A man uses a sun observation glass to watch the transit of Venus across the face of the sun on June 5, 2012, in Medellin, Antioquia department, Colombia. Astronomers around the world are training their telescopes on the skies to watch Venus pass in front of the Sun, a once-in-a-lifetime event that will not be seen for another 105 years. AFP PHOTO/Raul ARBOLEDA