Today at the time of sunset I saw this The sky is divided into two parts one In red and one in blue which are very distinctive Can anyone tell how? The upper part of the image points towards the East and the lower part west
The blue portion of the sky could be that way due to some far object shadowing it.
This picture gives an example of what I am saying.
It could be a mountain high enough to cast its shadow over an upper layer of very homogeneous clouds or simple humid air. The darker clouds in the bottom of the picture are completely overshadowed since they are not high enough in the sky to be hit by the sunset light.