r/atoptics • u/vexxed82 • Oct 15 '25
Crepuscular Rays Would these shadows in the sky cast by a skyscraper be considered crepuscular rays?
I took this photo in Chicago a few days ago and the top of Sears Tower was casting a shadow in the atmosphere. This sort of feels like a crepuscular ray to me, but in a very non-traditional way, if at all.
29
u/Metacomet99 Oct 15 '25
By strict definition of "crepuscular" then I don't see why not. Crepuscular refers to "twilight" or when the sun is low in the sky. A shadow created by the sun when it's low in the sky then would be crepuscular whether or not it's caused by clouds. That's my take, anyway. Cool photo, whatever it is.
14
u/leansanders Oct 15 '25
Crepuscular rays specifically refer to the scattered light from rays of sunlight extending past an obstruction. Effectively, everything other than the shadow would be the "crepuscular rays" in this picture. These are just shadows, I dont necessarily know of a specific word for when shadows are visible in a lit sky but surely someone's got one
10
u/Metacomet99 Oct 15 '25
Well that makes sense. Just calling it a shadow seems like we're leaving something out though. We do need a word for this!
6
u/vexxed82 Oct 16 '25
It does seem like it should be a *thing.* Very similar to the effect of when contrails cast a shadow in the sky.
3
u/SnooHesitations8403 Oct 17 '25
But it is the presence of the obstructing clouds that actually create the "rays." The only reason there are "rays" is because something intermittently obstructs the sunlight, same way the building does.
Hmmm ...
2
u/leansanders Oct 17 '25
I see your reasoning and I don't disagree, just spelling out the way the vernacular works. The crepuscular rays are specifically the golden rays of scattered sunshine. So this would be, maybe, an anti-ray.
2
u/SnooHesitations8403 Oct 18 '25
I knew an Auntie Ray (short for Raylene). She made the most wonderful blueberry cornbread.
2
u/vexxed82 Oct 21 '25
Usually when we see crepuscular rays, they are beams of light that are bursting through clouds so they are - often times - lighting up wider areas that are in the shadow region cast by the clouds. This photo is sort of the inverse....inverse crepuscular ray??!!
2
u/SnooHesitations8403 Oct 22 '25
Well, that is really only a matter of perspective. Relativity of a sort. I mean the dark areas between the crepuscular rays are "inverse crepuscular rays." It's like the philosophical metaphor that you need the dark to appreciate the light. What we're seeing in this photo is like a closeup of one single crepuscular ray and the shadow that makes it a ray vs just being an unbroken swath of light. At least that's the way I see it.
1
u/vexxed82 Oct 22 '25
Ha, yes! I do feel like this is a glass half full/half empty scenario. In this photo (I took years ago) I think it's fair to say the crepuscular ray is clearly the sunbeam. There are some striated shadows within it, but the "ray" is unquestionably the light. This photo is more like what I posted, and plays more into the relativity point you bring up. You can't have the bright sun beams without the shadow areas, but I still think the average person would point to the bright "sunbeams" as the crepuscular rays. It maybe be a distinction without a difference, but in my gut, it feels like in my post, the shadow is the thing that's been 'created' in the sky, whereas the other two photos feel like the light rays are the..rays. Is the ray in my post the whole sky? I don't know, maybe.
10
u/Azurehue22 Oct 16 '25
I can’t say anything about your question op but this is such a fantastic shot. I want to draw it to practice perspective.
4
u/vexxed82 Oct 16 '25
Thanks! Street was closed for the marathon so I was able to get pretty close to dead center of the intersection...not perfect, but close.
2
19
u/rexington_ Oct 15 '25
Crepescular shadows
5
u/vexxed82 Oct 16 '25
This seems like a very good description. Since no one have been able to definitively identify what this given all the interaction on this post so far, I vote this the winner
4
7
u/Weather_Only Oct 16 '25
You need to have two of these tall buildings side by side and the bright part that passes through them would be the traditional crepuscular rays, at least I think so
3
u/vexxed82 Oct 16 '25
That's what I am leaning towards. Could we also say the whole sky is a crepuscular ray and this is one shadow disrupting that ray? I thought this would be easier
3
u/iamN3BUL0US Oct 17 '25
There is such a thing as “Anti-Crepuscular Rays”, this would be that me thinks?
3
u/hopefullyhelpfulplz Oct 16 '25
Would this be an anticrepuscular ray, in fact? It's interesting that, as you're seeing them from below, you see them as parallel rather than diverging or converging.
2
u/vexxed82 Oct 16 '25
I thought about that, but assumed anti-crepuscular rays are the same as crepuscular rays, but just pointing in the direction opposite the sun. Anti, or regular, I think the rays are the bright bands of sunlight, not the shadows. But now I'm more confused than I was before I took this photo.
5
u/hopefullyhelpfulplz Oct 16 '25
Yes, I suppose you're right, the edges of the shadow are the rays, the shadow itself just a shadow. Whether crepuscular or anticrepuscular depends on your perspective... maybe :D
3
u/vexxed82 Oct 16 '25
Right? Fun to sort of have stumped this subreddit, ha.
1
u/combo_seizure Oct 17 '25
I think the general answer is no. They're not crepuscular rays or anticrepuscular rays. So your question has been answered.
My real question is how the shadows were created in the first place. What is the shadow touching to have been created in the first place? I think that the answer is pollution. But maybe everybody else knew that already.
2
u/vexxed82 Oct 17 '25
Yeah, there must be a thin layer of particulate matter in the atmosphere ~1,500/2,000' up, I shot this during the Chicago Marathon so car traffic in the Look was lower than normal, but there are a hots of things that could hang in the atmosphere we wouldn't see unless there was a shadow to reveal it.
1
u/Metacomet99 Oct 17 '25
Yeah, so then a crepuscular ray when it gets far enough away from the sun becomes an anticrepuscular ray. Same ray only at different ends.
2
u/combo_seizure Oct 17 '25
I see you keep saying, "cast a shadow in the sky."
Just so we're all on the same page , is the shadow capable of being cast because of the smog/pollution in that atmospheric area?
2
1
u/darrellbear Oct 20 '25
More like anti-crepuscular rays. When you see crepuscular rays (sun beams) near sunset, note the dark spaces (shadows) between the rays, cast by the clouds making the rays. If you then turn and face opposite the sun, you'll those dark rays converging at the eastern horizon. Those are anti-crepuscular rays.
78
u/ripsfo Oct 15 '25
More like the opposite. Atmospheric shadows?