Three hundred and seventy-eight years ago today, the father of modern science turned the world right-side up with his DialogoAt the turn of the 17th century, science was still dominated by the millennia-old ideas of Aristotle and Ptolemy -- ideas that were tightly aligned with the teachings of the Catholic Church.
But in March of 1610, the Italian astronomer Galileo Galilei published Sidereus Nuncius (Starry Messenger), a slender volume containing hefty discoveries that started to shake the scientific method from religious ideology.
Until that point, the moon was thought to have had a smooth surface (after all, the heavens were believed to have been more "perfect" than the Earth). But using a telescope, Galileo discovered that the moon was not smooth at all -- it was covered in mountains up to four miles high.
The book also described another, even more troubling discovery: four objects orbiting Jupiter.
This observation was a difficult one to accept for church leaders, as it threw into question one of the most cherished beliefs of the time: geocentrism. If Earth was at the center of the universe, with all celestial bodies revolving around it, how could Jupiter have its own moons?
In August, after Jesuit astronomers rejected these discoveries (even refusing to look through his telescope), a frustrated Galileo wrote a letter to his fellow astronomer Johannes Kepler:
"My dear Kepler, I wish that we might laugh at the remarkable stupidity of the common herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth."
During a sermon in Florence in 1614, a Dominican friar named Tommaso Caccini publicly denounced Galileo for promoting the radical theory of heliocentrism, which was originally devised by Copernicus in his famous 1543 text De revolutionibus orbium coelestium.
On February 22, 1632, Galileo published Dialogo sopra i due massimi sistemi del mondo (The Dialogue Concerning the Two Chief World Systems).
He got permission to publish the text from the Inquisition, provided that he presented heliocentrism as merely a hypothesis and gave equal treatment to geocentrism. He didn't.
The following year, Galileo was summoned to Rome to stand trial for heresy, while his
Dialogo was placed on the church's Index Librorum Prohibitorum ("List of Prohibited Books").
The aging and ailing scientist was found guilty and sentenced to house arrest for the rest of his life. The publication of any of his past or future books was prohibited.
Still, Dialogo managed to be a bestseller. It was finally taken off the Index in 1835.
In 1966, Pope Paul VI abolished the Index.
In 1989, NASA launched an unmanned spacecraft to study Jupiter and its telltale moons.
The name of the spacecraft? Galileo, of course.
image: Galileo before the Holy Office, 19th-century painting by Joseph-Nicolas Robert-Fleury
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