Along about sunset one day I looked around for some clouds to photograph, in case the light happened to be good. I found this 'Sierra Wave' right over my head. I had to jump into my pickup and race north. I got there just in time to get this one shot. Then the light was gone. If you look at the clouds way off in the distance you can see how the bottom is dark and the top still has light. That dark part is the shadow of the Earth.