Mark your calendar for June 5 or 6 of this year, as it will be the last chance in most of our lifetimes* to see one of most eagerly anticipated astronomical events: the 2012 transit of Venus. Such a transit occurs when the planet Venus passes directly between the Earth and Sun, appearing like a black dot skidding across the solar disk. Such transits are very rare, occurring in pairs that only repeat once a century. The last “T of V” was in 2004; the next will be in 2117—if the priests of the temples of Syrinx will allow it.** So, next month, plan accordingly; if you are in North America, the transit will occur on the evening of June 5 (but not too late, for obvious reasons). Elsewhere, it will be observable on June 6. (Check out a map of transit times here.) Oh, and public service announcement: plan your eye protection accordingly. Staring directly at the Sun is never a good idea. Transits of Venus were also of great scientific interest, as they enabled astronomers to determine the distance of the Earth to the Sun, and, eventually, the size of the Solar System. (For centuries, “really big” had to suffice.) You can even download a ToV app. And, yes, there are also transits of Mercury, which happen more frequently. The last was in 2006 and the next will be in 2016. But, no, there are no other planetary transits—again, for obvious reasons. However, if humans ever colonize Mars, they’d be treated to a transit of Earth. The next one is November 10, 2084, so let’s plan accordingly.   * Well, there could be some robots or Methuselae reading this. ** Of course the Solar Federation may have been defeated five years earlier.