shadows in the air and on haze layers. The cloud casts its
shadow more strongly onto lower layers of haze or cloud which then
appear dark to an observer beneath them. The sun's rays (yellow)
always shine downwards. The top edge of the cloud is in direction "c".
The top of the shadow on the uppermost layer is in direction "b" which
to the 'eye' looks higher in the sky than the cloud top. The diagram
at left shows the appearance from the 'eye'. A shadow is also cast
onto the lower haze level and the edge of this is in direction "a"
which appears to be even higher in the sky. The crepuscular rays appear,
by perspective, to fan out from the position of the sun but in fact
they are all parallel irregularities at the edges of the cloud's shadow