The Low Sun and Long, Long Cloud Shadows … FROM SPACE

Bad Astronomy
The entire universe in blog form
June 4 2013 11:54 AM

In Case You Miss Chris Hadfield …

Astronaut Chris Hadfield returned safely to Earth in May after spending several months in space. During that time, he took amazing and beautiful pictures of our world from his high perch, and when he came home, many people worried that it would mean a cessation of such photographs.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

Worry no more. Italian astronaut Luca Parmitano tweeted this jaw-dropper just this morning:

clouds from space
Going to space can literally give you perspective. Click to encumulenate.

Photo by ESA/NASA

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Wow. (You really want to click that to embiggen it, too.) When Parmitano tweeted it, he said, “The low sun creates beautiful contrasts with the #clouds: I just don’t get tired of it! #volare.” He didn’t say whether the Sun was rising or setting, and I couldn’t squeeze the info from the picture saying when it was taken. But either way, the long, long shadows coming from the clouds are lovely.

And I noticed something rather fun in the picture, too. The shadows look nearly but not quite parallel; on the sides of the picture the shadows are angled slightly outward. However, I think this is an illusion: They are actually parallel, but what you’re seeing is perspective. It’s exactly the same as a pair of railroad tracks appearing to converge in the distance at what’s called the vanishing point.

For all intents and purposes, the Sun is infinitely far away in this picture; the photo only covers a few hundred kilometers (at most) left to right, but the Sun is 150 million kilometers away. That means the direction to the Sun is the same for any cloud in this shot (I’m ignoring the curvature of the Earth, which isn’t important), and in turn that means their shadows are parallel. But Parmitano was shooting at a slight angle, pointing his camera toward the Sun a bit and not straight down. That adds perspective to the shot, like looking along railroad tracks as they go off in the distance. And that’s why the shadows don’t look parallel, even when they are.

I don’t think we have to worry about the new Space Station crew not holding on to the long tradition of tweeting beautiful views from space. And just to drive that point literally home, American astronaut Karen Nyberg tweeted this the other day:

Sunset from space
Not bad for a first-timer.

Photo by NASA

Her caption? Simply, “Sunset.” It was the first picture she took from her new home. I think Expedition 36 is going to work out just fine.

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