Ever seen anything like this before?
Alan Montgomery of Huntsville had never seen it before either. He writes:
“I came out of Walmart on south Parkway last night around 6:25/6:30 and was surprised to see the sky was sharply split between two shade of blue. I’ve never seen anything like it. Took several images both to the East toward Green Mountain and to the West toward RSA.
None of these images have been retouched. These are as they came out of my iPhone. Totally unable to explain the aberration.”
This is a cloud shadow cast across the sky from one end to the other. At the time Alan took these photos, there was a large area of showers and storms ranging from 30 to 60 miles northwest of Huntsville in Limestone, Lauderdale and Lawrence Counties.
Those storms blocked out a large part of the sun’s light at sunset, but since the sky wasn’t completely overcast, the remainder of the ‘full’ light at sunset was still visible over the unblocked part of the sky: all the way from the western horizon to the eastern horizon.
We’re able to see about 6 miles of sky from horizon to horizon (from ground level), so what Alan saw there was a thunderstorm’s shadow visible across that entire distance!
Don’t believe that?
This is what it looks like from above when that happens as the International Space Station orbited above the North Pacific Ocean (latitude 14.3, longitude -102.4) on 19 May 2011 at 12:20:26 GMT. (7:20:26 AM CDT)
Those shadows happen more often than you would think (as do crepuscular and anticrepuscular rays).
It’s the same ‘shadow,’ by the way, you just see the part of the shadow on the sun’s side of the sky more often than the fainter, less contrasted view on the opposite side.
The above photo from the International Space Station is a great example of how light travels in a straight line (physics experts just heard nails on a chalkboard). Light is both a particle and a wave, and as long as there is nothing blocking it, that wave will travel in a straight line. Yes, it’s true that light also scatters when it hits something (that’s why we’re actually able to see anything at all), and it can be bent by gravity, refracted in water or a pane of glass, etc.; however, in general it can be understood that light follows a straight line pattern. That’s why we get straight shadows like those seen here. (Straight is in the eye of the beholder, by the way.)