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View Full Version : What if the moon was green instead of gray? (Queen at Arms)



SerenityFrost
2014-07-20, 01:25 PM
So with our kickstarter coming on August 15th we've been focusing quite a lot on getting the hype up for our visual novel Queen at Arms (https://www.facebook.com/QueenAtArms). (That means no proper writing for a little bit, but that's okay, we could all use a small break now and again.) Anyway, while I was talking to the guy putting together our kickstarter appeal video, I started to think about Lusk's moon.

http://i.gyazo.com/61ad52627432f09cd8d61bc24a073f05.png

So, the moon in this setting is green. This tends to cause the people of Lusk to believe there is a garden there where Althea (their goddess) lives and gives the souls of the dead respite. However, there is no actual vegetation on the moon, it's just made of a material that reflects green rather than gray. When we thought it up this was just a neat idea to give the setting a more unique feel, but now I'm beginning to consider the effects a green moon would actually have. Especially in a game where we have a war going on.

I made a new thread for this because it's a science question rather than a military tactics one. Plus it's something that I think a lot of DMs might like to know about in order to flavor their settings better. I've done a little bit of my own research on the effects a green moon would have on how one sees at night. Seeing as our night vision doesn't have a means of perceiving color, I imagine a green tint in the night sky would only really occur when the moon is full. But a tinge of color isn't really what I'm wanting to properly figure out here. That requires more science knowledge than I currently have under my belt.

So, to have more accurate answers for the questions I'm about to pose, I've worked out a few extra details about the moon other than "it's green". (Thanks to this reddit thread here (http://www.reddit.com/r/askscience/comments/1pgacu/if_the_moons_surface_was_a_different_color_would/).) For one, it's made of a shiny green material so that it can reflect light with the same intensity as our moon (thus keeping the nights in the game from being too dark to have a battle in, we still have to consider game mechanics at the end of the day). Lusk's sun is yellow and emits the same colors as ours (it's in the middle of its main sequence, so there's no real threat of it becoming a red dwarf anytime soon.)

I don't think this is as relevant as the sun information, but I'm going to include it anyway. The main sea level of Lusk is higher than that of Earth causing Lusk to have more islands and smaller sized continents. I realize that this information would have relevance in regards to the size and position of the moon rather than it's color. (Their moon is the same size and distance as our own. Lusk is pretty much parallel to the earth in most regards save for MSL.)

This is also a little less relevant, but would allow for more flexibility in some areas. Lusk has magic, but isn't rich in it. The strength of magic comes in 10 year waves where their goddess Althea sleeps and wakes at the core of the world. The energies that fuel magic are a major source of life on Lusk (souls are made of it, and everything there gives off this energy to varying degrees). I talk more about how magic works in another Queen at Arms thread (http://www.giantitp.com/forums/showthread.php?341597-Designing-a-quot-Battle-of-Agincourt-quot-based-battle-(Queen-At-Arms)).


Now, with all that information set down, I'll get to some of the curiosities I had about how a green moon would actually influence the planet.

What would the moon actually need to be made of in order for it to be green and also shiny enough to reflect enough light onto the surface for nights to be as visible as the ones on Earth?

What colors would be visible during a full moon as opposed to a waxing or waning one?

Would this have an effect on the way certain animals see in the dark?

Would it have any major effect on vegetation?

How would this change temperature at night assuming it's already very cold to begin with during the day?

Feel free to mention any other answers to questions I haven't thought to ask. Thanks for your help in advance!

Lord Torath
2014-07-20, 03:40 PM
It's probably worth pointing out that our sun is a white star, not a yellow one. Passing its light through a prism gives you a rainbow. If it was yellow, we'd only get yellow light out of the prism.

Your magic cycle could also be based on the solar cycle. Our sun has a 12-13 year cycle from solar maximum (lots of sunspots, solar flares, and coronal mass ejections) to solar minimum and back again. That's pretty close to your 10-year cycle of magic. Gives the option of having solar flares cause "magic aurorae" on your planet. Of course, unless your planet's inhabitants have methods of viewing the sun and its coronosphere, they probably wouldn't even be aware of the flares and CMEs other than from their magical effects when they reach your planet.

You moon doesn't need to be terribly reflective. Our moon only reflects about 1/10th of the light that hits it. It's still pretty bright.

