As the radiation peak of the sun is in the UV region and since at around room temperature materials emit radiation at IR, I wonder why our eyes are not capable of using these wavelengths. I guess there is a reason why we exactly only see the region between these intensity peaks?
Usually we don't ask why in biology because the explanation is always the same, it was good enough for survival. But here are a couple of explanations. The radiation peak from the sun is in the visible range of the spectrum, between 400nm-700nm with the highest point around 550nm as can be seen here or calculated from Wien's law and the sun temperature. That's why photosynthetic pigments use the visible spectrum and following them the rest of the ecological system.
Our retina blocks most of the UV light and water absorbs the lower part of the IR, illustrated very nicely in this article, figure 1.
It is true that materials on earth emit more radiation in the IR than in the UV-visible spectrum due to their temperature but:
- most objects have the same temperature approximately
- the soil emits a lot of radiation
- the radiation from the sun in the IR is high compared to the radiation of earth. This is the best graph I found, emphasizing the great difference between sun & earth intensities in the IR range there isn't a lot of variance in the wavelength intensity and therefore it is less useful. Notice how uniform the IR reflection is from this leaf spectral signature
- UV light is dangerous so we filter it out and not use it
- IR light is uniform and not useful
- Visible light is the peak of sun emission and therefore the most efficient range to use