If you’re anywhere near Liberty Science Center, then you’ve surely been in awe at the unusual colors in the sky this week, a result of the Canadian wildfires. And maybe you, or someone in your family, has been curious about the science behind why the sky looks the way it does?

As long as these smoky conditions persist, it’s best (for now!) to avoid strenuous activity outdoors. The more we exercise outdoors, the more we are apt to pull those particles into our lungs. Being indoors significantly reduces exposure to the smoke particles.

Now, how about the color of the sky?

The sun’s light is made of all the colors of the rainbow, from violet/blue to orange/red. When there are a lot of smoke particles in the air, as during a wildfire, those smoke particles scatter blue light; that is, the short wavelengths of blue light in the sun’s light are bounced around by the particles of smoke in every direction and thus don’t continue on to your eyes.

The longer wavelengths of red and orange light in that sunlight are not bounced around so easily by those smoke particles, and thus continue through the smoke and to your eyes.

This is the same idea behind a very famous phenomenon: when the Moon often turns orange or red during a lunar eclipse (this is also where the term “Blood Moon” comes from.) During a lunar eclipse, the Earth is between the Sun and the Moon. The short wavelengths of blue sunlight are scattered, or blocked, by the Earth’s air; the longer wavelengths of red and orange sunlight continue through the Earth’s air and go on to strike the Moon.

On your next visit to LSC, be sure to stop by our Science on a Sphere interactive globe, where you can track real-time conditions on our planet, from tectonic plate motion to melting sea ice to volcanoes to hurricane paths and beyond.

Science on a Sphere