On July 20, 1969, Apollo 11 astronauts Neil Armstrong and Buzz
Aldrin climbed down from the Eagle lunar module (leaving behind poor Michael
Collins) to put the first footprints on the moon. That’s the story, at least. A
vocal minority believes that the moon landing was all an elaborate hoax filmed
on a sound stage in Hollywood.
Among their evidence is the fact that photographs and video
footage don’t show any stars in the sky. How could the Hollywood producers be
so careless in their conspiracy? In fact, there’s a pretty mundane explanation.
The camera settings weren’t adjusted to capture them.
If you wanted to take a picture of a friend in direct
sunlight, you’d adjust your camera settings in two ways. You’d narrow the
aperture, which keeps the light-collecting area on the lens small to avoid
letting in too much light, the same reason your pupils constrict in bright
sunlight.
You’d also speed up the shutter speed, so the camera sensor
would only let in light for a brief moment. If you wanted to take a picture of
that same friend at night, you’d probably slow down the shutter speed and widen
the aperture so you could let in enough light for a good shot.
But what if your friend was illuminated at nighttime? Then
you’d have to choose what you wanted in your photo. If you wanted to include
the stars in the sky, you’d need to make sure your friend stood extra still to
avoid blurring the shot while the slow shutter and wide aperture let in enough
light.
If you kept the aperture small and the shutter speed fast,
you’d capture a sharp, decently bright picture of your friend, but the sky
would be dark because it wouldn’t send enough light into the lens.
That’s the trade-off the Apollo astronauts had to make. The
sky on the moon is black as night not because it is night, but because there’s
no atmosphere to scatter the daylight the way ours does on Earth.
But make no mistake, there is every bit as much sunlight at
midday on the moon as there is on our home planet. That makes the lunar surface
incredibly bright.
The scenery on the moon was the most important thing to
capture in the Apollo photographs, so the camera was adjusted to make the most
out of that scenery. As a result, the relatively dim stars in the background
didn’t register in any of the shots. No hoax, just a trick of the camera lens
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