The centre of his universe

Galileo's Daughter by Dava Sobel (Fourth Estate £16.99)

Galileo's Daughter by Dava Sobel (Fourth Estate £16.99)

In 1633 the 69-year-old Galileo Galilei appeared before the Holy Office of the Inquisition in Rome on a charge of heresy. It was a horrifying outcome to a life devoted to the pursuit of scientific truth. Galileo was an unlikely candidate for the role of apostate. He appears to have been jovial and convivial, fond of wine and good food, delighting in poetry and sometimes scabrous humour, and relishing the learned dialogues he pursued in person and by letter with savants from all over Europe.

In her first book, Longitude, Dava Sobel demonstrated her ability to communicate complex ideas in lucid prose, and to win the reader's curiosity and sympathy by her powers as a storyteller. Galileo's Daughter provides the perfect vehicle for her talents. Her exemplary discussion of Galileo's research is interspersed with extracts from the letters of his daughter, which flesh out the domestic and emotional contexts to his work. Galileo was born at Pisa, the son of a musician, himself an experimenter, who endorsed a new method of tuning based on sound rather than theory, and filled a room with weighted strings to test his ideas about harmony. Attracted to monastic life, Galileo was deflected into the more profitable pursuit of mathematics, and procured a teaching post at the University of Pisa. Here he conducted the famous cannonball experiment, in which, according to legend, he dropped balls of various sizes from the Leaning Tower, to disprove Aristotle's theory that objects of different weights fall at different speeds. Galileo rapidly progressed to the chair of mathematics at Padua, where he met Marina Gamba, who bore him three children. In the meantime, he invented the geometric and military compass, and refined the Dutch invention of the spyglass.Galileo's superior telescope revolutionised the study of astronomy. For the first time, scientists were able to probe the structure of the heavens, and to challenge Aristotle's depiction of all celestial bodies as immutable perfect spheres. The immediate result was Galileo's discovery of Jupiter's four moons, named the "Medicean stars" in honour of Cosimo II of Florence and his brothers, for which Galileo was appointed "Chief Mathematician of the University of Pisa and Philosopher and Mathematician to the Grand Duke".

Galileo's summons before the Inquisition was a consequence of the Catholic Church's century-long battle to defend its intellectual supremacy against the Protestant Reformation, although rivalry and papal paranoia also played their parts. As the basis of Catholic belief, the Council of Trent had supported traditional scholasticism, with its reverence for the Aristotelian world-view, rather than biblical humanism. In developing the new science of experimental physics, Galileo inevitably sailed close to the wind. For some years, he had been attempting to find evidence to support the views of the Polish cleric Nicolaus Copernicus, that the planets orbited around the sun, and that the earth made a daily rotation on its own axis and an annual rotation around the sun, claims which contradicted Catholic teaching that a fixed and immovable earth was the centre of the universe. Galileo's "Theory of the Tides" which seemed to support Copernicus, provoked a flurry of defensive activity when it was presented to the authorities in 1616. The Congregation of the Index formally declared Copernican astronomy "false and contrary to Holy Scripture".

Temporarily discouraged, Galileo returned cheerfully to the attack in his Dialogue on the Two Chief World Systems: Ptolemaic and Copernican, published in 1632. There was nothing underhand in his behaviour. He believed that he had been given permission to engage in hypothetical discussion of the merits or otherwise of Copernican theory, and the manuscript was submitted to, and passed, the censor. The Dialogue was an immediate popular success, but provoked the ire of Pope Urban VIII, who reacted angrily to hints that it made mock of his own position on Copernicus. Galileo was summoned before the Holy Office of the Inquisition and forced to abjure. The Dialogue was placed on the Index of Prohibited Books, where it remained until 1835. It was not until 1992 that Pope John Paul II finally publicly endorsed Galileo, rationalising his clash with the Inquisition as a "tragic mutual incomprehension".

Nobody felt the tragedy more than Galileo. Like Copernicus, he professed himself a lifelong devout Catholic. His position on the relationship of discovered truth in nature to revealed truth in the Bible was, in his view, perfectly compatible with his Catholic faith. "Surely if the intention of the sacred scribes had been to teach the people astronomy, they would not have passed over the subject so completely!" he had written in 1613. As a cardinal had once remarked, the Bible was a book about how one goes to heaven, not how heaven goes.

Born out of wedlock, both Galileo's daughters became Poor Clares in the Convent of San Matteo near Florence. Dedicated to poverty and prayer, and living in an enclosed order, the elder, known as Suor Maria Celeste, nevertheless made herself indispensable to her father, stitching and laundering on his behalf, preparing pills and potions, and administering his household, in particular his beloved vines and kitchen garden, during his prolonged absence at the Inquisition's pleasure. Along with discussions about preserves and gamebirds, advice on family finances, and offers to copy manuscripts, Suor Maria Celeste's letters open a unique window on convent life. Closely confined, and frequently hungry and exhausted, nuns attempt suicide, fall sick, or fraternise with the worldly priests that a careless administration foists on them. Galileo's second daughter, the taciturn Suor Arcangela, frequently tries her sister's patience by moodiness, incompetence and malingering.

Having tirelessly supported her father through the terrors, and indignities of his trial the saintly Suor Maria Celeste died only three months after he had returned to permanent house arrest near Florence. Galileo was compelled to face the isolation and infirmities of his final years without the daughter whom he described as "a woman of exquisite mind, singular goodness, and most tenderly attached to me". Sobel's beautifully written history will ensure that she is not forgotten.