* Atmospheric Refraction: The Earth's atmosphere acts like a giant lens. As sunlight passes through the atmosphere, it bends or refracts. When the sun is near the horizon, the light has to travel through a thicker layer of air. This bending makes the sun appear higher than it actually is.
* Perspective: When the sun is low on the horizon, our brains compare its size to objects on the ground, like trees or buildings. This makes the sun appear larger in comparison.
In reality, the sun's size remains constant. The illusion of the sun being larger at sunrise and sunset is a neat trick of our atmosphere and how our brains perceive the world.
