Why is the sky blue?
Light from the Sun looks white, but it’s actually a mix of many colors. When sunlight reaches Earth's atmosphere, it collides with air molecules and tiny particles in the air.
- Blue light scatters the most: Blue light has a shorter wavelength, so it bounces off in many directions as it hits particles in the air.
- We see the scattered blue light: Because blue light is sent in many directions, our eyes pick up blue from everywhere you look, making the sky look blue most of the day.
So the sky isn’t blue because there is a blue color only in the air—it’s blue because blue light gets scattered around more than other colors.
Why not violet?
- Violet light is also scattered, but the Sun gives off less violet light, and the upper atmosphere absorbs some of it. Our eyes are also more sensitive to blue than to violet.
What about sunrises and sunsets?
- When the Sun is low, its light travels through more air. Blue light gets scattered out of our line of sight, so the remaining light is redder, giving sunrise and sunset colors like red, orange, and pink.
Quick analogy: think of the air as a crowded room. Blue light gets bumped around (scattered) a lot and comes to you from many directions, while red light travels straight through more easily.