The historical and social implications of the telescope and that instrument’s modern-day significance are brought into startling focus in this fascinating account. When Galileo looked to the sky with his perspicillum, or spyglass, roughly 400 years ago, he could not have fathomed the amount of change his astonishing findingsa seemingly flat moon magically transformed into a dynamic, crater-filled orb and a large, black sky suddenly held millions of galaxieswould have on civilizations. Reflecting on how Galileo’s world compares with contemporary society, this insightful analysis deftly moves from the cutting-edge technology available in 17th-century Europe to the unbelievable phenomena discovered during the last 50 years, documenting important astronomical advances and the effects they have had over the years.
|Publisher:||BenBella Books, Inc.|
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About the Author
Stephen P. Maran worked at NASA for more than 35 years, on projects including the Hubble Space Telescope. He is the author of more than 10 books, including The Astronomy and Astrophysics Encyclopedia and Astronomy for Dummies, and is the press officer for the American Astronomical Society. He has an asteroid named for him and has been awarded the NASA Medal for Exceptional Achievement, the George Van Biesbroeck Prize of the American Astronomical Society, and the Astronomical Society of the Pacific's Klumpke-Roberts Award. He lives in Chevy Chase, MD.
Laurence A. Marschall is the WKT Sahm Professor of Physics at Gettysburg College and the author of The Supernova Story. He is a regular columnist for Natural History, a contributing editor of Smithsonian Air and Space, and an astronomy contributor for The World Book Encyclopedia. He is the deputy press officer of the American Astronomical Society and has been published in numerous publications, including Astronomy, Discover, Harper's, Newsday, and The New York Times Book Review. He lives in Gettysburg, PA.
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THE LONG VIEW: GALILEO'S LIFE AND LEGACY
A BRIEF BIOGRAPHY OF GALILEO
Galileo Galilei, the eldest son of Vincenzo Galilei, was born in Pisa in 1564. He might have been a musician had he followed in the footsteps of his father, an accomplished lute player and composer whose songs and instrumental works are still performed today. Or, had he the inclination, he might have been a doctor, the course of study he (or more likely his father) chose when he enrolled at the University of Pisa at the age of 17. In the end, however, it was the beauty of numbers and geometry that caught his fancy, especially insofar as they applied to the real world. While watching a chandelier in the Cathedral of Pisa, the story goes, young Galileo realized that the time it takes a pendulum of a certain length to swing back and for this unaffected by the amplitude or extent of the swing. It is said that he used his pulse to time the oscillations. Many years later, near the end of his life, Galileo was to design a clock based on the regularity of a swinging pendulum. (He was, in effect, the father of the grandfather clock.)
Galileo found his vocation at the University of Pisa, but he never managed to complete his degree. It was not because of lack of motivation. The high cost of higher education is one of those things that hasn't changed over the centuries, and since his father earned little money as a musician and had other children to support, the Galileis were unable to come up with the tuition. Failing to win a scholarship that might have kept him in school, Galileo moved back home, but he continued to observe the workings of nature, to tinker, and to write. He displayed such a sharp mind and such skill in devising and building mechanical instruments (his design for a precision balance was particularly elegant) that his work began to attract local attention. In 1589, Ferdinand de' Medici, the Duke of Tuscany, was informed by an advisor that one of his subjects was not sufficiently rewarded for his talents. Ferdinand, who understood that inventive genius was as valuable as gold to a mercantile state, promptly arranged for Galileo's appointment to the faculty of the University of Pisa as a lecturer in mathematics.
Recognition of his abilities was all Galileo needed to make a mark in the world. Quick-witted and ambitious, he stayed in Pisa for only three years before he was offered the chair of mathematics at the University of Padua. It was a prestigious position, and Galileo, over the better part of the next two decades, did some of his most important scientific work there.
