Let me rephrase the question – Do we call the Visible Spectrum that because that’s what we can see or is there something different about that part of electromagnetic spectrum (ES) that allow vision to occur. Alternately, If light is dual in nature, being both a wave and a particle, is that the same for other parts of the ES?
Which brings me to the question that I’m most curious about; would it be possible for a creature exist that can see, the same way we see, but using frequencies from other areas of the ES?
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The colour spectrum that the human eye sees is fairly well matched to the *peak* in intensity of light from the sun on earth.
This graph is a good starting point, the blue line for 5000K isn’t too far from sunlight (sunlight is nearer 6500K so shifted a little further to the left).[https://en.wikipedia.org/wiki/Black-body_radiation#/media/File:Black_body.svg](https://en.wikipedia.org/wiki/Black-body_radiation#/media/File:Black_body.svg)
The sun won’t emit any UV shorter than about 200nm (that’s about as far beyond “blue” as “red” is the other way), but the earth’s atmosphere absorbs a lot of UV so you can only go a little way into the UV (UV-B is fairly absorbed, and UV-C is essentially totally absorbed) before it effectively “goes dark”.
This picture (somewhat small) indicates the solar spectrum at the earth’s surface: [https://www.fondriest.com/environmental-measurements/wp-content/uploads/2021/01/new_par_solar-radiation-1.jpg](https://www.fondriest.com/environmental-measurements/wp-content/uploads/2021/01/new_par_solar-radiation-1.jpg)
Quite a few insects see in the near-UV, and we can use special cameras to show UV “colours” and patterns on flowers which attract insects (also why use UV light is used to attract flies into fly-zappers).
Although not as strong as visible light, there is a lot of infra-red light from the sun, extending an extremely long way in to the IR… but again a lot is absorbed by the earth’s atmosphere. For eyes based on water, the water in the eye would probably absorb many IR wavelengths, so you might need a different eye-structure.
Another thing to consider with IR is that as the wavelengths get longer the resolution decreases – specifically you can’t focus IR on a retina (or camera sensor) as finely as you can visible – so that would also have implications. Possibly bigger animals with bigger eyes might be more-able to make use of IR…?
Conversely it might be that the reason small insects see in the UV is that it will be able to focus better in their tiny eyes.
ELI5 -> Visible light is not “special” in the physics sense, as longer and shorter wavelengths still have the same basic properties. It’s mostly that what we consider the “visible” spectrum is a fair chunk of the spectrum of light that reaches the ground from the sun, so from a biological and evolutionary perspective with “natural” light, it makes sense that that’s what we “see”.
The thing that’s special about the visible part of the spectrum (and nearby frequencies that are visible to other animals but not to humans) is that [it passes through Earth’s atmosphere very well](https://i.stack.imgur.com/l6tYD.jpg). That’s why every animal with eyes sees somewhere around those wavelengths- it would be useless to see any other wavelengths because those other ones aren’t very common on Earth, so the ability to see them just didn’t evolve.
The thing that’s special about the visible part of the spectrum (and nearby frequencies that are visible to other animals but not to humans) is that [it passes through Earth’s atmosphere very well](https://i.stack.imgur.com/l6tYD.jpg). That’s why every animal with eyes sees somewhere around those wavelengths- it would be useless to see any other wavelengths because those other ones aren’t very common on Earth, so the ability to see them just didn’t evolve.
The thing that’s special about the visible part of the spectrum (and nearby frequencies that are visible to other animals but not to humans) is that [it passes through Earth’s atmosphere very well](https://i.stack.imgur.com/l6tYD.jpg). That’s why every animal with eyes sees somewhere around those wavelengths- it would be useless to see any other wavelengths because those other ones aren’t very common on Earth, so the ability to see them just didn’t evolve.
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