Tomorrow, Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again, says NASA.
Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This transit, the bookend of a 2004-2012 pair, won't be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it.