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Why was Galileo unable to defend himself?

  1. Jan 18, 2013 #1
    Galileo was convicted of heresy and blasphemy for his heliocentric model.

    However, during the trial, wouldn't Galileo be able to provide experimental evidence and physical proof that would vindicate him?
  2. jcsd
  3. Jan 18, 2013 #2
    He have to prove it in Religious community not the Scientific.
  4. Jan 18, 2013 #3


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    You are assuming that Galileo's accusers were rational men acting rationally. If one is unwilling to overthrow an existing dogma or world view, then the amount of evidence presented is irrelevant.
  5. Jan 18, 2013 #4
    Well, if they had decided to shut themselves off.

    Anyway, what was the evidence for heliocentrism at that time? How conclusive was it?
  6. Jan 18, 2013 #5
    What you do when you Explain something well that is the Universal but the Front Learners don't want to hear that.
  7. Jan 18, 2013 #6
    Galileo was accused of heresy but he was absolved of it when he agreed to "abjure, curse, and detest the said errors and heresies..." In other words, he dodged the bullet by publicly renouncing the notion of Copernican Heliocentrism.


    Blasphemy was never charged.

    The 'crime' they actually pinned on him was that of rendering himself "vehemently suspect of heresy." What that means is that his writings about Copernicus sounded so much like he was supporting Copernicus that it had required a formal inquiry to sort the matter out. (Under direct questioning Galileo caved to fear and denied he ever subscribed to the idea of a heliocentric model. He claimed his thoughts about it were merely hypothetical. Anyone who reads his book knows better.) He was sentenced to "imprisonment" which actually took the form of a kind of lifelong probation where close watch would be paid to what he said and whom he talked to. Initially he was required to live in the household of a guy the inquisition trusted, but eventually he was allowed to return to his home, still constantly spied on, though.

    What's interesting is that only seven of the ten cardinals who judged the evidence signed the sentence. The other three, it's assumed, would have absolved him of all wrongdoing.

    Had Galileo made any attempt to convince the inquisition that the earth revolved around the sun he would have simply proven he was a heretic and been tortured and authentically imprisoned.
  8. Jan 19, 2013 #7
    That which constitutes a prevailing argument has varied in different places and different times, and still does.

    I know an attorney who works overseas. He was trained in the idea that a solid logical argument should prevail. What he found was that there are places where the winner of an argument is the one who keeps talking, says the most words, and has the last word.

    A logical argument is based on a series of steps, each one firmly grounded and contingent on the previous step, the failure of a single step destroys the argument. This is like a math proof.

    Some kinds of argument are based on a whole lot of "parallel" supports, stand alone supports - each of which contributes, the failure of any one is not critical. This is like "a preponderance of the evidence" majority rules kind of argument.

    Some arguments are much softer (debating style points).
    Some are just whomever makes the most noise... (internet) :)
    Last edited: Jan 19, 2013
  9. Jan 19, 2013 #8
    Bear in mind, Galileo ultimately won.


    The Catholic church has gone down in history as the bad guy in the Galileo affair. The solid logical argument did prevail, just not immediately.
  10. Jan 19, 2013 #9


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    And all of this occured during the golden age of techonolgical advances in torture devices courtesy of the inquisition. Galileo's reluctance to confront his accusers with mere facts was entirely understandable.
  11. Jan 20, 2013 #10


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    Galileo ( 1564-1642 ) lived before the Age of Enlightenment, 17th and 18th century, when tradition, faith, dogma began to be questioned, and scientific arguments took on a greater acceptance.

    Galileo had no defensible argument. He was either a heretic or was not, based upon the nature of the trials and permissable evidence at that time.

    In defence of the church, the perspective of social peace ( using the term loosely ) plays a part here. The church was part of the rulling class, or at least had a very close relationship. Following church doctrine meant you were a good citizen and by simple reasoning a loyal subject.
  12. Jan 22, 2013 #11
    so what was the physical evidence that led Galileo to his idea? was there strong evidence at that time?
  13. Jan 22, 2013 #12


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    If I remember correctly, one of the major things was that it was quite tricky to calculate the motion of the planets. They seemed to switch directions every once in a while, and people had to resolve to contorted constructions of circles on circles on circles .... to explain this. Assuming that all planets, including the earth, revolve around the sun in a normal circular (actually, elliptic) motion, resolves all that at once.
  14. Jan 22, 2013 #13


