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The lighter side of Neil Armstrong

Chip Somodevilla / Getty Images

Neil Armstrong's picture shines out from a TV screen during today's memorial service in Washington.

Even his friends acknowledge that it wasn't easy to make Neil Armstrong laugh: One of his crewmates on the historic Apollo 11 mission in 1969, Michael Collins, recalled this week that history's first moonwalker "always seemed serious and businesslike, but you could make him laugh if you tried."

Armstrong could make others laugh, too: That came through in a couple of the memories his friends shared today at the national memorial service at Washington National Cathedral. Here are two tales that sparked laughs amid the tears:

Apollo 17 commander Gene Cernan, the last man to walk on the moon, recalled that Armstrong was once asked how he felt when he was guiding the Eagle lunar module down to the moon's surface with only 15 seconds' worth of fuel left. The way Cernan remembered the story, Armstrong thought for a moment and answered, "Well, when the gauge says empty, we all know there's a gallon or two left in the tank." When the laughter subsided, Cernan added, "Now there is a man who has always been in control of his own destiny. And that, ladies and gentlemen, is vintage Neil Armstrong."

Former Treasury Secretary John Snow, a golfing buddy of Armstrong's, said the astronaut was notorious for sizing up his shots meticulously, to the point of calculating how dew on the green would affect the roll of a putt. "You'd sometimes wonder, 'Neil, are you ever going to hit the ball?" Snow said. "He couldn't help being the engineer."

For more about the lighter as well as the heavier side of Neil Armstrong, check out the complete video of today's ceremony on Ustream, NASA's Flickr photo gallery and this memorial video:

The people who worked with Neil Armstrong -- commander of the first Apollo crew to walk on the Moon -- pay tribute to his enduring friendship, work ethic, and sincerity.

More about Neil Armstrong:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the dwarf planet and the search for new worlds.