The Transit of Venus: Twice in a Lifetime

Mercury, March/April 2004 Table of Contents

by Louis Mayo

On the 8th of June Venus will pass across the face of the Sun—a rare event that in the 17th century permitted European scientists to determine the size of the Solar System.

Where will you be on 8 June 2004? If you don't yet know, you had better decide quickly or you may miss one of the rarest events in astronomy: the passage of Venus's dark silhouette across the bright disk of the Sun.

Such a "Venus transit" or "transit of Venus" will happen on June 8th of this year, again on June 6th in 2012, but after that not again until 2117. Besides being a geometric rarity, this type of celestial conjunction was once hugely important for astronomers trying to answer some of the most fundamental and central questions in astronomy: How far away is the Sun? How big is the Solar System? Is the Sun really at the Solar System's center? How far away are the stars? Upon answers to these questions are built many of the pillars of modern astronomy, and it is with this humbling thought in mind that we begin a story of discovery.

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