Visitors look at a model of a Saturn V rocket and its launch umbilical tower, which were used during the Apollo moon-landing program, at the Smithsonian National Air and Space Museum in Washington, D.C. Fifty years ago this July 20, Neil Armstrong and Buzz Aldrin became the first humans to walk on the moon.

Visitors look at a model of a Saturn V rocket and its launch umbilical tower, which were used during the Apollo moon-landing program, at the Smithsonian National Air and Space Museum in Washington, D.C. Fifty years ago this July 20, Neil Armstrong and Buzz Aldrin became the first humans to walk on the moon.