Vision is the detection of light and the conversion of that signal into electro-chemical impulses for neurons to interpret. That, for all that we humans instantly conceptualize light as eyeballs and the visible light spectrum and color and movement, leaves a lot to the imagination.
Even just on Earth, we have creatures with completely vestigial eyes in the deep ocean, and creatures like the anglerfish and shark who are attracted to light and can sense motion but not much else.
Then there are humans and all sorts of mammals that can see ‘visible light’ with varying levels of acuity. This spectrum covers light wavelengths of 390 to 750 nanometers, and it’s probable that we see these wavelengths because they are within the ‘optical window’ of the electromagnetic spectrum that the atmosphere lets through to the surface. We can see red to violet, and that’s about it.
We see the galaxy like this.
We can’t really see ultraviolet and infrared, which are the sections on either side the visible spectrum. This range includes ‘thermal’ light, or heat vision. Rattlesnakes, for example, can see fuzzy objects but also have heat-sensing pits that detect thermal radiation. It’s not like they see thermal images in shades of red, yellow, and purple (like heat vision is typically depicted) but if they did it would look like this:
Since rattlesnakes use this to search for prey at night, when deserts get pretty chilly, any aliens with this kind of sight would probably be predators, live in a desert environment – like Mars, but with advanced life – and maybe their soldiers have color-vision goggles.
Let’s go back to that optical window for a second. A lot of electromagnetic waves are blocked by the atmosphere. The waves that make it through are 300 nm (ultraviolet light) to 1100 nm, or thermal infrared. Some radio waves can also make it through. This window of light largely accounts for why we are so limited (I say this like vision isn’t awesome), and humans can’t even see all that we might have been able to, or might be able to in the future.
Other animals, on the other hand, can see much, much more. Bees and other insects that hunt for pollen can see ultraviolet light (300-400 nm). Birds can, too, and they also have patterns in their feathers that can only be seen in ultraviolet light. Ultraviolet light and beyond is also seen by the mistakenly overlooked and incredibly super-powered mantis shrimp.
And then there’s the placement of eyeballs. It’s not incredibly likely that aliens would be like that demented thing from Pan’s Labyrinth, where it sucks eyes into its hands and chases after little girls (though I’m not nixing the possibility). But maybe it’ll only have eyes on one side, like an adult flounder. Maybe it’ll have front-facing eyes, like we do, in order to have depth perception and see in three dimensions. Maybe a lot of aliens will have eyes on either side of their head so they have panoramic vision. Or eyes like flies, or eyes like the mantis shrimp where each individual eye can see in 3-D.
Or maybe none of these. Maybe have alien senses that we’re not capable of, and we have senses they’re not capable of. Who knows?
If you’d like to take a closer look at the galaxy through different wavelengths (like x-ray, gamma, or microwave), take a look at the webpage.
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Rachel is the co-founder of How To Survive Alien Invasion Novels, and spends her time writing, studying, and reading what would probably be considered far too many books. Connect with her and Rusty on Twitter and Facebook, and click here to read more of her articles about alien theories and how to survive alien invasion novels.