Why is the sky blue and sunsets often appear red?

The sky is blue because light from the sun travels through the air, and some parts of that light get scattered by tiny particles in the air.

Imagine you're playing with a big box of colorful marbles, red, yellow, blue, green. When you shake the box, the smaller marbles (like the blue ones) bounce around more easily than the bigger ones (like the red ones). That’s like what happens to light when it goes through the air.

Light from the sun is made up of many colors. When this light hits the air, the blue part bounces off the tiny particles in the air more than the other colors do. So we see blue all around us, that’s why the sky looks blue.

At sunset, the sun is lower in the sky, so its light has to travel through more air before it reaches you. That means most of the blue light gets scattered away. What's left is mostly red, orange, and yellow, like when you mix marbles and only the bigger ones remain. So the sun looks red or orange, and the sky turns warm colors too.