Galileo Galilei – His Birth
Galileo Galilei was born in 1564 in Pisa, Italy. From his earliest years he had a bright and inquiring mind. His father, Vincenzo, was a lutenist and a music theorist. The guitar-like lute was a significant instrument in Renaissance music, and young Galileo quickly learned how the pitch of a stretched string is related to the square root of its tension. In short, Galileo grew up in the Pythagorean tradition of music, and with a sound knowledge of the relation between it and mathematics.
When he became a student of medicine at the University of Pisa in 1581 and in 1583, he noticed that the oscillation or swing of a suspended lamp in the cathedral swung at the same speed whatever the amplitude of its swing, that is, no matter how far or near the lamp swung from its static position. Sixty years later, when he was on his deathbed, Galileo was to dictate the mechanism of the pendulum clock to his son. In the meantime, he had a lifetime of thinking to do.
Contrary to myth, Galileo did not invent the telescope. Dutch optometrists did this in the early 1600s. In 1609 Galileo and other astronomers used a refracting telescope to observe the moon, sun and planets. Galileo spotted its potential and subsequently constructed a version of his own. By 1610 he had discovered the four Galilean moons of Jupiter (we now know there are several more), lunar craters, sunspots and the millions of stars that make up the Milky Way. It was easy, however, to experiment with a new ‘seeing’ device. Anyone could do that and Galileo was not satisfied with this. It was the way he thought about what he saw that led him to challenge much of the accepted science of the day.
Aristotle and Ptolemy
Scientific thought had been subdued for centuries, much of it dictated by the work of the Greek philosopher, Aristotle. Although Aristotle had lived nearly 1800 years before Galileo, he had been among the first thinkers to observe nature directly and record his findings. Since then, many of his theories have been found to be accurate, and have entered orthodox science, but others have been disproved. Aristotle and his fellow Greek, Ptolemy, embraced the geocentric theory of the universe, that is, the theory that Earth is the centre of the universe and the sun and all other planets travel around it. What he saw through the telescope in the 1600s enabled Galileo to further challenge Aristotelian theory. By now, he had become a teacher at the University of Padua.
When Galileo observed the four moons of Jupiter; Ganymede, Europa, Callisto and Lo, he noticed that they travelled around that giant planet. In addition, his observations of sunspots and the stars of the Milky Way set him thinking that Earth may not, after all, be the centre of the universe. This theory was not exactly new. In 1543 the Polish mathematician and polymath Nicholas Copernicus had published De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), a book postulating the heliocentric view of the universe, that is, the theory that the Earth and other planets travel around the sun. Later in the century, German mathematician and philosopher Johannes Kepler was to defend Copernican theory. These scholars, however, were mathematicians and theorists. Unlike Galileo with his telescope, they could not directly observe celestial phenomena. Moreover, both lived in northern Europe where the Reformation had much diminished the power of the Church. As early as 1613, Galileo was denounced from the pulpit as spreading dangerous and heretical theories.
His first book
In 1623 Galileo published his first book, The Assayer (Il Saggitore) in Rome. It was a polemic against a treatise on comets written by the Jesuit mathematician, Orazio Grassi. In the book, Galileo asserts that mathematics is the language of God and consequently, that the world can only be understood through mathematics. Unfortunately, Galileo wrapped up this noble assertion in ridiculing the Aristotelian Grazzi. Oddly, on this occasion, both Grazzi and Aristotle were right; comets are solid objects and not, as Galileo theorized, plays of light. Galileo’s bravado in publishing the book may have been because his erstwhile supporter and friend, Cardinal Maffeo Barberini, became Pope Urban VIII the same year. No doubt Galileo felt assured of support from the highest papal office.
The crest of the Barberini – three bees – appeared on the title page of The Assayer, and the book dedicated to the new pope who did, indeed, endorse it – but Galileo had already gained the enmity of the Jesuits. In 1632 published Dialogue Concerning the Two Chief World Systems authorized by both the pope and the Inquisition. Pope Urban asked Galileo not to favour one world system over the other, but to put forward arguments fairly for either one. He also asked Galileo to include a declaration by him, Pope Urban. Galileo agreed but somehow, it all went wrong. Either Galileo was unskilled in the craft of writing or his own creativity carried him away. The Pope felt that the book was very heliocentric, indeed. The Vatican knives came out.
In 1633 Galileo was called before the Inquisition and accused, among other things, of heresy. At length he was found guilty and the book placed on the Index of Prohibited Books. Because of his age and growing infirmity, Galileo was sentenced to house arrest, rather than imprisonment. By 1636 he became totally blind, an affliction no doubt caused by his too-eager perusal of sunspots with early, primitive telescopes. But even then, the mind of this genius refused to stop working, inventing the pendulum clock in the last days of his life.
Given this evidence, it is impossible to sum Galileo up in few words. In addition to being a mathematician, writer and inventor, he was a physicist before such a profession had been defined. Galileo is deemed the founder of motion physics. He extrapolated both theoretical and experimental physics, theorizing about the speed of light centuries before Albert Einstein was born. Interestingly, in the year that Galileo died, 1642, another scientist was born, one that was to become the greatest motion physicist of all time. His name was Isaac Newton, but that, as they say, is another story.