A monochrome planet

Question

I am asking if a planet with shades of gray only is scientifically possible in our universe. Basically everything on the surface of this planet would seem black and white to the human eye.

Here are some settings of the planet that may work for the case:

• The sun of the planet produces white light.
• The atmosphere of the planet doesn't scatter the light so the white light stays white when entering the atmosphere.
• The natural components of the planet consists of monochrome matter.

But there are cases where these wouldn't work so it would be nice if you also provided help with these questions:

• What if I put a material that absorbs all light but red? Wouldn't that object seem red?
• What if I brought a red light source.

Answer 1

One novel solution to this: make the planet infested with a mostly harmless microbe that either inhibits the production of, or simply eats, the specific photopsins (vision pigments) found in the cone cells of the human eye. Photopsins convert light into usable energy (similar to chlorophyll), so it is plausible that a microbe might be to acquire limited photosynthesis by eating it. Humans who go to the planet without eye protection will get infected and contract total color blindness. The microbe might not be able to survive without a chemical found in the planet's atmosphere, so when humans leave the planet the microbe dies and they get their color vision back.

Answer 2

The definition of "white" is actually rather tricky. Obviously there is no "white light" in physics. All "white" light is made up of a distribution of photons in different wavelengths. The concept of white is something in the human mind, and as famously shown, its a complicated one:

Our concept of white is actually adjusted in real time based on our surroundings. A "white" object is one which reflects the same distribution of light as fell on it.

In theory, you could try to make a planet consisting of only compound which reflect all visible light equally. You'd have to never have an atmosphere, no translucent compounds like water or glass which could refract the light. You'd have to blot out the different colored stars.

However, there's another way. If you only provide monochromatic light, everything looks like shades of grey. If you want a hoot, go find some colorful candy wrappers (like those on airheads) and look at them under a sodium light. They look grey-scale (it's actually a bit unnerving). Of course, we still perceive the yellow of the sodium light, but the human mind is very good at adjusting for these things. I think that, within a few days, you would see the monochromatic light source as "white" because there's little incentive in your brain to do otherwise.

So, instead of a sun, what you really need is a world lit by neon (or sodium) lights!

Answer 3

If the ambient light were to be a bright, bright yellow, it would wash everything out, and the human eye would quickly adjust to seeing it as black & white, or at least black & yellow. There's not much you could do about interior environments though if they were shaded from this yellow lighting, unless you found a way to get the light inside every cave, etc. too.

For reference, I'm using this Olafur Eliasson exhibit I once saw at the MoMA, where a room was lit like this, washing out all color:

That photo was not converted to monochrome, it is what the room looked like (to the camera, to the eye it looked black & white after a while once you get used to it).

Here's a video of people leaving the room: https://www.youtube.com/watch?v=R5jGQKOV30M

I couldn't tell you why this happens, or whether or not it works with other colors besides yellow. But it was really cool.

Answer 4

Human standard white light is by definition a combination of colors and cannot be replicated using a single wavelength (monochrome). There are two ways to do something similar to do this.

In the First method, everything will look one color (make it green to ensure it being human friendly) and its shades. This can be accomplished by a filter in the atmosphere, reflecting all other wavelengths. As a bonus, this could be a terraforming mechanism to reduce incoming light, thus cooling the planet. Obviously, for locals, who are adapted to monochrome light, thus will have only single color cones, seeing everything in gray. But for humans, the planet will look colored.

The second way of doing this will make everything look grayish, even for humans, but will not be very hospitable. Humans see monochrome in low light situations using rod cells. But in order to do this, your planet should be very dark. In time humans will adapt. I read somewhere it would take more than a day in the dark for human eyes to reach its limit on low light vision. Thus local human populace would be adapted for this planet.

Edit: A third way. Since you do not have science-based tag, it is possible to handwave a material in the atmosphere that would alter frequencies of light. Any light having a frequency between some range would have its energy equally distributed to all frequencies in that range. In this case, everything will look grayish. Including from a far.

Answer 5

Despite the current lack of a science-based tag you clearly use the phrase "scientifically possible" so for a science based answer:

No, unless maybe the planet had

• no atmosphere,
• no liquid (which would evaporate in the absence of an atmosphere),
• no vulcanism,
• no radioactivity

and

• was artificially constructed from an extremely small number of elements
• with an asteroid shield
• and a radiation shield
• and a maintenance crew that hid any material that had a defect or fracture.

As noted by others, white light is composed of various colours of light. If the incoming light isn't white then from the offset everything is coloured other than shades of grey.

The only atmosphere that won't Rayleigh scatter light is the complete absence of atmosphere. Even at the top of Everest or in commercial airlines where air is too thin to provide a breathable oxygen content the sky is blue due to differntuial scattering of incoming white light. Dust storms will make the atmosphere appear red as will sunsets. Your planet would have to have no atmosphere or an atmosphere so thin as to be invisible and unable to suspend atmospheric dust and suspended water wouldn't be allowed to prevent rainbows.

Liquids in general would have to be eliminated as they are prone to similar colouring effects and they also absorb various wavelengths of light. Suspended particles can shift the colour spectrum as well.

For things to appear in shades of grey to a human there must either be low light so human colour sense doesn't work or everything on the planet's components must be only black and white.

The former is meaningless as humans supply their own light sources. This means the latter must be the case in order for the original proposition to be true.

