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Science is making mistakes towards to the truth
I liked a version of this (I believe) XKCD said once.
A perfectly valid response to the question, “why is the sky blue?” is simply, “because air is blue.”
Yes, you can give a lot of explanation about refractive index and Rayleigh scattering. But all this does is provide details of how light interacts with air. And the same reason anything is the color that it is is due to the way it reflects, transmits, or absorbs light. You’re citing real scientific principles, but you’re ultimately just explaining why air is blue.
Better question: “Why is the sky usually blue but sometimes red?”
Talking specifically about sunsets, not apocalyptic wildfire smoke
Incidentally it’s the same reason between a sunset and smoke - more scattering.
It’s a very good relevant XKCD.
The title text is more directly applicable: If you ask “why are leaves green?” the usual answer is “because they’re full of chlorophyll, and chlorophyll is green,” even though “why does chlorophyll scatter green light?” is a great question too.
“Don’t breathe air, it has sharks in it! BLUE HAS SHARKS IN IT!” -The funny purple man
First if all: don’t name your kid brayden.
“Don’t breathe air, it has sharks in it! BLUE HAS SHARKS IN IT
???
It’s a two minute comedy bit.
But it’s an incomplete answer.
“air is invisible at short distances, blue at longer distances, and takes on red green and orange at sunset” would be better
The same is true for all colors. Tell me the color of a single atom.
Yes, air can be colors other than blue at unusual light conditions, like sunset. But the same is true for any material.
You’re stuck on the urge to explain. You call “the air is blue” incomplete. But all answers are incomplete. When someone asks what color an object is, they mean under ordinary distances and conditions. Air is blue even in an ordinary room. It just takes miles worth of air for its slight blue color to be noticeable.
Why are plants purple?
Blue waves fast Red waves slow
Easy as
They’re not anymore
The crazy part is the exact science behind why plants reflect green specifically is still debated. One theory is that, because much of the sun’s energy is released on that wavelength, controlling for it specifically allows the plant to better manage energy fluctuations (highly simplified but you get the idea)
longer explanation and source
Plants are green specifically because the red and blue wavelengths of light are useful for breaking specific chemical bonds necessary for photosynthesis and as such are readily absorbed by the plant. The plant makes efficient use of the energy provided by only absorbing the wavelengths necessary for its processes. However, plants still absorb 90% of green light and green light holds the highest proportion of the energy radiated by the sun.
To be more clear, green light has too much energy. When plants absorb light it first enters a protein mesh containing pigments such as chlorophyll that function like an antenna or receiver for a range of wavelengths. The pigments then transfer the energy to a “reaction center” where it turns this electromagnetic energy into chemical energy (photosynthesis). This process is exceedingly efficient; almost all of the absorbed energy is converted into electrons the plants can use. However, this protein mesh antenna is not solid and is constantly moving. These movements affect how energy is absorbed and how it flows through the pigments. Think of diffraction in water. Fluctuation in the intensity of light can create noise in this process; a quick brush of shade or sudden increase of light intensity can decrease the efficiency of photosynthesis. For plants and really everything that lives, a steady input and output of energy is desirable. Not enough electrons making it to the reaction center causes energy failure while too much will cause general overcharging effects that can damage tissue. When the noise of this system fluctuates it makes it difficult for the plant to self regulate it’s energy flow and could cause the plant to kill it’s own tissue or essentially starve. So essentially, while absorbing all green light would provide the plant with more energy, it’s not capable of handling this energy so plants evolved to limit their intake of green light.
However, this is not to say that green lights ability to efficiently evaporate water is not a factor in this evolutionary development, hell it’s probable that these two things are heavily related. Green light might evaporate water so well because of some combination of its relatively high energy mixed with the size of its wavelength interacting with the hydrogen bonds between water molecules in a more efficient manner than other wavelengths of electromagnetic radiation.
source for those interested
this is a copy pasted comment from this post and as such not every part of it has context
Thank you so much for this comment. I have a graduate degree in plant genetics and I had never been exposed to this before and you just made my whole day by teaching me this!
How do you know so much about photosynthesis?
My partner recently graduated with a horticulture degree and at the time I originally learned this I was a physics major. Photosynthesis was a neat overlap of our fields.
