Venus in Transitby Eli Maor
In 2004, Venus crossed the sun's face for the first time since 1882. Some did not bother to step outside. Others planned for years, reserving tickets to see the transit in its entirety. But even this group of astronomers and experience seekers were attracted not by scientific purpose but by the event's beauty, rarity, and perhapsafter this bookhistory.
In 2004, Venus crossed the sun's face for the first time since 1882. Some did not bother to step outside. Others planned for years, reserving tickets to see the transit in its entirety. But even this group of astronomers and experience seekers were attracted not by scientific purpose but by the event's beauty, rarity, and perhapsafter this bookhistory. For previous sky-watchers, though, transits afforded the only chance to determine the all-important astronomical unit: the mean distance between earth and sun.
Eli Maor tells the intriguing tale of the five Venus transits previously observed and the fantastic efforts made to record them. This is a story of heroes and cowards, of reputations earned and squandered, all told against a backdrop of phenomenal geopolitical and scientific change.
With a novelist's talent for the details that keep readers reading late, Maor tells the stories of how Kepler's misguided theology led him to the laws of planetary motion; of obscure Jeremiah Horrocks, who predicted the 1639 transit only to die, at age 22, a day before he was to discuss the event with the only other human known to have seen it; of the unfortunate Le Gentil, whose decade of labor was rewarded with obscuring clouds, shipwreck, and the plundering of his estate by relatives who prematurely declared him dead; of David Rittenhouse, Father of American Astronomy, who was overcome by the 1769 transit's onset and failed to record its beginning; and of Maximilian Hell, whose good name long suffered from the perusal of his transit notes by a color-blind critic.
Moving beyond individual fates, Maor chronicles how governments' participation in the first international scientific effortthe observation of the 1761 transit from seventy stations, yielding a surprisingly accurate calculation of the astronomical unit using Edmund Halley's posthumous directionsintersected with the Seven Years' War, British South Seas expansion, and growing American scientific prominence. Throughout, Maor guides readers to the upcoming Venus transits in 2004 and 2012, opportunities to witness a phenomenon seen by no living person and not to be repeated until 2117
Laurence A. Marschall
David W. Hughes
Nobody alive has seen a transit of Venus, and if you miss the 2004 and 2012 events you will not have another chance. If you are interested in transit history, read Maor.
"Eli Maor's book is primarily a straightforward historical account of the five observed transits of Venus. . . . [It] will appeal to readers who enjoy an easy-going story."Journal of the British Astronomical Association
"[Maor] reminds the reader what a long and circuitous route science has traveled to take the measure of the world around us."Laurence A. Marschall, The Sciences
"In the course of recounting important transits of the past, Maor introduces us to some of the forgotten personalities in the history of astronomy."Dan Falk, The Toronto Globe and Mail
"Maor examines the international intrigue, history, mystery, and science of what was considered an extremely important event that helped determine the accurate measure of the distance from Earth to the Sun."Mercury
"A small gem of a book. . . . Maor explains with grace, clarity and wit why this event is so rare, and describes the heroic efforts and frequent misadventures involved in attempts to observe the five transits that have occurred in the almost 400 years since Johannes Kepler, the discoverer of the laws of planetary motion that bear his name, predicted their occurrence."Jeffrey Marsh, The Washington Times
"Brimming with historical anecdote and up-to-date information, this book provides much more than a simple introduction to two of the most anticipated celestial events of the 21st century. . . .It chronicles the fervor, triumph, and folly that accompanied the last five transits of Venus witnessed by Western civilization . . . This book will please the history aficionado and the most ardent amateur astronomer."William Schomaker, Astronomy
"[A] charming guide. . . . Maor weaves his tale with clarity and historical precision."Owen Gingerich,Times Literary Supplement
"This book will fascinate those interested in chasing rare astronomical events."Choice
"I enjoyed Maor's book; it is written in an easy, clear, anecdotal way that makes great bedtime reading."Done Fernie,Nature
"[A] snappy, enjoyable, and eminently readable historical account."David W. Hughes, The Observatory
"Nobody alive has seen a transit of Venus, and if you miss the 2004 and 2012 events you will not have another chance. If you are interested in transit history, read Maor."John Westfall, Sky and Telescope
"June 8, 2004: Venus in Transit is short and entertaining. This book is an engaging retelling of the story for a popular audience."James Evans, ISIS
"Venus in Transit is a well written and documented account of previous transits, giving a real flavor of the characters involved and their achievements and disappointments in observing this rare event."Astronomy Now
Astronomy, October 1, 2000
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June 8, 2004-Venus in Transit
By Eli Maor
Princeton University PressEli Maor
All right reserved.
