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So obviously, the Sun is yellow, right? That's the color we use when we draw it out on a piece of paper, maybe with some rays shooting out, and a cool and kind of confusing pair of sunglasses on its face. Why is it wearing sunglasses if all the light is coming from the thing itself? It's kinda weird. But anyways, clearly the Sun is yellow or maybe some sort of yellowish-white that we draw as yellow because that's the closest crayon.

Except when you split up sunlight, you get a lot of colors, and yellow is not the strongest. In the most "well, actually" sense, the Sun turns out to be green.

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Now, no one uses a green crayon for the Sun, which means the Sun isn't really green. If no human can see sunlight as green, then sunlight isn't green; colors are in our brains, not in the world. But light *is* in the world, and light from the Sun comes in all different wavelengths - different lengths passing between peaks as the light wave wiggles up and down on its way from the Sun to our eyes. Understanding those wavelengths helps us understand why the sun shines in the first place, and why we can say that sunlight peak in the green even though the Sun isn't green.

Different wavelengths of light interact with objects in different ways, which is why shining a flashlight at an antenna doesn't affect radio reception. The antenna works because long wavelength radio waves push around electrons inside it, but those electrons don't respond to shortish wavelength visible light. Atoms and molecules move differently when different kinds of light hit them. They're like swings: they only respond when they're kicked by light wiggling at the right rate. Conversely, they also give off different wavelengths depending on how they move around. Each kind of movement gives off its own kind of light. If only one or two kinds of movement are happening at once, you get something like a laser, where all the light coming out has the same wavelength.

Now, I promise that we'll get back to the Sun and its sunglasses, but first, we have to understand why stuff makes light, because atoms and molecules don't generally just move in one or two ways, otherwise lasers would be a lot more common. They also move around randomly, and we measure the amount of random motion as something's temperature. Higher temperature means more random motion and more kinds of light being emitted. The range of random light coming off of an object is called it's "blackbody spectrum." Starts like the Sun give off most of their energy in the infrared, even if they peak or have the highest intensity in the visible range.

So it's not like the Sun gives off just one color; when we're talking visible light, it happens to give off more green wavelengths than any other individual color. The difference isn't that huge though. Red, yellow, green, and blue just aren't that physically different. The main place they *feel* different is down here on Earth. Most sunlight might be infrared, but if our eyes had evolved to see in the infrared, they'd see themselves, since *we* give off infrared, too. Which, hey, maybe that's why the Sun wears sunglasses.

Instead, evolution shifted our vision a bit; we evolved to see sunlight as neutral illumination, since otherwise, the world would have always looked tinted in one way or another, and that would've been annoying or dangerous or whatever. Except now, it feels like we took a step backward. Now we have three colors: we use yellow crayons to illustrate a green Sun that millions of years of evolution should have trained us to see as white.

But white sunlight gets altered by our atmosphere, where blue light bounces off air molecules more easily than red light does. This scatters blue throughout the air and leaves yellow or redder light closer to the sun in the sky. The lower the sun is in the sky, the more atmosphere the light passes through, and the more blues are bounced away. leaving us with red and orange sunsets around a yellow-tinged Sun. Combine that with the fact that it's just no fun to draw a Sun without coloring it in, and that probably explains yellow Suns, even when the Sun should be white when it's higher in the sky.

And yet, we don't usually perceive green anywhere in the normal sky, even though sunlight peaks in that color. Why is it that all that green light enters our eyes but our brains don't show it to us? Well, the color-detecting cones in our eyes evolved to respond to three colors: red, green, and blue. But the best red for red cones is pretty similar to the best green for green cones; most reddish, orangish, yellowish, greenish light activates both of them. So sunlight with lots of red and yellow and green can't really appear uniquely green to us. There's too much other color fighting for our attention.

So the Sun is yellow and it's green and white, and really, it's mostly infrared. The blackbody spectrum covers all colors - visible *and* invisible - so sunlight is any color you want it to be. Because again, colors are in here [points to head] not out there [points out].

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