In 1592, Galileo became a professor in mathematics and astronomy at the University of Padua. There, he had a relation with a beautiful women from Venice, Marina Gamba. Together, they had three children. His oldest daughter Virginia (who became Sister Maria Celeste) would later be his mainstay. In Padua, Galileo was initially busy with problems of mechanics, such as motion on an inclined plane, the pendulum, the ballistic curve, and the principle behind the lever. Also, he attempted to measure the speed of light, which unfortunately failed. He believed that the light speed should be finite. In 1597, Galileo developed a commercial scientific instrument called the geometrical and military compasses, which was used as a pocket calculator and in ship-building.
Around 1600, most scientists and the church believed in the geocentric view of Aristotle and Ptolemy, which stated that the Earth had a fixed position in centre of the universe. The (irregular) movement of the other heavenly bodies was explained using circles and epicycles. Although Copernicus had proposed a much more elegant, heliocentric, solution in 1543, there was initially little support for his theory. Galileo knew the work of Copernicus, but he did not teach the heliocentric model yet. But in 1597, he did write in a letter to Johannes Kepler: "The model of Copernicus appears to be more plausible than that of Aristotle."
In the summer of 1609, a friend told Galileo about the Dutch invention of the telescope. He then decided to build a telescope of his own (with a magnification of 20x) and pointed it to the Moon, the constellation Orion and the Pleiades. The result was marvellous. He wrote: "I am eternally grateful to God that he is so kind to let me be the first to observe wonders that have been shrouded in darkness in all passed centuries." In January 1610, he also discovers four moons of Jupiter and his findings were quickly published in a booklet of 60 pages in March, entitled "Sidereus Nuncius" or "Messenger from the Stars". Because of this publication, Galileo became famous in Europe. In that same year, he was appointed "Mathematician and Philisopher" of the Grand Duke of Tuscany (Cosimo II de Medici). He also observed the crescent of Venus that supported the theory of Copernicus.
Despite problems with his health, Galileo traveled to Rome in 1611. There he was warmly welcomed by the pope, cardinals, prelates and kings. He defended his theories vigorously, but his success also made people jealous. Many refused to believe his theories.
When he returned to Florence, he observed sun spots. He concluded that these spots are really associated with the Sun. They revolve around the surface of the sun with the same speed and they change their shapes over time. This was in contradiction with the the theory of that time, which stated that the Sun was a perfect sphere. Around 1614, the discussion about the theory of Copernicus escalates. Galileo supported the heliocentric model, which lead to great controversy.
In this period, Galileo was frequently ill. Despite of his illness, he went to Rome in 1616 to defend himself against accusations of heresy. Unfortunately, his pleas were in vain, because the theory of Copernicus was declared heretical by the Holy Officie in 1616. Galileo heard that he was no longer allowed to advocate the heliocentric theory.
There are two different versions of the verdict by the cardinals:
- Galileo was only allowed to cite Copernicuss theory as being an unproved mathematical hypothesis, not as proven fact (in a letter from
cardinal Bellarmino to Galileo). - Galileo was not allowed to discuss, to advocate or defend the theory of Copernicus. He should neither speak nor write about it (official locument, which may have been falsified).
These two versions would play an essential role in the trial of 1633.
In October 1616, Galileo's daughter Virginia took her vows and became a nun in the order of the Poor Clares and changed her name to Maria Celeste (to pay tribute to her father). In the following years, Galileo continued his work in mechanics until an old acquaintance and supporter of Galileo (Cardinal Maffeo Barberini) was elected to be pope Urban VIII in 1623.
In the spring of 1623, Galileo went to Rome and had 6 private audiences with the new pope. He proposed to write a book about the solar system. The pope agreed and even wrote a letter of recommendation for Grand Duke Ferdinando II: "With fatherly love, we embrace this great man, who's fame shines on the sky and covers the Earth."
In the following years, Galileo wrote the Dialogue concerning the Two Chief World Systems, which was published in 1632. The Dialogo is a meeting of 3 persons:
- Salvati, scientist, defends Copernic (alter ego of Galileo).
- Simplicio, pompous philosofer, defends Aristotle.
- Sagredo, intelligent layman, referee.
The meetings take place in four days:
- Day 1: The (in)variability of the earth, sun, moon and stars
- Day 2: Rotation of the earth and principle of relativity (Can you measure absolute motion or is it always relative?)
