of holding and teaching the Copernican belief. He is placed under house arrest for eight years until his death.



Despite his house arrest Galileo publishes Discorsi e dimostrazioni mathematiche intorno a due nuove scienze attenenti alla meccanica (Dialogue Concerning Two New Sciences, a work about the principles of mechanics.



Galileo makes the discovery, months before he went completely blind, that the moon makes monthly wobbles on its axis, called liberations.


January 8, 1642

Galileo Galilei dies from a long illness.