Quick question of the Sun and Earth...

Hi,
I was just wondering, if the sky is blue and the sun is yellow, why don't we get a large green patch where the two are mixing (obviously viewing it from the surface of earth)?

cheers

We get the whole spectrum in the form of a rainbow.

Sanc'.

yeah but thats caused by white light being refracted into its composite colours by water. im talking about on a dry hot day with no clouds, why isnt there a big green ring around the sun where the blue of the sky and the yellow of the sun are fading into each other?

Here is a picture of the sun without a filter.

www-fusion.ciemat.es...

As you can see it is actually almost white. Stars have misleading names like "blue" "orange" and "red" because they lean toward them depending on age.

But in the end, stars pump out white light.

The sun looks orange because white - blue = orange. The atmosphere (Nitrogen/Oxygen) refracts blue, thus we see a blue sky. However, since it gets a stab at the white sun first, it fliters out a good bit of blue leaving a bight orange color. As the sun sets, its light passes through more atmosphere giving it a change to absorb even more blue and bend the spectrum toward red making the sunset VERY orange.

So we see the white sun as orange through a blue filter..

Hope that helps.

thanks a lot quest, very interesting!

i heard somewhere that if you looked at the galaxy from a distance to get a good view it is not millions of white dots, but a whole range of colours, i imagine it to be quite a spectacle! i would love to see it some day!

Diffraction of the various wavelengths of various colors. There is probably more blue and red light that reaches our eyes based on how the light scatters. Though it is possible durring a sunset to see green.

Originally posted by Quest
Here is a picture of the sun without a filter.

As you can see it is actually almost white. Stars have misleading names like "blue" "orange" and "red" because they lean toward them depending on age.

But in the end, stars pump out white light.

First of all color of stars doesn't depend directly from their age, color depends only from surface temperature.
And just try looking any bright light source, no matter what color cast its light has it tends to look whitish.

Sunlight contains all colors of optical spectrum but wavelength of radiation peak depends on temperature so there's certain color tint always.
(actually there ain't such thing as perfectly white light where amount of all radiation in all wavelengths would be equal)
Blue color of sky is caused because atmosphere scatter shorter wavelength light more effectively, while amount of scattered light from total is extremely small it's enough to cause blue color of sky. Without this scattering daytime sky would be black and stars would show like in moon.
Atmosphere's effect get's considerably bigger only when sun is lower than about 30 degrees. And when sun is near horizon effect gets so big that only longer wavelengths get through causing reddish/yellow colors of sunsets.

So we see the white sun as orange through a blue filter..

Completely wrong, have you ever happened to look anything through color filters?
You'll just see different shades of filter's color.


Green flash can occur at exact moment of sunset if atmospheric conditions are right.
antwrp.gsfc.nasa.gov...

the reason you see the sky as being blue is because of the light being shined on the planet. if the sun was a different colour the odds are the sky would be too.
(thats what i reckon anyway)

I saw the sun as being yellow, of course. So I asked my teacher,'If the sun is yellow, and the sky is blue, and blue and yellow make green, is that why almost all the plants are green?' My teacher said that wasn't likely, but had no real reason. If the sun is white, which makes sense, that is one thing against my childhood theory.

Originally posted by dirtyrat5000
if the sun was a different colour the odds are the sky would be too.

It wouldn't be different colored, unless light would be very strongly colored and even then it wouldn't make scattering of longer wavelength light any bigger...
So the less incoming light contains shorter wavelengths (blue light) the darker the sky would be.

Originally posted by BlackGuardXIII
So I asked my teacher,'If the sun is yellow, and the sky is blue, and blue and yellow make green, is that why almost all the plants are green?'

And again you're mixing our additive color systems to nature which doesn't need such methods.

There are actually 2 types of chlorophyll, named a and b. They differ only slightly, in the composition of a sidechain (in a it is -CH3, in b it is CHO). Both of these two chlorophylls are very effective photoreceptors because they contain a network of alternating single and double bonds, and the orbitals can delocalise stabilising the structure. Such delocalised polyenes have very strong absorption bands in the visible regions of the spectrum, allowing the plant to absorb the energy from sunlight.
The different sidegroups in the 2 chlorophylls 'tune' the absorption spectrum to slightly different wavelengths, so that light that is not significantly absorbed by chlorophyll a, at, say, 460nm, will instead be captured by chlorophyll b, which absorbs strongly at that wavelength. Thus these two kinds of chlorophyll complement each other in absorbing sunlight. Plants can obtain all their energy requirements from the blue and red parts of the spectrum, however, there is still a large spectral region, between 500-600nm, where very little light is absorbed. This light is in the green region of the spectrum, and since it is reflected, this is the reason plants appear green.
www.chm.bris.ac.uk...

www.ucmp.berkeley.edu...

And considering about colors, there isn't actually such thing, it's just that "wetware" (you hopefully have working) behind eyes interprets/presents different wavelength electromagnetic radiation as such. (actually wavelength of strongest radiation is what causes color)
Remember that many animals have "BW" vision which doesn't separate colors, only intensity of radiation.

mod edit to use "ex" instead of "quote"
Posting work written by others. **ALL MEMBERS READ**
Quote Reference.

