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Rickswan
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So I'm writing this comedy Sci-Fi story and I want it to have some realism. One of the main characters is a sentient alien, and I want to do a little better on the Sci-Fi hardness scale than "rubber forehead alien." The chances are high for any alien life we encounter to be synthetic, so to clarify, I'm talking about organic alien organisms and their planets. I was a social science major so I don't have a lot of background in the hard sciences, but I've done a little research.
What I'm looking for is a sort of guide for coming up with alien planets and the alien races and animals that live on those planets. In order to do that, I need to fill some gaps in my knowledge about why things are the way they are here on Earth.
Since a lot of this is TL;DR, I've put my big questions in bold. I hope your expertise can help, internet!
What I'm looking for is a sort of guide for coming up with alien planets and the alien races and animals that live on those planets. In order to do that, I need to fill some gaps in my knowledge about why things are the way they are here on Earth.
Since a lot of this is TL;DR, I've put my big questions in bold. I hope your expertise can help, internet!
From what I've gathered, the majority of plant color is determined by the dominant wavelengths on the electromagnetic (EM) spectrum emitted by their planet's star, which is determined by its temperature. On the extremes, plants on an exoplanet with a sun lower on the EM spectrum (a reddish sun) would need to soak up as much light as they can muster, and may be darker, maybe black, and could potentially host a rainbow of colors. On an exoplanet with a brighter star, the plants may be brighter to reflect some of the more energetic light back, maybe even white (and reflect "excess high energy photons and appearing slightly blue" according to this). In-between planets (like ours) may have plants somewhere in the middle of the spectrum. Here seems to be a handy, slightly more detailed guide on star-temps/plant-colors.
But there is an issue: plants on Earth would be more efficient if they were black, right? I'll quote this article:
"Origin of chlorophyll- The purple pigment absorbed all wavelengths of light except for the reds and violets. Thus, any bacteria using purple pigments that lived deeper in the water than the purple bacteria on the surface would have no light to use because it had all been absorbed by the surface bacteris (exploitative competition). Because red and violet wavelengths pass through to deeper water, bacteria that contained a pigment that was able to absorb these wavelengths would be able to coexist with the purple bacteria. This was the origin of chlorophyll... chlorophyll is the dominant photosynthetic pigment today (there are still examples of photosynthetic bacteria with purple pigments, but they are limited to very harsh environments). Interestingly, chlorophyll came to dominate, not because it was a better at absorbing light energy, but rather because the cyclic flow machinery associated with chlorophyll was more efficient at producing ATP than the machinery associated with the purple pigment was. Thus, it is an evolutionary accident that modern plants are green." (note that there are http://www.giss.nasa.gov/research/briefs/kiang_01/ theories as well). Also troublesome is that some plants here on Earth are colors other than green.
... so what does all this mean for exoplanet flora?
But there is an issue: plants on Earth would be more efficient if they were black, right? I'll quote this article:
"Origin of chlorophyll- The purple pigment absorbed all wavelengths of light except for the reds and violets. Thus, any bacteria using purple pigments that lived deeper in the water than the purple bacteria on the surface would have no light to use because it had all been absorbed by the surface bacteris (exploitative competition). Because red and violet wavelengths pass through to deeper water, bacteria that contained a pigment that was able to absorb these wavelengths would be able to coexist with the purple bacteria. This was the origin of chlorophyll... chlorophyll is the dominant photosynthetic pigment today (there are still examples of photosynthetic bacteria with purple pigments, but they are limited to very harsh environments). Interestingly, chlorophyll came to dominate, not because it was a better at absorbing light energy, but rather because the cyclic flow machinery associated with chlorophyll was more efficient at producing ATP than the machinery associated with the purple pigment was. Thus, it is an evolutionary accident that modern plants are green." (note that there are http://www.giss.nasa.gov/research/briefs/kiang_01/ theories as well). Also troublesome is that some plants here on Earth are colors other than green.
... so what does all this mean for exoplanet flora?
