Shouldn’t the moon be affected by the same phenomenon? I perceive the moon (full and high in the sky) as pure white, though the sky appears a mild shade of blue.
If we had a red sun, would it still appear yellow against a blue sky?
We’ve had this discussion before here.
To me the sun is definitely yellowish. Not an blatantly yellow, but certainly not white. Take a mirror and reflect some some sunlight through a crack in your curtains into a darkened room onto a white piece of paper. Place another piece of same paper face up out in the yard “looking up” at the blue sky AND sun.
Go look at both pieces of paper. IME the indoor one is most definitely more yellowish.
Better yet, take a picture of both pieces of paper. Compare the color histograms of the pictures. The color distribution will be fairly different.
And the blue scattering is not insignificant. IIRC its about 10 percent give or take at sea level.
Good observation, and it supports the idea that I posted earlier. With the moon, you commonly look at it when it’s high in the sky, and it looks white.
When the sun is high in the sky, it looks white too, but it hurts to look at it, so most people have experience looking at the sun when it’s lower in the sky and it looks more yellow.
The moon looks yellow too when it’s low in the sky.
That’s… a very good question. The spectrum of light coming from the Moon is basically the same as that from the Sun, just much less intense across the board. And it’s seen against the same background. And yet, the Sun and Moon are nearly universally regarded as different colors. The only difference I can think of between them is the brightness-- Perhaps the fact that we can’t comfortably look directly at the Sun makes it somehow appear yellower?
I’m not so sure of that last part. I occasionally see the moon against the blue daytime sky, but not very often, and it’s relatively faint. Most of the time I see the moon against the more or less black night sky.
The sun is definitely white. When we measure the temperature of the sun, physics models say it should be green, yet it certainly isn’t. Other stars can look red or blue, but no stars look green and the simple reason is we live around a green star. “Visible light” is simply the range of light centred around the light our star produces in greatest abundance: green light, but the sun produces light in frequencies straddling green as well, from red to blue (which is why we can see these colours in daylight). When all of these colours reach our eyes at once, we perceive white light. Red and blue stars produce equally-sized ranges of light on each side of their peak frequency, but usually a portion of one half of it is below or above the visible spectrum (ie if a red star produces red light the most, it will produce light tending towards green and light tending towards infrared. We cannot see the infrared, and so we only see the average of the wavelengths, which is somewhere around red (but slightly closer to yellow than the actual peak frequency) and the same can be said for blue stars, which shine a portion of their light into ultraviolet. Our sun is the definition of white because we are DESIGNED to see exactly the light that the sun gives off.
The blue light scattered by the sky is certainly enough to make the sun appear yellow (as I’m sure you know, yellow is essentially negative blue, as white light minus blue light = yellow light).
Are you sure you really looked at it before stating so? Because while most people assume that the sun looks yellow (that’s the colour we traditionally associate with it, starting with childhood drawings), in fact it looks pretty white.
If I look right at the sun, it’s almost too bright to even register as a color. (Unless maybe octarine is actually the color of pain.) But what sense of color I can get, especially around the edges, is definitely yellow.
The Moon is visible by day just as often as by night, and it’s not hard to see when it is. And when it is seen by day, it still looks whitish, certainly not yellowish.
Yes, but when you see the moon in the daylight you are seeing the moon PLUS the blue sky that is between you and the moon.
And given that moon isn’t that much brighter than the daytime blue sky…thats a good bit of blue you are adding back into the image.
Hm, that might be it.
Yes, I did. Even stole brief glances at it in the cloudless mid-day, when the sun is nearly overhead. Besides, there is always the question of why light seen on the ground appears yellow, too. At midday, with a white sun, we should be seeing white rays of light. Make a little hole in the roof and watch yellow sunlight streaming down from it. The sun is overwhelmingly yellow, unless it is a grand illusion along the lines of the Ponzo illusion.
I was taught that they would be equivalent, because (I was taught) frequency and wavelength are functions of each other given constant speed. Can you help me out here?
Can someone verify this if it is true? I thought most plants reflect green light because there is less green light than some other frequency(ies) meaning it’s not as worth the energy to absorb the green. (I read somewhere that it’s a fair bet that the color of a star and the colors of the plants evolving around it will tend to be opposites. For this reason I had the idea that our sun tends to peak around the reddish frequencies…)
Title of book?
The nearly full moon was up last night.
As my brother was leaving last night I asked him, does the moon look white or yellowish to you? (he has no dog in this fight and doesn’t even know about the fight)
At first he said white, then thinking and looking at it a bit more (without any prompting from me), said maybe a bit yellowish and more yellowish along the edges.
Comparing daytime viewing of the direct sun with nighttime view of the moon is problematic though. You are working at the limits of your vision being overwhelmed with brightness for the sun, and you are working where your night vision (vs day vision) is starting to become dominant for the moon. And day vs night vision are two significantly different beasts in several aspects.
Another part of the problem is if something is remotely white, your brain will try to make it look white. So, you need to do side by side comparisions if possible. Go to the paint store and see how many “whites” there are.
I’ve done the comparisons. I’ve take the photographs. The difference is there and detectable.
Either the sun is white and puffy clouds and snow covered mountains on a clear sunny day are whiter than white or the sun is a bit yellowish and the clouds and snow are regular old white.
The clouds and the snow don’t look whiter than white or blue white to me, so I’m going with the later.
They’re functions of each other, but it’s not a linear function. Equal intensities in all wavelength bands would mean, for instance, that the intensity in the band from 0 nm to 1000 nm would be equal to the intensity in the band from 1000 nm to 2000 nm. But now convert those to frequencies: 1000 nm is 300 THz, and 2000 nm is 150 THz. So we’d then have equal intensity in the band from 150 THz to 300 THz, and the band from 300 THz to infinity.
By contrast, if we had equal intensity in every frequency band, we’d have that same intensity in the 300 THz to 450 THz band, and the 450 THz to 600 THz band, and so on.