[edit on 20-1-2006 by sanctum]

Thank you for that very good account of the interaction between light waves and plants. I had already learned that long ago, but it did not answer for me the fundamental question of why is it the green waves that are reflected? It just is has been the best answer I have been given. I am not complaining, that is a very simple and possible answer, but it does not disprove the childhood theory I had. Of course a white sun sure throws a wrench into the works.
I appreciate all the information you shared, thank you.

Originally posted by E_T

So we see the white sun as orange through a blue filter..

Completely wrong, have you ever happened to look anything through color filters?
You'll just see different shades of filter's color.


Green flash can occur at exact moment of sunset if atmospheric conditions are right.

Thanks ET there was something about that post that didnt gell in my brain. But it still doesnt answer my original question. Are you saying that the sun is actually producing a wavelength of light that our eye interpret of yellow, or is it just white which is why there is no mixing of colours when shining through out atmosphere?

also would it be true to say if you viewed the galaxy from a good distance you would see a plethora of coloured stars and not just the white dots we see at night?

I find this topic interesting.Back in my young and silly days, I used to look directly at the sun for ages and after a bit it would turn green. Of course i couldn't see properly for a few minutes after all I could see even when I looked away was the green blob. Rainbows and the colour spectrum as awe inspiring.

I would actually love to see the Aurora one day, actually Id love to have a home that you could walk outside and see the aurora but then again I hate the cold ad there's no aurora on the equater. Im still undecided on white myself, when i look at white light long enough, it is a yellowy colour.

Originally posted by Mayet
I find this topic interesting.Back in my young and silly days, I used to look directly at the sun for ages and after a bit it would turn green.

what! ur crazy dude! staring at the sun is like holding a magnifiying glass directly to the back of your eyes! i would imaging the fluid inside your eyes starting to expand due to the heat and eventually your eyes would pop open spewing the liquid all over your face! well... maybe not exactly like that, but it would damage your eye sight a lot.

No my eyesight's fine. I am curious why people are told so strongly not to look t the sun, I don't disbelieve it can damage but its just a bright light, how does it "burn"?

Originally posted by Quest
Here is a picture of the sun without a filter.

www-fusion.ciemat.es...

As you can see it is actually almost white. Stars have misleading names like "blue" "orange" and "red" because they lean toward them depending on age.

But in the end, stars pump out white light.

The sun looks orange because white - blue = orange. The atmosphere (Nitrogen/Oxygen) refracts blue, thus we see a blue sky. However, since it gets a stab at the white sun first, it fliters out a good bit of blue leaving a bight orange color. As the sun sets, its light passes through more atmosphere giving it a change to absorb even more blue and bend the spectrum toward red making the sunset VERY orange.

So we see the white sun as orange through a blue filter..

Hope that helps.

The atmosphere's color has nothing to do with refraction but only absorbtion.

If you climb a high mountain the atmosphere is violet or dark blue because this part of the spectrum is the smallest wavelength and so is blocked first.

As you go further down the sky turns more greyish....

If you were to have a thick enough atmosphere such as Venus, the light continues down the spectrum...

Venus' atmosphere is orange at the region considered to be "sea level".

Originally posted by Mayet
I don't disbelieve it can damage but its just a bright light, how does it "burn"?

Because it contains also some other parts of spectrum than visible light, IR and UV.
While IR isn't damaging in moderate amounts strength of IR radiation increase in higher altitudes, especially in snowy condition. (and in larger amounts also it causes some damage)
UV radiation is harmfull even in smaller doses and exposure to it is big factor in developing cataracts among other permanent damage.
Now all sun glasses should filter 100% of UV in every case but especially sun glasses meant for high altitudes/snowy conditions have to filter also IR away because in higher altitudes amount of IR radiation is much higher and snow reflects almost all radiation. (as side note water surface is good UV reflector)

Also even visible light can cause temporary damage if brightness is big enough.

And if amount of radiation is big enough IR radiation can literally burn retina where light is focused. Fireball of nuclear explosion could cause this if looked directly, but also looking sun through telescope without full aperture filter would be equally effective way. (8cm/~3" magnifying glass is more than enough for igniting wood which requires ~250C/500F)

So never use filters which are attached to ocular for viewing sun, heating can burn those broken in few seconds!

Originally posted by Stratrf_Rus
The atmosphere's color has nothing to do with refraction but only absorbtion.

If you climb a high mountain the atmosphere is violet or dark blue because this part of the spectrum is the smallest wavelength and so is blocked first.

As you go further down the sky turns more greyish....

Wrong, if atmosphere would absorpt shorter wavelength light everything would look yellowish.
Sky is blue because atmosphere scatters some of the blue light. And sky becomes darker blue in higher altitudes because atmosphere is thinner meaning less scattered blue light. And if you go to high enough sky becomes black because of lack of any scattered light.

Neither does greyish color have anything to do with absorption, that's caused by aerosols, water vapour, dust, air pollutants, which scatter/reflect light throughout the spectrum. You can use this fact to determine how clean air is, just look how blue sky is and how much it turns lighter blue/greyish near horizon.

And color cast in Venus is caused by very different, almost pure carbon dioxide atmosphere combined with extremely dense clouds differing equally much from earth's clouds.

Quote from the future:

"Mommy, why is the sky blue?"

"It's not dear. That's just the blue tint of your suit's protective lenses."