A thought occurred to me that most animals try and blend into their environment in some way. Soils on our planet are mostly variations of reddish, yellowish, brown and beige, and a lot of natural camouflage reflects that. Aside from a few exceptions, sand and soil on Earthhttp://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/edu/?cid=nrcs142p2_054286. I know colors can vary, for example Mars has red soil due to iron that may be able to support life. The reflective properties may play a factor in what they look like, but I'm wondering about the soil itself, say under perfect white light. Organic life, minerals, etc. can affect soil color, but is planet-wide colorful soil that can still support life possible?
Our normal daily sky is blue due to Rayleigh scattering, and our ocean color has something to do with the sky... but could it be different on other planets?
So are these quotes correct? What could cause the sky to be purple, pink, yellow or green?
Our normal daily sky is blue due to Rayleigh scattering, and our ocean color has something to do with the sky... but could it be different on other planets?
- According to this, "stars with surface temperatures of 3,300 kelvins or lower (red dwarfs of spectral type M2.5 such as Gliese 581, or redder) would emit so fewer photons towards the bluish wavelengths compared to Sol that the sky would appear whitish down to reddish to Human eyes (more from Earth Science Picture of the Day). If comparatively more bluish or reddish light reaches a planet's surface than on Earth, photosynthetic plant-type life may may not be greenish in color, because such life will have evolved to different pigments in order to optimize their use of available and so color the appearance of the planet's land surfaces accordingly."
- According to "jjdebenedictis" http://absolutewrite.com/forums/showthread.php?246908-Sky-color-and-ocean-color-on-alien-planets: "The sky is blue because the molecules that make up most of it are "dipoles", i.e. there's an electrically negative end and an electrically positive end to the molecule.
Light is electromagnetic radiation. That means it will interact with these electrical dipoles. Specifically, there's a small chance that light passing close to a dipole molecule will bounce off that molecule. Furthermore, light with a short wavelength (i.e. bluer end of the spectrum) is more likely to bounce off than light with a long wavelength (redder end of the spectrum.)
So when you look at the sky, and see all the sunlight that has bounced off the air itself, there's more blue light reflecting down to you than red. Hence, a blue sky.
Another point: the light, when it bounces off a dipole, tends to bounce sideways.
And this explains why sunsets and sunrises look red. At those times of the day, the light has to travel through a lot more air because it's coming in at a glancing angle through the skin of atmosphere on our ball-shaped world. Thus, at sunrise and sunset, most of the bluer light scatters out sideways and there is only the redder light left to reach your eyeballs.
How does this impact alien worlds? Well, there are a lot of different gases that form dipoles, and those that don't form dipoles don't scatter light very effectively. So most atmospheres, regardless of the composition of the air, would produce a blue sky.
... however, impurities do have an effect. The sky of Mars looks red due to all the dust in it, and! (this is really cool) the sunsets and sunrises look blue because so much red light gets scattered off the dust that there's only blue light left to get through...
One way you could play around with sky colour on an alien world would be to have the star, i.e. the planet's sun, have a different spectrum than our Sun does.
If the planet's sun is a red star, then the sky might look green or yellow to human eyes. If it's a blue star, the sky might look purple or even black with the stars showing through because the light reflected is mostly in the non-visible ultraviolet. (Ouch. Sunburn city.)
Note that this is only how humans would see it, however. Creatures that had evolved on that world would have eyes that see best at wavelengths of light that their sun puts out. To them, the sky would look blue; it's just their idea of "blue" would be at a higher or lower wavelength than what we call "blue".
By the way, the colour of the sky is a darker blue at higher elevations because there's less air above you to scatter light. You're effectively seeing a bit of the black of space through the blue.
So a thicker or thinner atmosphere would be a way to change the colour of the sky also.
As for water, it forms a dipole too, so you should get similar effects from it, but that's not something I ever learned about specifically." - on the same site, YeonAh says: "White clouds are caused by CIE scattering, which is larger particles that scatter ALL wavelengths in all directions so they combine as white in our eyes.
