Transiting the Sun in 2004

by Joel Harris, Twilight Tours, Inc.

On June 8, 2004, an extremely rare and unusual astronomical event will be observed by those who know what to look for over approximately half of the Earth’s surface. It is so rare that not a person alive today has seen it – the last such event occurred some 121 years ago!

It will be what is called “a transit of the planet Venus,” where the solar system’s second closest planet to the sun will cross the sun's disk. Similar to a solar eclipse, where the moon passes in front of the sun, this will be an instance of a heavenly body interposing itself between the Earth and the sun. Unlike our moon, however, Venus is too distant from us to cover even a small percent of the solar disk. Its transit will not produce any of the highly dramatic effects that typically attend a total solar eclipse.

There will be no dramatic changes in the level of sunlight, no significant temperature drop, no eerie lighting effects or atmospheric anomalies that one associates with an eclipse. In fact, unless one is aware that the transit is occurring, it will pass completely unnoticed by the average person on the street.

Why all the interest in such a “non-event,” given the fact that it will likely go unseen by 95% of those living where the transit can be seen? Basically, two things account for it: rarity and opportunity. Rarity, because the event happens so seldom, and opportunity, because it affords travelers a worthwhile excuse to journey to the far ends of the earth to watch as our “sister planet” creeps across the bright, fiery surface of the sun.

In addition, since a number of astronomical expedition firms are mounting tours to see the transit, and their destinations will be eclectic, there will be some merit in traveling far to see a small black dot march across the disc of the sun for five hours.

The last time a transit of Venus took place, in 1882, a number of expeditions were mounted across the globe, to position astronomers in regions where the event could be observed. 

Probably the most famous transit expedition was headed by Captain James Cook, for the transit that occurred in 1769. Cook was charged with conducting an around-the-world sailing voyage, with an observation of the transit being an integral part of the trip. Cook visited the island of Tahiti in the South Pacific, where his expedition successfully observed the transit. In fact, the coastal site where Cook’s colleagues observed the transit still bears the name “Point Venus” in honor of that event.

Somewhat more recently, at the transit of 1882, the renowned American astronomer Prof. Simon Newcomb, Director of the U.S. Naval Observatory, lead an expedition to Wellington, South Africa. 

In both Cook and Newcomb’s day, expedition members faced nearly year-long voyages across endless tracks of open ocean in wooden sailing ships. Seasickness, poor food and the constant threat of serious illnesses, such as scurvy, malaria and cholera, were ever-present travelers’ companions.

Today, in the first portion of the 21^st century, we do not face the harrowing conditions attending past attempts to observe previous transits.  Apart from the momentary hassles of airport counter check-ins, security screenings and the prospect of a 12-to-15-hour airplane ride, travel to the regions of the world where the transit can be seen is relatively painless.