Cosmic Quiz – Flag Waving on the Moon

Seth Jarvis

Joseph Amundsen’s recent Cosmic Quiz Question asks why the flags placed on the moon by the Apollo astronauts appear to be flapping in the wind.

Placing flags on the moon is something NASA thought a lot about when they were planning the Apollo missions in the mid 1960’s. NASA even went so far as to create a “Committee on Symbolic Activities for the First Lunar Landing” to figure out how best to have the astronauts carry out their PR duties on the moon without jeopardizing either their safety or their extensive science to-do list.

The 1967 United Nations “Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies,” (which the U.S. signed) included this prohibition: “Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of occupation, or by any other means.”

So why then plant a flag on the moon? For the symbolism, of course! Just as people feel the need to stick flags on the summits of mountain peaks, NASA wanted to put a US flag on the moon as a way of saying, “Look everyone! Americans are on the moon!”

Having astronauts plant the flag once on they’re on the moon was easier said than done. The Lunar Module (LM) was already crowded with equipment and supplies and there was no room to spare in the LM for the flag. Weight was a critical issue. The astronaut’s bulky, pressurized space suits meant that they’d have limited range of motion and limited dexterity with their gloves. This meant that the flag had to be simultaneously lightweight, compact, and extremely simple to set up.

NASA engineers, being extremely clever people, figured out a way to package telescoping poles and a folded flag into a small, narrow container and mount it on the ladder the astronauts would use to get out of and back into the LM. nasa-flag-engineer_4502

NASA bought the flags that are on the moon for $5.50 each from a commercial flag manufacturer through standard government contracts, and then spent several hundred dollars insulating each flag kit package to protect them from the 2,000 degree temperatures that the packages would experience during landing because they were in the vicinity of the LM’s decent engine’s flaming exhaust.

July 20, 1969! “One small step for (a) man, one giant leap for mankind.” Millions of people around the world (including 14 year-old me) watched as Aldrin and Armstrong detached the flag kit from the ladder, placed the flag on its vertical and horizontal poles, and then… the telescoping mechanism on the horizontal pole stuck. It wouldn’t fully extend, leaving the flag still somewhat scrunched-up. The astronauts fiddled with it for a minute or two without success and then decided that, hey, it actually looks better this way!

Other Apollo astronauts, seeing this, all agreed that the flag in fact did look better this way, and decided that they, too, would only partially extend their horizontal flag supports and thus create a more “natural” looking flag when it was their turn to plant their flags on the moon – which they all did.apollo-11-flag_450

And regarding the “flapping” of the moon flags in certain movies of the Apollo astronauts working on the moon, remember that the moon is completely airless and has 1/6th the surface gravity of Earth. This means that the slightest bump will set the flag’s fabric into motion and it will continue to “flap” for far longer than you’d expect fabric to if were on Earth.

And if you’re part of the 6% of the population who really believe the moon landings were faked and you want to argue, well, I’m sorry, that’s an invitation to just waste both of our time.

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7 thoughts on “Cosmic Quiz – Flag Waving on the Moon

  1. I was wondering (actually my daughter asked me) how did the flag pole get stuck in the surface of the moon if the moon is rock? There isn’t that much dust to hold the flag in an upright postion.

  2. That is a great question!

    During the first moon landing (Apollo 11) Neil Armstrong and Buzz Aldrin did in fact have a really difficult time getting the flag into the moon’s surface deeply enough to get it to stay upright.

    The lunar surface is a mixture of very densely compacted dust and fractured rock.

    Here are Buzz Alrdin’s words on the subject:

    “During a pause in the experiments Neil suggested we proceed with the flag. It took both of us to set it up and it was nearly a disaster. Public Relations obviously needs practice just as everything else does. A small telescoping arm was attached to the flagpole to keep the flag extended and perpendicular. As hard as we tried, the telescope wouldn’t fully extend. Thus the flag, which should have been flat, had its own unique permanent wave. Then to our dismay the staff of the pole wouldn’t go far enough into the lunar surface to support itself in an upright position. After much struggling we finally coaxed it to remain upright, but in a most precarious position. I dreaded the possibility of the American flag collapsing into the lunar dust in front of the television camera.” (Excerpt taken from the book, “Apollo Expeditions to the Moon” published by NASA, SP-350, 1975)

    Armstrong and Alrdin twisted the flag staff back and forth while pushing down on it as hard as they could to get it just a little bit embedded into the lunar surface.

