Mercury, Venus, and the Dance of the Planets

For all of us, it's now or never to see Venus silhouetted against the face of the sun. On June 5 the goddess will transit the sun, a phenomenon not to be repeated until 11 December 2117. First observed by Jeremiah Horrox and William Crabtree in 1639, the subsequent transits in 1761, 1769, 1874 and 1882 brought about major international competition to observe this rare event. Talk by historian Owen Gingerich.