Neil Armstrong, who would have turned 87 years old today, is remembered as both a "reluctant American hero" and "the spiritual repository of spacefaring dreams and ambitions." He was a man of few words, but those he chose to share were significant and, occasionally, tongue-in-cheek. Here are some notable letters and notes written by the first man on the moon.

1. ITS TRUE BEAUTY, HOWEVER, WAS THAT IT WORKED.

There was little certainty about what to expect once Armstrong and Buzz Aldrin left the relative safety of the Apollo 11 spacecraft. This was not lost on Armstrong, who sent a letter of thanks to the crew who designed his spacesuit.

2. AMERICA MUST DECIDE IF IT WISHES TO REMAIN A LEADER IN SPACE.

It's no secret that NASA's budget has all but disappeared in recent years. Neil, along with James Lovell and Eugene Cernan, had a few things to say about that. The three wrote an open letter to President Obama, urging him not to forfeit the United States' progress in space exploration and technology. It ends with a sobering prediction, and some advice:

For The United States, the leading space faring nation for nearly half a century, to be without carriage to low Earth orbit and with no human exploration capability to go beyond Earth orbit for an indeterminate time into the future, destines our nation to become one of second or even third rate stature. While the President’s plan envisages humans traveling away from Earth and perhaps toward Mars at some time in the future, the lack of developed rockets and spacecraft will assure that ability will not be available for many years. Without the skill and experience that actual spacecraft operation provides, the USA is far too likely to be on a long downhill slide to mediocrity. America must decide if it wishes to remain a leader in space. If it does, we should institute a program which will give us the very best chance of achieving that goal.

(Here's the letter in full.)

3. ALL OF THIS KNOWLEDGE IS YOURS FOR THE TAKING.

In 1971, the children's librarian of Troy, Michigan's new public library wrote dozens of letters to notable figures across the globe, asking them to address the children of Troy and speak about the importance of libraries, books, and reading. Among the replies was this note from Armstrong:

Through books you will meet poets and novelists whose creations will fire your imagination. You will meet the great thinkers who will share with you their philosophies, their concepts of the world, of humanity and of creation. You will learn about events that have shaped our history, of deeds both noble and ignoble. All of this knowledge is yours for the taking… Your library is a storehouse for mind and spirit. Use it well.

4. I FIND THAT MYSTIFYING.

After NPR's Robert Krulwich wondered aloud on-air why the astronauts stayed so close to the landing site (less than 100 yards from their lander), a helpful Armstrong sent over a lengthy letter of explanation, which ended with a little insight about the importance of space exploration (emphasis added):

Later Apollo flights were able to do more and move further in order to cover larger areas, particularly when the Lunar Rover vehicle became available in 1971. But in KRULWICH WONDERS, you make an important point, which I emphasized to the House Science and Technology Committee. During my testimony in May I said, "Some question why Americans should return to the Moon. "After all," they say "we have already been there." I find that mystifying. It would be as if 16th century monarchs proclaimed that "we need not go to the New World, we have already been there." Or as if President Thomas Jefferson announced in 1803 that Americans "need not go west of the Mississippi, the Lewis and Clark Expedition has already been there." Americans have visited and examined 6 locations on Luna, varying in size from a suburban lot to a small township. That leaves more than 14 million square miles yet to explore. I have tried to give a small insight into your question “Who knew?” I hope it is helpful.

(Read the full transcript here.)

5. IT CERTAINLY WAS EXCITING FOR ME.

On the 40th anniversary of the Apollo landing, Armstrong wrote a personal letter of tribute to the Canberra Deep Space Communications Complex, which provided the communications between Apollo 11 and mission control. In part, it reads:

We were involved in doing what many thought to be impossible, putting humans on Earth’s moon. Science fiction writers thought it would be possible. H. G. Wells, Jules Verne, and other authors found ways to get people to the moon. But none of those writers foresaw any possibility of the lunar explorers being able to communicate with Earth, transmit data, position information, or transmit moving pictures of what they saw back to Earth. The authors foresaw my part of the adventure, but your part was beyond their comprehension. All the Apollo people were working hard, working long hours, and were dedicated to making certain everything they did, they were doing to the very best of their ability. And I am confident that those of you who were working with us forty years ago, were working at least that hard. It would be impossible to overstate the appreciation that we on the crew feel for your dedication and the quality of your work.

The full text is available on the Honeysuckle Creek Tracking Station website.

6. NEXT TIME, BUTT OUT OF OUR BUSINESS!

After a surprise appearance in "Mystery On the Moon," issue #98 of The Fantastic Four, wherein our intrepid explorers are saved by four mutants in space, this brief note arrived in Stan Lee and Jack Kirby's mailbox. Was it real? Who knows. But the sentiment remains: We don't need your superheroes to get to the moon—we have science.