June 22, 2022

The Trial of Galileo

The Trial of Galileo

June 22, 1633. The Inquisition forces Galileo to recant his support of the Copernican system, which argues that the Sun, not the Earth, is the center of the solar system


Cold Open

It’s January 20th, 1600 in Rome.

Inside a gloomy, candlelit courtroom on the edge of Vatican City, an assembly of Catholic cardinals is preparing to sentence a man to death. Standing before the dock, hunched and bedraggled in his filthy clothes, is the defendant – a Catholic monk and astronomer named Giordano Bruno.

Bruno looks up, as a severe-looking churchman stands, walks forward, and raises his hand to quiet the court.

Cardinal Bellarmino is the chief inquisitor of the Roman Inquisition – an agency responsible for silencing anyone who speaks out against the doctrines of the Catholic Church.

Bellarmino looks down at Bruno with a stern expression. He accuses Bruno of spreading blasphemy with his astronomical teachings and gives the defendant one final chance to recant his beliefs. But Bruno defiantly refuses.

Again, Bellarmino raises his hand to quiet the shocked whispers.

Then he clears his throat and sentences Bruno to burn at the stake for heresy. Bruno receives the verdict with steely composure. He looks at Bellarmino with disdain in his eyes and says: “Perhaps you pronounce this sentence against me with greater fear than I receive it.”

A few weeks later… onlookers crowd the streets… as they watch Bruno being dragged through the center of Rome, his wrists tethered to the back of a horse-drawn cart. Bruno grits his teeth as his body scrapes over the rough cobblestones.

Eventually, the cart reaches the Campo de Fiori, Rome’s main market square.

Bruno is hauled to his feet and carried to a scaffold above a pyre. 

The rebellious monk is stripped naked, before being hoisted up by his ankles.

The crowd laughs and jeers. Bruno closes his eyes and whispers a prayer, still refusing to renounce his beliefs, to renounce science… even as the executioner lights the pyre beneath him.

In Italy, the 17th century is a time of great scientific discovery. But it is also a period of widespread religious persecution, in which the Catholic Church forcefully suppresses ideas that run contrary to its doctrines. Giordano Bruno promoted astronomical theories that were seen to contradict the teachings of the Bible; and as a result, he paid the ultimate price.

And soon, another astronomer will confront the forces of orthodoxy, going further to challenge the status quo than any other scientist before him. Ultimately, this astronomer, Galileo Galilei, will be prosecuted for his genius and forced to either turn his back on science or suffer the deadly consequences at his trial before the Roman Inquisition on June 22nd, 1633.


From Noiser and Airship, I’m Lindsay Graham and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is June 22nd, 1633: The Trial of Galileo.

Act One: The Starry Messenger

It’s 1609 in Padua, Italy – twenty-four years before Galileo is sentenced by the Roman Inquisition.

A middle-aged man sits in his study, his head lowered over his work. Galileo Galilei is a professor of mathematics at the University of Padua. For the past 20 years, Galileo has been conducting research into the fields of geometry and mechanics, but the subject that fascinates Galileo more than any other is astronomy.

Before the dawn of the last century, humanity’s understanding of the cosmos has been dominated by the ideas of the Ancient Greeks. During the 4th century BC, the philosopher and scientist Aristotle argued that the earth was situated at the center of the universe and that all the stars and planets revolved around it. Aristotle’s theory is known as the “geocentric theory” of the universe, a view was developed further in the 2nd century AD by the Greek mathematician Ptolemy. Ptolemy believed that the earth was stationary, and located at the center of a universe consisting of 55 concentric circles, along which all celestial objects moved in orbit.

Ptolemy’s theory was accepted by most early Christians because it placed Earth – God’s most perfect creation – at the center of all things. And for fifteen hundred years, the geocentric model remained the unchallenged view of the universe.

But then, in the 1530s, a Polish astronomer named Nicolaus Copernicus conducted a series of experiments which he believed proved Aristotle and Ptolemy wrong. Copernicus measured the changing position of the sun in the sky in relation to Earth. And based on his findings, he concluded that the earth revolves around the sun – and not the other way around; a system known as the “heliocentric theory”.

Copernicus published his findings in 1543, and the heliocentric theory started to gain traction. Decades later, a German astronomer named Johannes Kepler studied the orbital paths of Venus and Mars. Kepler concluded that Copernicus was correct, and he too endorsed the heliocentric theory.

But despite the breakthroughs of Copernicus and Kepler, in the early 1600s, not everyone is convinced. There still isn’t enough scientific evidence to categorically disprove the geocentric view of the universe. Part of the problem is that neither Copernicus nor Kepler were able to observe the planets with anything except the naked eye. But today, as Galileo works in his office, he hopes to change that.

