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Non-Fiction Book Reviews - Retro
by Caroline Miniscule

June 8, 2004: Venus in Transit
Eli Maor
Princeton University Press
186 pages including index

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Caroline Miniscule has traveled around the world. She now stays in one place and reads science fiction. She is a graduate of D'Illyria University.

The passage of Venus in front of the sun is among the rarest of astronomical events, rarer even than the return of Halley's comet every seventy-six years. Only five transits of Venus, as the phenomenon is technically called, are known to have been observed by humans before: in 1639, 1761, 1769, 1874, and 1882. But should anyone miss the transit of 2004, all is not lost: the next transit will occur on June 6, 2012, although it will be visible in its entirety only from the Pacific Ocean and the extreme coasts of Siberia, Japan and Australia. Then it will be a long wait once again, until December 11, 2117, when Venus will again pass in front of the the sun—a bit too far in the future for most of us.

The transit of Venus is not a spectacular visual event, like a solar eclipse. Its attraction is its rarity - it happens twice (eight years apart) every 121 years. So everyone who witnessed the event in 2004, and everyone making plans to see it in 2012, are doing it not to observe it for any scientific purpose but because it won't happen again in our lifetimes.

That hasn't always been the case. In the past, observing the transit of Venus was a matter of scientific urgency and prestige...and fraught with danger.

1. The Dreamer
2. Dawn of a New Cosmology
3. A Sight Never Seen Before
4. Venus Stripped Bare
Solar and Stellar Parallax
5. The Dance of Two Planets
6. A Call for Action
7. Venus Returns
8. A Second Chance
9. The Next Two Appointments:
Father Hell: Falsely Accused
10. Transits of Fancy
11. A View From Other Worlds
12. June 8, 2004
1. Halley's Method
2. Times of the Transit of June 8, 2004, for Some Major Cities
3. Dates of Some Past and Future Transits
Illustration Credits

June 8, 2004: Venus in Transit, by Eli Maor is a slim volume that recounts the history of scientist's efforts to witness this rare event in the years 1639, 1761, 1769, 1874, and 1882. During these years the reason for witnessing the transit were quite different from what they are today. Back then, the only way to determine the distance from the earth to the sun was via the parallax.

Kepler's three laws gave astronomers a precise, quantitative theory on which to base their planetary calculations. In particular, his third law allowed them to compute the distance of one planet from the sun in terms of that of another. But it was still a comparison of distances, not an absolute determination. It is as if you were studying a road map that has no scale on it: you could tell that a certain town is twice as far from your location as another town, but you couldn't say how many miles it is to each town. If the distance from the sun of just one planet could somehow be found, those of all the other planets could be computed from Kepler's third law, and the dimensions of the solar system would be known. Naturally, the most obvious planet from which to start was our own. To determine Earth's distance from the sun - the length of the astronomical unit - thus became one of the most pressing challenges facing seventeenth-century astronomy.

Eli Maor takes us on a journey into the past and mankind's discovery of his place in the solar system. Not only does he recount the stories of some (but not all) of the scientists involved in the quest to witness - and measure - the transit of Venus, but he also provides explanations in easy-to-understand-prose on the mathematical concepts involved in measuring the solar system.

The 2004 Transit
Make plans to view the 212 Transit!

Suppose two observers at opposite points on the earth were to measure the sun's position in the sky. The sun is some 93 million miles away, while earth's equatorial diameter is only about 8,000 miles, so the change in the sun's position relative to the celestial sphere would be very small; but it could still be detected—if there were some reference stars visible in the background. Alas, during daytime the sun's glare washes out everything else in the sky, so a direct measurement of the sun's position relative to the fixed stars is impossible. This is where Edmond Halley stepped in: he proposed to use Venus instead of the sun—provided one was willing to wait for the rare occasion when the planet passes in front of the sun.

The transit of Venus is not viewable from everywhere on the globe. Future scientists had to travel by ship, sometimes into or through war-torn areas, in order to reach a location from which to observe the event.

Year Witnesses Events
December 4, 1639 Jeremy Horrocks and William Crabtree. The two young men witness the transit in England. Horrocks will die of unknown causes on January 3, 1641, not yet 23 years old.
June 6, 1761 Nevil Maskelyne, Charles Mason and Jeremiah Dixon, Alexandre-Gui Pingrè, Le Gentil. Interesting stories all. Mason and Dixon will become more famous for surveying the Mason-Dixon line between Pennsylvania and Maryland. Pingrè was a Frenchman trying to conduct scientific study during the Seven Years War, Le Gentil missed the transit completely but decides to stay in Mauritius, waiting out the eight years until the next transit.
June 3, 1769 Alexandre-Gui Pingrè, Le Gentil, the Abbè Chappe d'Auteroche, Captain James Cook. Chappe successfully witnessed the transit, then died a month later when an epidemic broke out in the village on Santo Domingo. Captain James Cook and the Endeavour went on to explore Terra Austrealis. Le Gentil had waited eight years on Mauritius. He planned to watch the transit from Manila, but was ordered by his superiors to go to Pondicherry, in India, even though only Venus' egress would be visable from there. On the day, Manila's weather was clear and the transiti visable, Pondicherry was overcast and a total failure.
December 9, 1874 Americans in Nagasaki, the Reverend Joseph Perry on Kerguelen Island, Germans also on Kerguelen. Maor spends little time on this transit.
December 6, 1882 Simon Newcomb. Once more Maor spends little time on the transit - by this time scientists had discovered that Venus' atmosphere conflicted at the moments of ingress and egress and prevented correct measurements. Yet the expeditions went on, funded by governments, even though scientists no longer wanted to conduct the expeditions!

This was an excellent introduction to the transit of Venus, but much too short. So many stories were left untold. The book was superseded, in this reviewer's opinion, by The Transits of Venus by William Sheehan and John Westfall. Nevertheless, if you can get this book from your local library, by all means do so as its a fun read. Return to:

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