How does the lighting in this photo work? It is strange.
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I expected a different question, not about shadows, but the lack thereof. One that nVidia ended up solving with their volumetric light system a few years ago (the 80% reflectivity of the space suits compared with the 20% reflectivity of the lunar surface). – Draco18s no longer trusts SE Oct 24 '19 at 16:47
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1@Draco18s That was addressed here a couple of years ago. – Russell Borogove Oct 24 '19 at 17:10
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@RussellBorogove Not surprised, its just the question I was expecting when I saw this one in HNQ. – Draco18s no longer trusts SE Oct 24 '19 at 18:55
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2The dictionary definition of "lighting" is: equipment in a home, workplace, studio, theater, or street for producing light. We don't usually refer to the sun as lighting... If you want to rephrase the question more neutrally you could focus on the shadows? – user2705196 Oct 25 '19 at 20:39
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This is the Apollo 11 photo designated AS11-40-5925, a popular shot with moon landing deniers.
The camera is facing generally north-north-west. The sun is low in the sky, about 10º-15º above the horizon on the east. The silver pole in the upper right of the photograph is pretty much straight up, casting shadow in the expected direction. The landing leg in the upper center is tilted away from the sun angle somewhat, not enough to significantly change the direction of the shadow. This is all really straightforward.
The confusing part is the probe in the right foreground. These probes hang down from the footpads of the lander, and when one of them touches the lunar surface, they activate an indicator in the cabin, alerting the crew that the LM is within about 2 meters of the surface. When the pad comes down to the surface, the probes are bent away in unpredictable directions depending on which way the LM is drifting at touchdown, as discussed in this QA.
In this image, the probe is bent outwards, generally toward east-north-east. The probe extends out of frame to the right; it's about twice as long as the diameter of the footpad. Since it's mostly pointing towards the sun, the shadow is severely foreshortened -- the shadow is cast nearly down the length of the probe. That’s why the angle of the shadow appears so different from the others.
Here's a quick reproduction of the situation with a couple of chopsticks stuck in a piece of styrofoam, lit by a single light, with shadows appearing to fall in very different directions:
It’s not a perfect match for the Apollo photo —- it’s taken from a higher angle. However, it does demonstrate that the direction the probe points can drastically change the direction the shadow extends over the surface.
Here's what the configuration looks like from above with additional lighting:
NASA has no explanation for Karloff the giant moon cat, however.
Russell Borogove
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The foreshortening seems extreme and makes it harder for the back shadow to have an acute angle... Seems to contradict your model... – user33625 Oct 24 '19 at 05:06
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6The Apollo photo was taken from a somewhat lower angle than my demo photo. Feel free to take the time, yourself, to do the experiment, and see if you can duplicate it. – Russell Borogove Oct 24 '19 at 05:09
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Can't mess up landlords yard. But the lower angle would result in the same foreshortening as evidenced by your model. – user33625 Oct 24 '19 at 05:16
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1Even if the answer weren't so great, I think I'd have to give you a +1 just for naming a hairless cat Karloff. – Omegacron Oct 25 '19 at 17:42
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In this image, the probe is bent outwards, generally toward east-north-east. The probe extends out of frame to the right; it's about twice as long as the diameter of the footpad.I will note that a depression that that pole made against the lunar surface is visible, indicating exactly which direction its aimed in. – Draco18s no longer trusts SE Oct 25 '19 at 22:08 -
Outstanding explanation. (Voted) The picture is confusing at first, but you've explained it very well. However, Karloff the giant moon-cat defies explanation. :) – Duncan C Oct 26 '19 at 01:36
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I am quite surprised how nobody had noticed the glaring flaw in your demonstration, namely the fact that the Styrofoam block would have to be lit by direct sunlight for it to be an accurate recreation. However, since you used artificial lighting, one could argue that you have proven the exact opposite of what you were trying to, namely the use of artificial lighting in the original photo. Not disagreeing with the conclusion written contents of the answer, though. I just think it is intellectually dishonest and a poor scientific practice to use an obviously flawed setup as {continue} – No Nonsense May 16 '22 at 22:08
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proof if all one needed was to just take it outside during daytime. It went smooth because 100% of the audience had already been in agreement with you, but it would not fly in any other setting. It also gives quite a bad and disappointing impression of this site's scientific quality once one reads all those superficial displays of approval in the comments, some of which even explicitly admit to having voted up just for the frivolous shot with the cat. Cheers. – No Nonsense May 16 '22 at 22:08
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2@user47149 I greatly, greatly resent the suggestion of intellectual dishonesty. At no point did I claim this was an "accurate recreation"; it was a demonstration of the basic phenomenon. I said "it does demonstrate that the direction the probe points can drastically change the direction the shadow extends over the surface," and it does. The use of nearby artificial lighting instead of natural light at effectively infinite distance would, of course, change the shadow angles; it wouldn't change them by ninety degrees! – Russell Borogove May 21 '22 at 15:03
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@user47149 I should confess that the nefarious reason I used artificial light for this demonstration: It was night-time when I made the post. – Russell Borogove May 21 '22 at 15:04
