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Thread: Why the Sun appears yellow

  1. #151

    Cool

    Quote Originally Posted by George
    That is a fair analogoy. The color of objects is usually a mixture of wavelengths; what we hear is a mixture, too. I would bet people will vary in their hearing perception much more than their variance in color perception, however. The dimensions within the ear may greatly affect the strength of certain wavelengths, whereas the eye would seem less susceptible.

    Nevertheless, there does seem to be some differences on how one sees very intense light such as the sun. That appears to be one conclusion we can draw from the poll, as some see a white midday sun and others see more yellow.
    What'll Be Even Weirder, Is If we Ever Discover Creatures, Who Evolved Under a Different Sun ...

    In The Latest Book, In his Worldwar/Colonization Series, Harry Turtledove Reveals The Main Aliens, a.k.a. The Race or The Lizards, See TWO Colours In The Infra-Red, And Can't See Violet to Boot ...

    Moreover, One of their Subject Species, The Halessi, Come From a Planet With an Even Redder Sun, And See a Further, Additional Colour in The Infra-Red, And Although it's Not Stipulated, Probably Can't Even See Indigo, Either!

  2. #152
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    Quote Originally Posted by ZaphodBeeblebrox
    In The Latest Book, In his Worldwar/Colonization Series, Harry Turtledove Reveals The Main Aliens, a.k.a. The Race or The Lizards, See TWO Colours In The Infra-Red, And Can't See Violet to Boot ...
    Hmm, so violet leisure suits would be a good option for night time covert ops? However, in the last book I read of the series I believe they were still swapping nukes in the 1940's so I guess the leisure suit hadn't become style yet.

  3. #153

    Cool

    Quote Originally Posted by eugenek
    Hmm, so violet leisure suits would be a good option for night time covert ops? However, in the last book I read of the series I believe they were still swapping nukes in the 1940's so I guess the leisure suit hadn't become style yet.
    Probably ...

    You REALLY Should Read, The Next Four Books In The Series ...

    It's Now 2031, Humans have Reached The Planets of The Star Tau Ceti, And Advances In String Theory, Are Beginning to Yield Interesting Experimental Results!


  4. #154
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    Quote Originally Posted by ZaphodBeeblebrox
    What'll Be Even Weirder, Is If we Ever Discover Creatures, Who Evolved Under a Different Sun ...

    In The Latest Book, In his Worldwar/Colonization Series, Harry Turtledove Reveals The Main Aliens, a.k.a. The Race or The Lizards, See TWO Colours In The Infra-Red, And Can't See Violet to Boot ...
    I read where white tail deer are dichromatic (two color cones). They can see blue and slightly into the uv range with one, and, green and yellow with the other, IIRC. This plus their larger eyes, should allow them to see all the deer hunters as they sneak into their deer blinds. I don't know if these have evolved from unnatural selective pressure.
    We know time flies, we just can't see its wings.

  5. #155
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    The way I see it, we've evolved to see "white" things illuminated during the day as "white".
    As they are illuminated both by the sun and the blue scattered light from the rest of the sky, the color we percieve as white is the color of the sun with some blue added, which is why the sun itself looks slightly yellow.

    Had we evolved under a different star, or in an atmosphere with a different composition, I believe we'd have had an intensity curve experienced as white, but it would be very different from the one here.
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  6. #156
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    Quote Originally Posted by HenrikOlsen
    The way I see it, we've evolved to see "white" things illuminated during the day as "white".
    As they are illuminated both by the sun and the blue scattered light from the rest of the sky, the color we percieve as white is the color of the sun with some blue added, which is why the sun itself looks slightly yellow.
    Evolving to a white appearnce for daylight is interesting and makes sense.

    However, surprisingly, the sun radiates with peak intensity in blue. The atmosphere does take about half of the blue, not just scattering effects though. The energy level for each wavelength (spectral irradiance) is almost flat when observing the sun from the surface.

    It is also interesting to see a flat curve for the sun in space if the curve plots the distribution of photons (using E=h*nu).
    We know time flies, we just can't see its wings.

  7. #157
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    i think most kids draw the sun as yellow because when the sun starts to set, its easyer to look at, yet isn't casting crazy colors everywhere like it does when it's low enough to be red.

    Even a little kid i think wouldn't beable to look at the sun at it's peak for long enough to think about what color it is, it just flat out hurts to look at it like that.

    when kids see the sun lower in the sky, easyer to look at and beign turned yellow by going through the atmosphere, thats probably where they get the idea, not to mention all the "yellow" suns in marketing and their parents saying "here is a yellow crayon for drawing the sun!"

