# Alien vision

#### chasrob

Gold Member
In a story I’m working on, the antagonists are (humanoid--almost identical to humans) aliens, with 2 eyes, binocular vision. Their tech and bio-engineering is several hundred years advanced from ours. They can see the (human) visual spectrum, but also into the infrared (how far I haven’t decided).
Since they can see the extra wavelengths, I had this idea: compared with humans; the visible wavelengths they see are slightly shifted to the red. Forex, what we would see as blue, they would see as, uh, lavender. The degree would be affected by the temperature of whatever they're looking at.
This make any sense at all?

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#### kuruman

Homework Helper
Gold Member
That makes sense. Are you familiar with blackbody radiation? A relevant result can be summarized with the equation $\lambda~T=const.$ which says that the peak wavelength of the distribution becomes shorter as the temperature rises. Have you ever wondered why you see the heating element on an electric stove glow red only when it's set on "High"? That's because your eyes are not sensitive enough to see the element glow at "Medium" or "Low" settings. As a stove element at room temperature is turned on and starts heating up, your aliens' eyes should be able to see it glow long before human eyes could.

#### Nik_2213

Neat ! Of course, their colours would have different names...

FWIW, I've been toying with the converse issue, where a bright, pre-teen Terran can see ~400~~750 nm, but the holly-green, humanoid-ish bipedal aliens only ~470~~570 nm. They, however, can easily distinguish many, many more shades of green-ish within that range. Their world is a strange mix of near-identical shades of green, plus garish or discordant materials whose 'out of band' colours are invisible to their eyes...

Think how many apparently 'plain' flower petals have vivid markings in UV, the better to attract bees etc.
Also, how some flowers trap infrared...

To add yet more frustration, the aliens' speech and hearing runs from ~20 kHz~~40 kHz, compared to the Terran's ~20 Hz~~20 kHz...

The unfortunate boy is kept as a pet, a 'dress up doll', until he happens upon a museum's preserved 'Victorian-ish school room with green-board & chalk'. Fortunately, his dad, uncles and cousins loved recreational math. He starts with counting in different bases. Then Operators & Constants.
Blows the aliens away with Euler's e^iπ + 1 = 0
;-)

#### kuruman

Homework Helper
Gold Member
Of course, their colours would have different names...
Of course, but you don't have to consider extraterrestrials for that to be true. "Yellow" is "jaune" in French and "amarillo" in Spanish.
You might wish to consider the survival advantage that is behind the reason why your aliens evolved the way they did. Good luck with your story.

#### pedro the swift

Why would these aliens not understand Eulers equation if they are several hundred years advanced. Maths doesn't differeniate(no pun). Should be the same everywhere. If not then we are all in trouble.

#### Nik_2213

Until he deploys his 'Recreational Math', they considered him an exotic pet, not a frustrated sapient.
'Chagrin-R-Us' ??

#### chasrob

Gold Member
Neat ! Of course, their colours would have different names...

FWIW, I've been toying with the converse issue, where a bright, pre-teen Terran can see ~400~~750 nm, but the holly-green, humanoid-ish bipedal aliens only ~470~~570 nm. They, however, can easily distinguish many, many more shades of green-ish within that range. Their world is a strange mix of near-identical shades of green, plus garish or discordant materials whose 'out of band' colours are invisible to their eyes...

Think how many apparently 'plain' flower petals have vivid markings in UV, the better to attract bees etc.
Also, how some flowers trap infrared...

To add yet more frustration, the aliens' speech and hearing runs from ~20 kHz~~40 kHz, compared to the Terran's ~20 Hz~~20 kHz...

The unfortunate boy is kept as a pet, a 'dress up doll', until he happens upon a museum's preserved 'Victorian-ish school room with green-board & chalk'. Fortunately, his dad, uncles and cousins loved recreational math. He starts with counting in different bases. Then Operators & Constants.
Blows the aliens away with Euler's e^iπ + 1 = 0
;-)
Clever. I never thought of restricting vision--always enhancing the ET capabilities.
So if the Terrans conversed with each other in low bass tones, the aliens wouldn't know what they said?

#### kuruman

Homework Helper
Gold Member
So if the Terrans conversed with each other in low bass tones, the aliens wouldn't know what they said?
Don't bet on it. If the aliens understand the Terran language, they can read lips. Or they can construct transducers and convert human frequencies to alien frequencies. Supposedly the technology exists to monitor conversations by using lasers to record the vibrations of the window panes of the room where these take place. The vibrations are then decoded to sounds. If we can do that now, why not someone who is presumably more technologically advanced than us?

#### chasrob

Gold Member
Don't bet on it. If the aliens understand the Terran language, they can read lips. Or they can construct transducers and convert human frequencies to alien frequencies. Supposedly the technology exists to monitor conversations by using lasers to record the vibrations of the window panes of the room where these take place. The vibrations are then decoded to sounds. If we can do that now, why not someone who is presumably more technologically advanced than us?
True, I didn't consider the tech possibilities

#### jim mcnamara

Mentor
Extending the color concept. In Navajo red does not match what English speakers agree is red. Same thing with blue - a kin* is supposed to have a blue roof. Most of the roof shingling I've seen is green. They consider it blue.

