Twelve people have walked on the surface of the Moon during the Apollo program, at a cost of more than $25 billion.
Granted, it's not something everyone gets to experience. But to this day some claim it never happened: seven percent of respondents, in some polls collected as recently as 2013. That's about one in every 15 people you meet -- potentially millions of Americans.
So why are so many convinced? Some conspiracy theorists have come up with some pretty compelling arguments that seem to question the reality -- but the scientists have answers too. Here are the big points -- and they're counterpoints.
1) "The American flag is waving in the breeze!" Moon landing deniers say there's clear photographic evidence of this, and point out that because there's no breeze on the moon, this must be fake.
According to NASA, this is just inertia: "Unfurling a piece of rolled-up cloth with stored angular momentum will naturally result in waves and ripples -- no breeze required!" NASA explains. The Apollo 11 crew bent some of the rods intended to hold the flag out straight, which added some ripples. The Apollo 12 astronauts had the same issue.
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2) "But there's no crater at Lunar Module landing sites! How do you land 36,000 pounds of spaceship and astronauts without digging out a bunch of that moon dust?"
The NASA response? Gravitational acceleration on the moon is roughly six times weaker than it is on Earth, so the Lunar Descent Engine didn't have to work all that hard: closer to 6,000 pounds of thrust, rather than 36,000. The LEM throttled back as it approached the surface, to make landing as smooth as possible. Less thrust means less crater.
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3) "What about the multiple light sources? Like those you might see illuminating a film set?" This is a point made by those who think the moon landing was staged in on a movie set.
NASA's response? Sunlight reflects off objects on the moon the same way it does here on Earth. So all of these images and videos include light reflecting from Earth, the lunar module, and from the dust on the surface.
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4) "There aren't any stars in the pictures that were 'supposedly' taken on the moon. Pretty amateur mistake by the set director, right? They should fire their art guys."
The debunk? This is a matter of camera settings. Apollo astronauts had to set the cameras they used — these Hasselblad 500ELs — to properly expose the environment and the work they were doing.
You could probably ramp up the exposure to get dim stars in the background, but it would blow out everything else. The astronauts would start looking like beings of pure luminous energy wandering the moonscape, which is an entirely different conspiracy theory.
5) "What about the bootprints? They're perfect. Too perfect. Done-ahead-of-time-in-concrete perfect."
NASA's response? You can thank dust for this one. Specifically, Lunar regolith. Individual granules of it are spiky and abrasive, closer to volcanic ash than beach sand. This means it packs together really well, and the absence of any wind on the surface — we've been over this, there's no atmosphere for wind — means those footprints won't degrade anytime soon.
You can only get a hammer and a feather to fall at the same speed in a vacuum. Know what you can't reliably stick in a vacuum? A film crew.
Repeated independent scientific examinations show the lunar samples returned with the Apollo missions do not naturally exist and cannot naturally form anywhere on Earth.
The Lunar Reconnaissance Orbiter can see the footpaths and installations of the Apollo missions.
Still not convinced? You could always ask Buzz Aldrin to prove it, but he has been known to punch deniers who get too persistent. Your call.
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