Galileo Read online

  Praise for Galileo

  “One would have hoped that the Galileo story could be treated just as the fascinating history this book makes clear it is—but we really need this story now, because we’re living through the next chapter of science denial, with stakes that couldn’t be higher.”

  —Bill McKibben, author of Falter: Has the Human Game Begun to Play Itself Out?

  “It is fashionable to invoke Galileo on both sides of any debate to claim the mantle of truth. In Galileo and the Science Deniers, Livio teaches us the method by which Galileo found the truth, using a process more powerful than rhetoric: examination. Today more than ever we need to understand what made Galileo synonymous with finding the truth.”

  —Adam Riess, Nobel Laureate in Physics

  “To better understand the perilous threat of science denialism today, Mario Livio looks back at the scientist who faced the greatest denial of them all: that the Earth revolves around the Sun. By offering us an astrophysicist’s unique perspective on Galileo’s life and fate, this engaging work is a must-read for anyone who values the contributions of science to society.”

  —Marcia Bartusiak, author of The Day We Found the Universe and Dispatches from Planet 3

  “Scientists have typically been fascinated and inspired by Galileo’s scientific achievements and by his struggle with the Catholic Church. In this book, astrophysicist Livio does an excellent job of conveying such fascination and inspiration in a manner that can be appreciated by scientists and nonscientists alike. An important lesson he emphasizes is Galileo’s bridging of the gap between the two cultures, namely the sciences and the humanities.”

  —Maurice A. Finocchiaro, author of On Trial for Reason: Science, Religion, and Culture in the Galileo Affair

  “Livio illuminates the parallels between the deniers of Galileo’s scientific findings and those today who ignore the evidence of climate change. Intriguing and accessible, and packed with clever insights, Livio’s latest gives readers plenty of think about.”

  —Publishers Weekly

  “This is an insightful, riveting, and deeply researched biography of Galileo Galilei that reveals not just his complex character but also how he was truly intellectually radical and well ahead of his time.”

  —Priyamvada Natarajan, Professor, Departments of Astronomy and Physics, Yale University, and author of Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos

  Thank you for downloading this Simon & Schuster ebook.

  Get a FREE ebook when you join our mailing list. Plus, get updates on new releases, deals, recommended reads, and more from Simon & Schuster. Click below to sign up and see terms and conditions.

  CLICK HERE TO SIGN UP

  Already a subscriber? Provide your email again so we can register this ebook and send you more of what you like to read. You will continue to receive exclusive offers in your inbox.

  To Sofie

  Preface

  Being an astrophysicist myself, I have always been fascinated by Galileo. He was, after all, not only the founder of modern astronomy and astrophysics—the person who turned an ancient profession into a window onto the universe’s deepest secrets and awe-inspiring wonders—but also a symbol of the fight for intellectual freedom.

  Using a simple arrangement of lenses fixed at the two ends of a hollow cylinder, Galileo was able to revolutionize our understanding of the cosmos and of our place within it. Fast-forward four centuries, and we find a great-great-great-grandson of Galileo’s telescope: the Hubble Space Telescope.

  Over the decades during which I worked as a scientist with Hubble (till 2015), I was often asked what I thought gave the Hubble telescope its iconic status as one of the most recognizable projects in scientific history. I’ve identified at least six main reasons for Hubble’s popularity. In no particular order, these are:

  The incredible images produced by the space telescope, dubbed by one journalist “the Sistine Chapel of the scientific age.”

  The actual scientific discoveries to which Hubble has significantly contributed. Those range from determining the composition of the atmospheres of extrasolar planets to the astounding discovery that the cosmic expansion is accelerating.

  The drama associated with the telescope. The transformation of what was initially considered a disastrous failure—a flaw in the telescope’s mirror was discovered within weeks after its launch—into a gigantic success.

  The ingenuity of scientists and engineers, coupled with the courage of astronauts, all of which helped to overcome the incredible technological challenges involved in making repairs and upgrades several hundred miles above the Earth.

  The telescope’s longevity: it was launched in 1990 and is still working beautifully in 2019.

  An extraordinarily effective dissemination and outreach program, which circulates the findings to scientists, to the general public, and to educators, in an efficient, attractive, and easily accessible fashion.

  Amazingly, when I carefully examined Galileo’s life and work, I realized that the same key words came to mind: images, discoveries, drama, ingenuity, courage, longevity, and dissemination.

  First, Galileo created breathtaking images from his observations of the lunar surface. Second, while his spectacular discoveries about the solar system and the Milky Way didn’t conclusively prove that the world was Copernican, with the Earth revolving around the Sun, they all but destroyed the stability of the Earth-centered Ptolemaic universe.

  Finally, the drama characterizing Galileo’s life, the brilliant ingenuity he showed in his experiments in mechanics, the courage he demonstrated in defending his views, his enormous success in disseminating his findings and in making them accessible, and the fact that his ideas became the basis on which modern science has been erected, are the main characteristics that make Galileo and his story immortal.

  You may wonder why I felt absolutely compelled to write another book about Galileo, when quite a few excellent biographies and analyses of his work exist already. There were three main reasons for my decision. First, I realized that very few of the known biographies were written by a research astronomer or astrophysicist. I believe, or at least hope, that someone actively engaged in astrophysical research can bring a novel perspective and fresh insights even to this seemingly overworked arena. In particular, I have attempted in this book to place Galileo’s discoveries in the context of today’s knowledge, ideas, and intellectual setting.

  Second, and most important, I am convinced that present-day readers will be amazed to discover how relevant Galileo’s story is for today. In a world of governmental antiscience attitudes with science deniers at key positions, unnecessary conflicts between science and religion, and the perception of a widening schism between the humanities and the sciences, Galileo’s tale serves, first of all, as a potent reminder of the importance of freedom of thought. At the same time, Galileo’s complex personality itself, grounded as it was in late-Renaissance Florence, Italy, provides a perfect example of the fact that all the achievements of the human mind are part of just one culture.

  Finally, many of the superb, scholarly written biographies include parts that are rather abstruse or far too detailed even for educated but nonexpert readers. My goal has been to provide an accurate yet relatively short and accessible account of the life and work of this captivating man. In some sense, I am humbly attempting to follow here in Galileo’s footsteps. He insisted on publishing many of his scientific findings in Italian (rather than Latin), for the benefit of every educated person rather than for a limited elite. I hope to do the same for Galileo’s tale and its vitally important message.

  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 Benedet
to 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.