While driving, I noticed the sky had weird rays that appeared converge at some point on the horizon. I took a few pictures in hopes I could figure out what they were. There was a storm coming from the other direction if that's relevant information.

large image small images

They don't show up quite as well on the pictures, but they were definitely visible in real-life so not an artifact from the camera or anything.

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    $\begingroup$ Naive question: Did the point that they converged at happen to be in the direction of the sun, by any chance? $\endgroup$
    – Philip
    Commented Aug 17, 2020 at 16:12
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    $\begingroup$ was that different direction 180 degrees opposite? $\endgroup$
    – JEB
    Commented Aug 17, 2020 at 20:19
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    $\begingroup$ @DavidZ Physics is the science of identifying things. Nobel prizes have been awarded for "identifying things", like radiation, argon, the neutron, the CMB, and many others (dark matter someday?). I think this is a great question which is helping make physics accessible to non-physicists, and it's a real shame that this SE is so closed-minded about what is and what is not physics. $\endgroup$
    – Yly
    Commented Aug 18, 2020 at 1:24
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    $\begingroup$ @DavidZ Literally the first bullet in the help center is "Explanations of observed physical or astronomical phenomena" which is exactly what is being asked. $\endgroup$ Commented Aug 18, 2020 at 14:45
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    $\begingroup$ @DavidStarkey It's important to include time-of-day, season, sun position, latitude in the question. In this case, not all matter, but we don't know that a priori. Had it been the zodiacal light, then spring/fall dusk/dawn northern/southern hemisphere all matter, for example. $\endgroup$
    – JEB
    Commented Aug 18, 2020 at 17:02

1 Answer 1


Those are definitely anticrepuscular rays. The Sun was in the antipodes of the point of convergence of those rays in the sky, when you took that image. Here you have a similar observation:

enter image description here

These are formed just like crepuscular rays; clouds in the direction of the Sun project parallel shadows that cross the entire sky over your head into the opposite direction where the Sun was setting. You see them converging instead of being parallel because of the spherical projection of your spherical field of view (you can reinterpret this as the shadows are closer when they go over your head and are farther from you at the horizon so that rays that are parallel seem to converge at some point at infinity).

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    $\begingroup$ I wouldn't mix spherical projection into this discussion: the convergence of the rays happens even in the simple perspective projection, which is demonstrated by the photos on this page. $\endgroup$
    – Ruslan
    Commented Aug 19, 2020 at 10:02

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