Perspective: When the sun is higher in the sky, it appears to be larger because it is closer to the horizon. This is due to the fact that the Earth is curved, so the sun appears to be smaller as it gets higher in the sky.
Atmospheric scattering: The Earth's atmosphere scatters sunlight in all directions, which can make the sun appear to be smaller. The amount of scattering depends on the wavelength of light, which is why the sun can appear to be different colors at different times of day.
Clouds: Clouds can also make the sun appear to be smaller, as they can block out direct sunlight.
It's important to note that the sun's actual size does not change, but it can appear to be smaller or larger depending on the time of day, the weather conditions, and the observer's location.
