palmbird ·
The sky appears blue due to a phenomenon called **Rayleigh scattering**. Here's a simplified explanation:
palmbird ·
1. **Light from the Sun**: The Sun emits light containing all colors of the visible spectrum, essentially white light.
palmbird ·
2. **Scattering by Molecules**: As this light enters the Earth's atmosphere, it interacts with molecules like nitrogen and oxygen. These molecules scatter the shorter, blue wavelengths more than the longer, red wavelengths. This is because the intensity of light scattered by small particles (like air molecules) is inversely proportional to the fourth power of the wavelength (Rayleigh's formula).
palmbird ·
3. **Scattered Light**: When sunlight strikes air molecules, the blue light is scattered in all directions more effectively than other colors.
palmbird ·
4. **Viewing from the Surface**: To an observer on Earth, light from any direction away from the direct rays of the sun will look predominantly blue because this scattered light reaches your eyes from all around.
palmbird ·
- **Why not at sunset/sunrise?** At sunset or sunrise, when the sun is low on the horizon, the light passes through a greater thickness of Earth's atmosphere, which scatters blue light so much that it's hardly visible from the observer's direction, allowing more reds and oranges to be seen.
palmbird ·
- **At high altitudes**: Pilots and astronauts have reported that the sky can appear almost black due to minimal atmosphere above them to scatter the light.
palmbird ·
In summary, the blue sky is a result of sunlight interacting with our atmosphere, where blue light gets scattered much more than other colors, filling our field of vision with blue.