Look out for rare space spectacle June 06 2004 at 04:12PM Hamburg - Tuesday's transit of Venus in front of the sun will be only the sixth such event observed by humans, and astronomers say nobody alive today has seen the phenomenon, which is barely noticeable because it only imperceptibly reduces visible sunlight. Past transits in 1639, 1761, 1769, 1874 and 1882 were monitored from Earth. Slight differences in the start and finish time were used to roughly calculate the distance of the sun from the Earth. The transit will be visible from all parts of Earth where the sun...