Less than 250 years ago, the brightest minds of the Enlightenment were stumped over how far the Earth is from the sun. The transits of the 1760s helped answer that question, providing a virtual yardstick for the universe.
A rare astronomical event will take place Tuesday evening: The planet Venus will pass between Earth and the sun, appearing as a small black dot moving across the sun's bright disk. It's known as the transit of Venus, and it won't happen again for more than 100 years.
Over the last few weeks, northern Arizonans have witnessed a lot of astronomical drama: the annular eclipse earlier this month and a partial lunar eclipse yesterday. Today. Flagstaff will have one of the most impressive views of the Transit of Venus. It's a rare event that happens when Venus passes between the sun and the Earth. And, as Arizona Public Radio's Gillian Ferris Kohl reports, it's an event most of us will never see again.