Sun-Earth Geometry

Just like navigation for a naval ship or airplane, we observe that time and space relations are linked together, and can be represented and communicated as geographic information. In this chapter we describe how to manipulate that geographic information in terms of angles, and use key relations from spherical trigonometry to make time and space relations easy to calculate with a computer. For our purposes: angles are coordinates in space and time. We describe the spatial and temporal relationships of the Sun relative to the Earth and for an Observer on the surface of Earth relative to the Sun at any given time. These angular relationships are then used to describe in detail the relative orientation of a Solar Energy Conversion System (SECS) surface relative to the moving Sun, while identifying the times that local shadows might obscure our SECS.