Ask Ethan: Why doesn’t Earth’s atmosphere turn sunlight into rainbows?
If a prism can do it, why not the air?
“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
Sunlight may be the bright, warming glow that heats and powers the Earth, but it’s so much more than that. If you pass sunlight through a prism, you can see how it’s actually composed of all the different wavelengths of visible light, from violet to red. If you had extended vision, you could see that ultraviolet and infrared radiation were part of that, too. Seeing that sunlight is composed of the full spectrum of colors doesn’t even require anything human-made, as properly oriented water drops can create this “rainbow” effect completely naturally. So why doesn’t Earth’s atmosphere do it on its own? That’s the question posed by Richard Harris, who wants to know:
I wondered why white light passing through the Earth’s atmosphere doesn’t separate into the colours of the rainbow. Is it because air is too diffuse and there is insufficient distance of travel when the sun is overhead? When the sun is close to the horizon, so that there is a greater distance to be traversed, it appears to be red. Would the…
