June 22 – Go To Heliocentric

Today’s factismal: Galileo was convicted of heresy 383 years ago today.

Today marks the 383rd anniversary of Galileo’s conviction for heresy. Why should you care? Because Galileo’s trial and subsequent exoneration (a mere 359 years later) show what happens when you let civil authority decide what is and isn’t true.

Galileo's sketch of the Moon

Galileo’s sketch of the Moon

His story starts out well. In 1610, Galileo had published The Starry Messenger (Sidereus Nuncius), a book based on observations of the heavens that he had made using the telescope that he had created. In addition to pointing out the planets orbiting Jupiter (today we call them the Galilean moons: Io, Europa, Callisto, and Europa), he made several statements supporting Copernicus’ heliocentric theory. At the time, the idea that the Earth orbited the Sun was considered to be heresy (Giordano Bruno had been burned at the stake in 1600 for espousing that view). Galileo’s views combined with his sometimes acerbic manner led Caccini and other priests to denounce him to the Inquisition. In 1616, the Inquisition ordered Galileo to stop teaching, promoting, defending, or even discussing heliocentrism and threatened him with torture if he failed to obey. Being no dummy, Galileo agreed.

But, being a scientist, he kept looking for evidence, and, being a bright guy, he kept finding it. He also amassed a few powerful friends, including a passing acquaintanceship with Urban VIII who became Pope in 1623. Those friends encouraged Galileo in his studies and encouraged him to return to the subject of what orbited what. In 1632, Galileo finally organized his thoughts and his evidence into a new book called A Dialogue On Two World Systems. To put it mildly, the book was a hit. Not only did it succinctly rebut the Church’s position, but it did it in an entertaining manner through an extended conversation between Sagredo (“thinker” in colloquial Italian), Salviati (“smart guy”) and Simplicio (“dummy”). As you might guess, Salviati had the right idea (heliocentrism) and all of the best lines. But what you might not guess is that Simplicio, who supported the Church’s position, did so using Urban’s own arguments.

Galileo faces the Inquisition (Painting by Cristiano Banti)

Galileo faces the Inquisition
(Painting by Cristiano Banti)

What followed was predictable. The pope was enraged by being called “dummy” and ordered Galileo brought before the Inquisition again. This time, they didn’t let him off with a slap on the wrist. They showed him the instruments of torture (excuse me – “gentle correction of heresy”) and threatened his life if he didn’t recant. Galileo promptly did so, and was sentenced to life under house arrest with every letter, book, and grocery list he wrote being subject to inspection and approval by the Inquisition. And there things remained for 359 years.

In the meantime, other scientists found yet more evidence that Copernicus was right and the Church was wrong. By 1835, there was enough evidence that Galileo’s book was removed from the Index Librorum Prohibitorum (“List of Forbidden Books”). In 1939, Pope Pius XII praised Galileo’s courage. And in 1979, the Roman Catholic Church began a new investigation into Galileo’s claims. Finally, on October 31, 1992, they announced what the rest of the world had known for centuries: Galileo wasn’t a heretic – he was right.

One thought on “June 22 – Go To Heliocentric

  1. Pingback: October 14 – Tone Deaf | Little facts about science

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