The promulgation of Kepler's Laws is a landmark in history. They were the first "natural laws" in the modern sense: precise, verifiable statements about universal relations governing particular phenomena, expressed in mathematical terms.
Arthur Koestler, The Watershed (1960)
In 1627 Johannes Kepler, mathematician, astronomer, astrologer and mystic, published his last major work, the Rudolphine Tables. Dedicated to his patron, Emperor Rudolph II of Bohemia, it was the most comprehensive compilation of astronomical data to date; it included rules and tables for finding the position of the sun, moon, and planets, a catalog of over one thousand stars begun by his late mentor Tycho Brahe, improved tables of logarithms, and the geographical coordinates of major cities of the world. In the making for over thirty years, the work had been eagerly awaited by navigators, astronomers, and horoscope casters. Publication was delayed time and again-first, by the Thirty Year War, then by lack of funds, and finally by lawsuits from creditors and from Brahe's sons, who accused Kepler of stealing their late father's observations. The work was finally published in September 1627, three years before Kepler's death (fig. 1.1).1
Kepler, universally regarded as the founder of modernastronomy, was perhaps the most controversial scientist in history. He was born on December 27, 1571 (by the old Julian calendar then in use) to a family of vagabond misfits in the small town of Weil in the district of Swabia in southwestern Germany. Young Kepler suffered from poor health-real and imagined-and had a very low image of himself. In his diary, which he wrote in the form of a family horoscope, we find this early entry:
That man has in every way a dog-like nature. His appearance is that of a little lap dog. . . . He liked gnawing bones and dry crusts of bread, and was so greedy that whatever his eyes chanced on he grabbed. His habits were similar. He continually sought the good will of others, was dependent on others for everything, ministered to their wishes . . . and was anxious to get back into their favor. He is bored with conversation, but greets visitors just like a little dog; yet when the least thing is snatched away from him, he flares up and growls. He tenaciously persecutes wrongdoers-that is, he barks at them. He is malicious and bites people with his sarcasm. He hates many people exceedingly and they avoid him, but his masters are fond of him. His recklessness knows no limits . . . yet he takes good care of his life. In this man there are two opposite tendencies: always to regret any wasted time, and always to waste it willingly. . . . Since his caution with money kept him away from play, he often played with himself. His miserliness did not aim at acquiring riches, but at removing his fear of poverty-although, perhaps avarice results from an excess of this fear.2
"That man" is Kepler himself, speaking in third person.
Nothing in Kepler's family history showed any hint of a future greatness. His grandfather served as the mayor of Weil, but was, by Kepler's own account, "arrogant, proudly dressed, short-tempered and obstinate . . . his face betrays his licentious past." Kepler's father, Heinrich, one of twelve siblings, was a mercenary who wandered throughout Germany, fighting on the side of whichever religious cause came his way, and narrowly escaping the hangman's rope. Kepler's mother, Katherine, was raised by an aunt who was later burned at the stake for witchcraft, and she herself would barely escape a similar fate late in life.
Johannes's opinion of his parents was as harsh as that of himself. His father was "vicious, inflexible, and doomed to a bad end. Saturn in VII [i.e., in Libra, the seventh constellation of the zodiac] made him study gunnery; many enemies, a quarrelsome marriage . . . a vain love of honors, and vain hopes about them; a wanderer . . . 1577 he ran the risk of hanging. . . . Treated my mother extremely ill, went finally into exile and died." His mother was "small, thin, swarthy, gossiping, quarrelsome, and of bad disposition." These are indeed harsh words with which to judge one's parents, and they were matched only by his low opinion of himself. This early flair for self-criticism and brutal honesty would stay with him to the end, and he would use it equally in his personal life and scientific work.
