Chapter 1: Rebel with a Cause CHAPTER 1 Rebel with a Cause
At a breakfast that took place at the Medici Palace in Pisa, Italy, in December 1613, Galileo’s former student Benedetto Castelli was asked to explain the significance of Galileo’s discoveries with the telescope. During the discussion that ensued, the Grand Duchess Christina of Lorraine badgered Castelli about what she perceived as contradictions between certain biblical passages and the Copernican view of an Earth orbiting a stationary Sun. She cited in particular the description from the book of Joshua, in which, at Joshua’s request, the Lord commanded the Sun (and not the Earth) to stand still over the ancient Canaanite city of Gibeon and the Moon to stop in its course over the Aijalon Valley. Castelli described the entire affair in a letter he sent to Galileo on December 14, 1613, claiming that he played the theologian “with such assurance and dignity” that it would have done Galileo good to hear him. Overall, Castelli summarized, he “carried things off like a paladin.”

Galileo was apparently less convinced of his student’s success in elucidating the issue, since in a long letter to Castelli that he sent on December 21, he explained in detail his own views on the impropriety of using Scripture to dispute science: “I believe that the authority of Holy Writ had only the aim of persuading men of those articles and propositions which, being necessary for our salvation and overriding all human reason, could not be made credible by any other science,” he wrote. In a style characterizing much of his writing, he was quick to add sarcastically that he did not think “that the same God who has given us our senses, reason, and intelligence wished us to abandon their use.” Simply put, Galileo argued that when an apparent conflict arises between Scripture and what experience and demonstration establish about nature, Scripture has to be reinterpreted in an alternative way. “Especially,” he noted, “in matters of which only a minimal part, and in partial conclusion, is to be read in Scripture, for such is astronomy, of which there is [in the Bible] so small a part that not even the planets are named.”

While the argument itself was not entirely new—theologian Saint Augustine had written already in the fifth century that the sacred writers did not intend to teach science, “since such knowledge was of no use to salvation”—Galileo’s bold statements were about to put him on a collision course with the Catholic Church. The Letter to Benedetto Castelli marked only the beginning of the risky road that would eventually lead to Galileo being pronounced “vehemently suspected of heresy” on June 22, 1633. Overall, if we examine the record of Galileo’s life in terms of his personal contentment, it traces something like an inverted-U shape, with a pronounced peak somewhere shortly after his numerous astronomical discoveries, followed by a fairly steep fall. Ironically, the parabolic paths of projectiles, which Galileo was the first to determine, form a similar curve.

As history would have it, Galileo’s tragic end only helped to transform him into one of those larger-than-life heroes of our intellectual history. There aren’t many scientists, after all, about whose lives and achievements entire plays (such as Bertolt Brecht’s unforgettable Life of Galileo, first performed in 1943), and scores of poems have been written, or an opera has been composed. Suffice it also to note that a Google search on “Galileo Galilei” produced no fewer than 36 million results, again demonstrating an impact that many of today’s academics would love to have.

Albert Einstein once wrote about Galileo that “he is the father of modern physics—indeed, of modern science altogether.” He was echoing here philosopher and mathematician Bertrand Russell, who also called Galileo “the greatest of the founders of modern science.” Einstein added that Galileo’s “discovery and use of scientific reasoning” was “one of the most important achievements in the history of human thought.” These two thinkers were not in the habit of offering profuse praise, but there was a solid base for these accolades. Through his pioneering, stubborn insistence that the book of nature was “written in the language of mathematics,” and his successful fusion of experimentation, idealization, and quantification, Galileo literally reshaped natural history. He transformed it from being a mere collection of vague, verbal, nebulous accounts embellished by metaphors, to a magnificent opus encompassing (when the contemporary knowledge allowed it) rigorous mathematical theories. Within those theories, observations, experiments, and reasoning became the only acceptable methods for discovering facts about the world and for investigating new connections in nature. As Max Born, winner of the 1954 Nobel Prize in Physics, once put it: “The scientific attitude and methods of experimental and theoretical research have been the same through the centuries since Galileo and will remain so.”