The boundaries between professional disciplines in the late 1500s were not as finely drawn as they are today. Though nominally professor of mathematics, Galileo's research and teaching in Padua involved much of what we would today call engineering and physics. He invented a device for measuring temperature, the forerunner of the thermometer, and made extensive observations of the mathematical behavior of moving bodies, a field we now call kinematics. He also gave lectures in military engineering and, as an offshoot of these classes, devised a tool called the "geometric and military compass," which was a sort of multipurpose slide rule and measuring device that saved time and effort in operating and targeting artillery. In the late 1590s, he wrote a manual describing the usefulness of his invention — his first published book — and established a profitable side-business manufacturing and selling the instruments.
We regard Galileo as one of the founding fathers of modern astronomy, but he had done nothing but terrestrial physics and practical engineering up to this time. Still, it is clear that his interests were wide-ranging. He was aware of the controversial Sun-centered system of Copernicus, and he carried on correspondence with many other active scientists of his time, including Johannes Kepler. But it was not until 1609, when he constructed his first telescope, that he made any systematic observations of the heavens.
Galileo's first thoughts about the telescope, even then, were primarily of a practical nature. It would be a very useful tool for military men, he knew, since it would allow them to assess the activities of approaching ships and armies from a distance. As a skilled craftsman, he even entertained the thought of manufacturing and selling his telescopes, which were the best in Europe. After 18 years at Padua, he was tiring of teaching and frustrated at the limited remuneration it provided. On the other hand, he realized that the life of an instrument maker would tie him down more than the life of a professor.
So Galileo, always creative, eagerly seized on another way to profit from the telescope. He presented one of his first instruments to the Venetian Senate, and in return was granted a request for an increased salary and what amounted to tenure — an assurance of a lifetime professorship at Padua. Had Galileo been satisfied with only financial security at this point, and had he not been curious about what his new instrument might reveal about the world around him, astronomers might not be celebrating his genius today.
Late in 1609, however, Galileo began to look skyward with his telescope and to make discoveries that were to change both his life and the course of science. He saw mountains on the Moon, satellites of Jupiter, phases of Venus, and countless faint stars in the Milky Way — discoveries that form the organizing themes for the later chapters of this book. By early 1610, Galileo was ready to announce his discoveries to the world, in the form of a short book — little more than a pamphlet — titled Sidereus Nuncius, or the "The Starry Messenger."
Galileo's book was slim, but its effect was profound. It quickly passed from reader to reader — the seventeenth-century version of mass-media coverage — and within a short time, the obscure professor of mathematics was a celebrity, not just in Tuscany, but throughout all of Europe. Less than five years after its publication, scholars in Peking were discussing its findings with interest: Jesuit missionaries had translated it into Chinese.
More important to Galileo, the little book soon elicited an offer of patronage from a wealthy admirer. Galileo had dedicated the book to Cosimo de' Medici, recent successor to Galileo's old patron, Ferdinand, as ruler of Tuscany. With a nod to continued patronage, Galileo proposed to name the new satellites of Jupiter that he had discovered after the Medici family. Duke Cosimo, flattered and impressed, made Galileo the chief mathematician and philosopher to the Medicis in Florence, relieving Galileo of the teaching and administrative duties of the university and freeing him to write, correspond, and carry out observations and experiments.
While Galileo's fame was virtually immediate, acceptance of his discoveries was not. The telescope was the first optical instrument to reveal sights invisible to the naked eye, and its principles were only beginning to be understood in the early 1600s. (Galileo actually devised an early form of the microscope, too, but microscopes did not come into wide use for another 50 years.) Scientists are by nature skeptical of new claims, and some astronomers suggested that the things Galileo saw were illusions produced in the tube itself — a sort of magician's trick. Others, using inferior instruments, were unable to see for themselves what Galileo had seen.
Those who hesitated to accept Galileo, however, were not just exercising healthy skepticism. The implications of the new discoveries, as we describe in the chapters of this book, contrasted so sharply with accepted principles of physics and cherished theological beliefs, that it seemed almost heresy to embrace them without further investigation.
