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The 2012 Transit of Venus

Mercury Summer 2011 Table of Contents

by Paul Deans

Transit of Venus

The June 8, 2004, transit of Venus at sunrise from an overlook above the Catawba River near Connelly's Springs, NC. Courtesy David Cortner.

Two astronomers observed it in 1639. Hundreds viewed it in 1769. Hundreds of thousands of spectators caught at least a glimpse of it in 1882. No one knows how many millions -- perhaps even hundreds of millions -- witnessed it in 2004. And June 5/6, 2012, is your only opportunity to see it. So, where will you be during next year's transit of Venus?

The phrase "once in a lifetime" denotes a rare event. A Venus transit is actually a twice-in-a-lifetime event, because two transits occur within a span of eight years. But each transit pair is separated from the next (and previous) pair by more than a century. Since the invention of the telescope, only three transit sets have occurred: 1631 and 1639; 1761 and 1769; and 1874 and 1882. The current pair (2004 and 2012) concludes next year. Miss 2012, and you'll have to wait 105 years -- until December 11, 2117 -- for the start of the next transit pair (2117 and 2125).

Why so rare? It's all in the tilt.

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