    Armstrong reported during the post-mission press conference, “We had some difficulty, at first, getting the pole of the flag to remain in the surface. In penetrating the surface, we found that most objects would go down about 5, maybe 6, inches and then it would meet with a gradual resistance. At the same time, there was not much of a support force on either side, so we had to lean the flag back slightly in order for it to maintain this position.” (

    It has been reported, but not verified, that Aldrin said he observed the Apollo 11 flag fall down from the blast of the ascent stage engine when he and Armstrong lifted off to rendezvous with Michael Collins in the orbiting Command Module.

    Beginning with Apollo 12, the flag poles were strengthened so that astronauts could use the hammers they brought for collecting rock samples to pound the flag poles down far enough into the lunar surface to keep them securely in place.

  3. I suspect the reason that the flagpole’s shadow isn’t visible in that photo is that the pole itself has a very small diameter, and therefore won’t cast much of a shadow on the surface of the Moon.

    The Sun has an angular diameter of nearly a half-degree, and for a strong shadow to be formed the pole would have to have an angular diameter (seen from the surface near the flagpole) significantly greater than the Sun’s angular diameter. Beyond a couple of feet from the base of the flagpole the angular diameter of the pole is less than a half degree, which would mean that the pole couldn no longer cast a shadow once it became smaller in angular diameter than the Sun.

    The astronaut’s legs and the LEM cast significant shadows because they are very large compared to the angular diameter of the Sun. Notice, however, that even though the astronaut’s legs are very thick because of his bulky spacesuit, the shadows cast by his legs are quite thin.

    The flagpole’s diameter is tiny and its shadow, such as it is, would rapidly disappear as it extended away from the base.

    Note also that in the photograph the ground near the base of the pole is very rough, and the shadow could easily be hidden by the uneven surface. A few feet back in the direction where the shadow might be I think I can actually see small bits of a thin, faint shadow peeking out from behind sections of the rough lunar surface. Then again, I could just be imagining that I see it.

    Try this for an experiment – take a tall, thin wooden dowel (maybe a fishing rod?) and stick it upright in a sandbox when the Sun is low on the horizon, step back several feet perpendicular to the sunlight, look at the scene through a camera viewfinder, and see how long the visible shadow is and how easy it is to observe against the sand in the sandbox.

    Finally, also notice that the Sun is at a very low angle in this photo, and therefore the shadow of the flag itself is probably well off the right side of the photo, which means the only thing you can reasonably look for in this image is the shadow of the flagpole itself, not the flag.

    I hope that helps.

  4. A close examination of the photograph of Buzz Aldrin and the flag reveals that the base of the flagpole is hidden behind a small mound of lunar soil, so any shadow in that area would be hidden. A very thin shadow from the pole can be seen in a high resolution image of that scene (it helps to enlarge the image). It is just above the shadows from Buzz’s legs. Because it is so thin, it is difficult to see and confirm that it is a shadow. However, this photograph taken 33 minutes later by Buzz clearly shows the flag and its shadow.

  5. Robert has, as usual, nailed the explanation by finding a better source of data – in this case a different, higher resolution photograph of the same scene.

    Since my original post I’ve played around briefly with both calculations of the angular diameter of the pole and experimented with dowels and lightbulbs.

    My idea that the flagpole is too thin to cast much of a shadow beyond several feet from the pole itself isn’t holding up so well.

    The second photo of that scene that Robert found makes it clear that the shadow is easily visible at quite a distance from the site of the flag.

    I’d say that pretty well settles it – the shadow really is there, the original photo (in the original post, above) simply doesn’t have the right resolution or camera angle to reveal it against the rough lunar surface.

    Thanks, Robert!

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