With all that said, by changing up the particles in the atmosphere (as mentioned above), you can easily change the color of the sky. Want a green sky? Knock off wavelengths on both extremes of the spectrum to get that green color in the middle. What happens if the clouds get rid of all the blue in the light and turn red? What if there's a gas between the sun and the planet that takes all the red wavelengths out of the light, so absolutely no red reaches the planet?
Also, about the ocean. According to my university teacher at least, the ocean is NOT blue because it's reflecting the sky. It's because the particles in the water absorb small amounts of light, starting with the wavelengths on the red side of the spectrum. In something like a glass of water, this amount is so small it doesn't matter and the water will appear clear. But in large, large amounts like the ocean, you can see the water as a deep blue because all the red's gone. When water appears green, it's mostly because green is the mid-point between red and blue in the spectrum, and the water isn't deep enough to be blue. Go deep enough, and all wavelengths will be absorbed so the water will be...dark."
So are these quotes correct? What could cause the sky to be purple, pink, yellow or green?
Plants are crazy, even on Earth. They adapt to their environment in every way, shape, and form, it seems, depending on all sorts of environmental factors - sources of energy, On an alien planet, there could be seas of algae (not a plant, granted), giant lillypad things, black trees, etc. I haven't even scratched the surface in my research for possible plant characteristics. Here are some ideas.
What do you think is most likely? Earth-like plants, or what?
What do you think is most likely? Earth-like plants, or what?
Information on skin color was tough to come by. I believe the way feathers, scales, and whatever things like Jellyfish have are structured is what allows them to get so colorful. I know that in humans, the lightness and darkness of pigmentation is caused by melanin and relates to the amount of UV light the area gets - more and the skin is darker, less and the skin is lighter. It can't be too dark in areas with less UV because we need some of those rays in order to get Vitamin D, and those with light skin are more prone to skin cancer in areas more exposed to UV. I get that, but what I have more difficulty finding is why our skin isn't more colorful - why isn't our skin, say, blue, green, bright fuchsia, red, purple, yellow, etc. (excluding disorders)?
The closest I found was http://www.sankofa.ch/texts/Melanin.htm site, which says "Pigments that contribute to skin color are called carotene, a yellowish hemoglobin, in blood vessels (pink-red), and melanin (black, brown, red). Darker skins are dominated by melanin, which is produced from the amino acid tyrosine, by pigment cells (melanocytes) in the skin. Melanocytes are characterized by long, fixed extensions of the outer cell membrane. In humans, other mammals, and birds, melanin is dispersed permantely throughout each melanocyte, including the extensions, and is also, transported to nearby skin cells. In other words, if you increase the amount of melanin in the skin you become darker and vice versa." This leads me to believe that our skin is almost translucent, and it's the color of the stuff under our skin (like blood vessels) that lend it the pinkish color... but then why does our skin tend to get dark brown instead of black (like some pigs)? Since our bloods have iron carried by hemoglobin, our blood is red; if what's under the skin can lend the creature its color, is it possible for an intelligent alien species, especially something mammalian, to have blood a color other than red?
The closest I found was http://www.sankofa.ch/texts/Melanin.htm site, which says "Pigments that contribute to skin color are called carotene, a yellowish hemoglobin, in blood vessels (pink-red), and melanin (black, brown, red). Darker skins are dominated by melanin, which is produced from the amino acid tyrosine, by pigment cells (melanocytes) in the skin. Melanocytes are characterized by long, fixed extensions of the outer cell membrane. In humans, other mammals, and birds, melanin is dispersed permantely throughout each melanocyte, including the extensions, and is also, transported to nearby skin cells. In other words, if you increase the amount of melanin in the skin you become darker and vice versa." This leads me to believe that our skin is almost translucent, and it's the color of the stuff under our skin (like blood vessels) that lend it the pinkish color... but then why does our skin tend to get dark brown instead of black (like some pigs)? Since our bloods have iron carried by hemoglobin, our blood is red; if what's under the skin can lend the creature its color, is it possible for an intelligent alien species, especially something mammalian, to have blood a color other than red?
