Today and Wednesday, people across the world will be able to see the Transit of Venus — a rare moment in astronomy that won't happen again for 105 years. During a six-hour window, the planet Venus will move between the Earth and Sun, appearing against the Sun as a small, slow-moving black dot. The rare spectacle occurs in pairs, eight years apart, and the last transit took place on June 8, 2004. The next pair? Dec. 10-11, 2117, and Dec. 8, 2125. In other words, this is your one lifetime opportunity to check out the Transit of Venus.Hoping to catch a glimpse yourself? Look for Venus as it moves from east to west across the Sun, but be cautious: as with a solar eclipse, you need to wear special eye protection to prevent damage as you stare at the Sun. If you can't view it from your location, not to worry — you can watch a live Transit of Venus NASA webcast.