30 December 2010


John L. Heilbron. Galileo. Oxford University Press, 2010.

Most of us are familiar with the popular writings in astronomy and cosmology which contain absurdly over-simplified and inaccurate accounts of Galileo's problems with the Inquisition, who allegedly refused to look through his telescope and declared his scientific theorising to be heretical.
Well, it wasn't so simple. As the author of this work remarks:"Galileo's biographers tend to rush their gladiator into an imaginary arena filled with pig-headed philosophers and fire-spitting priests." 

In this biography he attempts to place Galileo Galilei (1564-1642) in the Florentine culture of his time and to explore the complexities of his dealings with the senior clergy of the church of which he was a member, being a person that modern journalists would no doubt describe as a 'devout Catholic'.

Galileo had a wide range of interests: music, art, writing, philosophy, mathematics. However, he did not become a very well-known and controversial figure until he began to make his famous telescopic observations. He obtained his first telescope in 1609 and began by observing the moon. Whikle he was doing this he noticed that the Milky Way consisted of stars too faint to be resolved by the unaided eye and not a 'complex terrestrial exhalation', as Aristotle would have it".

Initially, acceptance of the validity of Galileo's observations was delayed by a number of factors, including a shortage of good telescopes, the difficulty of adjusting them to suit the observer's eyesight, and the problem of mounting them so that they would be both movable and fixable.

Observers in possession of good telescopes and good eyesight eventually had to assent to the reality of Galileo's observations, so they were not the source of his troubles. The problem was that his pioneeering astronomical observations went to his head. As Heilbron remarks: "To the surprise of his colleagues and against their advice, he attacked philosophers, theologians, and mathematicians, taunted the Jesuits, jousted with everyone who contested the priority of his opinions."

This made him many enemies, including Mafeo Barberini, his friend and adviser for many years. In 1623 he became Pope Urban VIII and in 1632 he was involved in the famous trial of Galileo.

There was nothing simple about this affair. Many people were involved in the arguments which led up to it over the years. Basically, Galileo had been instructed as to how to present his arguments on cosmology. A special panel was set up to review his publication and it concluded, among other things, that he had argued cosmology absolutely and not hypothetically.

This, apparently, was one of Galileo's main weaknesses. Once he had developed an idea he insisted that he had found the truth, and he was unwilling to accept corrections from other experts.He was thus eventually proved wrong about a number of his theories. For example, he accepted the Copernican model of the solar system which had the planets following circular orbits, and refused to consider Kepler's ellipses, which eventually proved to correspond with reality.

As a result of the deliberations of the panel, Galileo was ordered to abjure ex vehementi before the Congregation of the Holy Office and thereafter be imprisoned at the Inquistion's pleasure. The abjuration was required to clear the culprit from "vehement suspicion of heresy". But, as Heilbron remarks: "There was the sticky question, however, what heresy Galileo may have held that had raised vehement suspicion in inquisitorial minds."

Galileo read out the statement of abjuration prepared for him, but he did not end by muttering eppur si muove ("and still it moves"), as this apparently first appeared in a portrait representing the scene, perhaps by Murillo, made around 1650.

The controversy that led to Galileo ending up under permanent house arrest might seem to be based on the rejection by him and others of Ptolemy's earth-centred universe, in favour of the sun-centred Copernican system. However, the author notes that the censors "were not concerned with astronomical systems but with biblical interpretation."

This book provides readers with perhaps more detail than most of them will be able to absorb, and the author's witty comments on the people and events he describes might not be to everyone's taste. However, it is recommended to anyone seriously interested in the history of science and religion. -- John Harney. [See also The Galileo Fallacy, by John Harney]

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