- Day 3: Models by Ptolemae and Copernicus. The movement of the earth and planets around the sun and the role of sun spots.
- Day 4: Discussion about tides and movements of the sun and the earth (tides are caused by the movement and rotation of the earth).
The challenge for Galileo was to write the book in such a way that the church would not be offended. Therefore, Salvati says near the end of the book: "God could have made nature in many ways, which our minds would not be able to grasp. The heliocentric model might turn out to be a foolish delusion and a grand paradox."
In April 1630, Galileo traveled to Rome again and presented his work to the censor, Father Riccardi. Two months later, the Dialogo was in principle accepted by Riccardi, but the title, introduction, and conclusion had to be changed in line with the philosophy of the pope. After a long time, Galileo received the final permission to publish in June 1631. In February 1632, the book came of the press.
Suddenly, Pope Urban VIII reacts in a very negative way to the Dialogo and becomes very angry. A probable reason for his anger would be the political problems that he experienced. He was involved in the war in Germany and there were problems with Spain and several Italian states. There was also the religious war in Germany against the Protestants. Moreover, he assumed Simplicio (Simple man) represented the ideas of the pope.
In September 1632, the Dialogo was no longer allowed to be sold and Galileo was summoned to Rome because he was suspected of heresy.
In the period between April and june 1633, Galileo was interrogated four times by the Inquisition. The prosecutor asked his questions in Latin, but Galileo answered in Italian. During the first hearing, he emphasized that the model of Copernicus should just be seen as an hypothesis and not as reality, because it was in conflict with Scripture. But three theologians concluded that the Dialogo supported Copernicus. "It is clear that Galileo teaches the movement of the earth in writing." In the following hearings, Galileo tried to save himself by saying: "I have made my argument too strong. My failure, and I acknowledge that, is presumptuous ambition, pure ignorance, and disarray. I misinterpreted the order by cardinal Bellarmine of 1616." However, his conviction could not be avoided. He was sentenced on June 22nd 1633: "Galileo has made himself vehemently suspect of heresy", because he supported the theory of Copernicus.
Galileo had to publically confess his errors and heresies, which was very humiliating. He also had to go to prison and recite seven psalms each week on his knees for three years. The Dialogo was forbidden.
In July 1633, his imprisonment was converted into a life-long house arrest, because of health reasons. He was not allowed to have contact with the outside world. The conviction of Galileo was a sensation in Western Europe, and the Dialogo (Latin translation in 1636) was a great succes.
Although Galilei was ill and somewhat mentally disturbed, he started to write a book about mechanics, based on his research in Padua. This book, "Discorsi", was published by Louis Elzevier in Leiden, because no-one in and around Italy dared to publish it.
Although Galileo was ill and mentally exhausted, he started to write a book about mechanics, based on his research in Padua. This book, Discorsi, or Dialogues Concerning Two New Sciences was published by Elzevier in Leiden, because it could, of course, not be published in Catholic lands.
In March 1634, Maria Celeste died and Galileo became very depressed. Moreover, he became blind in 1637. He was not able to read the Discorsi himself anymore. On January 8th 1642, Galileo died in company of his son Vincenzio, and his last two students Evangelista Torricelli (the inventor of the barometer), and Vincenzo Viviani.
Galileo is burried in the Cappelle di Novizi of the church of Sante Croce in Florence. Maria Celeste lies next to him. She had a fine mind, and shared the diligence and sensitivity of her father. She wrote many letters to him (124 are preserved), maintained his clothes and medicines, helped with copying the manuscript of the Dialogo, was full of compassion and was his greatest comforted during the trial of 1633.
Literature used here:
- Dava Sobel “De Dochter van Galilei”
- Enrico Bellone “Galilei. Leven en werken van een onrustige geest”
- Don Nardo “The Trial of Galileo”
- Simon Singh “De Oerknal”
Galileo (1564-1642) was a brilliant theoretician, a master of experimental physics, a precise observer, a talented inventor and instrument builder, and a devout catholic. His main interests were problems in mechanics and astronomy. Galileo was the first man to point a telescope to the sky in 1609. He published his important discoveries very quickly in 1610. He also advocated the heliocentric model of Copernicus, which stated that the Earth revolves around the Sun. This view was in conflict with the holy beliefs of the church. Therefore, he was convicted and made to renounce his views in 1633. In addition, he was placed under house arrest for the rest of his life. Galileo had three children and a special bond with his oldest daughter Sister Maria Celeste.