His scientific prowess notwithstanding, we should not get the impression that Galileo was the easiest or kindest person, or, for that matter, even that he was an idealistic freethinker; an explorer who accidentally wandered into theological controversy. Whereas he could indeed be extremely empathic and supportive to members of his own family, he showed blistering intolerance and belligerence, wielding his sharp pen toward scientists who disagreed with him. A number of scholars labeled Galileo a zealot, although not always a zealot for the same cause. Some said it was for Copernicanism—the scheme in which the Earth and the other planets revolve around the Sun—others claimed he was a zealot for his own self-righteousness. Still others even believed he was fighting for the Catholic Church, anxious to stop it from making a mistake of historical proportions by condemning a scientific theory that he was convinced would be proven to represent a correct description of the cosmos. In defense of his zeal, though, one would probably expect nothing less from a man who set out not only to change a worldview that had existed for centuries but also to introduce entirely new approaches to what constitutes scientific knowledge.

Undoubtedly, Galileo owes much of his scholarly fame to his spectacular discoveries with the telescope and his extremely effective dissemination of his findings. Turning this new device to the heavens instead of watching sailing ships or his neighbors, he was able to show wonders such as: there are mountains on the surface of the Moon; Jupiter has four satellites orbiting it; Venus displays a series of changing phases like the Moon; and the Milky Way is composed of a vast number of stars. But even these proverbially out-of-this-world achievements are not sufficient to explain the enormous popularity that Galileo enjoys to this very day, and the fact that he, more than almost any other scientist (with the possible exceptions of Sir Isaac Newton and Einstein), has become the perennial symbol of scientific imagination and courage. In addition, the facts that Galileo was the first to firmly establish the laws of falling bodies and the founder of the crucial concept of dynamics in physics were clearly not enough to make him the hero of the scientific revolution. What at the end distinguished Galileo from most of his contemporaries was not so much what he believed in but rather why he believed it and how he reached that belief.

Galileo based his convictions on experimental evidence (sometimes real, sometimes in the form of “thought experiments”—thinking through the consequences of a hypothesis) and theoretical contemplation, and not on authority. He was prepared to recognize and internalize that what had been trusted for centuries might be wrong. He also had the foresight to assert forcefully that the road to scientific truth is paved with patient experimentation leading to mathematical laws that weave all the observed facts into one harmonious tapestry. As such, he can definitely be regarded as one of the inventors of what we call today the scientific method: a sequence of steps that ideally (although rarely in reality) needs to be taken for the development of a new theory, or for acquiring more advanced knowledge. The Scottish empiricist philosopher David Hume gave in 1759 this personal comparison between Galileo and another famous empiricist, English philosopher and statesman Francis Bacon: “Bacon pointed out at a distance the road to true philosophy: Galileo both pointed it out to others, and made himself considerable advances in it. The Englishman was ignorant of geometry; the Florentine revived that science, excelled in it, and was the first to apply it, together with experiment, to natural philosophy.”

All of Galileo’s impressive insights could not have happened in a vacuum. One could perhaps even argue that the age shapes individuals more than individuals shape the age. Art historian Heinrich Wolfflin wrote once: “Even the most original talent cannot proceed beyond certain limits which are fixed for it by the date of its birth.” What, then, was the backdrop against which Galileo acted and produced his unique magic?

Galileo was born in 1564, only a few days before the death of the great artist Michelangelo (and also the same year that brought the world the playwright William Shakespeare). He died in 1642, almost one year before the birth of Newton. One doesn’t have to believe in the transmigration at death of the soul of one human into a new body—nobody should—to realize that the torch of culture, knowledge, and creativity is always passed from one generation to the next.

