How it works
The remaining direct light is weighted toward longer wavelengths. Dust, smoke, moisture, clouds, and pollution can intensify or dull the display.
What people often miss
The Sun itself has not changed color. The effect depends on the path through the atmosphere and where scattered light reaches the observer.
Why this question comes up
A low Sun makes the same scattering process that colors the daytime sky easier to see.
Key points
- Sunsets look red and orange because sunlight travels through more atmosphere near the horizon, scattering much of the shorter blue light out of the direct path.
- The remaining direct light is weighted toward longer wavelengths. Dust, smoke, moisture, clouds, and pollution can intensify or dull the display.
- The Sun itself has not changed color. The effect depends on the path through the atmosphere and where scattered light reaches the observer.
Bottom line
Sunsets look red and orange because sunlight travels through more atmosphere near the horizon, scattering much of the shorter blue light out of the direct path.
Source and verification
This Answer was checked against NOAA SciJinks. Follow the source for the full official explanation and any later updates.