The planet Venus is seen crossing the sun in June 2004 as photographed through a telescope at Planetarium Urania in Hove, Belgium. The earliest known observation of such a transit was in 1639 by English astronomer Jeremiah Horrocks.
Geert Vanden Wijngaert/AP
Safety over style: In 2006, a Palestinian man and boy were careful to protect their eyes while watching a partial eclipse of the sun. The same cautions are in order for Venus' transit of the sun on Tuesday.
Saif Dahlah /AFP/Getty Images