structural:reformatting, linguistic:voice_change, structural:summarization
First Moon walk

The flight plan called for a crew rest period before leaving the module, but Armstrong asked for this to be moved to earlier in the evening, Houston time. When he and Aldrin were ready to go outside, Eagle was depressurized, the hatch was opened, and Armstrong made his way down the ladder. At the bottom of the ladder, while standing on a Lunar Module landing pad, Armstrong said, "I'm going to step off the LM now". He turned and set his left boot on the lunar surface at 02:56 UTC July 21, 1969, then said, "That's one small step for man, one giant leap for mankind." The exact time of Armstrong's first step on the Moon is unclear.

Armstrong prepared his famous epigram on his own. In a post-flight press conference, he said that he chose the words "just prior to leaving the LM." In a 1983 interview in Esquire magazine, he explained to George Plimpton: "I always knew there was a good chance of being able to return to Earth, but I thought the chances of a successful touch down on the moon surface were about even money—fifty–fifty... Most people don't realize how difficult the mission was. So it didn't seem to me there was much point in thinking of something to say if we'd have to abort landing." In 2012, his brother Dean Armstrong said that Neil showed him a draft of the line months before the launch. Historian Andrew Chaikin, who interviewed Armstrong in 1988 for his book A Man on the Moon, disputed that Armstrong claimed to have conceived the line during the mission.

Recordings of Armstrong's transmission do not provide evidence for the indefinite article "a" before "man", though NASA and Armstrong insisted for years that static obscured it. Armstrong stated he would never make such a mistake, but after repeated listenings to recordings, he eventually conceded he must have dropped the "a". He later said he "would hope that history would grant me leeway for dropping the syllable and understand that it was certainly intended, even if it was not said—although it might actually have been". There have since been claims and counter-claims about whether acoustic analysis of the recording reveals the presence of the missing "a"; Peter Shann Ford, an Australian computer programmer, conducted a digital audio analysis and claims that Armstrong did say "a man", but the "a" was inaudible due to the limitations of communications technology of the time. Ford and James R. Hansen, Armstrong's authorized biographer, presented these findings to Armstrong and NASA representatives, who conducted their own analysis. Armstrong found Ford's analysis "persuasive." Linguists David Beaver and Mark Liberman wrote of their skepticism of Ford's claims on the blog Language Log. A 2016 peer-reviewed study again concluded Armstrong had included the article. NASA's transcript continues to show the "a" in parentheses.

When Armstrong made his proclamation, Voice of America was rebroadcast live by the BBC and many other stations worldwide. An estimated 530 million people viewed the event, 20 percent out of a world population of approximately 3.6 billion.

Q: Did you misspeak?

A: There isn't any way of knowing.

Q: Several sources say you did.

A: I mean, there isn't any way of my knowing. When I listen to the tape, I can't hear the 'a', but that doesn't mean it wasn't there, because that was the fastest VOX ever built. There was no mike-switch — it was a voice-operated key or VOX. In a helmet you find you lose a lot of syllables. Sometimes a short syllable like 'a' might not be transmitted. However, when I listen to it, I can't hear it. But the 'a' is implied, so I'm happy if they just put it in parentheses.

Omni, June 1982, p. 126

About 19 minutes after Armstrong's first step, Aldrin joined him on the surface, becoming the second human to walk on the Moon. They began their tasks of investigating how easily a person could operate on the lunar surface. Armstrong unveiled a plaque commemorating the flight, and with Aldrin, planted the flag of the United States. Although Armstrong had wanted the flag to be draped on the flagpole, it was decided to use a metal rod to hold it horizontally. However, the rod did not fully extend, leaving the flag with a slightly wavy appearance, as if there were a breeze. Shortly after the flag planting, President Richard Nixon spoke to them by telephone from his office. He spoke for about a minute, after which Armstrong responded for about thirty seconds. In the Apollo 11 photographic record, there are only five images of Armstrong partly shown or reflected. The mission was planned to the minute, with the majority of photographic tasks performed by Armstrong with the single Hasselblad camera.

After helping to set up the Early Apollo Scientific Experiment Package, Armstrong went for a walk to what is now known as East Crater, 65 yards (59 m) east of the LM, the greatest distance traveled from the LM on the mission. His final task was to remind Aldrin to leave a small package of memorial items to Soviet cosmonauts Yuri Gagarin and Vladimir Komarov, and Apollo 1 astronauts Grissom, White and Chaffee. The Apollo 11 EVA lasted two and a half hours. Each of the subsequent five landings was allotted a progressively longer EVA period; the crew of Apollo 17 spent over 22 hours exploring the lunar surface. In a 2010 interview, Armstrong explained that NASA limited their Moon walk because they were unsure how the space suits would cope with the Moon's extremely high temperature.