In this July 20, 1969 file photo provided by NASA shows Apollo 11 astronauts Neil Armstrong and Edwin E. "Buzz" Aldrin, the first men to land on the moon, plant the U.S. flag on the lunar surface.
It was the kind of history that ignites the imagination of humanity.
On July 20, 1969, hundreds of millions of people around the world watched or listened as the lunar module Eagle carried astronauts Neil Armstrong and Buzz Aldrin to the surface of the moon. Armstrong got on the radio to let them know "the Eagle has landed."
Almost seven hours later, Armstrong stepped off the ladder in his bulky white space suitand said those famous words: "That's one small step for [a] man, one giant leap for mankind"
Astronaut Alan Bean became the fourth person to walk on the moon in November of 1969. He says Armstrong hadn't thought a lot about his historic words because he wasn't sure the landing would be successful.
"Neil thought he had about a 90 percent chance of getting back alive — that was a guess," Bean says. "But he thought he only had about a 50 percent chance of making a landing and that's why he says, and I believe him, that he didn't spend a lot of time thinking about what his first words would be."
Bean says a number of astronauts could have done the mission as well as Armstrong, but he's not sure how many could have dealt with the aftermath with such humility.
Astronaut Rusty Schweickart, who piloted the lunar module in March of 1969, says Armstrong had a great sense of humor.
"Not a lot of people were aware of [it], but he was a very modest and gracious person," Schweickart says.
Neil Alden Armstrong was born Aug. 5, 1930, and had been fascinated by flying since his first airplane ride as a 6-year-old boy in Ohio. He earned his pilot's license before his driver's license, and by the age of 16 was not only flying airplanes but also experimenting with a wind tunnel in his basement.
Armstrong earned a Navy scholarship to Purdue University, but was called to active duty and flew 78 combat missions in Korea. He became a test pilot for the forerunner of the National Aeronautics and Space Administration and was accepted into the second group of astronauts.
Armstrong made his first spaceflight in 1966, and just three years later, took humanity's first steps on the moon.
"Landing on the moon was a dream that millions of kids have had for hundreds of years," Schweickart says, "and Neil was lucky enough to have been in the right place at the right time."
But Armstrong — a quiet man who valued his privacy — left NASA in 1971 and moved his family back to Ohio, where for a time he was a professor of aerospace engineering at the University of Cincinnati.
Roger Launius, the senior curator in space history at the Smithsonian National Air and Space Museum, says Armstrong wanted to be remembered as a good engineer and a good research pilot.
"He could have done anything, and gone anywhere, made tons of money [and] done very high-profile sorts of activities," Launius says. "What he chose to do was go to work as a university professor and teach engineering. Can you imagine taking your Engineering 101 class from Neil Armstrong?"
In a 2009 appearance at the National Press Club, Armstrong displayed his sense of humor as he was asked whether he had dreams about being on the moon.
"I can honestly say, and it's a great surprise to me, that I have never had a dream about being on the moon," he said to a laughing crowd. "It's a great disappointment to me even more than to you."
A crater on the moon is named after the former astronaut, a hero to many around the world. But perhaps Schweickart says it best: "He was a symbol of what humanity can do when it sets its mind to it."
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