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Comment by swsieber | Hacker News Reader

So one of my friends is like "Moon landing is fake, here's a bunch of reasons". One of them was the shadows in the photos not acting like the come from a single distanct lightsource. Since this popped up here today, and I'm sure there are many more knowledgeable than I, I'd like to ask:

What's up with the shadows in this picture? (it's one from wikipedia page) https://en.wikipedia.org/wiki/Apollo_11#/media/File:Buzz_sal...

They seem odd. Thanks in advance for any insights.

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NVidia did a nice project a few years ago to model the moon landing in great detail.[1] It's a demo for their graphics cards. They did ray traced renders using actual reflectance data for the objects involved. The lunar surface is reflecting enough light to provide the effect of diffuse lighting from below. It's like being on sunlit sand under a dark sky.

NVidia comments that either the moon landing is real or NASA built a time machine to travel 50 years into the future to get a good GPU.

(For reference, the most powerful computer in the Apollo era, the CDC 6600, was about 10 MIPS. Modern desktop CPU, about 50,000 MIPS. Current top NVidia gamer GPU, about 10,000,000 MIPS. No way could computers of that era render photorealistic pictures.)

[1] https://blogs.nvidia.com/blog/2014/09/18/debunked/ [2] https://blogs.nvidia.com/blog/2018/10/11/turing-recreates-lu...

The other thing you might be subconsciously noticing as "odd" is the varying depth or darkness of the shadows. The lunar surface is only illuminated by direct sunlight in an otherwise black sky, so the shadows cast by Aldrin and the lander appear pitch-black. But Aldrin himself is being lit by both direct sunlight and indirect light bouncing off the surface, so the shadowed side of his suit still appears diffusely illuminated.

It makes sense when you stop to think about it (and you can fairly easily recreate the phenomenon in a raytracer) but it looks unnatural because we're used to direct sunlight always being accompanied by indirect skylight.

When you say 'odd', can you be more specific? If you think they aren't parallel, then I would suggest that is purely down the the terrain. They look fine to me. Have a look at the clavius moon base site [1] for much better informed discussion of any issues your friend may have.

[1] - http://clavius.org/

Instead of always trying to debunk conspiracy theories we can also talk about some of the proof that astronauts went to the moon. See if they can debunk that. For example, every mission with Extravehicular activity brought back samples of moon rock (some collecting over 100kg). I find that to be pretty conclusive.

Devil's advocate: how can we verify these rocks originated from the moon, and not somebody's back yard?

It's a valid question. The environment required to form these rocks is not found on Earth.[0] The chemistry and mineral composition of Moon rocks is different from Earth rocks. Some of the rocks are older than almost all rocks on Earth (Earth's crust is more active than the Moon's because of plate tectonics). One of the more famous rocks collected is the Genesis Rock.[1] Recently a few channels on YouTube did videos about where the Moon rocks are currently stored [2][3][4] (It's a lot of work and money to keep backyard rocks from getting contaminated if it really is a hoax.)

[0] http://meteorites.wustl.edu/lunar/howdoweknow.htm

[1] https://en.wikipedia.org/wiki/Genesis_Rock

[2] Where does NASA keep the Moon Rocks? - Smarter Every Day 220 https://www.youtube.com/watch?v=QxZ_iPldGtI

[3] Apollo’s Most Important Discovery (Inside NASA’s Moon Rock Vault!) https://www.youtube.com/watch?v=Qr28zMXQ3bU

[4] The Genesis Rock - Objectivity #208 https://www.youtube.com/watch?v=yvhLBzsDwSQ

There is also a mirror on the moon, placed by Apollo 14 (IIRC).

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