Question

Sun (or moon), when near the horizon, appears elliptical and not circular. Explain why?

Answer 1

At the time of sunrise or sunset, the sun is positioned just above the horizon. The lower edge of the sun is closer to the horizon compared to the upper edge. Due to this difference in position, the light rays coming from the lower edge of the sun undergo slightly more atmospheric refraction than those emanating from the upper edge. This causes the lower edge to appear lifted higher than the upper edge. As a result, the vertical diameter of the sun seems to decrease while its horizontal diameter remains unchanged, leading to the sun appearing elliptical rather than circular when near the horizon.