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DON PETTIT/ISS/NASA
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Editor's note: There is nothing wrong with your eyes. And this image has not been squashed!
Seen from the International Space Station, the setting Moon seems to squash itself into nothingness as it disappears below the horizon. Astronaut Don Pettit captured this moonset image with a handheld digital camera, one of more than 30 images that were later stitched together to form a short movie of the phenomenon.
The lunar squashing is an optical effect caused by refraction as moonlight passes through the Earth's atmosphere, which acts like a lens. Moonlight must pass through this atmospheric lens twice -- once as it enters and again as it leaves -- before reaching Pettit's camera aboard the orbiting station.
Light from the bottom of the Moon, its lower limb, is refracted upwards and so the orb appears to flatten. Air molecules and other tiny particles scatter blue light from the Moon, giving it a reddish pink hue. [The Sun can appear similarly squashed near the horizon.]
You don't have to make it to space to see a squashed Moon; when the satellite is close enough to the horizon, the effect can be visible from your backyard. A movie of Pettit's setting Moon is here. [Lunar Eclipse Coming May 15]
-- Tariq Malik
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