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[[Image:Galileo.jpg|right|thumb|200px|Galileo Galilei: Subterman's portrait, circa 1640]]

[[Image:Galileo.jpg|right|thumb|200px|Galileo Galilei: Subterman's portrait, circa 1640]]

'''Galileo Galilei''' (1564-1642), often referred to simply as '''Galileo''', was an [[Italy|Italian]] [[physicist]] and [[astronomer]] who improved the [[telescope]], contributed to the field of mechanical [[physics]], proposed the [[heliocentrism|heliocentric]] model of [[Copernicus]] as the accurate universal model, and later in life had a famous dispute with the [[Catholic Church]].

'''Galileo Galilei''' (1564-1642), often referred to simply as '''Galileo''', was an [[Italy|Italian]] [[physicist]] and [[astronomer]] who improved the [[telescope]], contributed to the field of [[mechanical]] [[physics]], proposed the [[heliocentrism|heliocentric]] model of [[Copernicus]] as the accurate universal model, and later in life had a famous dispute with the [[Catholic Church]].

Galileo first came to prominence when, in 1604, he demonstrated that a [[supernova]] was further away from the earth than the [[moon]].  At the time that was shocking as it was not expected within the earth-centered framework that existed at that time.  It was also around this time that he invented a geometric and military compass.  Galileo sought a patron, and made overtures to the Cosimo family, but had to supplement his income by selling his compass to students along with a handbook on how to use it.  He also invented a primitive [[thermometer]] and a [[barometer]].

Galileo first came to prominence when, in 1604, he demonstrated that a [[supernova]] was further away from the earth than the [[moon]].  At the time that was shocking as it was not expected within the earth-centered framework that existed at that time.  It was also around this time that he invented a geometric and military compass.  Galileo sought a patron, and made overtures to the Cosimo family, but had to supplement his income by selling his compass to students along with a handbook on how to use it.  He also invented a primitive [[thermometer]] and a [[barometer]].

== Advocacy of the Copernican system and conflict with Church authorities ==

== Advocacy of the Copernican system and conflict with Church authorities ==

Until the sixteenth century, the prevailing view was that the [[Sun]], [[Moon]], [[star]]s and [[planet]]s circled the [[Earth]] (the [[geocentrism|geocentric]] system, based on the second century work of [[Ptolemy]]). Puzzled astronomers noticed that [[Mars]], [[Jupiter]] and [[Saturn]] sometimes seemed to move backwards, but their motions were well within the predictions of Ptolemy's theory.  The moon was considered to have more freedom of movement.

Until the sixteenth century, the prevailing view was that the [[Sun]], Moon, [[star]]s and [[planet]]s circled the [[Earth]] (the [[geocentrism|geocentric]] system, based on the second century work of [[Ptolemy]]). Puzzled astronomers noticed that [[Mars]], [[Jupiter]] and [[Saturn]] sometimes seemed to move backwards, but their motions were well within the predictions of Ptolemy's theory.  The moon was considered to have more freedom of movement.

A Polish astronomer, Nicolaus [[Copernicus]] (1473-1543), published a model of the solar system ''De Revolutionibus'' in 1543, in which the earth and other planets circled the sun. The Catholic Church endorsed the book. The book’s preface (which was not written by Copernicus) argued that astronomical models have merit if they correctly predict observations, even if the underlying hypotheses cannot be proved.<ref>[http://webexhibits.org/calendars/year-text-Copernicus.html ''On the Revolutions'' - English translation.]</ref> The scientific evidence was inconclusive.

A Polish astronomer, Nicolaus [[Copernicus]] (1473-1543), published a model of the solar system ''De Revolutionibus'' in 1543, in which the earth and other planets circled the sun. The Catholic Church endorsed the book. The book’s preface (which was not written by Copernicus) argued that astronomical models have merit if they correctly predict observations, even if the underlying hypotheses cannot be proved.<ref>[http://webexhibits.org/calendars/year-text-Copernicus.html ''On the Revolutions'' - English translation.]</ref> The scientific evidence was inconclusive.

However, ancient Greek thought was idolized since it was re-discovered several hundred years before, being viewed almost on par with the [[Bible]] itself. The Ptolemaic system was the prevailing view at the time. Initially it was not the theologians who balked at Galileo's ideas, but rather mathematicians at the University of Pisa who were so outraged that he challenged Aristotle that they refused to even look through his telescope at the stars. Galileo wrote a privately-circulated pamphlet which argued that the Bible should be interpreted in the light of increasing knowledge, and warning that scientific opinion should not be treated as an article of faith.  In this way he matched the great church father [[Saint Augustine]].  Quoting another of the early church fathers Galileo wrote <blockquote>''The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.''</blockquote>

However, ancient [[Greek]] thought was idolized since it was re-discovered several hundred years before, being viewed almost on par with the [[Bible]] itself. The Ptolemaic system was the prevailing view at the time. Initially it was not the theologians who balked at Galileo's ideas, but rather mathematicians at the University of [[Pisa]] who were so outraged that he challenged Aristotle that they refused to even look through his telescope at the stars. Galileo wrote a privately-circulated pamphlet which argued that the Bible should be interpreted in the light of increasing knowledge, and warning that scientific opinion should not be treated as an article of faith.  In this way he matched the great church father [[Saint Augustine]].  Quoting another of the early church fathers Galileo wrote <blockquote>''The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.''</blockquote>