“Why” and “biology” famously do not get along. The best you can usually do is say it’s evolutionarily advantageous because the true answer is usually a neural network the size of life itself. There are plenty of decent reasons that play parts that we can quibble over, though.
In respect to green leaves I have read that it is most likely a peak. They can’t get to a better colour that doesn’t send away lots of energy because they would have to lose the ability to make energy from sunlight to get to a better way of doing it
Plants manage to use about 2% of the sunlight that hits them (the best get up to 6%) . Our rooftop solar does 22% (with the best managing 25%)
So why are some plants purple?
My wife is a horticulturist and she has showed me some plants with sun stress that have turned a reddish purple when they’re not supposed to. Eventually, the plant will die if not given a reprieve.
Maybe there is some sort of adaptation happening where the plants have been trying to survive in a low shade environment for a long time, and being purple helps in some way, so it became permanent. But I am just speculating.
Which curiously enough, can also photosynthesize, and more readily absorb energy from green light than chlorophyll!
Makes me wonder what could be achieved with some careful engineering…
Purple Humans who don’t need to eat.
there are plenty of purple plants, im guessing certain plants evolved to do this, and most remain green(there also other complicated mechanism like cam, c2,etc. plants can get sunburned if exposed to too much light.
That paper talks only about it producing red leaves, or “vermilion” as it calls them.
Cold nights while growing.
Wish I knew lol
They never got the update.
“Incandescent rage” is one of those phrases I have pocketed for a future conversation.
It was also a great pun for the topic being discussed.
I mean, technically they weren’t wrong.
Except the sun isn’t yellow, it’s white with a slight bias towards green.
Want to check, put something white outside, it looks white, not yellow.
The reason the sun appears to be yellow is the same reason that the sky appears to be blue.
Blue light is scattered more by the air in the atmosphere than other wavelengths. Remove blue from white light and you get yellow. So the light coming from the sun that isn’t scattered and dispersed through the sky (making the sky look blue) is yellow.
Still, the sun is white. Sun light is white.
Are you saying the blue light is removed from the spectrum when it’s passes through the atmosphere? I assume you aren’t since you said scattered, but also imply the sun is yellow because blue is removed.
If we’re talking about sun light during sunrise or sunset then yes it gets red at more extreme angles. But the sun isn’t that color all day.
Still, the sun is white. Sun light is white.
That’s why I said “appears to be yellow”.
Are you saying the blue light is removed from the spectrum when it’s passes through the atmosphere?
The light from the sun is made up of a whole variety of wavelengths. You can see that when there’s a rainbow and every wavelength from red to orange to yellow all the way to violet is represented. This light arrives in a continuous stream of individual photons.
When short wavelength photons (blue wavelengths down to violet wavelengths and below) hit the atmosphere, they’re more likely to be scattered by air in the atmosphere. Because of that, they still hit the ground, but they’re no longer coming from a direct line from the sun. That’s why when you look up at the sky you see it as being blue, because photons that weren’t originally heading toward you were scattered and come towards you from a random direction.
The longer wavelengths, from green on up aren’t as likely to be scattered by the atmosphere, so they mostly come in a direct line from the sun to your eye.
As a result, if you look directly at the sun (which you generally shouldn’t do) it will appear to be more yellow than it actually is. Astronauts above the atmosphere see the sun as appearing fully white. But, on the surface we see it as white minus all the blue that was scattered. The result is that the sun appears to be yellow when you’re on the surface with the atmosphere scattering things.
At sunrise and sunset there’s even more scattering. Now even larger particles are involved, and there’s more atmosphere to shine through. The blue is removed, but so is a lot of the green and yellow, leaving only the red, which is the least likely to be scattered since it has the longest wavelengths.
So, at sunrise and sunset the sun can appear reddish. At noon it can appear yellowish. But, if you go above the atmosphere so the blue doesn’t get scattered, you’ll see that it’s actually white.
