The twice-reflected moonlight...

[Michie]

American astronaut Ron Garan may be the single best promoter of space exploration we have today, if only because of his breathtaking photographs of the Earth from space. In July 2011, as he orbited our planet in the International Space Station, he took this gorgeous shot of the crescent Moon, setting over the Earth’s silhouetted limb:

[Click to enlunenate.]

This shows no fewer than three of my favorite optical effects! First, the colors of the sunset are due to the Earth’s air, which preferentially scatters away bluer light, leaving just the orange and red colors from the Sun to get through.

Second, the Moon is squashed! You can see it’s not perfectly round as it usually looks; again, that’s due to Earth’s air. It acts like a lens, bending the Moon’s light. Nearer the Earth’s limb, you’re looking through more air, so the effect is larger, making the moon look not just squashed, but squashed unevenly: the top part is rounder than the bottom. I explain in this in detail using a different picture of moonset from space.

Continued-
The twice-reflected moonlight...