Here's why:
* Atmospheric Refraction: As sunlight passes through the atmosphere, it is bent or refracted. This bending is more pronounced when the sun is low on the horizon, as the light has to travel through a greater thickness of air.
* Elongation: This refraction causes the sun to appear flattened or oval-shaped, especially near the horizon. The lower part of the sun is refracted more than the upper part, making it appear elongated.
* Noon: When the sun is directly overhead at noon, the light travels through a relatively short path in the atmosphere, minimizing the refraction effect. This results in the sun appearing more circular.
In summary: The sun's apparent shape at sunrise and sunset is an optical illusion due to atmospheric refraction, not an actual change in its shape.
