Is the sun really yellow?

[gib65]

I was having a conversation with a girl from Japan today, and it lead to a very interesting question: why do we think the sun is yellow?

 

The conversation started when someone mentioned the color of the sun being yellow, and she (the girl from Japan) interjected and said "No, it's orange". Eventually, she explained to us that in Japan, they actually think of the sun as orange, and children there, when they color drawings of the sun, will use orange.

 

It lead to speculations that during evening, when you look at the sun, it does look orange. So why do we in the west have a noon-time bias when it comes to the color of the sun? Furthermore, it stands to question how we can even know what the color of the sun is at high noon. I mean, one should never look directly at the sun, but in the evening it's not so bad, and when you do, you see orange. But who has ever looked directly into the sun at high noon without getting temporarily blinded? The blinding happens almost instantly, too quick to take any notice of what color the sun is.

 

So if we can't actually inspect the sun with our own eyes at high noon, how do we know it's yellow?

[J.C.MacSwell]

I was having a conversation with a girl from Japan today, and it lead to a very interesting question: why do we think the sun is yellow?

 

The conversation started when someone mentioned the color of the sun being yellow, and she (the girl from Japan) interjected and said "No, it's orange". Eventually, she explained to us that in Japan, they actually think of the sun as orange, and children there, when they color drawings of the sun, will use orange.

 

It lead to speculations that during evening, when you look at the sun, it does look orange. So why do we in the west have a noon-time bias when it comes to the color of the sun? Furthermore, it stands to question how we can even know what the color of the sun is at high noon. I mean, one should never look directly at the sun, but in the evening it's not so bad, and when you do, you see orange. But who has ever looked directly into the sun at high noon without getting temporarily blinded? The blinding happens almost instantly, too quick to take any notice of what color the sun is.

 

So if we can't actually inspect the sun with our own eyes at high noon, how do we know it's yellow?

We do see the noon day Sun with our peripheral vision...

[swansont]

One might also consider that haze will tend to accentuate the red end of the spectrum. It may be that in some regions, they sun tends to look more orange. Others see yellow, but it's actually white. Some loss at the blue end, and seeing it contrasted with a blue sky (and possibly other effects), and it looks yellow. But remove more blue and reduce the blue background because of haze, and maybe it looks more orange.

[gib65]

Interesting answers,

 

To be honest, I was expecting an answer involving filters--as in, when you want to study the sun, and really look at it, we have to use filters that tend to block out light at the low and high ends of the spectrum, leaving only the middle which happens to be yellow. Could this also be true?

[mathematic]

The main filter for sunlight is the atmosphere, which scatters blue light (resulting in a blue sky). The color we see is what is left. At sunset the light travels through more atmosphere than at noon.

[Moontanman]

In space with out the atmosphere the sun is white (to our eyes), through the atmosphere it can be from yellow to almost red depending on the conditions. I suspect that cultural differences cause the suns perceived color to be subjective...

[StringJunky]

Did some Googling. With respect to the reported conversation about the Japanese thinking of the sun symbolically as orange probably relates to fact that they historically believed their land was "The land of the rising sun" which apparently is what 'Nippon' (State of Japan) means. They believed they were the first place to see the sun every day. New Zealand was unknown at the time.

[abisha]

2000 years ago, it was more red *copper* 3000 Kelvin.

Now it's more yellow, around 3500 Kelvin.

when ages pass it will become more and more blue.

[ewmon]

You can use this simple technique with white paper, not to burn the paper, but to view the Sun's color and shape during the day (you may still want to use sunglasses). You can also make and use a camera obscura. I also used a modified pinhole camera / camera obscura to view the phases of a solar eclipse, and the small amount of light through the pinhole did not require sunglasses.

 

[swansont]

2000 years ago, it was more red *copper* 3000 Kelvin.

Now it's more yellow, around 3500 Kelvin.

when ages pass it will become more and more blue.

 

What?

[DarkStar8]

The Sun is Snow White not yellow... Well least above the atmosphere where the blue component isn't scattered. Snow and Clouds are white because they recombine and reemit both the blue of the sky along with the apparant yellow of the Sun.

[abisha]

What?

 

 

they talk about sun color, on earth.

not above atmosphere, I read somewhere sun is on Earth around 3500 Kelvin *depending on time*

[StringJunky]

 

 

they talk about sun color, on earth.

not above atmosphere, I read somewhere sun is on Earth around 3500 Kelvin *depending on time*

 

No, the true colour temperature is going down because as it uses it up it's fuel it's getting redder. I'm talking about outside the Earth's atmosphere here. Also on human scales no change will be noticeable anyway...definitely not 2000 years and, relatively, it would have been bluer not redder then.

 

The colour temperature on Earth peaks at noon (5500K) and round about 2000K at dawn and dusk depending on atmospheric conditions

Edited December 23, 2012 by StringJunky

[ox1111]

This really has to do with different cultures of people assigning different colors the different wavelengths of light. I was just watching a program about a tribe in Africa that only has five words for colors when asked what color the sky was the answer was black, where as Westerners would always say blue. Color is perceived by humans in two ways, one by the cones in her eyes which range anywhere from 2 to 4, four being in very rare. The second way people perceive color is cultural people tend to only know the colors or have words for colors when it is relative in her lifestyle.

