Why the Venus Transit Is One of the Most Important Events in Scientific History

On June 5, the planet Venus will appear to pass in front of the Sun as seen from the surface of the Earth. This phenomenon, called a transit of Venus, happens only a few times in 250 years. The next one will be in 2117 AD. Here's a guide to watching the once-in-a-lifetime event. But why does it matter? »6/05/12 4:02pm6/05/12 4:02pm