Liang stands on a cliff facing the sea with Sanaa standing directly behind him at a lower elevation. They are both observing a boat sail parallel to the coast. Can Liang and Sanaa see the same side of the boat's sail, and if so, how is it possible? Respond very briefly.
Liang and Sanaa can indeed see the same side of the boat's sail because the perspective from each person's view does not prevent visibility of the sail's side. Being at a higher elevation, Liang looks down at the boat and can clearly see the side of the sail facing them. Sanaa, even though at a lower elevation and behind Liang, can see the boat's sail because the difference in elevation between her and Liang allows her to look over or beside Liang without her view being completely obstructed. Furthermore, the sail being a vertical surface means it's visible from multiple angles horizontally. The fact that they are both facing the sea and the boat is sailing parallel to the coast suggests that the side of the sail facing the coast is the same side visible to both Liang and Sanaa.