* Atmospheric Refraction: Light bends as it passes through different densities of air. The atmosphere is denser near the Earth's surface and thinner higher up. When the sun is low on the horizon, its light travels through a longer path of denser air before reaching our eyes. This bending of light makes the sun appear more elongated, giving the impression of being flattened.
* Perspective: Our brains interpret the shape of objects based on their position relative to the horizon. When the sun is low, it's near the edges of our field of vision. This can make it appear wider than it actually is, further contributing to the illusion of flattening.
* Size Constancy: Our brains try to maintain a constant perceived size of objects even when they are at different distances. The sun appears smaller at the horizon due to its greater distance, but our brains try to compensate for this by making it appear wider.
In reality, the sun is a sphere and doesn't change shape. The flattened appearance is simply an illusion created by the way light interacts with our atmosphere and the way our brains process visual information.