Recently, Galileo heard of a new invention by a Dutch spectacle-maker; a contraption consisting of two glass lenses fixed at different ends of a metal tube. Immediately, Galileo realized that the invention – known as the “telescope” – could have significant applications in his field of astronomy. And so, Galileo set to work building a telescope of his own. And before long, he finishes his first prototype.

On a clear cold night in Padua, Galileo takes his telescope outside and points it at the sky. By using specially measured convex lenses, Galileo has created a telescope capable of magnifying objects to thirty times their original size. Galileo is now able to peer into the heavens and see things more clearly than ever was thought possible. Tonight, he is studying the moon – writing down observations about the strange markings that appear on the lunar surface. He concludes that contrary to prevailing scientific opinion, the moon is not smooth, but is actually covered in craters and mountains. 

And over the next few months, Galileo makes even more amazing discoveries. In January of 1610, he observes three stars dotted around Jupiter. Galileo notes though that on some nights, the stars are hidden behind the planet, but on other nights, they’re visible. He concludes that these are not stars at all, but rather moons orbiting Jupiter. This is a momentous breakthrough: the first time that a celestial object has been seen orbiting a planet… other than Earth.

Galileo makes further discoveries about the planets. With the aid of his telescope, he records observations about the phases of Venus. Similar to how Earth's moon waxes and wanes, Venus appears to reflect light differently depending on its position relative to the sun. And this suggests to Galileo that Venus is orbiting the sun and not the Earth.

Soon, Galileo has amassed enough evidence to demonstrate that Copernicus’ heliocentric view of the universe is no longer a hypothesis. But he knows his findings will be controversial.

The Catholic Church is the most powerful institution in Italy, and it forbids any suggestion that the Earth is not located at the center of God’s creation. The Church has even created an agency called the Roman Inquisition that has been tasked with silencing anyone who speaks out against Church doctrine. Just ten years ago, the Inquisition executed an astronomer named Giordano Bruno for promoting theories that are contrary to Biblical teaching. But Galileo refuses to be cowed by fear.

In 1610, he publishes his findings in a book entitled The Starry Messenger,in which he presents the heliocentric view of the universe as fact, instead of theory. And very soon, Galileo’s discoveries will come to the attention of the Roman Inquisition, sparking a long and bitter struggle between the defenders of tradition and the forces of science. 

Act Two: Ye Men of Galilee

It’s December 13th, 1613, in Florence, Italy; twenty years before Galileo is sentenced by the Roman Inquisition.

Galileo sits at his desk writing a letter. Beneath his wiry, graying beard, the famous astronomer mutters angrily as he scribbles on the parchment with an intense, feverish energy. Since publishing The Starry Messengerin 1610, Galileo’s discoveries about the solar system have made him famous; but they have also made him enemies.

Here in his new home of Florence, a collection of theologians have united in their mutual opposition to Galileo’s views. The group is led by a scholar named Lodovico Delle Colombe, and he and his associates maintain the Galileo's assertion that the Earth revolves around the Sun is blasphemous because the Bible explicitly states that God intended Earth to be at the center of his creation – fixed, perfect and immovable. The group of theologians meets regularly to ridicule Galileo’s theories, and to discuss how to destroy his reputation.

Galileo is infuriated by what he sees as the obstinate foolishness of these theologians, and he’s not shy about venting his frustrations in strongly-worded letters to his friends. A few years back, he wrote to fellow astronomer, Johannes Kepler, saying: “I wish that we might laugh at the remarkable stupidity of the common herd, who are filled with the stubbornness of an asp.”

Today, Galileo writes to another friend, a mathematician named Benedetto Castelli. In the letter, Galileo explains how the arguments of the theologians are based on a false premise, because science and religion are separate and distinct, and one cannot be used to support or discredit the other. When he finishes writing, Galileo seals the letter with wax and delivers it to Castelli’s home in Pisa. In Galileo’s mind, the letter he’s just sent is nothing if not the truth. But soon, it will fall into the hands of his enemies, and plunge him into the midst of a scandal.

One year later, a Dominican friar named Tommaso Caccini addresses a congregation in a church in Florence. Caccini is a religious fanatic known for his fiery sermons. He is also a member of the group of theologians taking aim at the teachings of Galileo.

Today, Caccini quotes a passage from the Bible, proclaiming: “ye men of Galilee, why stand ye gazing up into heaven?” His message is clear: how dare Galileo and his fellow astronomers question God’s infinite wisdom?

Many in the congregation nod their heads in grave assent. But one man stands, his heart thumping, a plan forming in his mind. He is another devout Dominican friar named Nicolo Lorini.

And recently, he came across a copy of a letter written by Galileo just last year. He thought Galileo's arguments sounded heretical. Now hearing Caccini’s fiery sermon, he knows it is and is determined to do something about it.

