Sunlight is very intense. It can cause glare to appear around the sun, and as a result, the sun can appear larger than its actual size. To observe the sun’s actual size, we need to eliminate the glare by reducing the camera’s exposure or using a solar filter.
During sunset, sunlight gradually becomes less intense, and sun glare gradually becomes smaller. If the glare is not eliminated, the sun can appear as if it is shrinking, and flat-Earthers incorrectly use it as “evidence” that the sun is moving away from us.
Sun glare is caused by the scattering of sunlight in the atmosphere. And internal reflections in the optical system can also cause it.
The intensity of sun glare is less than the strength of the light coming directly from the Sun, but it is still too bright for our eyes to distinguish it from the sun itself. It is the reason the Sun and its glare appear as a single bright object.
To observe the Sun without its glare, we have to reduce the exposure by using the in-camera exposure settings or using a solar filter. By eliminating the glare, we can observe that the sun’s size remains constant throughout the day.
Reference
- Glare (vision) – Wikipedia
- Sun apparently shrinking as it sets – Metabunk