I am entering the world of making flat earth debunking videos on YouTube. I would like to focus on the concept of shadows ascending up a mountain at sunset. I plan to make a few table top demonstrations showing that as long as a light source is higher in elevation than an object, that object cannot cast a shadow whose vertical height exceeds its own. I will then show that when we lower the light below the height of the object, the shadow can then cast upward due to the negative angle of the light. The culmination of my video will be this time lapse of Mount Everest: https://www.istockphoto.com/my/video/mt-everest-at-sunset-gm539252432-98158951 Since nothing is taller or equal height to Everest, the ascending shadow must be caused by curvature. That is the gist of it. However, I am also interested in demonstrating that the vertical speed of the shadow ascent up the mountain (feet or meters per minute) is consistent with a 15 degree per hour sun movement. Is there any way I can correlate that? I am guessing there would be enough topography data for me to call out specific elevation points in the video. Just not sure how I would calculate this speed, if it is even calculable.