River in the Sky Yesterday, I saw a most curious bright streak in the sky which, at first, I could not explain. It looked like an anti-crepuscular ray, but it was curved and going the wrong way (not towards the antisolar point). Then I realized that it was a reflection of the river Rhine on which the very low sun was shining. The Rhine, at that moment, was flat like a mirror. Usually there are little ripples which scatter reflections. So we literally see the shape of the Rhine projected on to the underside of the stratocumulus clouds. A rare event. We need bright sun on the river but thick cloud away from the sun to show the reflection. The sun must be low. Water and all surfaces other than metals reflect best when light glances across at a low angle. The river must be mirror smooth. No wind, ducks, swans or boat wakes. Another of Juerg Aleanís river scenes.?Anticrepuscular rays produced by rain shadowing converge on the antisolar point.