Such is the tribe in Africa which really only needs Brown black green yellow and orange, because this tribe lives in the area that these are the only colors that are relevant. Most people are often surprised to find out how very much difference there is between people when it comes to color detection, from one end of the spectrum or people only see shades of gray to the other end where people see hundreds of thousands a shades.

[ewmon]

 

This spectrum is given here as the solar spectrum that reaches Earth, and it reminds me of my first thought on this subject that the Sun is really "green", but that such stars have such broad spectrums that they appear whitish (that is, all colors). The linked article says that the solar spectrum before filtering by the atmosphere is toward the blue. The broadness of star spectrums is why their apparent colors jump from "blue" to "white" to "red", while missing the specific colors in between. Here's another article on star color.

[JohnStu]

It's not yellow, it's a bit reddish on the charts. Our eyes decipher it as white if we ever look at it from space with some strong UV sun glasses.

 

The yellow appearance is largely caused by the elimination of some blue from the blue sky.

 

There, perfect answer above.

[Moontanman]

The sun is a yellow dwarf star John, it appears yellow to the human eye, but combined with the blue sky the light is white, the sun is not reddish....

[StringJunky]

The sun is a yellow dwarf star John, it appears yellow to the human eye, but combined with the blue sky the light is white, the sun is not reddish....

 

The human eye is a fairly poor judge of the hue of an object as it has it's own 'white-balance' called chromatic adaptation. What this means is that the eye/brain interface will alter it's colour-balance controls, on a white object for instance, to keep it white until it goes beyond it's range of adjustment. I think it evolved to do this to maximise the amount of detail it can extract and preserve the ability to identify familiar objects in diverse light conditions, which would be important when looking for food...a very long time ago of course.

 

The thrust of what I'm saying is that our eyes are not reliable tools for assessing the objective colour properties of an object.

Edited December 26, 2012 by StringJunky

[Moontanman]

 

The human eye is a fairly poor judge of the hue of an object as it has it's own 'white-balance' called chromatic adaptation. What this means is that the eye/brain interface will alter it's colour-balance controls, on a white object for instance, to keep it white until it goes beyond it's range of adjustment. I think it evolved to do this to maximise the amount of detail it can extract and preserve the ability to identify familiar objects in diverse light conditions, which would be important when looking for food...a very long time ago of course.

 

The thrust of what I'm saying is that our eyes are not reliable tools for assessing the objective colour properties of an object.

 

 

yes, I would have to agree with that, my own attempts to imitate the sun for growing coral showed the human eye is a very poor judge of both color and light intensity but the sun does have an objective color, 5800 kelvin average temp and color temp... We perceive it as white light but the atmosphere scatters the blue making the actual disc of the sun appear yellow...

 

http://www.universetoday.com/18689/color-of-the-sun/

Edited December 26, 2012 by Moontanman

[StringJunky]

 

 

yes, I would have to agree with that, my own attempts to imitate the sun for growing coral showed the human eye is a very poor judge of both color and light intensity but the sun does have an objective color, 5800 kelvin average temp and color temp... We perceive it as white light but the atmosphere scatters the blue making the actual disc of the sun appear yellow...

 

http://www.universetoday.com/18689/color-of-the-sun/

 

Yes I agree that a light-source does have an objective colour but reflective surfaces don't because that's dependent on the frequency of the light-source...the sky is more purple objectively.

 

In fact, the Rayleigh scattering indicates that even the sky should be violet light . Moreover the law of blackbody radiation states that the Sun radiation is more important in the field of purple (and more to the ultraviolet but the ultraviolet filter is ozone) than for blue .

But the photopic vision of the human eyes presents a peak sensitivity around the green (wavelength 555 nm) while the violet sensitivity is 100 times lower.

The "green shift" thus leads to a light sky seen blue by the human eyes.

 

Light sensitivity for photopic vision.

 

http://www.raman-scattering.eu/raman/texts/022_text_12.php

 

 

As you can see our eyes are not very objective at all. What this boils down to is that what we perceive is subjective due to the way I visual system works...our perception of something is a construct which doesn't necessarily mirror reality.

 

As an aside, I think this example illustrates quite well why scientists rely on data from their instruments, rather than commonsense, to draw conclusions from.

Edited December 26, 2012 by StringJunky

[ox1111]

You people do know that color is a fabrication of the brain right. It does not exist. Different wave leangths of light exist for sure, but that is not the color you see. The color you see is asigned by the mind. Just like you can color code a map with a computer showing different elevation as different colors. The human mind does this with reality.

[CarbonCopy]

Well the sun emits light of all kinds of wavelengths. The most prominent one in the visible region is yellow I guess. Anyway,

 

You people do know that color is a fabrication of the brain right. It does not exist. Different wave lengths of light exist for sure, but that is not the color you see. The color you see is assigned by the mind. Just like you can color code a map with a computer showing different elevation as different colors. The human mind does this with reality.

 

your right.