The apparent size of the Sun in our sky remains relatively constant throughout the day and the year, and it appears as a nearly constant, familiar size. There are a few key reasons why we don’t see the Sun as getting bigger or smaller in the sky:
- Vast Distance: The Sun is incredibly far from Earth, located at an average distance of about 93 million miles (150 million kilometers). Due to this great distance, even though the Sun is much larger than Earth, it appears relatively small in our sky.
- Emission of Light: The Sun emits an enormous amount of light, which travels in all directions from its surface. This light spreads out as it moves away from the Sun, creating a sphere of light known as the “solar disk.” As this light reaches Earth, it appears as a nearly constant-size circle in our sky.
- Angular Size: The apparent size of an object in the sky is determined by its angular size, which is the angle it subtends as observed from a specific location. While the Sun’s actual size is quite large, its small angular size when viewed from Earth is what makes it appear roughly the same size in our sky.
- Earth’s Orbit: Earth orbits the Sun in an elliptical (oval-shaped) path. This means that the distance between Earth and the Sun varies slightly throughout the year. However, this variation is relatively small compared to the vast distance between the two, so the change in the apparent size of the Sun in our sky is minimal.
In summary, the Sun’s immense distance from Earth and the resulting small angular size are the primary reasons why it appears as a consistent, familiar size in our sky. While it may vary slightly due to Earth’s elliptical orbit, these variations are not significant enough for us to perceive a substantial change in the Sun’s size.