Weather 101: Why is the Sky Blue? - Tucson News Now

In this edition of Weather 101, we explore the reason behind our blue sky.

Every color of light has a different wavelength.  Wavelength is the distance between peaks of the light's wave.  Think of light traveling along just like an ocean wave.  The wavelength is the distance between the tops of the waves.

On the rainbow, the inside color, violet, has the shortest wavelength.  The outside color, red, has the longest wavelength.

Blue's wavelength is somewhere in the middle.

It just so happens that the size of gas molecules in our air are just the right size to interrupt the blue's wave pattern.  They interfere with light that has a wavelength like blue's wavelength.

The molecules, therefore, scatter out the blue from the rest of the colors.  While the other colors pass right through the atmosphere, blue is captured and re-emitted in all directions by things in the air around us.

That's what makes the sky blue!