Immediately following the publication of Sidereus Nuncius, Galileo sent telescopes around Europe so that others, using instruments of suitable quality, could view the sights he described with their own eyes. In 1611, he went to Rome and demonstrated the instrument to Jesuit mathematicians there. The visit was a great success, and Galileo was feted with feasts and honorific dinner speeches. He was made member of one of the first scientific organizations, the Accademia dei Lincei ("Academy of the Lynx-eyed"), a society of learned men who corresponded regularly about new discoveries and new ideas of the time. (Galileo was the sixth member of that select group.) It was during Galileo's initiation into the Lincei that Greek poet and theologian John Demisiani lyrically referred to the new invention as a "telescope" — a far-seeing device — the name it has borne ever since.
Galileo's fame was assured, but ironically, his period of astronomical discovery was relatively short. Between 1610 and 1613, he carried on systematic observations of the heavens, making important discoveries about Venus, the Sun, and Saturn. But after that, he used the telescope only sporadically. In part, this was because he ran out of things to study. There were myriads of lights in the sky, but the ones he wrote about first were the easiest targets. The other planets — Mercury and Mars — and all of the stars, were featureless blobs of light, not much different through the telescope than to the unaided eye.
By 1615, Galileo was past 50 years old, and he suffered increasingly from physical ailments. Yet his mind was as sharp as ever, and until his death in 1642, he was an active correspondent, polemicist, and writer. His observations with the telescope had convinced him of the absolute truth of Copernicus's system, a Universe in which all the planets orbited the Sun. He presented the evidence for a Sun centered Universe with such clarity and forcefulness that he soon raised the hackles of more conservative clergy and academics, who held to the ancient belief that the Earth was the center of all creation. Galileo was beginning to be regarded as a threat to the established order, a dangerous state of affairs in the days of the Roman Inquisition.
Aware of growing controversy, Galileo went to Rome in 1616 to try to rally support for his point of view. Though there was considerable respect for his intelligence and integrity among the Church fathers, Galileo was unable to prevail. Naturally argumentative, he did not suffer fools gladly, a trait he shared with his father, who had written (in a book on music theory): "It appears to me that those who try to prove an assertion by relying simply on the weight of authority act very absurdly." Cardinal Robert Bellarmine, acting for the Inquisition, admonished Galileo that henceforth he was not to teach or to advocate the doctrine of a moving Earth or a Sun-centered Universe. Galileo left Rome overtly chastened and obedient, though in his heart he knew he was right.
The injunction not to teach Copernicanism ultimately led Galileo into great difficulty with the Church, but despite his precarious position, Galileo managed to write three of the most important scientific works of the seventeenth century during the last 25 years of his life. Spirited, lucid, and entertaining, these books are important milestones on the road to modern science.
The first, The Assayer, published in 1623, was a response to criticism he faced, not on Copernicanism, but on comets. The book did not advance our knowledge of the subject — Galileo was dead wrong in maintaining that comets are meteorological rather than astronomical phenomena. But it is a powerful statement of the role of observation, experiment, and mathematics in the understanding of the physical world. Science, wrote Galileo, "is written in this grand book, the Universe ... . It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures...." This view, which we take for granted today, was revolutionary at the time. It set the agenda for the next four centuries of science and inspired thinkers like Newton, Einstein, and Heisenberg to look for the mathematical laws which govern the cosmos. When scientists today speak of discovering a Theory of Everything, they are following in the footsteps of Galileo.
The second great book of Galileo, which brought him into direct conflict with the Church, was the Dialogue on the Great World Systems, written in the decade following The Assayer and published in 1632. Itis Galileo's ultimate defense of Copernicanism, thinly disguised as a conversation on the pros and cons of both the Sun-centered and the Earth- centered Universe. Though Galileo believed he had the support of the Pope to publish it, his obvious bias immediately brought matters to a head, and Galileo was summoned before the Inquisition. Tried for heresy in 1633, he was forced to renounce all claims that the Earth moved, and his book was withdrawn from circulation. For the remainder of his life, Galileo remained under house arrest at his home near Florence.