In 1613 a Dominican friar, Tommaso Caccini, got a hold of Galileo's writing and preached a sermon against him. A mangled version of Galileo's writing was sent to Rome.  Galileo heard of this and sent the full version.  He was not terribly alarmed, knowing that many of the best minds in Italy, including the Vatican's mathematicians, were convinced on the heliocentric universe that his works had help to substantiate.  Caccini's Dominican superior was so embarrassed that he sent a letter of apology to Galileo.

In 1613 a [[Dominican]] friar, [[Tommaso Caccini]], got a hold of Galileo's writing and preached a sermon against him. A mangled version of Galileo's writing was sent to [[Rome]].  Galileo heard of this and sent the full version.  He was not terribly alarmed, knowing that many of the best minds in [[Italy]], including the [[Vatican]]'s mathematicians, were convinced on the heliocentric universe that his works had help to substantiate.  Caccini's Dominican superior was so embarrassed that he sent a letter of apology to Galileo.

Caccini wasn't through, however, and gave an unsolicited deposition to the Inquisition about Galileo's views, which largely demonstrated his own ignorance on the subject.  Nevertheless, the theologians who were given the case ruled in a manner that was not pleasing to Galileo when it was handed down. Galileo was told by the Inquisition that he must only use Copernican concepts as a hypothesis for the sake of calculation, without claiming that they had been literally proven true. Because Galileo had overstated the scientific case for the heliocentric theory and given some dubious theological arguments, the Inquisition ruling decided that: 1) the immobility of the Sun at the center of the universe was absurd in philosophy and formally heretical, and that 2) the mobility of Earth was absurd in philosophy and at least erroneous in theology. <ref> [http://www.hps.cam.ac.uk/starry/galileo.html ''University of Cambridge, Department of History and Philosophy of Science'' - Galileo Galilei]</ref> The following month the Church’s [[Index of Forbidden Books]] required that nine sentences in Copernicus's book be corrected.  

Caccini wasn't through, however, and gave an unsolicited deposition to the Inquisition about Galileo's views, which largely demonstrated his own ignorance on the subject.  Nevertheless, the theologians who were given the case ruled in a manner that was not pleasing to Galileo when it was handed down. Galileo was told by the Inquisition that he must only use Copernican concepts as a hypothesis for the sake of calculation, without claiming that they had been literally proven true. Because Galileo had overstated the scientific case for the heliocentric theory and given some dubious theological arguments, the Inquisition ruling decided that: 1) the immobility of the Sun at the center of the universe was absurd in philosophy and formally heretical, and that 2) the mobility of Earth was absurd in [[philosophy]] and at least erroneous in theology. <ref> [http://www.hps.cam.ac.uk/starry/galileo.html ''[[University of Cambridge]], Department of History and Philosophy of Science'' - Galileo Galilei]</ref> The following month the Church’s [[Index of Forbidden Books]] required that nine sentences in Copernicus's book be corrected.  

Looking back, it is hard to understand the decision, but in defense of the arbitors of that time, the view through Galileo's telescope was nothing like the quality of telescopes today.  To untrained laymen, it would be difficult to know what was being viewed.  Also, the concept of stellar parallax, a condition that had to exist if Galileo was right, turned out to be completely false. (Parallax is real, but due to the incredibly far distances of the stars in relationship to the earth's movement around the sun, it could not be detected until 1838, over 200 years later.)

Looking back, it is hard to understand the decision, but in defense of the arbitors of that time, the view through Galileo's telescope was nothing like the quality of telescopes today.  To untrained laymen, it would be difficult to know what was being viewed.  Also, the concept of stellar parallax, a condition that had to exist if Galileo was right, turned out to be completely false. (Parallax is real, but due to the incredibly far distances of the stars in relationship to the earth's movement around the sun, it could not be detected until 1838, over 200 years later.)

Galileo got approval from Rome to write his book ''Dialogue on the Tides'', which discussed both the Ptolemaic and Copernican hypotheses, as long as it discussed both systems and did not draw a conclusion that would make the heliocentric world view be viewed as fact instead of theory.  Rome changed the title to ''Dialogue on the Two Chief World Systems'' and it was published in Florence in 1632.  Unfortunately for Galileo, the work was not made to be evenhanded. Indeed, the Ptolemaic character, called 'Simplicius' often stumbled over his own errors and seemed quite foolish. Galileo had moved out of bounds.  The Church felt they had made themselves clear. At a different time, the reaction might have been different, but it was in the middle of the [[30 years war]], the most deadly war in Europe ever fought between Catholics and Protestants. The Catholic Church had to show it had authority and strength.