All kinds of variables exist of course, such as differences in gravity, that would affect organisms - low gravity could mean weaker and taller aliens, high gravity could mean stout and strong aliens, for example. silicone-carbon hybrid life forms may exist. Here on Earth, young planthopper insects actually have mechanical gear wheels in their legs to help with jumping. The environment may promote things Earth doesn't seem to have, light a thick atmosphere causing creatures to be able to communicate non-visually (sensing electrical pulses through the thick humid air) or aliens with bio-luminescent patches on their skin. Especially for non-intelligent animals, the possibilities seem endless.
There are some specific things that intelligent life most likely possesses. I have a whole document of notes from a variety of sources.
There are some specific things that intelligent life most likely possesses. I have a whole document of notes from a variety of sources.
- They likely need to be land-based because fire is the basis for the development for a lot of technology (water doesn't mix with fire); this means they would probably have something like lungs to breathe the atmosphere and an internal (skeletal) structure to support life on land.
- Being on land, they probably wouldn't be too squishy so they would have something protecting their internals (chitin or bones and a coating like skin).
- They need delicate grasping manipulators (like hands), and thus probably aren't quadrupeds (we can't manipulate with our feet very well, they're our workhorse limbs).
- Most creatures are bilaterally symmetrical. They need good enough senses to detect predators and prey from a distance (probably needing light and auditory sensors).
- They would need to be social and have the ability to pass on information to younger generations (a decent memory and a complex way to communicate).
- Eyes on the side of the head allows you to spot predators from a greater viewing angle, but forward binocular eyes give one better depth-perception (which also means they need at least two eyes, probably with a lens and an iris), which aids in capturing prey; predators are more intelligent than prey and since an intelligent, sapient species would likely be an apex predator, they may be more likely to have forward-facing eyes.
- delicate parts are generally protected, which is why our eyes are recessed, our brain is within a skull, we have a rib cage, etc.
- Since evolution doesn't like having things that are unnecessary, creatures like Minotaurs are unlikely (why have 4 legs when you can have 2?).
- The main sensors would probably be on or close to the head, like most creatures on Earth, because it provides the brain with the fastest and best signal.
- It would need a brain and nervous system of some sort in order to feel, control its body, and process information.
- If it had an olfactory sense, especially in the form of a nose like ours, it would probably be above the mouth and under the eyes, for the same reasons ours is (better for swimming, doesn't get in the way when consuming, nasal drainage isn't pleasant if it gets into the eyes, sharing the windpipe allows us to breathe with our mouth closed, etc.).
- Its eyes would be above the mouth and nose, because when consuming nutrients, you don't want the food to fall into the eyes or block the field of view.
- Auditory sensors (ears) would likely be on the sides of the head, close to the brain to ensure a good signal, and on the sides because this is the best way to detect the directional source of a sound.
- It would need something to spurn a bigger brain, so it probably wouldn't be stationary, overly slow (like armored animals) or plant-based, as those forms of life do not promote complex survival strategies (and thus, a bigger brain).
- A feathered, flying creature would probably need to be light, and thus have a small brain, making them less likely candidates. Scales are generally useful for ectothermic organisms, which seem less likely to be intelligent. Some combination, like scaly skin may be possible.
- Eyes would probably be near the brain to reduce time delay and degradation of the signal
- an elevated head is useful because it allows one to spot predators - the head and eyes being on the bottom of the body, for example, is unlikely.
- They would need a means to extract and consume energy (meaning they're probably endothermic) from their surroundings to power their brains and limbs and excrete the waste from the energy somehow (probably a mouth or some analogue). Plants became fibrous to prevent being consumed, so their predators developed teeth to bypass that, and so on.
- http://blog.sciencefictionbiology.com/2007/04/color-of-alien-flora.html
- http://biol1404hon2015.blogspot.com/2015/02/why-arent-plants-black.html
- http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html
- http://www.giss.nasa.gov/research/briefs/kiang_01/
- http://www.astrobio.net/topic/deep-space/alien-life/colors-of-alien-plants/
- http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html
- http://www.nature.com/news/2007/070409/full/news070409-7.html
- http://www.solstation.com/life/a-plants.htm
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