June 8, 2004--Venus in Transit

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 perhaps--after this book--history. 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 effort--the observation of the 1761 transit from seventy stations, yielding a surprisingly accurate calculation of the astronomical unit using Edmund Halley's posthumous directions--intersected 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

I bought this book because the transit of Venus in 1874 was significant in the history of Campbell Island (French expedition)and Auckland Island (German expedition) in the sub-Antarctic region. There were also Americans on Kerguelen and French on St. Paul Island, and probably others. Maor mentions only the British and German expeditions to Kerguelen, where the Brits released rabbits that devastated the native vegetation. The scale of the effort is not apparent from his tale.

My second objective was to learn what other mmethods were used to measure the astronomical unit when the transit of Venus proved inadequate. Maor mentions only that a measurement of the parallaz of Mars was used, but gives no hint how. Apparently there were other methods before WWII, but they are not in this book. Too much space is devoted to failures and speculations, pleasant stories properly used as side dishes, too little to the main course.

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.

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 suggest that you provide that young person with a copy of this book (if old enough to appreciate it on their own) or read it to them and explain its meaning (if they are not advanced enough to appreciate it unaided). Then make a date to see the following transit 8 years later with the same person.

Acquire inspiration from the heavens . . . and closeness with a young person you care about!