Transit of Venus

In a week and a half, at about 6pm Boston time there will be a Transit of Venus.

"On 5/6 June 2012 a celestial takes place that is so rare that it will not be seen again by anyone now living. On June 8, 2004 Venus crossed the face of the Sun for the first time since the 19th century. This spectacle will be repeated again this June for the last time until 2117. Astronomers Without Borders has some special plans for this rare event, which will be seen by most of the world's population."

"Mercury and Venus are the only planets closer to the Sun than Earth, both moving faster in their orbits and passing us regularly. But rather than crossing directly between us and the Sun, these planets are usually slightly above or below the Sun as we see them. When they line up just right we see the round, black silhouette of the planet slowly crossing the Sun, an even referred to as a "transit." Mercury transits the Sun 13 or 14 times each century. But Venus transits happen in pairs - two transits eight years apart - with more than 100 years between each pair."

The transit of Venus has been used to determine the Earth's distance from the Sun. "The coming Venus transit offers a chance for modern-day stargazers to repeat the experiments conducted by expeditions around the world in the 18th and 19th centuries - with a modern twist. The free phone app created by the Transit of Venus Project allows every observer with a telescope to record timings of this rare event. Available for Apple and Android devices."

Here's a cheesy but informative 4 minute video about the transit of Venus.