The Renaissance man from Pisa

A man of many talents, Galileo Galilei was a pugnacious and committed scientist who achieved world renown even in his own day

February 12, 2014

He revolutionised astronomy and is viewed as the pioneer of the modern sciences: Galileo Galilei. The Italian polymath – philosopher, astronomer, mathematician, physicist, engineer and talented author – was born more than 450 years ago, and became a legend in his own time after his trial and condemnation by the Roman Inquisition.


Text: Helmut Hornung

“For the Galaxy is nothing else than a congeries of innumerable stars distributed in clusters. To whatever region of it you direct your spyglass, an immense number of stars immediately offer themselves to view, of which very many appear rather large and very conspicuous but the multitude of small ones is truly unfathomable.”

Like many others in the pamphlet Sidereus Nuncius (Starry Messenger), of which 550 copies were printed in 1610, these sentences made scientific history. In addition to the nature of the galaxy, Galileo Galilei describes the surface of the moon and the four Jupiter moons he discovered in this work. Moreover, he used the telescope to revolutionise astronomy which had relied for millennia on observations and measurements made with the naked eye.

But who was Galileo Galilei? He was born on 15 February 1564 in Pisa – three days before the death of Michelangelo and the year in which William Shakespeare was born. His father was a fabric merchant, although music was his true passion. In 1562 he married Galileo’s mother Giulia Ammannati from Pescia. When Galileo was twelve, the family moved to Florence; however, the young Galileo did not remain there for very long and was sent to the monastery of Santa Maria di Vallombrosa. At the age of 17 he enrolled to study medicine at the University of Pisa. This was his father’s wish; Galileo himself was less keen on this course of study.

He soon developed a liking for mathematics, developed a strong interest in geometry, made his first observations on pendulum motion and published studies on problems of mechanics. In 1589 Galileo was appointed professor of mathematics at the University of Pisa. Three years later he moved to the University of Padua where he established a workshop where he worked on ballistics and fortress construction. While in Padua he began a relationship with Marina Gamba, which resulted in the birth of their three illegitimate children: two daughters, Virginia and Livia, and a son, Vincenzo.

In December 1604, Galileo observed a “new star”, a supernova shining in the constellation of Orphiuchus. In 1609 he heard about an instrument that could provide a magnified view of distant objects, and was reputed to have been built by Dutch spectacle makers. He immediately copied it and in doing so opened up a new window on the universe. Galilei promptly published the Sidereus Nuncius. He is celebrated as the “Columbus of the skies” and appointed court philosopher of the Medici in Florence.

The discovery of the moons circling Jupiter confirmed him in his acceptance of the Copernican worldview, according to which the Earth is not at the centre of the universe, but rather the Sun. And he also observed spots on the latter which contradicted the dogma of the sol immaculata and opposed theological orthodoxy.

Nevertheless, Galileo’s relationship with the church remained unproblematic at this stage. He had personal contact with Cardinal Maffeo Barberini, who later became Pope Urban VIII, and was admitted to the Roman Accademia dei Lincei, the academy of sciences, at the latter’s instigation. In 1616, Galileo developed his theory of the tides, in which he worked on the (incorrect) assumption that high and low tide are caused by the movement of the Earth around the Sun and its rotation on its own axis. He viewed his theoretical construct as proof that the heliocentric system was correct.

This was the point at which the Inquisition intervened. Roberto Bellarmino, the Cardinal Inquisitor in Rome, “cautioned” Galileo to refrain from presenting Copernican theory as fact. Galileo was though still spared by the church, and in 1621 was elected Consul of the Florentine Academy.

Two years later he published his book Saggiatore (The Assayer), which he dedicated to Pope Urban VIII. In this work he expressed the conviction that the book of nature is written in mathematical language and that “its characters are triangles, circles and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth”.

In 1630, Galileo travelled to Rome to obtain permission to print the Dialogo sopra i due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems). The “complete satisfaction”, with which he soon returned to Florence, was not to last: the Inquisitor of Florence ordered Galileo to appear before the General Commissar of the Inquisition in Rome in October 1632 at the latest. Galileo, who was already suffering from a disorder of the eyes, was granted a postponement but eventually travelled to the Italian capital in January 1633.

Pope Urban VIII abandoned his favourite scholar and other trusted advisors. Following several interrogations and under the threat of torture, Galileo was forced to deny Copernican theory on 22 June 1633. He was sentenced to lifelong house arrest, initially in Siena and then in his villa in Arcetri near Florence. During this period, he started work on the Discorsi (Discourses), in which he succeeded in providing pioneering proof that nature is describable using mathematics.

Some years later, in 1639, Galileo, by now 75 years of age, went completely blind. He was granted permission to go to Florence occasionally and to visit the nearest church on feast days. However, his health continued to deteriorate and he died on 8 January 1642. He was interred in the Chapel Del Noviziato in Santa Croce in Florence. The Dialogue was removed from the Index of forbidden books in 1835 and the great scientist was formally rehabilitated by the Catholic Church on 2 November 1992.

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