http://www.youtube.com/watch?v=mefEKqzq8cg&feature=related

http://www.youtube.com/watch?NR=1&v=RfKItI-cHPM

http://www.youtube.com/watch?feature=fvwp&v=NOv_zvM-oJQ&NR=1

http://www.youtube.com/watch?v=oCNV1hiKpLI&feature=related

http://www.youtube.com/watch?NR=1&v=0dTATMEJSuQ

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!

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.

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.” (http://www.hq.nasa.gov/office/pao/History/alsj/a11/a11.step.html)

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.