Cosmic Rays and Particles

Over the last month, those of you living in the West have been able to observe how particles in the air can change how cosmic rays are viewed by our eyes.  This last weekend in Portland, OR, the smoke from the wildfires in the region were blown in and focused the Willamette Valley, causing unhealthy air conditions (151-200 Air Quality Index).  The morning sun was red and throughout the day, the clouds and sun looked orange.

That is because the radiation from our sun that we see as red and orange are long wavelength, low frequency cosmic rays within the human visible light spectrum.  These colors are less likely to be scattered by atmospheric particles compared with the other visible light colors (yellow, green, blue, purple).  On days with high pollution or smoke, the sun and the clouds will appear red or orange because the other colors in the light spectrum are scattered by the air particles.

For more information, check out "the Physics Classroom".  You can also model this effect by shining a flashlight through a glass of water.  Watch the color change in the steam of light through the cup while using a dropper to add milk to the water.  It's a sunset in a cup!