Since you're talking about a planet with a surface you're referencing a terrestrial planet. The surface of terrestrial planets are made largely of rocks which are themselves made of minerals and fragments of other rocks. Such a planet would have to have to have formed from no almost no transition elements as transition elements often form colourful compounds. You'd have no gold, copper, iron, manganese, chromium, silver, etc, which aside from making many pretty colours are also useful for industrial purposes. Since planets are formed from star-stuff and stars inherently go about making transition elements this is all but impossible. The planet would have to be artificially constructed to avoid these.

Your planet would have to be shielded from asteroids/meteors as many of these are made from transitions elements and over geologic time you can expect substantial numbers of these to impact a planet.

Radiation shielding would be required to prevent radiation from initiating nuclear changes that could result in the formation of transition elements. This would also necessitate the planet being made from only non-radioactive isotopes to prevent them decaying into colour-producing transition elements. Radiation can also effect colour changes, such as causing quartz, clear and colourless, to be converted to smoky quartz, clear and brown.

However, transition elements are not the only things that produce colour. Other elements are also coloured such as sulphur, chlorine, iodine, bromine, fluorine and these often produce coloured compounds. Minerals can also change colour through tenebrescence. And normally colourless elements can also form coloured substances, such as sugar solutions in water.

All the discussion on minerals above involves colour centres, regions in the solid where incoming photons interact with the electron stucture of the material but there are other mechanisms such as rainbow-like inteference patterns seen when stones have an internal fracture. These are actually also visible when fractures occur near the surface of otherwise opaque rocks, including obsidian which is opaque and black. Rainbows have been mentioned but one also needs to prevent dispersion through other clear materials such as occurs in prisms.

Vulcanism isn't allowed simply because molten rock glows red.

The only way around this is to have manufactured the planet from a limited number of materials that are not coloured and which are maintained to prevent the formation of colour.

Answer 6

Well... yes, the planet itself can be entirely gray.

...although there were some exceptions to the rule.

Although the color in this image is heavily exaggerated, the astronauts of Apollo 17 were very excited to find orange-colored lunar soil near Shorty Crater, because the Moon is otherwise expected to be entirely grey.

But can it be made so that everything else seems grey as well, no matter what color it "actually" is?

Not unless you invent an atmosphere that permits only one (narrow band of) wavelength of light to pass through it and that effectively absorbs everything else, or invent a LED/laser-star.

Answer 7

Even if you could create an entirely monochrome planet: Things you would bring there, will remain colored. So if you brought a red flashlight with you, objects would appear red. Moreover, you could not entirely protect the planet from extraterrestrial changes: Stars change their color in their life cycle, for example.

Anyway, a planet could be almost monochrome. In an ideal situation, you as a human might not even notice the minor side-effects of a planet not being entirely monochrome.

There are also many useful aspects which were mentioned by other users. Hope I could help you :)

Answer 8

White light contains all of the colors(i.e. wavelengths) in the visible spectrum. So when white light shines on an object, that object will appear different colors depending what wavelengths are reflected and absorbed. The only way to make the human eye not distinguish objects based on color is if those objects are illuminated with light from a single wavelength or a very narrow range of wavelengths. At first, humans would view a single wavelenght world as all one color, red for example. Everything would appear various shades of red, but no other color would be visible. This red scale would eventually fade to a grayscale as after about an hour or so for the same reason your eyes compensate the color correction when wearing tinted sunglasses or ski goggles. More on color detection

While most objects would appear colorless, other than slightly tinted red, it might still be obvious what color the single wavelength of light illuminating the environment was if one knew the color of objects before going to the new single color environment. While other colors would appear in grayscale of brightness, reds and whites would be indistinguishable if they were equally as reflective since they same amount of red light would reach your eye. For example, red paint on a white wall would be not be visible since the red paint and white wall would both reflect and equal amount of red light. This effect is used in some board games to obscure answers with colored patterns only visible through a card reader.

Illumination with a single wavelength is the only way to create a grayscale world, outside of microbes, as mentioned before, or chemical deficiencies in the people seeing but is subject to breakdown if a light source of a different color is present. Solar illumination with only a narrow range of wavelengths, such as if you planet was around a red dwarf that produces very little light of other colors, would not prevent other light sources from showing the true color of other objects, such as if your explorers brought a flashlight to the planet or they set a fire. Therefore, I think the best solution is an atmosphere that absorbs all wavelengths but one.

The Earth's atmosphere absorbs light from the sun at different wavelengths but allows most of the visible light to pass through. Your planet's atmosphere could have a number of gases that absorb all but a very narrow range of visible light, making the light that reaches your monochromatic. If the atmosphere was thick enough, light produced at the surface would also be absorbed and the explorers would not be able to see any color except the one unabsorbed color. A white flashlight would turn red after some distance, depending on the optical depth of the other wavelengths in white light in the atmosphere.

An almost totally absorbing atmosphere would cause some problems with life since very little energy would reach the surface. Photosynthesis on Earth occurs at nearly all wavelengths in the visible spectrum, so whatever plant life existed on the planet would have only the one wavelength to use. Also, animals on the planet would never develop color perception because it would be useless. The plants could use a different wavelength, just outside of the range that humans can see, potentially solving the energy problem. Also, if the atmosphere didn't block ultraviolet and infrared light that is outside of the human visible spectrum, animals on the planet probably will have developed eyes that can see in those wavelengths. Perhaps the dull monochromatic world to humans is actually a very vibrant, colorful world to those who can see the 'colors' we can't.

And one final other proposal would be to have a similar absorbing atmosphere but with nearly no light reaching the surface and have some sort of bioluminescence illuminating the environment at one wavelength as another way to create a monochromatic world.