We all remember—those of us old enough—where we were when Armstrong walked down the ladder. But few of us had a clue, at the time, how dicey Eagle's descent was.

As Armstrong and Aldrin neared the surface, an alarm went off. The computer displayed the alarm code 1202. Neither astronaut knew what it meant. It was, in fact, the computer announcing that it was being overloaded with data. At mission control in Houston, the experts decided to ignore it and let Eagle continue its descent.

Armstrong, piloting the lander, saw that they were heading straight for a crater full of boulders. He had to fly over the crater as he searched for a new landing spot—miles beyond the planned target. And they were running low on fuel.

"Sixty seconds," said mission control. A minute of fuel left.

Armstrong could barely see anything. The rockets were throwing up dust. It was like flying in a cloud.

"Thirty seconds."

They were having heart attacks in Houston. The world was watching but had no ability to grasp how close the astronauts were to disaster. The men themselves, by training and nature, were not emotive. Yet Armstrong, the prototype of the calm, almost robotic astronaut, clocked a pulse of 156 beats a minute as he struggled to land the craft.

"Contact light!" shouted Aldrin. A light indicated that a prong at the bottom of one of the lander's legs had touched solid ground.

Humankind is an imperfect species, and so perhaps it is fitting that the first words spoken by a man walking on the moon were botched. "That's one small step for man, one giant leap for mankind," Armstrong said. He meant to say "small step for a man," and there are those who insist the missing article was lost in transmission.

Ultimately it's moot: Although we speak imperfectly, we also have learned to get the gist of what people are trying to say. We knew what he meant. And we liked what he said.