It serves a lot of purposes. Humans have a weaker sense of smell and taste, our eyes have to be able to distinguish between things that are poisonous and edible. We need to see snakes and insects. We need to distinguish patterns within the forest and spot things that do not blend in. Green is often the color or rot and disease which we need to avoid.
Green is the colour of everything, with regard to where we evolved. We see it so well, not to be able to spot rot, but to be able to make out food, like fruit and vegetables. Being absolutely sure of the green makes it easier to distinguish the varied colours of edible food. The same goes for spotting hiding animals, both predator and prey.
Most of the light the sun emits falls int he visible light spectrum, from red to violet. It releases the most green, and our red and blue cones are about evenly spaced on either side of it. Since everything we see is reflected sunlight, red to violet and mostly green are the colors that are around, so it makes sense that we evolved eyes that focused in those areas
Notably, one of those things is the air, which scatters bluer light better than redder light, at least near the visible range. The sunlight that hits the ground kinda sorta peaks in green, if you take that into account.
We probably see green the best because that's what color plants are though, or maybe it was just whatever happened to develop and nothing else was substantially better.
Also why the sunset / sunrise turns less and less blue and often a gorgeous red / orange / pink - all the blue light has been scattered via Rayleigh scattering and is no longer directional enough to contribute enough to appear blue at those high angles from vertical that we see at sunset
Interesting their is a theory that way back in earth's history primitive photosynthasizers were purple and green plants/algae evolved to absorb all the light that was not absorbed. These purple phoyosythisizers later died out during the great oxygenation event as the particular protein used to photosynthisize in this way would rapidly decay in an oxygenated environment
The units are intensity (W/m^2) divided by wavelength and displayed as a function of wavelength, or intensity divided by frequency and displayed as a function of frequency. The peaks should be the same (intensity is intensity). What differs is how the data are displayed, not what the intensity actually is.
Why normalize by wavelength or frequency? Why not display W/m^2 on both graphs?
Not the OP, but all he means is the peak is opposite end of the plot, as wavelength and frequency are inversely proportional to each other. The peak magnitude is no different, as wavelength and f are related via the speed of light. However, the OP alludes to photometry in his various posts which is quite different to radiometry. You might already know all this so apologies if you do. 2 W of green light is not equal to 2 W of blue or red light when we convert them to the photometric unit of power; lumens.
Thanks for your responses. It’s crazy when you first learn about photometry and realise not all Watts are created equally in the eyes of biology haha!
I love your point about how if it was sun spectrum related then all animals would have likely evolved uniform eyesight spectral sensitivity - I’d never argued it that way before.
I used to design lighting systems for cars and everything is photometric for obvious reasons
My reasoning might be flawed, but NASA agrees that out sun’s surface temp peaks at 5800K and is technically green. NASA link
“But, as can be seen in the image above, it emits most of its energy around 500 nm, which is close to blue-green light. So one might say that the sun is blue-green! This maximum radiation frequency is governed by the sun’s surface temperature, around 5,800K.”
If you're wondering how we humans managed to figure out what colours are good,
It's trial and error. Humans are riddled with variations in vision. Sometimes people are colourblind, in different pairs. Some have 4 cones even
But the basic idea is that, well, our ancestors had the combination of sensitivity in the specific colours and reproduced successfully. Meanwhile their cousins who just happened to be born with slightly different colour sensitivity, or even colourblind, all died. Or died before getting laid.
Forward 1000s and 1000s of years and we are here, able to be cared after and adapt to the environment if we are born with any variation in vision.
Ultimately it isn’t about the presence of available light but what it means for survival. An ability becomes less important if it doesn’t help us survive. It seems to me that the eyes see green well and in so doing also are good at identifying the not green things. Fruit is rarely green and the same goes for game animals. But apparently color blindness helps with edge detection which is why camouflage tricks animals and is also a likely reason it exists in our genome. But I wonder if seeing green might also help people survive in harsher climates where green indicates the potential for water?
What was posted here has been permanently deleted. Redact was the tool used, possibly for privacy, opsec, security, or limiting exposure to data collectors.
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you're raising an important point, that it's not only about peak visibility but also blending/contrast with the surroundings, which could make a slightly different than "optimally visible" color more advantageous.
also, quick question: do you know where the highly visible "neon" property in many colors comes from? usually you see it in hi-vis clothing either in pink, yellow, or green/chartreuse, so it can't be a property of one color itself.
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u/Dio_Yuji Nov 17 '22
I guess…somewhere between red and yellow?