Weather Whys; Sky Color

This is Weatherwise. Throughout the ages, parents have endured many questions from their inquisitive offspring about the world in general. One of those is the ever-popular Mommy Why is the sky blue? Well, from Mommy's and Daddy's everywhere, the short answer is, Rayleigh scattering. But the next question is likely to be, what's that? Well, Rayleigh scattering is simply the light from the sun being scattered at different wavelengths to produce the color. If your children need more of an explanation, try this. When sunlight passes through a prism, you can see that it separates into bands of colored light. There's a red band, an orange one, a yellow, a green, a blue, and finally a violet band. All of those colors are present in sunlight, but when they're combined, the color they create is a brilliant white. The colors each represent a different wavelength of light, with the red being the longest wavelength and violet being the shortest. When sunlight comes into the atmosphere, air molecules tend to scatter at somewhat,

with the shorter wavelength bands being scattered the most. That's the violet, blue, and green bands. When you look up into the sky, those scattered light waves are what reach your eye. They make the sky appear blue. But because many of those shorter wavelength bands are lost in that scattering process, the sunlight that makes it through has a yellow orange cast. Now if your children are really the curious type, you might go on to explain why, on hazy days, the sky appears more white. That's because on those days, there are tiny particles suspended in the atmosphere, which can scatter all wavelengths of light to about the same degree. So the scattered light is a combination of all the visible wavelengths, just like the white sunlight. Weather-wise is produced by KGOU radio at the University of Oklahoma in cooperation with the School of Meteorology and the Center for Analysis and Prediction of Storms. For Weather-wise, I'm Drew Barlow.