Why Is the Sky Blue?

On a sunny day, the sky above us is a clear, bright blue. Have you ever wondered why it is blue and not white or green? The answer is in the light that comes from the sun.

Sunlight looks white, but it is really a mix of all the colors of the rainbow. You can see these colors in a rainbow after the rain. Each color travels as a wave, and blue waves are shorter than red waves. When sunlight enters the air, it hits tiny pieces of gas called molecules.

These molecules scatter blue light much more than red light. To scatter means to send something in many different directions. So blue light comes to our eyes from every part of the sky. Violet light is scattered even more, but our eyes see blue more easily.

At sunset, the sun is low, and its light passes through much more air. On this long trip, most of the blue light is scattered away. Mostly red and orange light reaches us, so the evening sky glows with warm colors. Next time you watch an orange sunset, you will know the reason.