Galileo was, in many respects, an example of a product of the late Renaissance. In the words of Galileo scholar Giorgio de Santillana: “a classic type of humanist, trying to bring his culture to the awareness of the new scientific ideas.” Galileo’s last disciple and first biographer (or perhaps more of a hagiographer), Vincenzo Viviani, wrote about his master: “he praised the good things that had been written in philosophy and in geometry to elucidate and awaken the mind to their own order of thinking and maybe higher, but he said that the main entrance to the very rich treasure of material philosophy was observations and experiments, which through the senses as keys, could reach the most noble and inquisitive intellects.” Precisely the same sentiments had been expressed by the great polymath Leonardo da Vinci about a century earlier, when he defied those who had mocked him for not being “well read,” by exclaiming: “Those who study the ancients and not the works of Nature are stepsons and not sons of Nature, the mother of all good authors.” Viviani further tells us that the judgment Galileo passed on various works of art was highly valued by celebrated artists such as the painter and architect Lodovico Cigoli, who was Galileo’s personal friend and sometimes collaborator. Indeed, apparently in response to a request from Cigoli, Galileo wrote an essay in which he discussed the superiority of painting over sculpture. Even the famous Baroque painter Artemisia Gentileschi approached Galileo when she thought that the French noble Charles de Lorraine, 4th Duke of Guise, had not sufficiently appreciated one of her paintings. Moreover, in her painting Judith Slaying Holofernes, her depiction of blood squirting was in accordance with Galileo’s discovery of the parabolic trajectory of projectiles.

Viviani’s encomium doesn’t stop there. His plaudits just go on and on. In a style very reminiscent of that of the first art historian, Giorgio Vasari, in his biographies of the greatest painters, Viviani writes that Galileo was a superb lutenist whose playing “surpassed in beauty and grace even that of his father.” This particular praise appears to have been at least somewhat misplaced: while it is true that Galileo’s father, Vincenzo Galilei, was a composer, lutenist, and music theorist, and that Galileo himself played the lute quite well, it was Galileo’s younger brother Michelangelo who was a true lute virtuoso.

Finally, to top it all, Viviani relates that Galileo could recite at length by heart from the works of the famous Italian poets Dante Alighieri, Ludovico Ariosto, and Torquato Tasso. This was not exaggerated adulation. Galileo’s favorite poem truly was Ariosto’s Orlando Furioso, a rich, chivalric fantasy, and he devoted a serious literary work to a comparison between Ariosto and Tasso, in which he extolled Ariosto while brutally criticizing Tasso. He once told his neighbor (and later biographer) Niccolò Gherardini that reading Tasso after Ariosto was like eating sour lemons after delicious melons. True to his Renaissance spirit, Galileo continued to be deeply interested in art and in contemporary poetry throughout his entire life, and his writings, even on scientific matters, both reflected and were informed by his literary erudition.

In addition to this splendid artistic and humanistic background, there were, of course, important scientific advances—a few genuinely revolutionary—that helped pave the way for the type of conceptual breakthroughs that Galileo was about to produce. The year 1543, in particular, witnessed the publication of not one but two books that were about to change humanity’s views on both the microcosm and the macrocosm. Nicolaus Copernicus published On the Revolutions of the Heavenly Spheres, which proposed to demote the Earth from its central position in the solar system, and the Flemish anatomist Andreas Vesalius published On the Fabric of the Human Body, in which he presented a new understanding of human anatomy. Both books went against prevailing beliefs that had dominated thought since antiquity. Copernicus’s book inspired others, such as philosopher Giordano Bruno and later astronomers Johannes Kepler and indeed Galileo himself, to expand the Copernican heliocentric ideas even further. Similarly, by elbowing out ancient authorities such as the Greek physician Galen, Vesalius’s book incentivized William Harvey, the first anatomist to recognize the full circulation of blood in the human body, to advocate the primacy of visual evidence. Major advances happened in other branches of science as well. The English physicist William Gilbert published his influential book on the magnet in 1600, and the Swiss physician Paracelsus introduced in the sixteenth century a new perspective on diseases and toxicology.

All of these discoveries created a certain openness to science not seen in the earlier Dark Ages. Still, the intellectual outlook of even the most educated people at the end of the sixteenth century was predominantly medieval. This was about to change dramatically in the seventeenth century. There must have been additional factors, therefore, that were responsible for what we might call the “Galileo phenomenon.” Other things ought to have been radically revised to create the fertile ground that was eventually ready to receive Galileo and promote him to the status of protomartyr and an icon of scientific freedom.

An important new sociopsychological element in the late sixteenth and early seventeenth centuries was the rise of individualism—the notion that a person can achieve self-fulfillment irrespective of social circumstances. This novel perspective manifested itself in areas ranging from the acquisition of knowledge to the accumulation of wealth, and from the determination of moral truths to the evaluation of entrepreneurial success. The individualist attitude was very different from the values inherited from the ancient Greek philosophy, in which people were considered primarily members of the larger community rather than individuals. Plato’s The Republic, for instance, aimed to define and help construct a superior society, not a better person.

