4 of 20:
Former astronaut Neil Armstrong, left, is congratualted by fellow ex-astronaut Gene Cernan following the dedication ceremony of the Neil Armstrong Hall of Engineering at Purdue University in West Lafayette, Ind., Saturday, Oct. 27, 2007. Armstrong, a Purdue alum, became the first man to walk on the Moon in 1969. Cernan, also a Purdue alum, was the last person to walk on the Moon.
(AP Photo/ Michael Conroy)