Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air.
All light travels in a straight line unless something gets in the way and does one of these things:—
- reflect it (like a mirror)
- bend it (like a prism)
- or scatter it (like molecules of the gases in the atmosphere)
Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.