June 8, 2004: Venus in Transit

A transit of Venus is a kind of solar eclipse in which the planet Venus, rather than our moon, crosses in front of the Sun. A century-long interval between transits makes the normal kind of solar eclipse seem like a frequent event. The transits occur in pairs separated by eight years, with over one hundred-year separations between the pairs. The last transit of Venus was in 1882. However, we can look forward to the transits of 2004 and 2012. By traveling thousands of miles, I have been able to place myself in the path of the shadow for six total and two annular solar eclipses. With careful planning, and some last minute scurrying to avoid clouds, my success rate for viewing of the critical event is seven of eight. How ironic that today I was able to walk into my own back yard to view a partial solar eclipse under a clear cloudless sky.By contrast with total solar eclipses, which may be viewed only within a narrow corridor, a transit of Venus may be viewed from any place on the Earth that faces the Sun during the event. Thus, simultaneous observations may be made from distant locations.The author tells the story of the pursuit of transits of Venus by scientists whose aim was to establish a precision measurement of the distance between the Earth and the Sun. It is a great adventure story. There are the usual disasters: there are wars; ships are intercepted; natives run off with the instruments; and there are clouds. Finally, an unexpected optical effect, the "black drop", appears. In the end science triumphs, although not as expected. We no longer need to measure the transits of Venus to establish the astronomical unit. However, our ability to calculate and predict precise locations and times for the occurrence of such events as eclipses and transits is a confirmation of the success of our formulation of mechanics and an affirmation of the scientific method. This work is primarily a history with the basic information on the details of the transit of 2004 and very little on the transit of 2012. The reader will have to go to the web for more. However, the eastern Mediterranean looks promising for 2004, while the transit of 2012 should provide an excuse for a trip to Hawaii.

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 bette

A delightful short book about an astronomical event both dynamic and rare, and one that has an important place in the history of science. Venus is the closest planet to earth, and having an inferior orbit (closer to the sun than us), can occasionally be seen to cross the face of the sun - a transit. Such events can be observed with the naked eye (appropriately filtered) but are relatively rare, occurring in pairs separated by about 8 years, 100 years apart. Only five times in recorded history have Venus transits been observed, and Maor tells the story of each encounter painted in lively narrative against the historical backdrop of the times. From theorist Kepler, whose accurate calculations of the orbits of the planets first permitted accurate prediction, to observers Gassendi and Horrocks in the 17th century, Maor intersperses the story with well written nontechnical explanations of the celestial mechanics that lie behind the transit phenomenon, including the best explanation I have ever read of the reason behind the curious pairing of two transits just 8 years apart, with each pair separated by 100 years or more.The historical importance comes due to the fact that as astronomers were slowly unraveling the mysteries of the solar system, the absolute distance scale remained elusive. Kepler's 3rd law allowed scientists to compute the relative distances of the planets from the sun, but absolute distances couldn't be obtained unless one knew the exact distance from the sun to the earth. In 1677, Edmund Halley observed a transit of Mercury, and realized that a transit event could serve as an excellent opportunity to obtain measurements of the transiting planet's parallax, from which could be calculated the distance of the transiting body. Then, using Kepler's 3rd law, the distances of all other planets - including the earth - could be calculated. Halley worked on the problem for almost 40 years, and in 1716 published a detailed plan for using the next transit of Venus to determine the size of the solar system. Already 60 when he published his plan, Halley knew he would be long dead before the next transit in 1761, but his scientific stature and eloquent appeal was all that was necessary - when the time came, the scientific world was ready (Halley's posthumous reputation was further enhanced when the periodic comet that now bears his name reappeared in 1758, just as he had predicted).Alas, Venus transits proved not to be the answer to the scale of the solar system (exact timing of transit events proved unreliable due to Venus's thick atmosphere), but the stories of the explorers who traveled to the corners of the earth in 1761, 1769, 1874 and 1882 are worth the price of the book. Maor concludes by pointing out that the upcoming event in June of 2004 will the only the sixth opportunity in recorded history to observe such an event, and while scientists are no longer watching for the same reasons as two centuries a

Even if all you know about Venus is that "Men are from Mars, women are from Venus", you will still enjoy this book. Maor is a both a great writer and a mathematician, and he combines clear explanations with great narrative. But anybody who's read any of his other books knows this already!

As he did with E and Trigonometric Delights, Maor combines technical expertise with a sure sense of narrative to tell the story (or rather the many different stories) of the transits of Venus. Gives a different meaning to the slogan "Four More Years."