Robert Gardner's "Venus Transit 2004" Webpage


The ETSU Venus "expedition" to the Kroger parking lot in Johnson City, TN.

The event was attended by Robert Gardner of the ETSU Math Department, Lev Yu. Yampolsky of the ETSU Department of Biological Sciences (who both saw the event), as well as Kathleen Grover of the ETSU Department of English and a guy delivering newspapers to Kroger (both of whom missed the event). Cloudy conditions prevailed, but Gardner brought donuts and coffee.

SOME HISTORY
Transits of Venus occur in pairs separated by 8 years. So the next transit of Venus will occur in 2012 (June 5-6). The pairs of transits are separated by about 120 years. So the last transit occured in 1882 (December 6) and the one before that in 1874 (December 9). The next pair of transits will be December 11, 2117 (I'll be 154 years old!) and December 8, 2125.

Johannes Kepler, the first person to give an accurate way to qualitatively predict the location of planets, predicted a transit of Mercury on November 7, 1631 and a transit of Venus on December 6, 1631. The Mercury transit was observed by the French astronomer Pierre Gassendi, but the Venus transit was not visible in Europe and presumably went unobserved. Before the 1600's, an accurate method of predicting such events was not available and presumably no such events were observed. After all, an Earth centered model of the solar system was assumed and such an event would not have even been suggested before the 1600's (at least not in Catholic Europe).

The second Venus transit in the pairing occured on December 4, 1639. Though Kepler's math failed to predict this event, the British mathematician Jeremiah Horrocks successfully predicted the event and observed about a half hour of it. This makes Horrocks the first person known in history to observe such an event. Only one other person, William Crabtree a friend of Horrocks', is known to have seen the event.

The audience grew for the June 6, 1761 and June 3-4, 1769 transits. Weather conditions, political conditions, and an atmospherically induced "halo" around Venus squelched plans for precise timings of the transit. In 1769, the transit was observed by Captain James Cook near Tahiti. The transit was also observed by David Rittenhouse in Philadelphia, PA. Subsequent computations based on these observations estimated the distance from Earth to the Sun (called an "astronomical unit" and a fundamental unit of cosmic measurement) as 95,280,000 miles (now known to be closer to 93,000,000 miles). This estimate was 2.5% off.

The next pair of Venus transits occured on December 9, 1874 and December 6, 1882. During the 1874 transit, observations narrowed the estimate of the astronomical unit to within 0.2% of its actual value. As a consequence, the 1882 transit was not of such great scientific importance. It was, instead, a matter of popular media interest. Again this year, we the public have the opportunity to observe a truly rare event. Though not of great scientific interest, we can still enjoy the rarety of this transit. NO ONE ALIVE TODAY has seen such an event!

CONCLUSION
No one alive today has seen a transit of Venus. This alone, makes the event interesting and novel. Historically, such an event has a significant role in measurements of the solar system. Today, there is little scientific interest in a transit of Venus. Nonetheless, Tuesday's event is rare and interesting! It starts at 1:13 a.m. EDT Tuesday June 8, 2004 and ends 7:26 a.m. EDT. The transit is best observed in Europe, Asia, and Africa. However, those in Australia see the beginning of the event before sunset, and those of us in North and South America see the end of the event after sunrise. Here in Johnson City, we can watch the transit for about one hour and fifteen minutes. Starting at sunrise around 6:10 a.m. we can see the last part of the transit. At 7:06 a.m. Venus starts to exit the disk of the Sun (called "third contact"). Venus continues to move over the face of the Sun for the next 20 minutes until the transit ends at 7:26 a.m. (called "fourth contact").

This is only the sixth such event which humans have known to observe before-hand! For details of this transit, see the "Sky and Telescope" website: http://skyandtelescope.com/observing/objects/article_1258_1.asp

REFERENCES
  1. The Transit of Venus: Tales from the 18th Century, William Sheehan, Sky and Telescope 107(2) February 2004, 46-54.
  2. The Transit of Venus: Tales from the 19th Century, William Sheehan, Sky and Telescope 107(5) May 2004, 33-37.
  3. The June 8th Transit of Venus, John Westfall, Sky and Telescope 107(6) June 2004, 73-79.

For images of the event, see Sky and Telescope, in particular: http://skyandtelescope.com/news/article_1283_1.asp.

Return to Bob Gardner's webpage.