Unable to teach Copernicanism, Galileo spent his latter years consolidating his work on the motion of bodies and the nature of matter. He published a final book on this subject, Two New Sciences, in 1638, four years before his death. The laws of motion he set down there pointed the way to an explanation of the most vexing question his telescopic observations had raised: what was it that made the planets go around the Sun? Isaac Newton, directly built on Galileo's work in his 1687 Mathematical Principles of Natural Philosophy, in which he set down the mathematical laws that governed the motion of everything in the Universe, from apples to planets. Newton once wrote that if he saw further than others, it was because he was standing on the shoulders of giants. Foremost among them, without a doubt, was Galileo.
Anyone can go out today and buy a telescope that will show the satellites of Jupiter, the craters on the Moon, and the phases of Venus at least as clearly as Galileo's first telescope, so it is tempting to think that anyone with a well- designed instrument in the seventeenth century could have discovered what Galileo did. Perhaps that is true, but Galileo did much more than build good telescopes; he used them to their best advantage. His systematic observations, which we describe in the later chapters of this book, elegantly established the fundamental nature of the new bodies that a cursory look might have revealed as mere curiosities. He not only saw mountains on the Moon, he recorded how their shadows changed as the Sun rose and set over the lunar landscape, and he measured their altitude as compared to terrestrial mountains. He not only discovered four moons of Jupiter, he patiently traced their orbits and determined their periods of revolution.
Galileo was driven by a faith in the ability of systematic observation to penetrate the innermost workings of nature. His eloquent, popular writings, written in Italian rather than the recondite Latin of medieval scholars, brought these findings to a wide audience, stimulating new ways of thinking about matter and motion, as well as about the order and structure of the Universe.
Looking through a telescope, indeed, was something anyone could do. Seeing through a telescope, however — and communicating that vision to others — was the mark of Galileo's true genius.
THE LEGACY OF GALILEO
After Galileo, as the telescope took its place as the quintessential tool of astronomy, clever optical designers began to look for ways to improve on Galileo's original design. The Galilean telescope, for instance, had a very small field of view, making it difficult to point accurately. Simply replacing the concave eyepiece with a convex lens, Johannes Kepler found, produced a telescope with a wider field. Its images were upside down, unlike those of Galileo's telescope, but that was not a critical drawback when looking into the sky, where no particular direction is more natural than any other. By the time Galileo died, the optical principles needed to design better instruments were well understood, and optical masters all over Europe were vying for excellence in the field. Telescopes became bigger in diameter, thus capturing more light, and longer, yielding higher magnification. Lens-grinding improved, resulting in sharper images.
One of the most important improvements in telescope design was made in 1704 by Isaac Newton. In place of lenses to collect and focus light, Newton recommended using curved mirrors. Mirrors had the advantage of being easier to make, since only one surface needed to be shaped, unlike a lens, which required two shaped sides. Mirrors could be made larger than lenses, since it was easier to cast metal than to produce disks of clear glass larger than a few inches in diameter. Most important, mirrors focused all colors of light at the same point, regardless of color. Lenses acted like prisms, bending light rays of different colors in different directions, thus making it impossible to avoid out- of-focus rainbows of light around brilliant objects like stars and planets.(Continues…)
Excerpted from "Galileo's New Universe"
Copyright © 2009 Stephen P. Maran and Laurence A. Marschall.
Excerpted by permission of BenBella Books, Inc..
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Table of Contents
Chapter 1 The Long View: Galileo's Life and Legacy,
Chapter 2 Telescopes,
Chapter 3 The Moon,
Chapter 4 The Sun,
Chapter 5 Jupiter,
Chapter 6 Saturn,
Chapter 7 Venus,
Chapter 8 Comets,
Chapter 9 The Stars and the Milky Way,
Chapter 10 Cosmology,
About the Authors,