  8. #158
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    I agree, the sun is much more observable near the horizon, not only because of the pain factor but because it is so hard to not see it. Sunsets are often quite attractive.

    The crayon factor is also very likely.

    You might enjoy the master formula.
    We know time flies, we just can't see its wings.

  9. #159
    Why not check to see if children colour the sun red in Japan?

    Anyways, the sun is white. At least it is where I am here in Australia. It typically it gets a bit of a yellow tinge when it goes down. But usually that's just a tinge. I don't own a yellow crayon light enough to draw it. I imagine that a lot of people in the Northen hemisphere look at the sun through a lot more air and filth than here. I know in Japan the setting sun often looked like a filthy wobbly orange thing.

  10. #160
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    Quote Originally Posted by Ronald Brak
    Why not check to see if children colour the sun red in Japan?
    Interesting question. Perhaps the drawings they color only have a rising sun?

    Anyways, the sun is white. At least it is where I am here in Australia. It typically it gets a bit of a yellow tinge when it goes down. [/quote]
    I agree with the white sun appearance, though others see a midday sun as yellow-white. I would have guessed a dusty sunset would produce a orange-red sun for ya'll. A clean atmosphere is not thick enough in scattering material to produce a redish sun; dust or other material must exist in the sky, too.
    We know time flies, we just can't see its wings.

  11. #161
    I've always seen the sun as just white.

    with regards

  12. #162

  13. #163
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    Quote Originally Posted by derick
    This site is a good example why there is much confusion as to the sun's color.

    Quote Originally Posted by link article
    For the sun, this works out to 5014 Å, which is in the green part of the visual spectrum. Therefore, the sun's true color is green.
    Assuming 5014 Angstroms is correct for the peak intensity of the solar spectrum, and assuming the peak color determines what color the eye observes, it still would not be green. A monochromatic beam of light at 5014 Angstroms would appear cyan in color (blue green). It is possible, that the 5014 Angstrom value is wrong, too. I get about 5,850K as the Planck curve temperature by matching the sun's known spectral irradiance (AM0) to a Planck BB curve at 5850K. If this is correct, then the peak wavelength is 4954 Angstroms (blue). The actual spectral irradiance happens to have two peaks deeper into the blue end of the spectrum.

    From the Hyperphysics solar irradiance graph, you can see the two peaks are located between 4500 and 4900 Angstroms. [I do not have an explanation for these, but they are there and are the actual peaks.]

    The other assumption the article seems to make (that the color at peak intensity would produce the color the eye would behold) is likley false. [Albeit, there are times when the peak intensity does produce the color seen by the eye, but not in this case, IMO.] The eye/brain will combine all the colors it sees and then tell you the color. The other colors will blend together to produce a result. This is how a television scrren, or monitor, produces such a wide range of color - by combining the three color dots, each at different intensities. If the only color you saw was the strongest color dot illuminated, you would see everything as either red, green, or blue (using an RGB system), which we don't, of course.

    However, if you look at it (which you should never do, for it can cause severe eye damage and in some cases blindness), the sun appears yellow.
    It only appears yellow when the sun is close to the horizion due to the "bleaching", or removal, of more of the shorter wavelengths. This means the remaining longer wavelength colors will begin to dominate your view of the sun, which is why the sun, when closer to the horizon, appears orange and, in some cases, red.

    No one has yet successfully explained why the sun appears to be yellow instead of green.
    Not to worry, heliochromology is still colorfully ramping-up to meet the needs of the world.

    The very first article I read regarding the sun's true color claimed the sun was green. But, it is clear to me now, that it is not green because of the way the eye blends all the colors together, and because the peak isn't green, as I stated before.

    However, an interesting fact is that our eyes are best able to see green light at approximately that wavelength.
    This is correct, our eyes are more receptive to a light shade of green over any other color. You may have noticed emergency vehicles now being this color for this very reason. However, it does not cause the sun to appear green. The eye has three color cones, but they each see more than one color. The combined sensitivity of each gives light green the advantage, apparently.
    We know time flies, we just can't see its wings.

  14. #164
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    I have to say that even at the horizon, it is a rare occurence that it looks anything but white to me.

  15. #165
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    Perhaps your altitude makes a difference. The change in color of the sun requires several air masses to scatter enough of the shorter wavelength colors. Dust and other small particles greatly increase scattering, too. If mountains block a normal horizon view of a setting or rising sun, this would further decrease your chances for seeing color changes.
    We know time flies, we just can't see its wings.