At the age of thirteen he was sent to a theological seminary, where the official language was Latin and strict discipline was the order. Irritable and quarrelsome like his forebears, he made few friends and many enemies; by his own account, he disliked his teachers, and they reciprocated in kind. At seventeen he entered the University of Tübingen, graduating three years later in theology. There he met the one teacher who left a positive impact on him-Michael Mästlin, a professor of astronomy. Through Mästlin he became acquainted with Copernicus's heliocentric (sun-centered) system, and immediately became a fervent believer. But, typically, his beliefs were based on theological rather than sound astronomical reasons: a sun-centered universe made sense to him because God would naturally place the sun, giver of light and heat, at the center of creation. This mixture of true science with religious and mystical reasoning was to be Kepler's hallmark for his entire life.
When he was twenty-three, his life suddenly changed for the better: he was offered a position at the university of Gratz in Austria as a teacher of mathematics and astronomy. He accepted, but only reluctantly, citing "the unexpected and lowly nature of the position, and my scant knowledge of this branch of philosophy." At this stage of his life he was still set on a career in theology; but only a year later, while giving his weekly lecture to a nearly empty class, an idea struck him that would remain his credo for the rest of his life.
It happened on July 9, 1595. He was drawing a geometric figure on the board when suddenly a revelation came to him: God designed the cosmos along simple, geometric proportions. "The delight that I took in my discovery," he wrote later, "I shall never be able to describe in words." His "discovery"-already expressed two thousand years earlier by the Pythagoreans-was that number and shape are the essence of the universe. But Kepler went further: he proposed that the orbits of the planets around the sun were determined by the geometry of the five regular solids. In the two-dimensional plane, one can construct regular polygons with any number of sides-an equilateral triangle, a square, a regular pentagon, etc. (in a regular polygon, all sides are of equal length, and all angles have the same measure); but in space there exist just five regular solids: the tetrahedron, which has four equal faces, each an equilateral triangle; the cube (six faces, each a square); the octahedron (eight equilateral triangles); the dodecahedron (twelve regular pentagons); and the icosahedron (twenty equilateral triangles). These five solids (fig. 1.2) were already known to the Greeks and have come to symbolize the perfect symmetry of God's design; now Kepler made them the cornerstone of his cosmos. "Why are there exactly six planets," he asked, "and not twenty or a hundred?" His answer: because six planetary orbits leave five gaps between them, and naturally these five gaps had to be filled with the five regular solids! It was too good a fit to be a mere coincidence; it had to be God's design. One almost feels grateful that Kepler did not know of the three remaining planets of the solar system, for they would have at once destroyed this perfect celestial harmony.
Having made his great "discovery," he now set out to perfect it with a tenacity unparalleled in the annals of science. When the observational data didn't quite fit his vision, he often changed the data-and willingly admitted so later. And when even that didn't quite help, he turned to the laws of musical harmony, assigning to each planet a tune to be sung according to its distance from the sun. Mercury, the closest planet to the sun, was given the highest notes, Saturn the lowest. This "harmony of the spheres" became an idée fixe with Kepler, guiding (perhaps "misguiding" would be a better word) him for the next thirty years. Eventually, aided by the meticulous observations made by the Danish nobleman Tycho Brahe at his elaborate observatory on the island of Hven, he finally discovered the true laws of planetary motion that bear his name. Kepler's three laws are:
- The planets move around the sun in ellipses, the sun being at one focus of each ellipse.
- The straight line connecting each planet to the sun sweeps equal areas in equal times.
- The square of the period of each planet is proportional to the cube (the third power) of its mean distances from the sun.3
With these laws, modern astronomy was born.
