Jay H. Beder
Well, it happened, and it was well worth seeing. I viewed it at Atwater Park in Shorewood. The Urban Ecology Center made a particular effort to publicize it, and a number of people brought telescopes. Using the appropriate welder's glass, I found it a bit hard to see the dot without magnification, but a small binoculars did the trick. I simply held the glass over the lense and looked. The sun appeared to have a birthmark on its cheek.
Since the transit occurred around sunrise in our part of the world, our local position on the west bank of Lake Michigan was a perfect viewing location. We had an unobstructed horizon, and fortunately the weather cooperated.
A photo gallery may be found here , including a rare "double-transit" photo (the International Space Station crossing Venus as it crossed the sun). To find it, view the Archives for around June 20, 2004.
Venus transits occur twice in 130-year cycles: The next will be June 6, 2012, and then not again until 2117. I'll say more about their historical importance in a moment.
There is an excellent book by Eli Maor on the subject:
June 8, 2004: Venus in Transit, Princeton University Press, 2000. 186 pages.
It gives the history of human observation of transits of Venus, their role in science, and plenty more.
THE SCIENCE
You should really read the book. But briefly: Kepler was the first (1631) to predict a transit of Venus (and of Mercury). Horrocks, an amateur, was the first (and with his friend Crabtree, the only) person to observe one, in 1639, and was thereby the first to measure the apparent size of any planet besides Earth. (Subsequent observations also hinted at a Venusian atmosphere.)
But it was Edmund Halley (1656-1742) who realized that the transit of Venus could be used to calculate our distance to the sun, and thereby the actual scale of the solar system. (Appendix 1 of Maor's book describes Halley's method.) Halley's idea led to what was probably the first international scientific project, in 1761. How did it work out? Well, you should really read the book.
It probably goes without saying that we now have long since developed far more precise ways of determining planetary distances. While the transit of Venus is no longer of great scientific importance, it is still an inspiring sight.
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