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==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 [[geocentric]] system, based on the second century work of [[Ptolemy]]). Puzzled astronomers noticed that [[Mars]], [[Jupiter]] and [[Saturn]] sometimes seemed to move backwards, and Ptolemy's theory was increasingly elaborated to account for this.

Until the sixteenth century, the prevailing view was that the [[Sun]], [[Moon]], [[star]]s and [[planet]]s circled the [[Earth]] (the [[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 predicted by Ptolemy's theory.

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. At first, the Church saw no immediate danger in this work, as Copernicus was a monk and dedicated his book to Pope Paul III. The book’s preface (which was not written by Copernicus) said that the proposed heliocentric system did not claim to represent the reality of the universe and was only a mathematical hypothesis.<ref> http://galileo.rice.edu/chr/congregation.html </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>On the Revolutions, English translation. [http://webexhibits.org/calendars/year-text-Copernicus.html]</ref> The scientific evidence was inconclusive.

However, belief in a moving earth was widely held at the time to be contrary to the [[Bible]], and consequently Galileo’s support of Copernican theories was denounced by [[Dominican]] friars in [[Florence]], who sent criticisms of Galileo’s work to the [[Inquisition]] in 1615. <ref> http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 </ref> Galileo later 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.

However, belief in a moving earth was widely held at the time to be contrary to the [[Bible]], and consequently Galileo’s support of Copernican theories was denounced by [[Dominican]] friars in [[Florence]], who sent criticisms of Galileo’s work to the [[Inquisition]] in 1615. <ref> http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 </ref> Galileo later 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.

By 1616, books that dealt with the Copernican theories were added to the church’s [[Index of Forbidden Books]], and Galileo was told by the Inquisition that he must only use Copernican concepts as a hypothesis for the sake of calculation, without making them seem literally true. Because Galileo had treated the heliocentric theory as if it represented the truth of the structure of the universe rather than a hypothesis, the [[Catholic Church]] decided against Galileo in 1616 and said 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 </ref>

By 1616, the Church’s [[Index of Forbidden Books]] required that nine sentences in Copernicus's book be corrected, and 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 [[Catholic Church]] decided against Galileo in 1616 and said 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 </ref>

==Using the principle of falsifiability to improve the scientific method==

==Using the principle of falsifiability to improve the scientific method==

Galileo tested [[Aristotle]]'s theory that heavy objects fall faster than light ones and found it was a consequence of air resistance, not gravity. By making careful measurements he found he could use mathematics to predict how things fell and the movements of pendulums and tides. His 1632 book ''Dialogue on the Tides'', which discussed both the Ptolemaic and Copernican hypotheses, was originally given permission to be published by Catholic censors, but the title was changed to ''Dialogue on the Two Chief World Systems''. This led to Galileo’s summons to Rome by the Inquisition, to be tried for [[heresy]]. Galileo had erred by treating Copernicus’ theories as ‘probable’, which was not compatible with the Inquisition’s 1616 ruling. In 1633 Galileo was forced to renounce his beliefs. At first he was sentenced to life imprisonment, but this was commuted to permanent house arrest. This sentence was read aloud in public in every university. His book was ordered to be burned. <ref> http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 </ref> Galileo went back to studying motion and mechanics.

Galileo tested [[Aristotle]]'s theory that heavy objects fall faster than light ones and found it was a consequence of air resistance, not gravity. By making careful measurements he found he could use mathematics to predict how things fell and the movements of pendulums and tides. His 1632 book ''Dialogue on the Tides'', which discussed both the Ptolemaic and Copernican hypotheses, was originally given permission to be published by Catholic censors, but the title was changed to ''Dialogue on the Two Chief World Systems''. This led to Galileo’s summons to Rome by the Inquisition, to be tried for suspicion of [[heresy]]. Galileo had erred by treating Copernicus’ theories as ‘probable’, which was not compatible with the Inquisition’s 1616 ruling. In 1633 Galileo was forced to renounce his beliefs. At first he was sentenced to life imprisonment, but this was commuted to permanent house arrest. This sentence was read aloud in public in every university. Some of his books were burned. <ref> http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761557587&pn=3 </ref> Galileo went back to studying motion and mechanics.

His theory of tides turned out to be mistaken but its importance was in establishing the principles of the [[scientific method]], involving testing a theory by experiment and observations that can be repeated and [[falsifiable|falsified]] by other scientists. In that sense, the errors discovered in Galileo’s work are a validation of the scientific method itself.

His theory of tides turned out to be mistaken but its importance was in establishing the principles of the [[scientific method]], involving testing a theory by experiment and observations that can be repeated and [[falsifiable|falsified]] by other scientists. In that sense, the errors discovered in Galileo’s work are a validation of the scientific method itself.