Sharp and cutting mind

Galileo Galilei took up mathematics after being kicked out of medical school for his bad attitude towards elders.

Today it would hardly pass muster as a child's toy: a wooden telescope whose crude lenses struggle to give an 8x magnification. But exactly 400 years ago this month, it created a sensation, sparked a scientific revolution and turned its maker into a hero. The story of how Galileo Galilei turned his telescope to the night sky and incurred the wrath of the authorities is well known. For centuries he has been seen as the quintessential champion of rational science over outdated dogma. Yet the real story of Galileo's struggles with authority is altogether less Apollonian. At its core is the all too familiar issue of what people will do to keep their jobs.

For his academic contemporaries, Galileo's principal crime was not heresy but something far more mundane. He debunked the age-old assertions of Aristotle - and thus threatened the livelihoods of those who taught the ancient Greek philosopher's works as unimpeachable fact. Galileo became the target of a plot which compelled the Vatican to take action and silence their irksome opponent. Nor should he be thought of as a blameless martyr to his cause. The blunt fact is that he brought a lot of trouble down on his own head through his own vaulting arrogance. He never passed up the chance to insult academics he viewed as pseudo-intellectuals, and repeatedly pushed his luck with authority.

But then, as the late historian of science Jacob Bronowski pointed out, the ascent of man is not made by lovable people. Galileo may have been a genius, but he was certainly not lovable. By his early 20s he had been kicked out of medical school for his bad attitude towards his elders and betters, and decided to become a mathematician. Rejected by five universities, he was on the brink of emigrating when he landed a three-year contract at the University of Pisa.

Once in post, Galileo soon set about irritating his academic colleagues by challenging the claims of Aristotle. He did more than merely criticise the ancient Greek philosopher, however. When one of his colleagues declared Aristotle was right to assert that different weights fall to the ground at different speeds, Galileo designed an experiment that proved him wrong (though not by dropping weights off the Leaning Tower of Pisa - one of the many myths surrounding Galileo's exploits).

Sure enough, when the three-year contract in Pisa came to an end, Galileo was booted out. Some influential friends managed to get him another job, this time at the University of Padua. But before long, he was causing trouble again - this time using his newly developed telescope, the quadricentenary of which falls this month. Galileo had learnt of the invention of the telescope by Dutch optical experts a year earlier and seized on the chance to make some money by building one for commercial use. But it was his use of the telescope for astronomy that sparked the scientific revolution that made him famous. He was not the first to do so - that is another myth - but his discoveries backed the sun-centred model of the solar system proposed by Copernicus.

At the time, the Catholic church had no formal ban on the teachings of Copernicus. Indeed, when Galileo published his findings, the Pope's own astronomers asked to look through his telescope and happily confirmed his claims. Contrary to yet another myth, it was not the Vatican's scholars but Galileo's fellow academics who refused to look through his telescope, lest it challenge their teachings. What they did instead was to set about engineering a conflict between Galileo and the Vatican, by claiming to have found Biblical texts directly contradicting the claims of Copernicus. They then brought these supposed conflicts to the attention of the Vatican's much-feared Inquisition, which was duty-bound to investigate them.

After reviewing the evidence, the Inquisition reached its judgment and firmly instructed Galileo to give up his support of Copernicus. For some years, he managed to keep his head down and mouth shut. But in 1632, 16 years after the original furore, he broke his silence with The Dialogue, a book spelling out the evidence for Copernicus's view of the solar system. Ever the troublemaker, Galileo could not resist including insults about a Jesuit academic - and making one of the dim-witted characters in the book appear to be based on the Pope.

Faced with so much gratuitous abuse, the Vatican finally acted. In 1633, the 69-year-old Galileo was called to Rome on charges of heresy. After long interrogation and threats of torture, he was compelled to recant his Copernican belief that the Earth orbits the Sun. He was then sentenced to life imprisonment, a terrified and broken man. As a humane gesture, Galileo was permitted to serve his sentence under house arrest on his little estate near Florence. There Galileo spent the last nine years of his life. They were far from sterile years. He made telescopic observations of the Moon, revealing a "wobble" in its movement and even wrote another book, Discourses and Mathematical Demonstrations, on the entirely safe subject of mechanics.

Galileo died in 1642, aged 77. Exactly 350 years later the Vatican admitted it had been wrong about the Earth being at the centre of the universe, and declared: "These errors must be frankly recognised." It is doubtful Galileo could ever have mustered a similar apology for his own role in the debacle. Robert Matthews is visiting Reader in Science at Aston University, Birmingham, England