Ask Ethan: Why doesn't Earth's atmosphere turn sunlight into rainbows? (Synopsis)

"It's a brilliant surface in that sunlight. The horizon seems quite close to you because the curvature is so much more pronounced than here on earth. It's an interesting place to be. I recommend it." -Neil Armstrong

There are many impressive optical phenomena that we can see with our own eyes here on Earth. The right configuration of raindrops or ice crystals can produce rainbows, shining light through a prism will separate it into its individual wavelengths, and from high altitudes in the pre-sunrise or post-sunset skies, a full spectrum of colors become visible.

From very high altitudes in the pre-sunrise or post-sunset skies, a spectrum of colors can be seen, but it isn't due to the same rainbow effects you're used to. Public domain image. From very high altitudes in the pre-sunrise or post-sunset skies, a spectrum of colors can be seen, but it isn't due to the same rainbow effects you're used to. Public domain image.

Yet despite the beauty and similarities of these phenomena, they don’t arise from the same physics. While ice, water, glass or acrylic will slow down light to anywhere from 66% to 76% of its vacuum speed, air itself will only knock it down to 99.97% of its initial value. In fact, you have to look extremely hard -- and under ideal conditions -- to see any evidence of atmospheric refraction at all.

The rising or setting Sun (or Moon) can produce an image of greener or even bluer light atop it (L) and redder light beneath it (R), due to the minuscule refractive effects of Earth's atmosphere. Images credit: Mario Cogo (L) and Stefan Seip (R). The rising or setting Sun (or Moon) can produce an image of greener or even bluer light atop it (L) and redder light beneath it (R), due to the minuscule refractive effects of Earth's atmosphere. Images credit: Mario Cogo (L) and Stefan Seip (R).

Why doesn’t our atmosphere turn sunlight into rainbows? And how does the blue day sky and the red sunset/sunrise sky work? Find out on this week’s Ask Ethan!

More like this

“That's a misconception, Lennie. The sky is everywhere, it begins at your feet.” -Jandy Nelson There are all sorts of explanations that people give for why the sky is blue. Some say that it’s because of the fact that oxygen is a light blue gas. Others contend that the sky reflects the blue ocean,…
"It does no harm to the romance of the sunset to know a little bit about it." -Carl Sagan I would argue the exact opposite, in fact: the beauty of a sunset, in all of its varieties and variations, is only enhanced the more you know about it. Image credit: Dan Schroeder, via Picasa. The next time…
"My dad took me out to see a meteor shower when I was a little kid, and it was scary for me because he woke me up in the middle of the night. My heart was beating; I didn't know what he wanted to do. He wouldn't tell me, and he put me in the car and we went off, and I saw all these people lying on…
"Tell me what you feel in your room when the full moon is shining in upon you and your lamp is dying out, and I will tell you how old you are, and I shall know if you are happy." -Henri Frederic Amiel Tonight is a special night, although not for the reasons you may think. Yes, it's just a few days…