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I would imagine that during a sunset, for a brief moment of time, there would be a shadow of the earth seen in the clouds but I have never seen this. Why does it not happen?

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    $\begingroup$ During sunsets you sometimes see nearby clouds lit from underneath, whereas distant clouds are darker. Isn't this the effect you're looking for? $\endgroup$ – pela Aug 5 '18 at 7:42
  • $\begingroup$ Depends if that is just night, or a shadow from the earth obstructing the light that is sent from the sun towards the clouds. Night is more like when the sun goes out of view and everything is slowly darker, but there is no immediate "shadow" once the sun sets down. $\endgroup$ – Orangeball3 Aug 5 '18 at 16:29
  • $\begingroup$ A few minutes after sunset, a bluish gray band of sky grows upward from the opposite horizon as that part of the atmosphere passes into shadow. $\endgroup$ – Mike G Aug 5 '18 at 18:37
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    $\begingroup$ skyandtelescope.com/astronomy-news/observing-news/… $\endgroup$ – userLTK Aug 6 '18 at 3:42
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To have a sharp shadow, you need a point source of light. But the Sun is extended enough that it does not set all at once, so there is not a sharp shadow. Also, there is refraction of the redder light, so instead of seeing a shadow, you'd see reddish clouds-- which I wager you see quite often (though much of that effect is from the way the atmosphere scatters away the blue light-- those effects are hard to disentangle but you know refraction matters because you see how the Sun's shape is distorted upon setting).

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