Weather Whys; Stars

This is weather wise. When you look into the night sky at the twinkling stars above, you may not realize the atmosphere is playing a slight trick, because those stars may not be located exactly where they appear to be. The effects of the Earth's atmosphere not only cause that illusion, but also give the stars their twinkling appearance. The reason stars may not appear to be in their actual locations can be illustrated in a rather simple manner. If you see a fish in the water, its actual position isn't quite where it appears to be. That's because the light rays which are reflected off the fish undergo a process called refraction, as they leave the water. Refraction means the light is bent slightly as it passes through materials of different densities like water and air. That's similar to what happens when starlight enters the atmosphere. The starlight is refracted as it passes through air of different densities, so the star appears to be in a different place, just like the fish in the water.

And it appears to twinkle for another reason. The air is composed of trillions upon trillions of molecules, which are in constant motion. And because of that, the density of air in a very small region is always changing. So the path the light takes through the atmosphere changes a little bit too. And that tiny amount of change is enough to cause the twinkling effect. Whether wise is produced with the assistance of the National Weather Service Forecast Office and the National Severe Storms Laboratory, both in Norman, Oklahoma, and the Cooperative Institute for Mesoscale Meteorological Studies, the Oklahoma Climateological Survey, and the School of Meteorology, all at the University of Oklahoma. The writer is Christine Harbour, our editor is Brian Walkie, and our executive producer is Karen Hope. Whether wise is made possible by a grant from the National Science Foundation. Or whether wise, I'm Drew Barlow.