>>12394628The scale was made by people, and people can only see the colors on that scale. That's the point - human eyes can only perceive the "visible" spectrum of radiation wavelengths. Light colors are a sequential spectrum of radiation wavelengths.
"Infrared" is the name we gave to the invisible radiation wavelengths that go past red, where we can no longer see them. "Ultraviolet" is the same thing, for the wavelengths that go past violet, where they're invisible to us. These terms are the scientific equivalent to "here there be dragons". Except we also started to then measure the invisible wavelengths, and name them, and find that they can do completely horrifying things to every part of our bodies if they go too far in either direction.
The human retina contains 3 kinds of color-receptive cells - Red, Green, and Blue. Big surprise. However, biologists discovered that certain species of animals have more than 3 kinds of colors-receptive cells in the their retinas. Some have 4, some 5, one has 8, and I think one has even more. One of these animals is the mantis shrimp; beyond the color vision, their eyes are also extremely complex, functionally. Also the "laser punch" claw thing, and looking like a fucking rainbow chinese dragon parade puppet.
