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I understand that - although appearing yellow - the sun is white. And that this is because the other light colours are scattered by the atmosphere. For example:

Google image search for "The Sun from Space"

That was difficult for me to come to terms with.

But if yellow light is what's getting through the atmosphere - why doesn't everything have a yellow tinge to it?

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  • $\begingroup$ It does to me ;) $\endgroup$ – LocalFluff Jan 6 '16 at 12:27
  • $\begingroup$ Are you asking for an explanation on colour? Because I can give you that. $\endgroup$ – Daniel Cann Jan 6 '16 at 16:19
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    $\begingroup$ It does have a yellow ting, but your eyes adapt to it. Step into a building that's brightly lit with fluorescent lights and notice the difference: it's much bluer than outdoors under the sun. $\endgroup$ – Pete Becker Jan 6 '16 at 16:27
  • $\begingroup$ The sun appears yellow and the sky blue. If you look at the ground, the mix of yellow from the sun and blue from the sky light creates a white "shine", except at sunrise/sunset when there's a reddish color. math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html $\endgroup$ – userLTK Jan 7 '16 at 1:57
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But if yellow light is what's getting through the atmosphere - why doesn't everything have a yellow tinge to it?

Everything does have a yellowish tinge to it, but only for roughly the hour after sunrise and the hour before sunset. These a photographer's golden hours:

enter image description here


As the Sun rises, its color changes from reddish to orangish to yellowish -- and then to nearly white, even when the Sun never does get very high.

enter image description here


You must not (and cannot) look at the Sun, even for the most fleeting of moments, once the Sun gets above 10 to 15 or so degrees above the horizon. The only time you can look at the Sun, even briefly, is when the Sun is low on the horizon and air mass is high. We think the Sun is yellow (or in some civilizations, orange or even red) because we cannot see the Sun for what it truly is, which is nearly white.

What bit of off-white color sunlight does have when the Sun is 10 to 15 or so degrees above the horizon is offset by the blue light from the sky, aka "diffuse sky radiation". The color of the light from the Sun and the sky when the Sun is high in the sky is about as white as light can get.

There's a bit of physiology going on here as well. To those who have lived their most of their lives inside buildings, bright sunlight is a bit yellowish and a bit too harsh. To those who spend much of their time outdoors, the fluorescent lighting that now dominates the urban landscape is a bit bluish and a bit too harsh. What city dwellers who rarely ventures outdoors thinks of as white light is not very white to those who spends most of their waking hours outdoors, and vice versa.

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The solar spectrum peaks somewhere near green, but that is not directly relevant to its apparent colour which is a result of the actual spectrum and the sensor response. If there is enough intensity in the pass bands of the three colour sensors for them to saturate the sensor will apparently record "white". This is true of camera sensors, film and the eye.

The light from the Sun at the bottom of the atmosphere peaking in the yellow is only a secondary factor in your perception of the colour of objects around you. If Sun light were mono-chromatic, that is concentrated in a very narrow band, say at yellow, then everything would appear yellow, like under sodium street lighting. But it is not mono-chromatic and the eyes perception of the colour of an object is effectively the result of the different reflectivity at different frequencies as sensed through three relatively wide bandwidth colour filters. the visual system is also doing a lot of other things to make the perceived colour of objects more or less constant under differing lighting conditions.

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  • $\begingroup$ That just went way over my head! :-) $\endgroup$ – Richard Heyes Jan 6 '16 at 12:46
  • $\begingroup$ @RichardHeyes Briefly: Sun light at the Earth's surface may have a spectrum that peaks in the yellow but it still contains all colours, You see colour because objects reflect different coloured light differently and the result is processed by the visual system to give you the sensation of different coloured objects. $\endgroup$ – Conrad Turner Jan 6 '16 at 13:42
  • $\begingroup$ If the sun actually were lemon yellow, I expect the receptors in our eyes would compensate for it to an extent that would give us useful color vision even in the red and blue regions. Y/G receptors would be down-sensitized to the point where stuff would still appear mostly its regular color. Our eyes are under no requirement to show us wavelength mixes as they actually are, but it is evolutionarily advantageous to be able to distinguish subtle differences in reflectivity. $\endgroup$ – Wayfaring Stranger Jan 7 '16 at 9:17
  • $\begingroup$ @WayfaringStranger Not if the sensors saturate, and for objects seen in reflected light, yes the visual system does compensate for the "colour" of the illumination as long as it is sufficiently broad band, It is why to a significant extent the colour of a object is perceived as the same even under significantly different lighting conditions. But note as I said above, under sodium street lighting everything is yellow. $\endgroup$ – Conrad Turner Jan 7 '16 at 13:41

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