Reflected Sun and Long, Long Stormcloud Shadows from Space

The entire universe in blog form
July 14 2013 8:00 AM

A Stormy View from Space

clouds from space
It's not often a spaceship gets in the way of your view of the clouds. Click to encumulunate.

Photo by NASA

There are times a single photo from space makes me stop and truly gawk. This is one of those times.

The photo above was taken by an astronaut on the International Space Station on July 4, 2013. It shows the Sun low to the horizon, illuminating storm clouds off the coast of Brazil. There are two clues the Sun is low. One is that the reflected sunlight off the ocean is near the horizon. The horizon is thousands of kilometers away from the space station, so this picture was taken with the astronaut facing more out than down. The only way to see the Sun reflecting off the water from that angle is if it’s near the horizon too.

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That’s a bit tricky to picture, but happily there’s a more obvious clue: The cloud shadows are very, very long; that’s clearest on the left side of the picture. Long shadows means the Sun was either rising or setting, but either way it was low to the horizon at the time.

Also, see how the clouds on the left cast shadows that point down and to the left, while the clouds on the right have shadows that point down and to the right? That’s an illusion, caused by perspective! Those shadows are all very nearly parallel, and only appear slanted because the camera collapses three dimensional information into two. Our brains do this too, but we tend to ignore it, folding it up into the way we perceive the world. If you’ve ever seen railroad tracks appear to converge in the distance, then you’ve seen this illusion. This also tangentially plays into the Moon Illusion as well—when the Moon looks huge as it rises or sets. Our brains try to judge size and distance using subtle clues, and tend to get them screwed up.

Speaking of the Moon, a lot of people who say the Apollo Moon landings were faked claim that non-parallel shadows in the pictures show the photos taken by the astronauts were hoaxed. This photo shows they are wrong…and the best part is that this photo was itself taken from space.

Ah, irony. It can be both delicious and exquisitely beautiful.

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death from the Skies! Follow him on Twitter.