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Our Inspiration > GALILEO GALILEI




"Take note, theologians, that in your desire to make matters of faith out of propositions relating to the fixity of Sun and Earth you run the risk of eventually having to condemn as heretics those who would declare the Earth to stand still and the Sun to change position -- eventually, I say, at such a time as it might be proved that the Earth moves and the Sun stands still."

Born 15 February 1564 in Pisa (Italy) and died at Arcetri on 8 January 1642. Galileo Galilei was a teacher, scholar and writer whose passion for mathematics and natural philosophy led to a number of groundbreaking discoveries that society was not altogether ready for. Son of a professional musician in Florence, Galileo studied medicine in Pisa before becoming a teacher at the University of Pisa, and later professor of mathematics at the University of Padua.
His observations on the Milky Way, Jupiter's moons, and the mountains on the Earth's moon brought him recognition and an offer to become 'mathematician and [natural] philosopher' to the Grand Duke of Tuscany. However, his relentless pursuit of Copernican theories relating to the movement of the Earth and Sun in our solar system challenged religious teaching, which led to his condemnation and exile.
He enunciated and systematically applied the scientific method and used mathematics to describe physical phenomena. We can confidently say that modern science begins with him.

Ask the scientist?

- Who named Jupiter's moons?
- Who put us on the right path in physics?

Curriculum Vitae

1564 (15 Feb.) Galileo's birth in Pisa, Italy
1589-1592 Appointed Chair of mathematics, University of Pisa & later Padua
1598 In a letter to Kepler, announces he is a believer in Copernican theory
1609 (summer) Using a Dutch prototype, begins work on a finely tuned telescope
1610 (May) Publishes Message from the stars
1610-1613 Appointed 'mathematician and philosopher' to Grand Duke of Tuscany, later announces Venus orbits the Sun not the Earth
1616 Admonished by Cardinal Bellarmino for supporting Copernican astronomy
1622-1623 Wrote and published Saggiatore (The Assayer)
1632 Writes Dialogue concerning the two chief world systems - suspected of heresy
1638 Publishes Discourses on two new sciences , despite publishing ban
1642 (8 Jan.) Galileo dies in Arcetri after a nine-year professional exile


MATHEMATICS & MECHANICS: formulated the basic law of falling bodies; a model of the inclined plane, the brachistochrone descent, devised a machine for raising water, and a geometric and military compass

ASTRONOMY: discovered the satellites of Jupiter and formulated a model for determining longitudes at sea; discovered mountains on the moon and proved the Milky Way was composed of millions of stars

OPTICS: developed a telescope to study the stars; worked on building a microscope called a occhialinii

HEAT & MAGNETISM: studied magnetism and attempted to increase the strength of lodestones; invented the thermoscope, an early ancestor of the thermometer

WRITINGS: wrote Message from the stars ; Saggiatore (The Assayer) ; Dialogue concerning the two chief world systems . Post-exile he wrote Discourses on two new sciences; and several 'vernacular' works translated into Latin

Talk Back

A family of stars
The four celestial bodies, discovered and written about by Galileo in 1610 in his short book, Message from the star s, represents one of the pivotal discoveries in the history of science and astronomy.

Galileo calculated the movements and appearance of the Jupiter's satellites and announced in Sidereus Nuncius that he believed that these moons/stars rotated around a body other than the earth, which supported Copernicus' earlier works and contradicted the Aristotelian/Ptolemaic system.

On the parabolic path
The modern view of projectile motion requires study of modern concepts such as velocity and acceleration. It is ironic that Galileo himself is responsible for these "modern" concepts that we still use and teach today:

A projectile which is carried by a uniform horizontal motion compounded with a naturally accelerated vertical motion describes a path which is a semi-parabola

Galileo exposed his physical findings to the world in a book entitled Discourses Concerning Two New Sciences . The three characters in the book discuss his findings with each other and therefore Galileo shed some of the responsibility of his concepts. As Galileo would have been aware, those who dared to expound ideas contrary to Church held beliefs were ridiculed and punished.



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