Colors: Your moon could be rich in copper ores (which tend to have a green color). Malachite is another green mineral. Or the whole thing could be made of emeralds, though that's probably going too far. I'm sure there are other green minerals as well. A Google search might help. Green cheese is also obviously an option. :smallwink:

Night-time colors and vision: The objects that would be most visible at night would be those that are green in white light (daytime sun). Any objects that don't reflect at least a little green light would be black, even in the full moon. Objects have color because they reflect that color (wavelength) of light, but absorb the rest. So objects that aren't green would absorb the green light, and reflect nothing back.

Temperature at night would be unaffected. Earth isn't noticeably warmer on full moons that it is on new moons. Nighttime temperature will be based on cloud cover and the previous day's temperature. More cloud cover = less temperature drop. Of course, rain tends to bring the cooler temperatures in the low atmosphere down with it, so that will tend to lower the temperature, even with cloud cover.

I don't think this would significantly affect vegetation, as plants usually get all their light during the day, and your star is pretty much the same as ours.

SerenityFrost
2014-07-20, 04:05 PM
Bully, Lord Torath! This was a lot of help already. Culturally they have a lot of religious answers for their scientific questions (they have 14th century technology with black powder having been introduced about a decade ago) but as the writer I need the scientific answers for them. I actually hadn't considered using the sun for their magic cycle, but I think I'm going to implement that.

I'll also keep in mind that one can see green at night and nothing else color wise, which would probably have some cultural and/or religious significance for them. (I'll also make sure the artists know to hue up the green a little in night backgrounds and CGs.)

Knaight
2014-07-20, 10:01 PM
IColors: Your moon could be rich in copper ores (which tend to have a green color). Malachite is another green mineral. Or the whole thing could be made of emeralds, though that's probably going too far. I'm sure there are other green minerals as well. A Google search might help. Green cheese is also obviously an option. :smallwink:

Night-time colors and vision: The objects that would be most visible at night would be those that are green in white light (daytime sun). Any objects that don't reflect at least a little green light would be black, even in the full moon. Objects have color because they reflect that color (wavelength) of light, but absorb the rest. So objects that aren't green would absorb the green light, and reflect nothing back.
This is oversimplified. The moon appears green, but that doesn't mean that only green light is reflected - merely that the balance of light reflected is skewed strongly enough towards green that it appears green. This means that non-green things would still be plenty visible, even if they did absorb all green wavelengths reflected*.

*Which is pretty unlikely. While molecular spectra tend to encompass way more than the few lines of atomic spectra, complete absorption of an entire color is relatively uncommon.

Sith_Happens
2014-07-20, 11:01 PM
Not a physical effect, but most cultures on Lusk will probably associate the color green with nighttime (in addition to its other typical associations), which could affect certain rituals and superstitions.

HighWater
2014-07-22, 04:41 PM
I'd like to add the following:

Our sun emits the most light at something very close to the green wavelength (http://blogs.discovermagazine.com/badastronomy/2008/07/29/why-are-there-no-green-stars/#.U87IZbGvSUk) (which is 510nm). We see it as white, because it also outputs other colours and that stuff activates our other cones as well. This is also quite likely the reason that our black/white rods are most sensitive to the green-blue wavelength.

If a moon is to be composed of a material that only reflects part of the light (only the green waveband) while still providing the same light-intensity required for rod-activation, the material would have to be significantly more reflective in the green spectrum than the surface of our moon, to compensate for all the energy effectively lost outside it. It would also have to be very absorbent of other wavelengths. Remember that green is about the worst colour to have to single-out: any bleed into blue or red cones will diminish the green effect quickly.

Personally, I don't know of a material green nd reflective enough to cause a green moon with the exact same brightness as our own moon, given the same moon-planet and planet-star distance. Since you feature a (low) Magic world, might I suggest you use Magic in your explanation or don't try to explain at all? No matter how sound our scientific advice may be, someone with more knowledge will eventually shoot a hole in any explanation of a green moon around an Earthlike planet and it will likely be so obvious that in hindsight it's impossible to unsee. (Why would the moon be green in the first place? Previously mentioned copper is not a good candidate, for copper to turn green, you need chemical reactions that, as far as I know, mostly occur in an atmosphere, and I reckon this moon doesn't have one (or the reflection question just got a lot more complicated). You're going to have trouble explaining the presence of a green moon without resorting to magic/tech...) On to some physical consequences of a green moon:


Seeing in the Dark

To most "normal" humans, everything will still look black/white/grey (with normally green objects being somewhat brighter than others, because they reflect more light) because rods are much, much, MUCH more sensitive to light than cones.