It’s the opposite, no? Red and green light have shorter wavelengths, so they get scattered before they reach our eyes, but the blue wavelengths are long enough that we actually see them
No, it’s well known Raleigh scattering. Red and green have longer wavelengths than blue. Just past red, in the “wavelengths too long to be seen” direction is infrared which we feel as heat, and which just makes things warm. If you go the other direction into “wavelengths too short to be seen” direction, past violet, you get into Ultra Violet or UV, which is ionizing radiation, and that’s why UV is a skin cancer danger. The short wavelength blue light gets scattered, the longer wavelengths don’t, so the sky appears blue, and the sun appears yellow.
And here’s the correct answer, boys and girls.
with a slight bias towards green
And it’s my understanding THATS why plants are green
Actually, leaves look green because they don’t absorb green light (that’s why grow bulbs are red & blue)
That’s why I never developed super powers.
Neither water is blue
They take us for absolute fools
Maybe not the water you drink (chugs Gatorade frost)
So, what color were plants during the Hadean æon?
Same color as animals were
Purple leaves are a thing.
That’s from plants that get their air mostly from the shade and sunsets, so obviously they’d be less yellow and more dark and red.
I know this is a joke, but to be fair: the scientific consensus (now) is that the purple pigmentation acts as a sort of sunscreen against too much sunlight.
they are more dark green if they a understory plant, or a shaded plant. there of course plants that have no chlorophyll whatsoever. 2 types, one is mostly albino plants where they lose all thier chlorophyll, the other is mycoheterotrophic plants(either partial or fully). ever seen a albino redwood, apparently it lives off being attached to the roots of the parent plant where it came from or from nearby trees.
There’s also an extremely tiny percent of plants that are entirely white, they don’t get their energy through photosynthesis but instead a parasitic relationship of fungi and other plants.
Albino plants are a thing, but they usually are attached to the main plant where they came from. albino redwoods is an example. fully parasitic plants usually dont have leaves or have a small nonfunctional ones. some parasitic plants is exist as filaments inside a host(no stem no, leaves whatsoever)(rafflesia, pilostyles). the most famous is miseltoe, which is hemiparasitics, as it can sitll fully photosynthesize.
Mycoheterotrophs! Love them, such bizarre little plants
I was so disappointed when I learned how hard (I mean I haven’t actually tried it) to culture them, but it makes sense given how they occur.
Yeah I wouldn’t try that in a million years, you need, like, an actual functioning ecosystem for them to flourish
Whinging about a fact being wrong without providing a correction is worse than the one being wrong.
The thing is it’s kinda right, just lacking detail
This is indeed a valid theory, but not very powerful since it can only explain the color of green plants and not for example the color of non green plants or animals.
More powerful theories have been developed which can work on a much broader range of applications. For example the theory that plants are the color they are because God painted them that way.
Plants look green because the green spectrum has a lot of energy, and to stop over heating and leaf burning and messing with the delicate photosynthesis, plants reflect or let green mostly pass through and only use about 20% of green soecturm energy, while mostly use all of red end and blue end… At least that’s what I heard on a science show.
And why does the green spectrum have a lot of energy?
I’d have to go back and find the science article, but it was something about sunrise, sunset which would often provide end of spectrum red or blue, while full daylight provided a lot of green light spectrum. Plants having to balalnce processes in full spectrum would overload/oveheat so they evolved to reflect or transmit through 80% of that spectrum.
They mostly use red and blue for photosynthesis because those seem more steady during daylight hours in various seasons and hours of the day. Cloudy day still gets infrared end through etc.
The green overlaps into red and blue zones. Its not so much that it is higher energy than blue, but a wider amount of spectrum total energy the plant wants to avoid.
Explain this then
Because evolution isn’t actually guided and is really just a process of mutation, reassembly (for sexual species), then checking to see if it works well enough to pass genes on. Apparently red leaves work for that plant
We have diverse geography, and genetic diversity. Obviously this plant worked out a way to use the high energy of the wide green ranhe, without overcooking itself. But if you compare all plamt leaves and grasses of plant life green is the most common.
Cab you help explain it? I thought that the sky was blue because it reflects the ocean and because of rayleigh scattering, but do either of these affect the color of plants?
Sky isn’t yellow over a cornfield
Wow, wrong, Do some research, but I will help if needed (seriously, DM me or whatever) but why not do it publicly, You’re asking the right questions and that counts for a lot.
