Our brains are wired to believe that light generally comes from above. This makes sense–here on Earth, light from the sun pretty much always is coming from either directly above us, or above us at an angle. This is such a persistent phenomenon that we use it to determine the shape of objects. If an object has a shadow beneath it, we assume it is convex, whereas if it has a shadow above it, we assume it is concave. This, as explained in this MinutePhysics video, is why we struggle to discern whether a formation is a mountain or a valley when a photo is taken from far away, like space… More at PM.
Something to ponder on a lazy Sunday.