If anything, you'd see that the moon appears green much sooner than you'd see that everything was bathed in green moonlight (due to photon density and cone sensitivity).

Seeing everything in green/black has no survival-value over seeing everything in grey/black. Seeing anything other than green at night will be impossible with a green-only moon.This means in practise that nothing can see colour at night as green is the only viable wavelength. This is not a problem for humans, as we don't have color-nightvision anyways, but a lot of nighttime animals wouldn't function the same way they did now. If the moon only reflects in visible-green and doesn't reflect in ultraviolet or infrared, even more creatures are boned... Basically, if you make your moon reflect only green, there is no such thing as colour-nightvision.


I think you're making this unnecessarely complicated by trying to find a scientific explanation for a green moon, make it somehow have the required brightness without changing distances or sun-intensity and wondering what the impact of all that green might have on your world... You're overthinking this. The world with some magic has a green moon and at nightime everything looks green? Just snap your fingers and it is so, nobody will wonder the scientific why. I know I never wondered too much at the strange arrangements of fantasy worlds that explicitly contained magic.


Explanations
Here's a semi-scientific explanation that evades a ton of the "science-issue" questions:
There's an actual, real-life effect that makes nighttime views appear blue if you sit still and stare long enough. One possible explanation for this effect is that the blue cones "suffer" from activation bleeding in from the much more sensitive rods as the moonlight itself is insufficient to activate them.
Well, there's an explanation for making that stuff green instead!: a magic/technological experiment conducted on the people of Planet Lusk, or a simple genetic mutation in an ancient ancestor, has made the green cones much more sensitive to bleed-in from the rods, which makes the world a shade of green at nighttime. Incidentally, this also explains MORE green activation during full moons (more rod-activation to bleed into the green cones, without affecting the red and blue cones).

Another semi-scientific explanation:
It is caused by the upper atmosphere. At low light intensities, it converts a lot of the light into green (or just filters it out). Because the red and blue cones aren't activated, the nightly appearance of the planet is dominated by a green hue, as is the appearance of the moon, which is not intense enough to push the other colours through this filter. The sun is a FAR more powerful lightsource and completely oversaturates this effect, which means daytime conditions look normal.This will lead to the exact same vision effects as an actual green lightsource: green objects will be more reflective and therefore less dark.

Another semi-scientific explanation:
The day/night difference in lightsensitivity for green cones in Lusk's people is much more profound than that found in Earth's humans. Because it's only the green cones that fire, while the reds and blues are left out, the whole world and the moon appear covered in green at nighttime, while this effect goes away when enough sunlight creeps in to activate the red and blue cones. This will lead to the exact same vision effects as an actual green lightsource: green objects will be more reflective and therefore less dark.

Here's a magic/scientific explanation that evades a ton of the "science-issue" questions:
The green effect is actually not in the moon, but on every surface. A certain kind of magic/micro-organism that lives on living beings as well as dead rock converts other wavelengths into the green wavelength at night. It lies dormant at day because the daylight is much too powerful for it too handle, but at night it activates and releases a green glow. Upside? It also releases its creepy green illumination when there is, for instance, a storm. Ominous! Downside? Your moon doesn't appear green! It has a much smaller effect on the relative brightness of green objects vs other objects as it's not reflectivity but an actual lightsource (which the underlying green objects will still reflect more).

Another magic explanation:
Wizard did it.

Or a God.

Or it simply is... Which brings me to the final suggestion:

Not an explanation at all but it still works:
The people of Lusk don't know why, they don't question why. The entire matter of wh the moon and moonlight are green doesn't occur to them. It just is.

Hope it was of some use.

SerenityFrost
2014-07-22, 06:41 PM
In the game there isn't any scientific explanation as to why the moon is green. No one questions it as it's not new for them. There are a lot of religious allusions to the green moon, and a lot of people believe the moon is green because their goddess lives in a lush garden on the moon. The question was posed mostly because I as the writer am interested in knowing how a green moon would work scientifically. d: And because all the information given would be a good resource for any DMs out there who want to have a fun colored moon in their setting.

I could honestly just make up a green reflective material for the moon since the setting is a fantasy one and that sort of thing is usually expected, but I do like the genetic and/or planet atmosphere idea for seeing green at night. I may play with that theory a little more if the game's Archmagus ever offers up a magical explanation for why the night is green as a means of explaining how some other spell works. Since magic is something permeable on Lusk, it's very reasonable to me that it would have an effect on the environment or the creatures living in said environment.

