The Sun appears red primarily because of a phenomenon called Rayleigh scattering. When the Sun is low on the horizon during sunrise or sunset, its light has to travel through a thicker layer of Earth's atmosphere. The atmosphere scatters shorter wavelengths of light (like blue and violet) more strongly, while the longer wavelengths (like red and orange) pass through more easily. This scattering removes much of the blue light from the direct path to the observer, so the Sun looks red or orange.
Why the Sun Looks Red
- Sunlight contains all colors, but as it travels through the atmosphere, shorter wavelengths (blue, violet) scatter out more than longer wavelengths (red, orange).
- When the Sun is near the horizon, sunlight travels a longer path through the atmosphere, increasing the scattering of blue light and leaving mostly red and orange light to reach the eye.
- This is why the Sun at midday appears yellowish (less atmosphere) but during sunrise or sunset looks red or orange.
Additional Factors
- The density and composition of the atmosphere affect this effect. More particles like dust or smoke enhance the scattering of blue light, making sunsets and sunrises even redder.
- This scattering effect is named after Lord Rayleigh, who explained why the sky is blue during the day and why the Sun changes color at dawn and dusk.
This explanation applies to the color of the Sun as seen from Earth because of the atmosphere's unique scattering properties, not changes in the Sun itself.
