Respect, sympathy and a passion for evidence

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

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

THIS WONDERFUL book blends brilliant storytelling with an elegant, modest take on the history of science, that impossible subject which asks you to sift ambiguous evidence, evaluate the implications of theory, and write the lot up subtly enough to satisfy both historians and scientists.

Sobel puts the story back into history without sacrificing any nuances in evaluating the evidence. We get all the areas in which Galileo worked: from the telescope and what it revealed to the mathematics of parabolas. We discover how his theories look in the light of later science; the complexities of Vatican doctrine; and the tortuous relations of the Tuscan ambassadors, who tried to protect Galileo, with successive Popes.

Sobel never loses sight of the emotional complexities of Galileo's position. The man whom Einstein called the founder of modern physics was piercingly, creatively and sceptically intelligent, but also deeply reverent, "a Catholic who had come to believe something Catholics were forbidden to believe" - that the earth moved and the sun did not. The Biblical basis for regarding this as heresy was Joshua's battle. God made "the Sun stand still in the heavens", something he would never have bothered to do if the Sun always stood still. "Rather than break with the Church, Galileo tried to hold - and at the same time not to hold - this problematic hypothesis, this image of the mobile Earth."

Sobel's way into Galileo's story is his relationship with his eldest daughter, who entered a convent aged 13, took the name Sister Marie Celeste, and never left it as a living woman. Marie Celeste wrote to Galileo throughout her short life, and clearly had very similar wit, integrity, and intellectual energy. She adored him and helped him from afar, sewing his linen, making him "marzipan shaped like little fish", and copying out his writings in her beautiful script.

While researching her bestseller Longitude, Sobel stumbled across Marie Celeste's 124 letters, with their vivid portrait of life in a 17th-century Tuscan convent. She uses them as Homer uses similes comparing men wounded in battle to craftswomen tinting ivory at home. The minutiae of nunnery life (from the nuns' ailments, both mental and appallingly physical, to the financial shenanigans behind room allocation) counterpoint Galileo's story, giving it a deep social and domestic perspective.

On 19 June 1633, for instance, the daughter writes anxiously about the convent's little mule, who has grown "so haughty" on her privileged broad-beanstalk diet that "she refuses to carry anyone, and has several times thrown poor Geppo so as to make him turn somersaults." This was three days before her dad entered the Inquisition chamber for the last time, to be sentenced to life imprisonment (later commuted to house arrest). His Dialogue, about Copernicus's heliocentric theory, was put on the Index, where it remained for 200 years.

The magic is in the way Sobel handles that inexorable heart of all science and all history: evidence. She shows how Galileo's greatness lay in arguing from experiment and observation. In an age that believed that ice was heavier than water and just happened to end up on top of it, he floated all kinds of objects in cups. When everyone believed bigger things fell faster than smaller ones of the same material, he dropped cannonballs from towers. All his work involved recording, and working out how (rather than why) bodies fall, roll or float.

This was what made him such fatally envious enemies. In an age whose belief-system reposed on untested Greek theory, many lesser minds resented any invitation to open themselves up via observation. Luckily, Sobel's own passion for evidence mirrors Galileo's. She fell in love with Marie Celeste's letters, felt they spoke for themselves, and wanted to do an edition. No, said her publisher, make it a story. So she did: the story of Galileo, punctuated by his daughter's gorgeous, intelligent letters.

She ends with an ungiveable-away secret: what Galileo's last pupil (and first biographer) placed in his tomb to offer him comfort beyond the grave. Her delighted respect and sympathy for the minds of the people whose lives she tells shines through all the complexities of the story and the science. And her very last, very short, sentence brings tears to the eyes.