A few days later, Lorini brings the letter to Caccini at his place of work, the Convent of St. Mark in Florence. Caccini reads the letter, his eyes ablaze with vindication. The two friars then make a copy of Galileo’s letter and send it to the office of the Roman Inquisition.

The letter arrives in Rome in February of 1615. The Secretary of the Inquisition opens the seal and finds an attached note. It explains that the letter from Galileo “includes many statements which are… suspect… as when it states that in discussions about natural phenomena, the authority of scripture should rank last.

Just as Lorini and Caccini hoped, the Inquisition is shocked by Galileo’s letter. Soon, a commission is established to examine Galileo’s work and determine whether the astronomer is guilty of heresy – a crime punishable by death. The senior priest brought in to lead the commission is Cardinal Roberto Bellarmino – the man who previously sentenced Giordano Bruno to death. The commission deliberates for a full year. And eventually, in February 1616, Galileo is summoned to the private home of Bellarmino.

Galileo is nervous and overwrought as he announces his arrival at the door of Bellarmino’s grand residence. A servant shows Galileo to the Cardinal’s private study. And there, Bellarmino informs Galileo that the Roman Inquisition has decreed helio-centrism false and heretical. Bellarmino orders Galielo “to abstain completely from teaching or defending the opinion that the sun stands still at the center of the world and the earth moves around it.” If Galileo disobeys this command, Bellarmino explains, the repercussions will be severe.

Galileo bows his head and agrees to do as the Church wishes. Bellarmino watches him go, satisfied that this troublesome astronomer will finally fall into line. But Galileo has no intention of backing down. He will continue to speak out about his discoveries until he finds himself hauled back in front of the Roman Inquisition, who will force him either to turn his back on science or die for his beliefs.

Act Three: The Verdict

It’s June 22nd, 1633 in Rome.

Galileo stands inside the Holy Office of the Roman Inquisition, sweating in his heavy black robes. A beam of sunlight filters through the high window, and Galileo watches as dust particles dance and swirl. Before him, a panel of stern-looking Church officials quietly deliberate, occasionally throwing glances in the direction of the aging astronomer.

In 1616, the Roman Inquisition declared the heliocentric theory of the universe a heretical falsehood. The Church banned the books written by Galileo, Kepler, and Copernicus. They forbade scholars from defending or teaching the controversial hypothesis that the Earth revolves around the sun.

But Galileo refused to stay silent. 

He set to work on a new book, written as a dialogue between two philosophers. One of the philosophers advocates the Copernican or helio-centric view. The other – a foolish man named Simplicio – presents the traditional, geo-centric view of Aristotle and Ptolemy. The book intends to illustrate how the geo-centric view is outdated and false, while the heliocentric view is irrefutable.

Galileo’s book, The Dialogue Concerning the Two Chief World Systems,caused immediate controversy. And publishing it, Galileo had clearly disobeyed the orders of the Inquisition, and before long, he was summoned to Rome to stand trial.

Now, Galileo awaits the verdict of the Inquisition. Suddenly, the Cardinals stop conferring and turn to face the defendant. The Head Inquisitor, a scowling priest with dark, vengeful eyes, turns his nose up as he delivers the final judgment. Galileo is found to be “vehemently suspect of heresy” and sentenced to life in prison. Not only that, he must publicly reject the notion that the Earth revolves around the sun.

Galileo nods slowly. He holds out his hands, and in a soft, measured voice, he admits that he was wrong: the Earth is at the center of the universe, fixed and constant, and all the planets and stars revolve around it. The Cardinals nod approvingly. Then, under his breath, Galileo mutters his last, defiant words: “and yet it moves.”

Galileo will spend the rest of his life under house arrest in his villa outside Florence. He will dedicate his remaining years to completing one of his finest works, entitled Two New Sciences; a book that lays the conceptual foundations for modern physics. Nine years after his sentence, Galileo will die, at the age of 77. The great astronomer was a visionary genius during a period of widespread ignorance and brutal oppression.

350 years later, In 1992, Pope John Paul II gives Galileo an official pardon, calling him “a brilliant physicist.” Though these words do not undo the injustice he suffered in his lifetime, the Pope’s pardon serves as a testament to Galileo’s enduring legacy; one that even the Roman Inquisition failed to snuff out when they accused Galileo of heresy on June 22nd, 1633.


Next onHistory Daily.June 23rd, 1943. To recover artwork stolen by the Nazis, the US Government establishes a special army unit known as the Monuments Men.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Mollie Baack.

Sound design by Derek Behrens.

Music by Lindsay Graham.

This episode is written and researched by Joe Viner.

Executive Producers are Steven Walters for Airship, and Pascal Hughes for Noiser.