As Neil Armstrong became the first man to walk on the moon, a global audience of 500 million people were watching and listening. "That's one small step for man, one giant leap for mankind," they heard him say as he dropped from the ladder of his spacecraft to make the first human footprint on the lunar surface. It was the perfect quote for such a momentous occasion. But from the moment he said it, people have argued about whether the NASA astronaut got his lines wrong. In the tense six hours and forty minutes between landing on the moon and stepping out of the capsule, Armstrong wrote what he knew would become some of the most 37 words in history.