*(kin=male house, round house=hoogan -- proper nouns (nouns=sentences mostly) are pretty much both male and female and different words. Male rain. Female rain. And so on. )

https://psycnet.apa.org/record/2004-21166-006 Start of a series of studies. Himba people can see some shades of green as different colors. Non-himba speakers cannot differentiate them. i.e., you and me. We see them as exactly the same color. This is psychology so take the results from a weakly designed study with a grain of salt. But the idea remains.

What does this mean? What colors could aliens perceive as different that we see as identical? and vice-versa?

#### chasrob

Gold Member
That makes sense. Are you familiar with blackbody radiation? A relevant result can be summarized with the equation $\lambda~T=const.$ which says that the peak wavelength of the distribution becomes shorter as the temperature rises. Have you ever wondered why you see the heating element on an electric stove glow red only when it's set on "High"? That's because your eyes are not sensitive enough to see the element glow at "Medium" or "Low" settings. As a stove element at room temperature is turned on and starts heating up, your aliens' eyes should be able to see it glow long before human eyes could.
Interesting. I’m toying with extending the aliens vision into the UV but don’t know what advantage that would be to their soldiers. Something very cold could be detected?
My aliens are militaristic thugs, numbering in the millions on a planet with many, many billions. They’re considered outlaws there, but have recently perfected FTL travel via wormhole, unfortunately for us.

#### kuruman

Homework Helper
Gold Member
Something very cold could be detected?
No. The expression $\lambda T=const.$ says that when T becomes lower, the wavelength must become longer for the product to remain the same. Requiring longer wavelengths means moving away from UV towards IR.

My aliens are militaristic thugs ... unfortunately for us.
Why "unfortunately"? We should be very comfortable with them. The Earth's population is not "many, many billions", only about 8, but we have our proportional share of militaristic thugs, several hundred thousand I guess. Just look at how many people worldwide are presently forced to flee their homelands and seek refuge elsewhere because of guess who in their countries.

#### chasrob

Gold Member
No. The expression $\lambda T=const.$ says that when T becomes lower, the wavelength must become longer for the product to remain the same. Requiring longer wavelengths means moving away from UV towards IR.

Why "unfortunately"? We should be very comfortable with them. The Earth's population is not "many, many billions", only about 8, but we have our proportional share of militaristic thugs, several hundred thousand I guess. Just look at how many people worldwide are presently forced to flee their homelands and seek refuge elsewhere because of guess who in their countries.
There's small comfort in this crowd. Their plans are to leave their city-planet, where they're not welcome, squash the bugs infesting the 3rd planet, and anyone left is brain engineered to be compliant slaves. They're the antagonists of the story.

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#### essenmein

Neat ! Of course, their colours would have different names...

FWIW, I've been toying with the converse issue, where a bright, pre-teen Terran can see ~400~~750 nm, but the holly-green, humanoid-ish bipedal aliens only ~470~~570 nm. They, however, can easily distinguish many, many more shades of green-ish within that range. Their world is a strange mix of near-identical shades of green, plus garish or discordant materials whose 'out of band' colours are invisible to their eyes...

Think how many apparently 'plain' flower petals have vivid markings in UV, the better to attract bees etc.
Also, how some flowers trap infrared...

To add yet more frustration, the aliens' speech and hearing runs from ~20 kHz~~40 kHz, compared to the Terran's ~20 Hz~~20 kHz...

The unfortunate boy is kept as a pet, a 'dress up doll', until he happens upon a museum's preserved 'Victorian-ish school room with green-board & chalk'. Fortunately, his dad, uncles and cousins loved recreational math. He starts with counting in different bases. Then Operators & Constants.
Blows the aliens away with Euler's e^iπ + 1 = 0
;-)

Regarding the sound thing, something to consider is that we hear from ~20Hz to 20kHz, that is about 10 octaves, whereas 20kHz to 40kHz is only one octave, I'm sure this has an implication on data rate or speech formation etc. Ultrasonic music wouldn't be as interesting for example?

Then ultrasonic communication would suffer from issues like combing, line of sight, attenuation in air etc. There are probably physics reasons most of the biological's on our planet operate sub 20-25kHz.

#### stefan r

Gold Member
The mantis shrimp is worth reading about. Humans use 3 color sensing cells mantis shrimp have between 12 and 16. Some species can tune their eyes to accent particular colors. Their vision includes infra red and UV. They can see linear and circular polarized light and distinguish which is which.

Regarding the sound thing, something to consider is that we hear from ~20Hz to 20kHz, that is about 10 octaves, whereas 20kHz to 40kHz is only one octave, I'm sure this has an implication on data rate or speech formation etc. Ultrasonic music wouldn't be as interesting for example?

Then ultrasonic communication would suffer from issues like combing, line of sight, attenuation in air etc. There are probably physics reasons most of the biological's on our planet operate sub 20-25kHz.
There are possibilities for communication that do not include sound. Cephalopods have iridophores, leucophores, chromatophores and photophores. You could be very expressive if your face could change color as you spoke. Vocal speach could be equivalent to whistling or clapping your hands. The details of what you are trying to say would be clear whenever someone looked at you. Some alien that only changes color when left in the sun too long would clearly be incapable of communication. "Maybe humans have words for vomit and embarrassed. That is not really language."

"Alien vision"

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