Kepler was not the first one to ask, how do the planets move in their orbits, but he was the first to give the correct answer. By replacing the hallowed circular orbits of the Greeks with elliptical orbits, he discovered the true geometry of the planetary clockwork. Half a century later, Isaac Newton would use Kepler's laws to answer the why-to discover the physical cause that drives this clockwork, the universal force of gravitation.
Notes and Sources
1. For a more detailed description of the Tables, see Owen Gingerich, The Great Copernicus Chase and Other Adventures in Astronomical History (Cambridge, Mass.: Sky Publishing Corporation, and Cambridge, U.K.: Cambridge University Press, 1992), chapter 15.
2. Kepler's quotations in this chapter are taken from Arthur Koestler's classic, The Watershed: A Biography of Johannes Kepler (New York: Anchor Books, 1960).
3. Expressed mathematically, (T1/T2)2=(d1/d2)3, where T1 and T2 denote the periods of any two planets, and d1 and d2 their mean distances from the sun. (Continues...)
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Well, if you missed this transit of Venus in 2012, the next one is in 2117! Maor presents the observational history and astronomical importance of the transit of Venus in a very readable and enjoyable style. This book is a nice edition to the history of science. Highly recommended for those interested in the history of science and astronomy.
Whether you are interested in astronomy or not, you will find this book to be a rewarding expansion of your understanding of that important, awe-inspiring part of the scientific pantheon. The phrase, transit of Venus, describes the process whereby Venus appears to cross the Sun during daylight hours from earth. For most of recorded history, few probably paid attention. And for good reason. You would have been blinded by looking directly into the sun except very near sunrise and sunset. And you had to know when and where to be looking because transits of Venus are rare. Besides, you could see Venus on most nights anyway. In this delightful background preparation for the next transit of Venus on June 8, 2004, Professor Maor provides all the background you could hope for to help you understand how celestial events (especially this one) are forecast so accurately, their scientific implications, and how to enjoy them yourself. Many famous astronomers were encouraged to enter the field by first observing an eclipse. The ability to accurately predict the timing and the nature of the event left them with awe. Perhaps this transit of Venus will be our most productive ever for generating scholars for the 21st century. Oh, by the way, if you miss this one, there's another one coming along 8 years later in 2012. Although ostensibly focused on a type of celestial event, the book has a broader theme: How humankind can use reason to deduce new understanding of the physical world. The book begins with the origins of modern astronomy, by describing the observations of Galileo, the conclusions about the solar system by Copernicus, careful measurements of Brahe, Kepler's deductions from those observations, and Newton's application of these lessons into his Principia. All of that work made it possible to predict transits of Venus. Since we all can see Venus with the unaided eye (unless blind or very near-sighted), why did anyone care? The main reason was that astronomers wanted to establish the distance between the earth and the Sun. They obviously could not pace it off. How could Venus help? By measuring the duration of the transit from far apart locations of known distance, one could construct a triangle and use standard trigonometry to calculate the distance to the Sun. This point is clearly and simply described in the book. The illustrations are wonderfully done to help. Then the author gets down to the reality of executing on that simple concept. Many problems occur. At first, not enough observers are involved. Bad weather at the time of the transit can always obscure observations. The combination of our atmosphere and that of Venus also combine to create a black dot effect that makes it uncertain when the transit begins and ends. Some observers are accused of making mistakes. Other observers notice things that are not planetary transits. Thus, the realities and challenges of experimental science are well documented. Astronomers have better ways to measure the distance to the Sun now. As a result, the transit of Venus takes on for us a combined role of aesthetic experience and honoring of the astronomical history associated with it. Professor Maor makes a nice transition in making this point clear. He provides many tips for watching, including where to go, and how to watch safely. He describes a potential viewing from Jerusalem. That could be combined with a very nice religious pilgrimage, if you are so inclined, for those who have not been to Jerusalem before. I especially liked his commentaries about seeing Earth transits from Mars, and transits of the inner planets from the outer ones as our ability to pursue space travel improves. I think the most important question that this book raises is who to have with you when you observe the transit. A young person somewhere between the ages of 6 and 16 would probably be ideal. You could probably change a life with the experience that this event provides. I su