So far I've been very happy with all the cool stuff I've been learning. If you guys don't mind, I'd like to try posing another question in regards to moons.

Would it be viable for the moon to have vegetation on it and still give off light?

VoxRationis
2014-07-22, 08:37 PM
I'd like to add the following:

Our sun emits the most light at something very close to the green wavelength (http://blogs.discovermagazine.com/badastronomy/2008/07/29/why-are-there-no-green-stars/#.U87IZbGvSUk) (which is 510nm). We see it as white, because it also outputs other colours and that stuff activates our other cones as well. This is also quite likely the reason that our black/white rods are most sensitive to the green-blue wavelength.

If a moon is to be composed of a material that only reflects part of the light (only the green waveband) while still providing the same light-intensity required for rod-activation, the material would have to be significantly more reflective in the green spectrum than the surface of our moon, to compensate for all the energy effectively lost outside it. It would also have to be very absorbent of other wavelengths. Remember that green is about the worst colour to have to single-out: any bleed into blue or red cones will diminish the green effect quickly.

Personally, I don't know of a material green nd reflective enough to cause a green moon with the exact same brightness as our own moon, given the same moon-planet and planet-star distance. Since you feature a (low) Magic world, might I suggest you use Magic in your explanation or don't try to explain at all? No matter how sound our scientific advice may be, someone with more knowledge will eventually shoot a hole in any explanation of a green moon around an Earthlike planet and it will likely be so obvious that in hindsight it's impossible to unsee. (Why would the moon be green in the first place? Previously mentioned copper is not a good candidate, for copper to turn green, you need chemical reactions that, as far as I know, mostly occur in an atmosphere, and I reckon this moon doesn't have one (or the reflection question just got a lot more complicated). You're going to have trouble explaining the presence of a green moon without resorting to magic/tech...) On to some physical consequences of a green moon:


Seeing in the Dark

To most "normal" humans, everything will still look black/white/grey (with normally green objects being somewhat brighter than others, because they reflect more light) because rods are much, much, MUCH more sensitive to light than cones.

If anything, you'd see that the moon appears green much sooner than you'd see that everything was bathed in green moonlight (due to photon density and cone sensitivity).

Seeing everything in green/black has no survival-value over seeing everything in grey/black. Seeing anything other than green at night will be impossible with a green-only moon.This means in practise that nothing can see colour at night as green is the only viable wavelength. This is not a problem for humans, as we don't have color-nightvision anyways, but a lot of nighttime animals wouldn't function the same way they did now. If the moon only reflects in visible-green and doesn't reflect in ultraviolet or infrared, even more creatures are boned... Basically, if you make your moon reflect only green, there is no such thing as colour-nightvision.


I think you're making this unnecessarely complicated by trying to find a scientific explanation for a green moon, make it somehow have the required brightness without changing distances or sun-intensity and wondering what the impact of all that green might have on your world... You're overthinking this. The world with some magic has a green moon and at nightime everything looks green? Just snap your fingers and it is so, nobody will wonder the scientific why. I know I never wondered too much at the strange arrangements of fantasy worlds that explicitly contained magic.


Explanations
Here's a semi-scientific explanation that evades a ton of the "science-issue" questions:
There's an actual, real-life effect that makes nighttime views appear blue if you sit still and stare long enough. One possible explanation for this effect is that the blue cones "suffer" from activation bleeding in from the much more sensitive rods as the moonlight itself is insufficient to activate them.
Well, there's an explanation for making that stuff green instead!: a magic/technological experiment conducted on the people of Planet Lusk, or a simple genetic mutation in an ancient ancestor, has made the green cones much more sensitive to bleed-in from the rods, which makes the world a shade of green at nighttime. Incidentally, this also explains MORE green activation during full moons (more rod-activation to bleed into the green cones, without affecting the red and blue cones).

Another semi-scientific explanation:
It is caused by the upper atmosphere. At low light intensities, it converts a lot of the light into green (or just filters it out). Because the red and blue cones aren't activated, the nightly appearance of the planet is dominated by a green hue, as is the appearance of the moon, which is not intense enough to push the other colours through this filter. The sun is a FAR more powerful lightsource and completely oversaturates this effect, which means daytime conditions look normal.This will lead to the exact same vision effects as an actual green lightsource: green objects will be more reflective and therefore less dark.

