Hi Roger: Sounds like you have done a great deal of work preparing your paper on the Chichen-Itza pyrimid shadows. I look forward to your presentation. Since the shadow phenomenon at equnox is well known, I wonder if somebody else besides yourself has investigated the math behind it. It would be interesting to compare your results with others.
Building sand castles of pyramids may seem unrelated to their design, but maybe not. I saw a progaram on the history of pyramid building in Egypt, and it said that the slope of some of the earliest ones was so steep as to make them unstable. Later pyramids used lower angled slopes. In college I took a soil science course in which we discussed slumping of different types of soil. To illustrate, if you take a bucket of sand and dump it on the ground, it will form a cone-shaped pile with a particular slope. Sands have a lower slope angle than clays. If you think about it, a pile of sand has about the same slope as the Chitzen-Itza pyramid. Therefore, it could be possible that the slope angle of the pyrimid, with steps (like the terraces used by farmers on steep slopes) was determined by an effort to make a stong, errosion resistant structure rather than by solar angles. Just a thought, John C. >
