What color is the sun?

[instinct]

I think this is a funny question. The sun is white of course!

For some reason kids always draw it as yellow, but we all know that kids are idiots most of the time. It is interesting however to think about why they chose yellow. I suspect that it's simply because yellow is the complementary color to blue (which undoubtedly is the color of the sky).

I'm pretty sure kids draw it as yellow, because when you look at it, it looks yellow on the outside ridges, kind of how my Violet often looks like a white dot in the middle with purple around the edges. I'm pretty sure it's not because they are dumb.

http://goflorida.about.com/library/graphics/sunset3.jpg

http://www.electronics-lab.com/blog/...nrmcmedium.jpg

[JimBo]

Just seen this thread and I'm amazed at how little you all know.

It is a fact that the sun is actually the light in gods house, the reason it appears different colours is that when the bulb breaks, he replaces it sometimes from a different manufacture, ie Philips, GEC, Osram etc..
It has been rumoured that St Peter has recently bought some energy efficiency ones and that accounts for it being a bit cooler in the UK this summer.

Jim

[Zoof]

Just seen this thread and I'm amazed at how little you all know.

It is a fact that the sun is actually the light in gods house, the reason it appears different colours is that when the bulb breaks, he replaces it sometimes from a different manufacture, ie Philips, GEC, Osram etc..
It has been rumoured that St Peter has recently bought some energy efficiency ones and that accounts for it being a bit cooler in the UK this summer.

Jim

Finally someone starts making sense... We can now all rely on god to stop global warming :-)

[JimBo]

I just want him to stop taking showers, my garden is water logged LOL

Colours always amaze me, and how they are described, it is OK for sighted people, when you are young you learn that an orange (fruit) is orange, a banana is yellow and grass is green. Now when people are colour blind that green grass may well appear to them what we know as blue. So they are taught that the colour they see as blue is known as green!
What I always wonder is how people that are blind from birth understand what colours are, they obviously can't see an orange to know what orange is!
Another conundrum, what colour is a mirror?

Jim

[Zoof]

A perfect mirror is white ...

[Doc]

Another conundrum, what colour is a mirror?

Jim

I dunno, everytime I look; some bloke has his big fat head in the way.

[The_Doctor]

In short, bodies hot enough to peak their emission in the green portion of the spectrum are also radiating at lots of other wavelengths, and the combination of those wavelengths is interpreted by our (imperfect) human color vision as white.

I think there's more to it than this, our brains interpret greens as whites, and this isn't a purely metaphysical or perceptual thing. If you take a green DPSS and leave it shining at a white wall, after a while you'll quickly accept it as white light, despite consciously reminding yourself that blues and reds are absent. We don't see green as green, except in contrast with other colours. We see red and blue for what they are, but green, only in context. Another oddity: the Tardis console in the Jon Pertwee era, on monochrome TV, was to be as bright as possible. I don't know if they went so far as to paint it with barium sulphate but what they did find was that an industrial workshop green, a light lime, I think, appeared far brighter after it passed via imaging tubes and eyes and brains than every white paint they tried. I don't know how these things relate to each other but I'm sure they do, and are related to why when green dominates a black body spectrum, we fail to see it. The sun apparently DOES appear green at times, during a spectral shift at the moment of sundown when the horizon is distant, cleanly defined, and the intervening air is clean and stable. Again, I think it is the transition, the contrast made by it, that allows it to be perceived as green, where normally it would not be.

Weirdly, we see green all around us in fertile lanscapes. But again, it's the contast when we look around, or compare with sky, or bricks. I've taken pictures in a woodland where I perceived the light as mostly grey, then when reviewing them later seen how much greener they looked compared with the recent memory of being there. I guess green is so much a part of life that a lot of extremely primal mechanisms, physical as well as mental, allow us to tune it out so we perceive smaller and more signifcant info.

[The_Doctor]

The instructor shines a bright lamp through a tall, narrow tank of water. The light appears yellowish-white. Then he adds some chloride salts and a bit of silver nitrate. The silver nitrate grabs the chloride ions, creating a precipitate that begins to turn the water turbid. As this progresses, the filtered light will first appear blue (just like the sky), but after a few seconds it will rapidly shift through orange and red before becoming opaque. The lesson here is that increased particle size changes the wavelength that is scattered.

Sometimes colour change in the low end of the spectrum is percieved from an increase in the amount of material, rather than its size. Samuel R Delany wrote a vivid description of this, about how a spaceport's sky might look as ships departed, he analogised with an image of a diamond (I think) dropped into oil, starting white, fading through yellow, orange, red... Clearly there is no change in particle size, yet the similarity with the lower end of the visible black body spectrum exists. Probably due to the amount of diffraction though as there is a proportion between wavelength and light lost off axis. What matters is that it is clearly not a linear relation, if it were it would be seen as dimmer, not also different in colour.

[buffo]

our brains interpret greens as whites

Which is another way of saying that humans have lousy color perception - a point which is lost on most people. Bottom line: the sun's actual color (as measured on a spectrograph) is closer to yellow, but due to the specific color peaks in our imperfect vision (coupled with our tendency to perceive anything really bright as "white"), the sun looks white to our eyes.

Sometimes colour change in the low end of the spectrum is percieved from an increase in the amount of material, rather than its size.

This is true, but in the example I posted the experiment is specifically designed to demonstrate the effect of particle size on rayleigh scattering.

Adam

[The_Doctor]

Just saying, why limit the discussion? I recognise the purpose of the experiment, but I find it more interesting that two apparently unrelated situations can have similar aspects regarding perception of green, and that two apparently unrelated systems can exhibit the same colour shifts in reds, oranges, yellows... Sure, human eyes and brains aren't great at colour perception, but lumping the disparities of various observations into a catch-all like that is far less interesting that looking into what appear to be a few very curious parallels. As it appears that the results of the perception can be the same when different mechanisms are involved, it may be that this is part of life's development just as certain similar features of anatomy arise out of different needs in animal evolution. And it prompts us to consider that things like colour blindness might not just be errors in life's mechanics, but might have strengths that haven't been looked at. Science falls back too readily on its models, especially when looking at what it thinks is old territory.