Another semi-scientific explanation:
The day/night difference in lightsensitivity for green cones in Lusk's people is much more profound than that found in Earth's humans. Because it's only the green cones that fire, while the reds and blues are left out, the whole world and the moon appear covered in green at nighttime, while this effect goes away when enough sunlight creeps in to activate the red and blue cones. This will lead to the exact same vision effects as an actual green lightsource: green objects will be more reflective and therefore less dark.

Here's a magic/scientific explanation that evades a ton of the "science-issue" questions:
The green effect is actually not in the moon, but on every surface. A certain kind of magic/micro-organism that lives on living beings as well as dead rock converts other wavelengths into the green wavelength at night. It lies dormant at day because the daylight is much too powerful for it too handle, but at night it activates and releases a green glow. Upside? It also releases its creepy green illumination when there is, for instance, a storm. Ominous! Downside? Your moon doesn't appear green! It has a much smaller effect on the relative brightness of green objects vs other objects as it's not reflectivity but an actual lightsource (which the underlying green objects will still reflect more).

Another magic explanation:
Wizard did it.

Or a God.

Or it simply is... Which brings me to the final suggestion:

Not an explanation at all but it still works:
The people of Lusk don't know why, they don't question why. The entire matter of wh the moon and moonlight are green doesn't occur to them. It just is.

Hope it was of some use.

Wait, don't most animals have black-and-white nightvision? Most mammals have fewer kinds of cones than humans anyway.

Lord Torath
2014-07-22, 10:53 PM
Would it be viable for the moon to have vegetation on it and still give off light?Yes. The earth reflects more light than the moon does, and it has lots of plants. Of course, it also has lots of white clouds, as well as Ice Caps, which tend to be far more reflective than the plants, but there's no reason a plant-covered moon wouldn't still be bright in the night sky. In fact, the albedo of a cloudless, forest-covered moon would be in the range of 7-13% (http://en.wikipedia.org/wiki/Albedo). The moon's albedo is about 12% (http://www.asterism.org/tutorials/tut26-1.htm).

HighWater
2014-07-23, 06:36 AM
Wait, don't most animals have black-and-white nightvision? Most mammals have fewer kinds of cones than humans anyway.

It appears I vastly overstated the number of species with colour-lowlight vision, I guess that's what you get when picking the wrong nocturnal creature to generalise from and not double-checking because you're tired. Most nocturnal creatures seem to only have rods, even. I'm gonna go ahead and call this a "whoops", revised text:

For most night-time animals, nothing would change at all. It would provide more options for cone-optimalization as a viable nightvision alternative, but as I stated above, all-green nightvision seems to have no survival-value over all-grey nightvision. You'd only expect those animals with already strong green vision to detect the green at night, humans may or may not be among them (see below).

This brings me back to the point where it's unclear if you'd perceive the moonlight as green, even if it were green: the light's intensity may be just too low to activate the cones, even if it is of the right wavelengths. Cones are generally only sensitive to direct light and are unable to pick up scattered light. Creatures that compensate for low light-intensity through big eyes, a tapetum lucidum (http://en.wikipedia.org/wiki/Tapetum_lucidum) and more refined neuronal networks rather than upping the rod-ratio will see the green effect sooner (provided they have green cones).

Estimates of visibility: There's not just colour vision (photopic) and black/white vision (scotopic), but also an intermediate state called mesopic, where there is some colour detection and both rods and cones contribute to eyesight. This stage is actually often active at night, because the night often isn't dark enough to go full-blown scotopic.

The tables I found on these (http://en.wikipedia.org/wiki/Orders_of_magnitude_%28luminance%29) websites (http://www.visualexpert.com/Resources/nightvision.html) suggest that the moon itself would definitely look green, and the moonlit environment may look green if you account for the added green intensity if it is to compensate for the loss of other wavelengths (same total light intensity). So it appears things may actually have a bit of a green hue to them, though probably not as powerful as in the depiction (but depictions tend to be dramatisations anyway).

The vegetation question has been answered succinctly. I'd like to add that if you want your moon to be cloudless, you'd have to make up something to prevent clouds from forming in the atmosphere, or a way around the need for an atmosphere for the vegetation (complete soil-dependence, any produced waste products are excreted as solids or liquids, rather than being expelled as gasses).

Rosstin
2014-09-02, 07:35 PM
We're on Kickstarter now :-)

https://www.kickstarter.com/projects/1297221353/queen-at-arms