A ray of coincidence

By Phil Plait | July 11, 2012 2:32 pm

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

CATEGORIZED UNDER: Cool stuff, Pretty pictures, Science

Comments (15)

  1. I posted a photo from my camera phone of this phenomena a couple of years ago.


    I have better pics taken with my DLSR. Have to dig some of them up sometime.

  2. Lab Rat Jason

    Technically, those rays aren’t exactly paralell, they are slightly convergent, and slightly divergent. (the sun is bigger than the earth)… but due to rounding errors they appear paralell. :)

  3. Chris A.

    Technically, Phil, they are only crepuscular rays when they converge on the sun. When they converge on the anti-solar point (as they do here), they are “anticrepuscular rays,” (one of MY all-time favorite terms!).

  4. RAF

    Thanks Phil…I did not know that…

    Now if I just had a clear view of the horizon to the east…DOH!

  5. Valdis Kletnieks

    “anti-crepuscular” is one of those words that looks quite cromulent, but isn’t. :)

  6. Kurt Erlenbach

    And of course, there’s also Crepuscule With Nellie by John Coltrane and the Thelonius Monk Quartet, a classic if there ever was one.

  7. Hedin

    And im watching the shadow of the earth, on the eastern horizon, here in Calgary as i write this :)

  8. Messier Tidy Upper

    @5. Valdis Kletnieks : It isn’t? (Puzzled)

    Beach walk today with the dogs early morning – spectacular sky with anti-crepuscular rays visible in the sky and a greenish haze layer on the horizon. Few hours after sunrise locally, anyone know what causes that effect? Vaguely sunrise-y like greenish colouration in a band few degrees above looking out to sea, flat calm conditions, FWIW.

    (Then anyhow, just had an extreme thunderstorm warning for my Adelaide hills region conveyed online for now~ish!)


  10. Atmospheric Nitpicker

    To be precise, the shadow of the Earth is just called the shadow of the Earth. The pinkish band (upper bit of the shadow) is the antitwilight arch, or the Belt of Venus. :)

  11. ceramicfundamentalist

    was out last evening to watch the sun set and look at sunspots and this exact thing happened – crepuscular rays in the west and the shadow of the earth in the east. coincidence???

  12. F16 guy

    What kind of man lets the wife drive ?

    LOL !!

  13. Ilkka

    Technically you can see the shadow of the Earth if you look into a mirror, outside, at night. :-)

  14. Some anticrepuscular rays I saw in South Africa a couple of years back. It’s taken from 3 photos at different exposures which is why the shadow of myself looks a little artificial. There is no additional photoshopping done though: http://www.flickr.com/photos/jonstraveladventures/4616150389/

  15. Matt B.

    @8 MTU – From what I can tell, “cromulent” means “accepted as correct, despite actually being improper” (like the pronunciation of “ornery” as /awn-ree/). So “anti-crepuscular” isn’t cromulent because it’s a correctly formed word.


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