Reflecting the ocean is not a thing, but rayleigh scattering is a real reason for blue sky.
Science rocks.
Deeper, I would simply say that the sky is blue because air is blue. You cite Rayleigh scattering, but you’re just describing how light interacts with air. The only reason any material has any color is because how it interacts with light.
Air is blue. You can explain its blueness just like you can the physics origin of any other object’s color. But ultimately the sky is blue because air is blue.
Steve Mould has a great video digging into why things look white: https://www.youtube.com/watch?v=gug67f1_8jM
Probably not strictly translatable to all other colors, but a helpful illustration of how color is a result of the way objects interact with light, not inherent properties of the object itself.
Plants are green because they absorb all other wavelengths of light. And bounce the green into your eye. In actual fact, color only exists in your brain as a way to understand the world around us. Our eyes are just sensors that detect light. And color is how we process it. We could have evolved into understanding it in different ways too, like smell. Therefore color doesnt even exist in the natural world. Green is just an illusion of our mind.
Color exists physically as different wavelengths of light. The thing “in your mind” is about non-natural colors which trigger multiple light cones in your eye and your brain interprets them a certain way different than the natural colors. In that sense you do interpret the wavelengths one way or another in your head, but the actual light wavelengths so exist.
Yeah wavelengths exist. But ALL color only exists in your mind as perception. Natural and non natural.
If color existed outside of light touching your eye, you would be able to deduce it without light.
Fun to think about.
You’ve got it partially backwards. The sky is blue because of Rayleigh scattering, but it doesn’t reflect the ocean; the ocean is blue because it reflects the sky.
Incidentally, I’ve heard it said (I think it was xkcd) that we use the term “Rayleigh scattering” because it sounds silly to say that the air is blue (via the mechanism of Rayleigh scattering); so maybe that’s part of it?
The bit about the ocean being blue because it reflects the sky is unfortunately mostly wrong. Water is slightly more blue than ozone, so the more of it there is (big water in big ocean) the more blue it will look. The fact that it’s also reflecting the blue sky adds to the color, but on a cloudy day the ocean is still blue.
I’m still not following. What part of “blue air” imparts chlorophyll with its color? I get the sun. I understand how light works (reflection, refraction, and scattering). I understand our perception of light on a neuological level (including post-processing) to an extent that most people haven’t studied. Why “blue” air make green plant?
Air is light blue because it filters out red, which is why chlorophyl has optimized for the mix of the remaining wavelengths yellow and blue, which is green. Color theory of additive blending.
(Our sun is slightly yellow, which is why the sky isn’t cyan and why alot of tropical plants are darker green close to brown)
Are you saying that chlorophyll naturally evolved to take in specific wavelengths of light given the availability of light in specific frequencies in response to how the sun’s light moves through our amosphere? I would get it, but that would be so frustrating of a response to, “why air blue matter”.
I mean, yeah. I’m reaching for the, “why”, though. Specifically for chlorophyll, which reflects light with a specificity. As does carotene in dying trees in the fall.
My guess would be that plants optimize also for absorbing a significant amount of the light they receive from the blue sky, so they still get some when direct sunlight isn’t available.
I hate that one misclick can delete my comment.
Would that be a natural, logical discernment for someone trying to figure out why chlorophyll is green? I say that this is an unhinged take and everyone siding with it should feel like… an amount of bad. It’s pretty misleading by virtue.
This comment here had a much more grounded explanation
I mean, I love it and thanks for sharing, but it’s a pretty poor discernment for why “blue air” makes chlorophyll green. Sure, plants might be opportunistic in a respect and attempt to move to a color direction that gathers the maximum amount of the sun’s rays. Why was the initial post, “sky blue, sun yellowish = plant green”? Why was that met with agreement?
It’s not something that any Biologist would yield to as an explanation. Even if they respected themselves. (Sorry, Biologists. I know.)
Mix blue and yellow paint and you end up with green paint.
Oh, damn. Reductionist.
lemmy poster here. both of these people are annoying, unfunny fucks.
bet you didn’t see that one coming!
btw i have a masters degree in internet posting.
Lemme guess, reddit transplant?
Wouldn’t it be a “lemmy” guess? I’ll go ahead and see myself out.
Isn’t everybody?