Galileo got approval from Rome to write his book ''Dialogue on the Tides'', which discussed both the Ptolemaic and Copernican hypotheses, as long as it discussed both systems and did not draw a conclusion that would make the heliocentric world view be viewed as fact instead of theory.  Rome changed the title to ''Dialogue on the Two Chief World Systems'' and it was published in Florence in 1632.  Unfortunately for Galileo, the work was not made to be evenhanded. Indeed, the Ptolemaic character, called 'Simplicius' often stumbled over his own errors and seemed quite foolish. Galileo had moved out of bounds.  The Church felt they had made themselves clear. At a different time, the reaction might have been different, but it was in the middle of the [[30 years war]], the most deadly war in Europe ever fought between Catholics and Protestants. The Catholic Church had to show it had authority and strength.

The Church officials, who felt Galileo had embarrassed them, found that Galileo had erred by advocating heliocentrism as scientifically proven, which was not compatible with the Inquisition’s 1616 ruling or what Galileo had recently been told. In 1633 Galileo voluntarily submitted to Church authority and renounced his thesis of his book. At first he was sentenced to life imprisonment, but this was immediately commuted to luxurious house arrest.  His book was burned, and the sentence against him was read aloud in public in every university. <ref>[http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 ''MSN Encarta'' - Galileo (p3)]</ref> Galileo went back to studying motion and mechanics in his private villa.

The Church officials, who felt Galileo had embarrassed them, found that Galileo had erred by advocating heliocentrism as scientifically proven, which was not compatible with the Inquisition’s 1616 ruling or what Galileo had recently been told. In 1633 Galileo voluntarily submitted to Church authority and renounced his [[thesis]] of his [[book]]. At first he was sentenced to life imprisonment, but this was immediately commuted to luxurious house arrest.  His book was burned, and the sentence against him was read aloud in public in every university. <ref>[http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 ''MSN Encarta'' - Galileo (p3)]</ref> Galileo went back to studying motion and mechanics in his private villa.

His theory of tides turned out to be mistaken.

His theory of tides turned out to be mistaken.

[[Image:Galileobones.jpg|right|thumb|200px|Galileo's drawing of how the dimensions of different-sized bones need to vary to make them equally strong in relation to their function]]

[[Image:Galileobones.jpg|right|thumb|200px|Galileo's drawing of how the dimensions of different-sized bones need to vary to make them equally strong in relation to their function]]

In ''Two New Sciences,'' Galileo revealed a sophisticated understanding of engineering and what now would be called [[dimensional analysis]], the way in which the proportions of an engineering structure need to change as the size of the structure is scaled up. He applied this to biology, explaining why the bones of a large animal need to be thicker in proportion to their size than those of smaller animals.  

In ''Two New Sciences,'' Galileo revealed a sophisticated understanding of engineering and what now would be called [[dimensional analysis]], the way in which the proportions of an engineering structure need to change as the size of the structure is scaled up. He applied this to [[biology]], explaining why the bones of a large animal need to be thicker in proportion to their size than those of smaller animals.  

In an age before stopwatches, Galileo was able to make quantitative observations of uniformly-accelerated motion, using his pulse as a time reference and watching the slow acceleration of objects moving down inclined planes.  

In an age before stopwatches, Galileo was able to make quantitative observations of uniformly-accelerated motion, using his pulse as a time reference and watching the slow acceleration of objects moving down inclined planes.  

It is interesting to see how Galileo was able to obtain quantitative results in physics before algebra and calculus were invented. The book uses the methods of geometry, and lays out "proofs" of physical relationships using a style and terminology similar to [[Euclid]]'s Elements.

It is interesting to see how Galileo was able to obtain quantitative results in physics before algebra and calculus were invented. The book uses the methods of geometry, and lays out "proofs" of physical relationships using a style and terminology similar to [[Euclid]]'s Elements.

In 1741, a century after Galileo's death in January 1642, the dispute with the Catholic Church was finally settled officially when the Church under Pope Benedict XIV bid the Holy Office grant an imprimatur to the first edition of the <i>Complete Works of Galileo</i>.<ref>  [http://www.catholiceducation.org/articles/history/world/wh0005.html  The Galileo Affair]</ref>

In 1741, a century after Galileo's death in January 1642, the dispute with the Catholic Church was finally settled officially when the Church under [[Pope Benedict XIV]] bid the [[Holy Office]] grant an imprimatur to the first edition of the <i>Complete Works of Galileo</i>.<ref>  [http://www.catholiceducation.org/articles/history/world/wh0005.html  The Galileo Affair]</ref>

Stillman Drake of the University of Toronto [http://www.utpjournals.com/product/utq/701/galileo46.html] was for the last decades of his life the most original and important scholar to study this seventeenth-century physicist.<ref>[http://www.chass.utoronto.ca/imago/drake.html|The Stillman Drake Collection]</ref>

Stillman Drake of the [[University of Toronto]] [http://www.utpjournals.com/product/utq/701/galileo46.html] was for the last decades of his life the most original and important scholar to study this seventeenth-century physicist.<ref>[http://www.chass.utoronto.ca/imago/drake.html|The Stillman Drake Collection]</ref>

== References ==  

== References ==