Galileo's championing of
heliocentrism was controversial within his lifetime, when most subscribed to either
geocentrism or the
Tychonic system. He met with opposition from astronomers, who doubted heliocentrism due to the absence of an observed
stellar parallax. The matter was investigated by the
Roman Inquisition in 1615, and they concluded that it could be supported as only a possibility, not an established fact. Galileo later defended his views in
Dialogue Concerning the Two Chief World Systems, which appeared to attack Pope
Urban VIII and thus alienated him and the
Jesuits, who had both supported Galileo up until this point.
He was tried by the Inquisition, found "vehemently suspect of heresy",
forced to recant, and spent the rest of his life under house arrest. It was while Galileo was under house arrest that he wrote one of his finest works,
Two New Sciences, in which he summarised the work he had done some forty years earlier, on the two sciences now called
kinematics and
strength of materials.
Biblical references
Psalm 93:1,
96:10, and
1 Chronicles 16:30 include text stating that "the world is firmly established, it cannot be moved." In the same manner,
Psalm 104:5 says, "the Lord set the earth on its foundations; it can never be moved." Further,
Ecclesiastes 1:5 states that "And the sun rises and sets and returns to its place."
Galileo defended
heliocentrism, and claimed it was not contrary to those Scripture passages. He took
Augustine's
position on Scripture: not to take every passage literally,
particularly when the scripture in question is a book of poetry and
songs, not a book of instructions or history. He believed that the
writers of the Scripture merely wrote from the perspective of the
terrestrial world, from that vantage point that the sun does rise and
set. Another way to put this is that the writers would have been writing
from a phenomenological point of view, or style. So Galileo claimed
that science did not contradict Scripture, as Scripture was discussing a
different kind of "movement" of the earth, and not rotations.
By 1616 the attacks on the ideas of
Copernicus
had reached a head, and Galileo went to Rome to try to persuade
Catholic Church authorities not to ban Copernicus' ideas. In the end, a
decree of the
Congregation of the Index
was issued, declaring that the ideas that the Sun stood still and that
the Earth moved were "false" and "altogether contrary to Holy
Scripture", and suspending Copernicus's
De Revolutionibus until it could be corrected. Acting on instructions from the Pope before the decree was issued,
Cardinal Bellarmine
informed Galileo that it was forthcoming, that the ideas it condemned
could not be "defended or held", and ordered him to abandon them.
Galileo promised to obey. Bellarmine's instruction did not prohibit
Galileo from discussing heliocentrism as a mathematical fiction but was
dangerously ambiguous as to whether he could treat it as a physical
possibility.
For the next several years Galileo stayed well away from the
controversy. He revived his project of writing a book on the subject,
encouraged by the election of Cardinal Maffeo
Barberini as
Pope Urban VIII in 1623. Barberini was a friend and admirer of Galileo, and had opposed the condemnation of Galileo in 1616. The book,
Dialogue Concerning the Two Chief World Systems, was published in 1632, with formal authorization from the
Inquisition and papal permission.
Dava Sobel
explains that during this time, Urban had begun to fall more and more
under the influence of court intrigue and problems of state. His
friendship with Galileo began to take second place to his feelings of
persecution and fear for his own life. At this low point in Urban's
life, the problem of Galileo was presented to the pope by court insiders
and enemies of Galileo. Coming on top of the recent claim by the then
Spanish cardinal that Urban was soft on defending the church, he
reacted out of anger and fear. This situation did not bode well for
Galileo's defence of his book.
Earlier, Pope Urban VIII had personally asked Galileo to give arguments
for and against heliocentrism in the book, and to be careful not to
advocate heliocentrism. He made another request, that his own views on
the matter be included in Galileo's book. Only the latter of those
requests was fulfilled by Galileo. Whether unknowingly or deliberately,
Simplicio, the defender of the Aristotelian Geocentric view in
Dialogue Concerning the Two Chief World Systems,
was often caught in his own errors and sometimes came across as a
fool. Indeed, although Galileo states in the preface of his book that
the character is named after a famous Aristotelian philosopher (
Simplicius in Latin, Simplicio in Italian), the name "Simplicio" in Italian also has the connotation of "simpleton". This portrayal of Simplicio made
Dialogue Concerning the Two Chief World Systems
appear as an advocacy book: an attack on Aristotelian geocentrism and
defence of the Copernican theory. Unfortunately for his relationship
with the Pope, Galileo put the words of Urban VIII into the mouth of
Simplicio. Most historians agree Galileo did not act out of malice and
felt blindsided by the reaction to his book.
However, the Pope did not take the suspected public ridicule lightly,
nor the Copernican advocacy. Galileo had alienated one of his biggest
and most powerful supporters, the Pope, and was called to Rome to defend
his writings.
In September 1632, Galileo was ordered to come to Rome to stand trial.
He finally arrived in February 1633 and was brought before inquisitor
Vincenzo Maculani to be
charged.
Throughout his trial Galileo steadfastly maintained that since 1616 he
had faithfully kept his promise not to hold any of the condemned
opinions, and initially he denied even defending them. However, he was
eventually persuaded to admit that, contrary to his true intention, a
reader of his
Dialogue could well have obtained the impression
that it was intended to be a defence of Copernicanism. In view of
Galileo's rather implausible denial that he had ever held Copernican
ideas after 1616 or ever intended to defend them in the
Dialogue,
his final interrogation, in July 1633, concluded with his being
threatened with torture if he did not tell the truth, but he maintained
his denial despite the threat.
The sentence of the Inquisition was delivered on June 22. It was in three essential parts:
- Galileo was found "vehemently suspect of heresy", namely of having
held the opinions that the Sun lies motionless at the centre of the
universe, that the Earth is not at its centre and moves, and that one
may hold and defend an opinion as probable after it has been declared
contrary to Holy Scripture. He was required to "abjure, curse and detest" those opinions.
- He was sentenced to formal imprisonment at the pleasure of the Inquisition. On the following day this was commuted to house arrest, which he remained under for the rest of his life.
- His offending Dialogue was banned; and in an action not
announced at the trial, publication of any of his works was forbidden,
including any he might write in the future.
According to popular legend, after recanting his theory that the
Earth moved around the Sun, Galileo allegedly muttered the rebellious
phrase
And yet it moves (
italian:
Eppur si muove)
but there is no evidence that he actually said this or anything
similar. The first account of the legend dates to a century after his
death.
After a period with the friendly
Ascanio Piccolomini (the Archbishop of
Siena), Galileo was allowed to return to his villa at
Arcetri
near Florence in 1634, where he spent the remainder of his life under
house arrest. Galileo was ordered to read the seven penitential psalms
once a week for the next three years. However his daughter Maria Celeste
relieved him of the burden after securing ecclesiastical permission to
take it upon herself.
It was while Galileo was under house arrest that he dedicated his time to one of his finest works,
Two New Sciences. Here he summarised work he had done some forty years earlier, on the two sciences now called
kinematics and
strength of materials. This book has received high praise from
Albert Einstein.
As a result of this work, Galileo is often called the "father of modern
physics". He went completely blind in 1638 and was suffering from a
painful
hernia and
insomnia, so he was permitted to travel to Florence for medical advice.
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