  16. #166
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    True - the only time I see the sun truly at the horizon is in the morning - when it is setting, the mountains block it from about 3 degrees above the actual horizon. This might make some difference in appearance.

  17. #167
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    Quote Originally Posted by cjl
    True - the only time I see the sun truly at the horizon is in the morning - when it is setting, the mountains block it from about 3 degrees above the actual horizon. This might make some difference in appearance.
    Though there is less dust in the air at sunrise, I would still think you would see a yellow rising sun. Is it usually white, or yellow-white (and not yellow)?
    We know time flies, we just can't see its wings.

  18. #168
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    White, every single time I can remember (in normal conditions). It was definitely white this morning...

    Can't remember ever seeing it yellow, though I can remember once (when there was a lot of smoke in the air from a forest fire) that it looked orange.

  19. #169
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    That is surprising. What color is the adjacent sky, during sunrise? Are you over a mile high?
    We know time flies, we just can't see its wings.

  20. #170
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    Adjacent sky is usually blue at sunrise. I am over a mile - 5600 feet actually.

  21. #171
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    Interesting. Perhaps the altitude makes the difference.
    We know time flies, we just can't see its wings.

  22. #172
    I watched the sun raise here in South Australia and it looked deep yellow. I looked at the clouds to see what colour they were and they were tan. There was a rim of pink haze all around the horizon. It didn't take long for the sun to appear white, once it got a little higher, however. (Not that I could look at it directly however.)

  23. #173
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    That sounds normal. Are your sunsets orange or yellow-orange?
    We know time flies, we just can't see its wings.

  24. #174
    Usually yellow, although I haven't paid attention lately.

  25. #175
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    Allow me to be a bit more colorful. These were taken in sequence through an 8" SCT during sunset (no filter due to clouds and haze, surprisingly). The first was when the sun was several degrees above a flat horizon. The second when about 1/2 degree (the diameter of the sun).







    The colors are quite representative of what I beheld.
    We know time flies, we just can't see its wings.

  26. #176
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    Quote Originally Posted by Eroica
    "of all the colours of the rainbow, which color does the Sun produce the most? ... The answer is green. Surprise! So why doesn't the Sun look green?"
    Ummm, because we're talking about additive color mixing here (as happens with stage lights, or any other combined light sources, where yellow+cyan=white, not green)? If we were talking about paint, or color theory as applied to reflected light, then a predominance of green would "look" green.

    Since we're talking additive mixing, though, any other colors mixed in with the green will tend to shift our perception of the color closer to white. (A perfectly balanced mix, would appear white, give or take some anatomical quirks or filtering properties of the atmosphere.

    http://www.yorku.ca/eye/colormx2.htm

    has one simplistic illustration of the difference between additive and subtractive mixing.

  27. #177
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    Quote Originally Posted by ebbixx
    Ummm, because we're talking about additive color mixing here (as happens with stage lights, or any other combined light sources, where yellow+cyan=white, not green)? If we were talking about paint, or color theory as applied to reflected light, then a predominance of green would "look" green.
    Yes, it is a matter of degree; a slight majority of one color may, or may not, alter the color observed.

    I am not all that knowledgeable on color theory, however. You must be quite diligent to have read much of this thread, so I will assume you do know something about color theory.

    It would be nice to know if the number of photons registering in our color cones is a more refined approach to color determination. Since blue has almost twice the energy of red, it would take almost twice as much intensity of blue to match red; thus, in this example, the photon flux would be the same for these two colors. Unfortunately, as logical as it sounds, the eye has very few blue receptor cones compared to the green and red ones. Also, the spectral response of each of the three color cones will overlap into other color zones. Then the brain processes all this with its own pecularities. The end result is compounded complexity.

    Nevertheless, perhaps an even flux of photons at each wavelength would produce an optimum white. If so, it would support further the appearance of a white sun when seen beyond the horizon.
    We know time flies, we just can't see its wings.

  28. #178
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    Well it looks pretty yellow in my rear vision mirror driving from home to work and then back afterwards at the moment.

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    Quote Originally Posted by PhantomWolf
    Well it looks pretty yellow in my rear vision mirror driving from home to work and then back afterwards at the moment.
    The additional atmosphere its light travels through scatters the blue end of the spectrum more than the red end. For dusty atmospheres, the sun can look red.

    The old sailor warning, "red in the morning, sailor taking warning" would not get busted on Mythbusters.
    We know time flies, we just can't see its wings.

  30. #180
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    I already knew that, was just pointing out that when it is low, and that's the time most people notice, it is very yellow, infact the light was yellow enough that standard silver coloured aluminium siding appeared gold when I saw it last night on my way home.

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