Blowing out Both Ways

Bennett and Percy's entire theory of double flags and screeching whistles depends on one unspoken assumption: that the US flag is impervious to light.

On page 45 the authors gave a diagram of how they believe sunlight should reflect off a billowing flag. But since I can't keep scanning their book forever, here's my illustration of their theory:

Sunlight bouncing off a wall: A and B see different light patterns.

Imagine the sun is shining down the length of a zig-zagging brick wall. The sunlight can only strike those areas marked in yellow, leaving the rest in shadow. On either side of the wall are two observers named, creatively enough, A and B. Observer A sees mostly dark shadow with a slice of light between, while B can see either end of the wall lit by the sun with the middle in shadow.

The views of A and B are represented by the two horizontal black and yellow lines. Where A sees light, B sees shadow. Their two views complement each other. This effect is what Dark Moon's photo expert claims we should have seen on the still and TV images of the Apollo 17 flag.

But what if the sun can shine through the flag? Would that make a difference?

Indeed it would. To illustrate, let's return to our observers at the zig-zagging wall, but this time we'll replace the bricks with something less lightproof (such as flag nylon).

Sunlight shines through and reflects off a translucent wall: A sees the same light pattern as B

As before, the sunlight reflects off parts of the wall, but some of the light passes through those same places onto the other side marked with orange. This time, both A and B see three patches of light separated by two shadows, and with the same widths. Each observer's view is identical, positive, and mirror image--exactly what we see in the Apollo flag pictures.

When we see a billowing flag, our mind uses the shadow patterns to help get a mental picture of how the flag is draped. But because the sun is shining through the material and cancelling out the shadows on the opposite side, we might get the wrong idea--we might imagine concave when the flag is actually convex (especially if the flag is seen through a monoscopic camera). It's a common mistake, and we continue to make it because it's not life-threatening and we have no way of knowing we've guessed wrong. The only way to discover our mental mistake is to see both sides of a flag at the same time, and how often does that happen?

You don't believe me? Take a look.

Canadian flag in front of reflective glass building--detail (Author)

...And reflection of its other side--detail (rohtuA)

These two images are from a single picture of my dear country's flag waving before a glass-fronted office building; the second image is the reflection of the flag's opposite side at the exact same instant. (For comparison's sake I put the two images side by side; you can see the intact picture by clicking on either flag or here.) Notice how both sides show the same "positive" complementary billow and shadow pattern that so saddened David Percy.

If it weren't for some distortion caused by different viewing angles and building clutter, the double-positive illusion would be even more impressive--as it was on the moon.

You still don't believe me? Try it yourself.

Of course, all the above is based on the assumption that the flags on the moon were as translucent as flags on earth. It's a safe assumption: the Apollo missions had no reason to pack customized thick and lightproof flags on voyages where ounces mattered. And there was nothing special about these flags; they were bought at Sears for $5 each (Platoff). (However, the Apollo 17 flag had a different pedigree: it had hung in the Mission Operations Control Room, but there's still no reason to think it was used as blackout curtain.)

However, in science it is not enough to believe something. One must also prove it. And yes, I can prove that light did indeed shine through the Apollo flags. That proof is waiting right over on the next page.