During the Middle Ages, individualism was prevented from taking root by the actions of the Catholic Church, through the principle that truths and ethics were determined by religious councils composed of a collection of “wise men” rather than by the experiences, contemplations, or opinions of freethinkers. This type of dogmatic rigidity started to crack with the rise of the Protestant movements, which rebelled against the assertion that those councils were infallible. Ideas espoused by the ensuing Reformation war penetrated other areas of culture. The war was waged not only on the battlefield and with propaganda pamphlets, one-page broadsheets, and essays, but also with paintings by artists such as Lucas Cranach the Elder, that contrasted Protestant and Catholic Christianity. It was partly the diffusion of these individualist convictions into philosophy that enabled the Galileo phenomenon. The same ideas were later put squarely center stage by the French philosopher René Descartes, who argued that an individual’s thoughts are the best, if not the only, proof of existence. (“I think, therefore I am.”)

There was also a new technology—printing—that made possible both the individual’s access to knowledge and the standardization of information. The invention of movable type and the printing press in mid-fifteenth-century Europe had an immense impact. Literacy was suddenly not the preserve of a rich elite, and the dissemination of data and scholarship through printed books continuously increased the numbers of educated people. But that was not all. More people, from different walks of life, were now exposed to precisely the same books, leading to the establishment of a new information basis and a more democratic education. In the seventeenth century, students of botany, astronomy, anatomy, or even the Bible in, say, Rome could be using the same texts as their counterparts in Venice or Prague.

The resemblance of this proliferation of sources of information to the effects and ramifications of the internet, social media, and communication devices today immediately jumps to mind. As an early precursor to e-mail, Twitter, Instagram, and Facebook, printing also allowed individuals to transmit their ideas to the masses more rapidly and efficiently. When the German theologian Martin Luther campaigned for church reform, he was assisted greatly by the existence of printing. In particular, his translation of the Bible from Latin into German vernacular, to represent his ideal of a world in which ordinary people could consult the word of God for themselves, had a profound impact on both the modern German language and the Church in general. About two hundred thousand copies in hundreds of reprinted editions appeared before Luther’s death. Similarly, no scientist at the time had a greater talent than Galileo for communicating his discoveries to others. Convinced that his message was ushering in a new science, he saw his role as that of the great persuader, and printing books in Italian rather than in the traditional Latin (which benefited only a few learned individuals) proved to be a potent tool to this end.

Perhaps less obvious was the fact that printing also had an effect on mathematics. The ability to relatively easily reproduce diagrams, coupled with the printing of classical Greek manuscripts, renewed interest in Euclidean geometry, which Galileo was to make creative use of. Archimedes, the greatest mathematician of antiquity, would become his role model. Among many other achievements, Archimedes formulated the law of the lever and used it capably against the Romans in his legendary war machines. “Give me a place to stand, and I will move the Earth!” he was reported to have exclaimed. Galileo was only too happy to demonstrate that most machines could, at their basic principles, be reduced to something resembling a lever. Eventually he also came to believe in the Copernican model, in which the Earth was moving even without human intervention.

More broadly, the recovery, fresh editing, and translation of texts from the classical past provided a basis for more skeptical, investigative, observational attitudes. The primacy of mathematics as key to both practical and theoretical advances was becoming apparent, and it burgeoned into Galileo’s guiding light. Mathematics proved essential in areas ranging from painting (where it was used for working out vanishing points and foreshortening in perspective) to business transactions (where mathematician Luca Pacioli introduced double-entry accounting in his influential book The Collected Knowledge of Arithmetic, Geometry, Proportion and Proportionality). The upsurge in the numerical thinking of the time was perhaps best illustrated by an amusing anecdote involving Lord Burghley (William Cecil), the chief advisor to Queen Elizabeth I of England. According to this story, in 1555 he took the surprising step of weighing himself, his wife, his son, and all his household servants, and listing all the results.

