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SYFY WIRE Bad Astronomy

A ray of coincidence

By Phil Plait

I love a good coincidence!

Yesterday, I posted this for the daily #BAFact:

It says, "#BAFact: Face east just after sunset. That dark band across the horizon? The Earth's shadow on the sky." It also has a link to an article I wrote that mentions this shadow of the Earth on the sky. It's called the Belt of Venus, and I wrote a somewhat longer explanation on my Google+ page.

So last night, the same day I posted that, I'm coming home from shopping. My wife is driving, and I glance out my window, to the east. Guess what I saw?

Yup. I snapped this with my phone (which is why the foreground is motion blurred). That dark band on the horizon is the shadow of the Earth itself being cast on the sky. Well, technically, cast on junk in the sky like haze. Also, technically, those are the shadows of the Rocky Mountains to our west, but they still count as being the Earth.

Also, there were clouds that night to the west also casting shadows and letting rays of light through. Those are called crepuscular rays - one of my all-time favorite terms. They can actually stretch all the way across the sky and reach the horizon again. A funny thing: those rays are parallel! Perspective makes them appear to diverge away from the sunset, like railroad tracks appear to converge in the distance. But they also reconverge on the point on the horizon directly opposite the Sun. That's what you're seeing here; the brightest one is coming down from the upper left.

Even better: tomorrow I'm heading out to Comic Con, where I will see my pal Gail Simone. She's a comic book creator, one of the best. She likes putting scientific and skeptical quotes in her books, and in 2007 she quoted me... about crepuscular rays!

COINCIDENCE??? Well, yeah.

You may take this as a giant reminder: always keep perspective on coincidence. It's like a ray of hope.

Related Posts:

- Crepuscular rays are parallel!
- BAFacts archive
- Time lapse: Crater Lake
- My comic book premier

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