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    The major influence on Galileo in supporting heliocentrism was philosophical. He was charmed by the idea the planets moved in simple circles. His evidence was, however, not compelling. His observations of the moons of Juptiter [which were rather obviously orbiting Jupiter] and the moon-like phases of Venus would have favored his case, but, were not conclusive. Furthermore, these observations required use of the telescope, which was regarded with ambivalence by the church. Actually, Galileo did not incur the wrath of the church until 1632 when he published 'Dialogue Concerning the Two Chief World Systems', which included a gratuitous slap at his former friend Pope Urban VIII. This led to his trial for suspicion of heresy. He had been investigated by the inquistion in 1615, but absolved of any wrongdoing in that case. The first compelling evidence favoring heliocentrism was probably Bessel's discovery of stellar parallax in 1832.
  15. Jan 22, 2013 #14
    Galileo was persuaded by Copernicus' logic in interpreting the physical evidence. The observations Copernicus drew on didn't contain any revolutionary new information. He was simply able to think outside the box and envision a pattern that made a great deal more sense in explaining what we see in the sky than the other "chief world system," which was subscribed to by the followers of Aristotle, who were very influential in the Church.


    Galileo's professional life was all about debunking the Aristotelian Natural Philosophers. Those Philosophers, however, had long been something like pets or mascots of the Catholic Church. The Church liked their vision of the heavens as an embodiment of perfection. Regardless, the Church was intrigued by both Copernicus and Galileo at first, in a positive way. Seeing this, the Aristotelians, who feared losing their favored status, began collecting bits of scripture that could be taken as assertions that the earth was the center of the universe, and that the sun revolved around the earth. Armed with these, they poisoned as many minds in the Church as they could against Copernicus/Galileo, saying he was contradicting scripture.
  16. Jan 22, 2013 #15
    At the time you must understand that science was expected to be kept compatible with Christian theology. Developing ideas that contradicted the Church was one thing, but the notion of mocking the Church would not be tolerated.

    Galileo essentially stole credit for the invention and innovation of the Telescope. Upon observing the rough surface of the moon he did not simply record his observations, he decided to take shots at the bible. He declared, "The astronomical language of the Bible [was] designed for the comprehension of the ignorant". That comment is was really got him into trouble, he was summoned into rome in 1616 by a papal admonition. Instead of behaving himself, he then decided to publish another text which essentially stated Copernicus was correct and Ptolemy was wrong. The inquisition then formally tried him. One does not simply throw numbers at the Inquisition and expect to walk away, he was convicted and forced to recant.
  17. Jan 22, 2013 #16
  18. Jan 22, 2013 #17
    Of course everyone had to adhere to church doctrine, but what numbers (if any) did he throw at the church?
  19. Jan 22, 2013 #18
    So after the papal admonition, he went ahead and published Dialogue on the two main world systems (1632). In the book he pretended to be bringing light to both sides of the argument, but essentially he was writing to say Ptolemy was wrong.

    By numbers I meant proofs and anything logical in nature. He had brought up some major points, that were scientific in nature, while arguing for Copernicus. I'm not too familiar with the entire trial, but I was getting at the idea that he couldn't expect to go into that trial and say here is the logic and reasoning behind my notions, I'll be on my way.
  20. Jan 23, 2013 #19
    No, he couldn't - Galileo wasn't the only one using logic and reasoning. There were a number of valid arguments against the Copernican model and both alternative explanations for some observations and lack of explanation for others in the Copernican model. Several of the people examining Galileo's arguments would likely have been as well versed as Galileo in logic and reasoning, but they would have been arguing from the POV that the Bible and the Ptolemaic system were valid (ie, they provided their axiomatic base) - it's fairly standard to assume the validity of the status quo and for arguments against it to carry the burden of proof.

    It is worth bearing in mind that the Earth-centric, epicyclic model was capable of giving good agreement with observation and could, in principle, be refined to give more exact agreement.
  21. Jan 23, 2013 #20


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    This was the selling point. This was in the preface introducing the points that Galileo intended to discuss. In actuality, claiming this was intended as an insult to the Pope was pretty thin, but if enough people believed it was an insult, then the Pope had to act on it, whether he believed it to be an insult or not. The Pope had problems of his own and standing up for Galileo would have just made his own problems worse. In other words, the church really did do Galileo wrong.

    Who knows what the motivation for persecuting him was. Different members of the church had different views on celestial mechanics - a Copernican model, a Ptolemaic model, and Tycho Brahe's model (that said the Sun and Moon orbited the Earth, while the planets orbited the Sun). There were legitimate arguments for and against each at the time, but the arguments tended to be as much personal attacks on people holding opposing view points as they were logical discussions.

    In any event, the actual offense Galileo was found guilty of wasn't as important as finding him guilty of something, with his advocacy of the Copernican model being only one of his offenses.

    Defending himself with physical evidence or logic really would have been inadequate for his era. He really needed his allies to mount more substantial personal attacks on his enemies and that involved risk. Personal attacks were not only decided by reputation, but winning these helped a person's reputation while losing these damaged a person's reputation. It wasn't an age dominated by science.
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