Finally, another factor that helped to enhance the reverberations of Galileo’s findings was the intense curiosity about newly discovered worlds brought about by the great explorers. Together with the geographical horizons, the span of knowledge also rolled wider starting with the last decade of the fifteenth century. Explorers such as Christopher Columbus, John Cabot, and Vasco da Gama reached the Caribbean islands, landed in North America, and found the sea route to India, respectively, just between 1492 and 1498. Then, by the 1520s, humans had circled the globe. No wonder that when the nineteenth-century French historian Jules Michelet tried to summarize the thirst for new wisdom and humanism that characterized the Renaissance, he concluded that it encompassed “the discovery of the world and of man.”
A MAN OF HIS TIME AND BEFORE HIS TIME
Galileo’s journey as a scientist started in 1583, when he dropped out of medical school and began to study mathematics. By 1590, at the age of twenty-six he already had the audacity to criticize the teachings on motion of the great Greek philosopher Aristotle, according to which things moved because of a built-in impetus. About thirteen years later, following a series of ingenious experiments with inclined planes and pendulums, Galileo formulated the very first “laws of motion” concerning free fall, even though he would not publish those until 1638.

He presented his first breathtaking discoveries with the telescope in 1610, and five years later, in a famous Letter to the Grand Duchess Christina, expressed his risky opinion that the biblical language had to be interpreted in light of what science reveals, and not the other way around.

In spite of his personal disagreements with some orthodox church dicta, as late as May 18, 1630, Galileo was still received in Rome as an honored guest by Pope Urban VIII, and he left the city under the impression that the Pope had approved the printing of his book Dialogue Concerning the Two Chief World Systems after only a few minor corrections and a change of title. Overestimating the strength of his friendship with the pontiff and underestimating the fragility of the delicate psychological and political position of the Pope in that turbulent post-Reformation era, Galileo continued to believe that reason would prevail. “Facts, which at first seem improbable, will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty,” he once wrote. Imprudently neglecting his own safety, he proceeded to get the book to print, and, after a rather convoluted series of events, the book finally went to press on February 21, 1632. Whereas in the preface to the book Galileo purported to discuss the Earth’s motion merely as a “mathematical caprice,” the text itself had a very different flavor. In fact, Galileo taunted and derided those who still refused to accept the Copernican view in which the Earth revolved around the Sun.

Einstein said about this book:

[It] is a mine of information for anyone interested in the cultural history of the Western world and its influence upon economic and political development. A man is here revealed who possesses the passionate will, the intelligence, and the courage to stand up as the representative of rational thinking against the host of those who, relying on the ignorance of the people and the indolence of teachers in priest’s and scholar’s garb, maintain and defend their positions of authority.

For Galileo, however, the publication of the Dialogo, as it is commonly referred to, marked the beginning of the end of his life, though not of his fame. He was tried by the inquisition in 1633, pronounced a suspected heretic, forced to recant his Copernican ideas, and eventually placed under house arrest. The Dialogo was put on the Vatican’s Index of Prohibited Books, where it remained until 1835.

In 1634 Galileo suffered another devastating blow with the death of his beloved daughter Sister Maria Celeste. He still managed to write one more book, Discourses and Mathematical Demonstrations Concerning Two New Sciences (commonly known as Discorsi), which was smuggled out of Italy to Holland and published there in Leiden. The book summarized much of his life’s work, from his early days in Pisa, some fifty years earlier. Although his own travel was forbidden, Galileo was allowed to have occasional visitors. One of his callers during that late period of his life was the young John Milton, of Paradise Lost fame.

Galileo died in 1642 at his villa in Arcetri, near Florence, after having been blind and bedridden for a while. But as we shall clearly see in this book, his science and the tale of Galileo and his times resonate strongly today. There is a striking similarity between some of the religious, social, economic, and cultural problems that a person in the seventeenth century had to struggle with, and those we encounter in the twenty-first century. Indeed, whose story is better to tell than that of Galileo if we are to shine light on current concerns such as the continuing debate about the proper realms of science and religion, the support for the teaching of creationist ideas, and the uninformed attacks on intellectualism and expertise? The blatant dismissal in some circles of the research on climate change, the mocking attitude directed at the funding of basic research, and the elimination of budgets for the arts and public radio in the United States are only a few of the manifestations of such assaults.

There are additional reasons why Galileo and his seventeenth-century world are extremely relevant for us and our cultural needs. An important one is the apparent schism between the sciences and the humanities first identified and exposed in a 1959 talk (and later a book) by British physical chemist and novelist C. P. Snow, with his coinage of the term “the Two Cultures.” Snow presented his concern with great clarity: “A good many times, I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists.” At the same time, Snow pointed out, had he asked those very same erudite essayists to define mass or acceleration—to him, the scientific equivalent of “Can you read?”—for nine in ten of the highly educated, he might as well have been speaking a foreign language. On the whole, Snow noted that during the 1930s and onward, literary scholars started referring to themselves as “the intellectuals,” thereby excluding scientists from this coterie. Some of those intellectuals even resented the penetration of scientific methods into areas not traditionally associated with the exact sciences, such as sociology, linguistics, and the arts. While surely not as extreme, their stance was not entirely dissimilar from the indignation expressed by church officials who reacted against what they regarded as Galileo’s unwelcome intrusion into theology.

A few scholars argue that the problem of the two cultures is less acute today than it was when Snow gave his lecture. Others, however, claim that a proper dialogue between the two cultures is still mostly absent. Historian of science David Wootton, for example, feels that the problem has even deepened. In his book The Invention of Science: A New History of the Scientific Revolution, Wootton writes: “History of science, far from serving as a bridge between the arts and sciences, nowadays offers the scientists a picture of themselves that most of them cannot recognize.”

In 1991 author and literary agent John Brockman introduced the concept of a “third culture,” in online conversation and later in a book with that title. According to Brockman, the third culture “consists of those scientists and other thinkers in the empirical world who, through their work and expository writing, are taking the place of the traditional intellectuals in rendering visible the deeper meaning of our lives, redefining who and what we are.” As we shall see in this book, four hundred years ago, Galileo would have secured himself a place of honor in the third culture.

The border between art and science was largely blurred during the Renaissance, with artists such as Leonardo da Vinci, Piero della Francesca, Albrecht Dürer, and Filippo Brunelleschi having been involved in serious scientific research or in mathematics. Consequently, Galileo himself embodied an integration of the humanities and the sciences that can serve as a model to be examined, even if not easily emulated today. Consider, for instance, that at age twenty-four, he presented two lectures on the topic of “On the Shape, Location, and Size of Dante’s Inferno,” or the fact that even Galileo’s science involved, to a great extent, the visual arts. For example, in his book The Sidereal Messenger (Sidereus Nuncius), a booklet of sixty pages that was rushed to print in 1610, he tells his scientific story of the Moon through a series of wonderful wash drawings, probably relying on the lessons in art he had received from the painter Cigoli at the Accademia delle Arti del Disegno (Academy of the Arts of Drawing) in Florence.

Perhaps most important, Galileo was the pioneer and star of advancing the new art of experimental science. He realized that he could test or suggest theories by artificially manipulating various terrestrial phenomena. He was also the first scientist whose vision and scientific outlook incorporated both methods and results that were applicable to all branches of science.

Galileo made numerous discoveries, but, in four areas, he literally revolutionized the field: astronomy and astrophysics; the laws of motion and mechanics; the astonishing relationship between mathematics and physical reality (dubbed in 1960 by physicist Eugene Wigner “the unreasonable effectiveness of mathematics”); and experimental science. Largely through his unparalleled intuition and partly through his training in chiaroscuro—the art of representing three dimensions in two through a clever use of light and shadows—he was able to transform what would have otherwise been simple visual experiences into intellectual conclusions about the heavens.

Following Galileo’s numerous observations and the confirmation of his findings by other astronomers, no one could cogently argue anymore that what one saw through the telescope must have been an optical illusion and not a faithful reproduction of reality. The only defense remaining to those obstinately refusing to accept the conclusions implied by the accumulating weight of empirical facts and scientific reasoning was to reject the interpretation of the results almost solely on the basis of religious or political ideology. If such a reaction sounds disturbingly similar to the present-day denial by some people of the reality of climate change, or of the theory of evolution by means of natural selection, it’s because it is!